here - national seed industry council
TRANSCRIPT
1
P R E F A C E
The Root Crops Varietal Improvement Group (also called Root Crops Technical
Working Group or RTWG) of the Philippine Seed Board (now National Seed Industry
Council) was organized in 1981. One of the first activities of this group was to formulate
guidelines/procedures for the conduct of regional trials of root crops. A guide for
conducting varietal evaluation of sweetpotato, cassava, yams (ubi and tugui), and gabi
was prepared and distributed to the different cooperating stations. That early set of
directions for conducting root crops variety trials emphasized the field plot techniques
and cultural practices to be followed for each of the crops mentioned. However,
procedures to rate pests commonly observed in these crops as well as procedures to
evaluate characters related to quality such as root dry matter and starch contents are
lacking.
To come up with a set of procedures for conducting the national cooperative trials
for root crops that will cover all aspects of variety testing with modified field plot
techniques and more reliable results, a training-workshop participated by the RTWG
members was held at the Philippine Root Crops Research and Training Center, VISCA
Baybay, Leyte on 27-28 April 1993. The output of the training workshop was further
discussed and modified during subsequent RTWG meetings. This manual on
Standardized Techniques for Root Crop Evaluation is, thus, a product of the combined
efforts of past and present members of the RTWG.
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TABLE OF CONTENTS
Preface
Procedure for Specific Crop Evaluation
Cassava -------------------------------------------------------------------
Sweetpotato -------------------------------------------------------------------
Gabi -------------------------------------------------------------------
Ubi and Tugui -------------------------------------------------------------------
Potato -------------------------------------------------------------------
Procedure for Rating of the Different Root Crop Anthropod Pests
Cassava -------------------------------------------------------------------
Sweetpotato -------------------------------------------------------------------
Gabi -------------------------------------------------------------------
Ubi and Tugui -------------------------------------------------------------------
Potato -------------------------------------------------------------------
Procedure for Rating Different Root Crop Diseases
Cassava -------------------------------------------------------------------
Sweetpotato -------------------------------------------------------------------
Gabi -------------------------------------------------------------------
Ubi and Tugui -------------------------------------------------------------------
Potato -------------------------------------------------------------------
Standard Method of Preparing Root Crops Sample for:
Dry Matter and Starch Determination ---------------------------------------
Rapid Evaluation of Cyanide Content of Cassava Roots -----------------
Techniques in Sensory Evaluation -------------------------------------------------
Importance of Uniform Field Plot Techniques in the Conduct
of Variety Trials ----------------------------------------------------------
Appendix Forms -------------------------------------------------------------------
Appendix Tables -------------------------------------------------------------------
List of Participants -------------------------------------------------------------------
3
PROCEDURE FOR CASSAVA EVALUATION TRIALS
General Procedure
Choice of Land. Select an area which is well drained and more or less uniform in
fertility and slope. Ideally, use an area for one cassava cropping only. However, if land is
limited, at most two cropping evaluations may be done in the same area. Only areas
previously used for trials with uniform cultural management can be used for varietal
evaluation. Control soil facility evaluation to the minimum.
Land Preparation. Plow the area twice when carabao drawn implement is used.
Afterwards, harrow twice at one week interval. One plowing and one harrowing may be
sufficient when tractor-drawn plow and harrow are used. After the last harrowing,
construct ridges 1.0 m apart.
Experimental Design. Use the randomized complete block design (RCBD) with
four (4) replications.
Size of Plot. The plot for each entry should have five (5) rows. Each row should
be 4.5 m long and spaced 1 m apart. The hills should be spaced at 0.75 m.
Plot Layout. Ensure that a replication (block) is as square as possible. The
difference between the length and width of the block must be minimized. Ideally all
blocks must be contained in one contiguous area. However, if a contiguous area to
accommodate the four replicates is not available, separate the blocks such that each block
will contain all the etries. A sample layout for a 12-entry trial is shown in Figs. 1-5.
Border Rows of the Experimental Area. To safeguard the experimental area
from grazing animals and other invading mammals, place at least two border rows on
each side and at least two hills on each end of the area.
Planting Materials. Select stems from at least 7 month-old cassava plants that
are free from insect pests and diseases. Cut into 20 cm long stakes for planting.
Pre-planting Treatment. To ensure that the planting materials are free from
scale insects, soak them in any systemic insecticide such as tamaron or silicrone. If stakes
are infected with fungus, soak them in fungicide.
Planting Time. The specific schedule for planting will be discussed during the
annual NCT meeting. However, the planting period for each year must be from May to
early July.
Replanting. If missing hills are present, replant not later than 2 weeks after
planting.
4
Planting Method. Plant the stakes vertically at the crest of ridges with two-thirds
(2/3) of the length buried in the ground.
Fertilizer Application. Have the soil in each site analyzed. Adjust the fertilizer to
be applied to the rate of 60-60-60 kg N, P2O5, K2O per hectare. Apply the fertilizer
basally on a per row basis at 10 cm from the plant base towards the side of the ridge.
Fertilize at planting or within 2 weeks after planting.
Irrigation. When irrigation water is available, irrigate the plants during long dry
spells especially during the first 3 months of the growing season.
Pest Control. Depending on pest incidence and severity, apply appropriate
pesticide whenever necessary. Before applying control measures, be sure to take the
incidence and severity ratings.
Weed Control. Control weeds regularly during the first 2 months after planting.
After this, weed only when necessary.
Harvesting. Harvest at 8-10 months after planting. Specify on the data sheet the
age of the plant at harvest. In each plot, harvest the three middle rows except the end
hills. Record the actual number of hills harvested per plot.
After lifting and separating the roots from the stem, remove/scrape off adhering
soil. Classify storage roots having at least 3 cm in diameter as marketable and those
below 3 cm in diameters as non-marketable. Weigh the storage roots according to class.
Data to be gathered:
1. Field Stand – Record the number of plants in the three middle rows per entry,
excluding end hill, at 2 weeks after planting and at harvesting. Ideally, there
should be 12 plants/hills per plot.
2. Dry Matter Content – Do actual dry matter analysis for selected stations and use
specific gravity method for the rest.
3. HCN Content – Determine this in selected stations only.
4. Length of Peduncle – Measure the peduncle (in cm) of all roots in one randomly
selected hill in each replication.
5. Lodging – Use the rating scale of 1, 5 and 9 (Rating must be done at harvest).
Lodging 1 – no lodging (straight)
5 – medium lodging
9 – heavy (total) lodging
5
6. Rating for Pests – Rate the incidence first at 2 months after planting, then at
bimonthly interval and lastly at 1 month before harvest. Use five randomly chosen
sample plants from three replications.
7. Sensory Evaluation – This will be done in selected stations only. Acceptability
and eating quality scores of sweet varieties only will be taken.
8. Marketable Yield – Consider all usable roots, at least 3 cm in diameter, that can
be sold in local market. Count and weigh them on per plot basis.
9. Non-marketable Yield – Consider all roots which are not worth selling although
may be used as animal feeds. Count and record their number and weigh them.
10. Total Yield – Add the weights obtained in nos. 7 and 8 to get the total root weight
per plot basis.
11. Remarks – Record any other observations considered pertinent such as soil and
agroclimatic data.
The formula and procedure in calculating yield are given below.
Yield (ton/ha) = Yield in kg/plot x 1.1111
In yield calculation, consider only plots with at least 10 hills. Result from an entry
with less than three replications should not be included for that location test.
SAMPLE FIELD LAYOUT FOR A 12 ENTRY CASSAVA TRIAL
Number of entries : 12
Number of replications/blocks : 4
Plot size : 5 row with 6 hill for each row starting from
the end
Planting distance : 0.75 m x 1 m (3.75 m from end hill to end
hill
Harvestable area : 3 rows with 4 hills per row (12 inner hills)
Border rows around the experimental area : At least two rows on each side of the area
6
Alley way : 1.5 m between sub-blocks (3 sub-blocks per replication)
Figure 1. Contiguous block allocation when an experimental area can accommodate
all four replications. The experimental area is almost square.
Alleyway : 1.5 m between sub-blocks
Figure 2. An alternate blocking when an area allotted for the trial is long and can
accommodate all four replicates.
20 m
14.25
m Block I
Block IV Block II
Block III
Border
Rows
20 m
14.25m 14.25m 14.25m 14.25m
Block I Block II Block III Block IV
7
14.25m
Border Row
Border Row
Area A
Area B
Alleyway: 1.5 m between sub-blocks
Figure 3. If only 3 blocks can be accommodated in Area A, the fourth block may be
constructed in another site, Area B. However, each block must contain the
same entries. Also, two blocks may be located in Area A and the other two
in Area B. However, border rows must be placed around the perimeter of
the experimental area, even when blocks are separated.
Block I 20 m
14.25m 14.25m
Block II Block III
Block IV
20 m
8
Figure 4. Each plant has an effective area of 0.75 sq. m.
A: Plot (P) distribution in each block
14.25 m
* * * * *
* * * * *
* * * * *
* * * * *
* * * * *
* * * * * P2 P3 P4
P8 P7 P5
P9 P10
P6
P11 P12
20 m
5 m 5 m 5 m 5 m
3.75 m
3.75 m
3.75 m
1.5 m
1.5 m
9
Figure 5. How each plot should look. Each * corresponds to a plant. The harvestable
area is enclosed in the rectangle (effective plot area is 9 m square)
* * *
*
*
*
*
*
*
*
*
*
*
* * *
* * *
* * *
* *
* * *
* * *
1.5 m
0.75 m
3.75 m
11
NRCCTP Form No. 1
NATIONAL ROOT CROP COOPERATIVE TESTING PTOGRAM
CASSAVA REGIONAL TRIAL
LOCATION: ___________________________ PLANTING DATE: _____________
SEASON: ___________________________ HARVEST DATE: _____________
Plot
No.
Rep.
No.
Entry
Name
Maturity Survival
Rate
Lodging
Resistance
Number
of Plants Harvested
No. of Roots Wt. of Roots/Plot (kg) Starch
Content
Dry
Matter Content
HCN
Content
Pest/Disease Rating Remarks
Marketable Non-
Marketable
Marketable Non-
Marketable
Scale Mites CBB
NRCCTP Form No. 2
12
DATA SUMMARY FOR CASSAVA EVALUATION TRIAL
Plot
No.
Entry Name No. of
Plants Harvested
Dry
Matter Content
HCN
Content
Lodging
Rating
Acceptability
Score
Pest and Disases Weight and Number/Plot or Hectare Remarks
Mite CBB No. Wt. No. Wt. No. Wt.
13
PROCEDURE FOR SWEETPOTATO EVALUATION TRIALS
General Procedure
Choice of Land. Select an area which is well-drained and more or less uniform in
fertility and slope. Use an area for one sweetpotato cropping only. However, the same
area can be planted again to sweetpotato if fallowed for at least 4 months or planted to
other crops. Only areas previously used for trials with uniform cultural management can
be used for varietal evaluation. Soil fertility variation must be minimized.
Land Preparation. Plow the area twice when carabao drawn implement is used.
Two harrowings at one week interval should be done after. One plowing and one
harrowing maybe sufficient when tractor drawn plow and harrow are used. After the last
harrowing, construct ridges 1.0 m apart.
Experimental Design. Use the randomized complete block design (RCBD) with
at least four (4) replications.
Size of Plot. Each plot must have two rows, each measuring 6 m x 2 m. Space
between rows should be 1 m.
Number of Entries. Entries for each trial should not exceed 16 test cultivars
including checks.
Planting Distance. In each row, space the plants at 30 cm between hills.
Field Layout. Make each replication/block as square as possible. An example of
blocking for a 16 entry trial is shown in Figure 7. It is best to set sub-blocks 1.0 m apart
(i.e., each alleyway will be 1.0 m wide)/
Border Rows of the Experimental Area. Provide at least two rows in each side
and at least seven border hills on each end of the area. There should be no border rows or
vacant spaces between sub-blocks except between replications.
Planting Materials. Planting materials for the trial must be 25 cm long tip vine
cuttings. If terminal cuttings are insufficient, secondary cuttings may be used provided
that these materials will be planted in separate blocks. Set aside a separate area for the
multiplication of planting materials. Clip expanded leaves of materials which will be
transported from one station to another.
Pre-planting Treatment. For pest control, pre-planting treatment with a
fungicide- insecticide mixture maybe done whenever necessary.
Planting Method. Plant on the ridges leaving about 6 cm of the tip of the cutting
above the ground. Distance between hills should be 30 cm. Plant only 1 cutting per hill.
14
Re-planting. Replant missing hills within one week after planting.
Fertilizer Application. Have the soil in each site analyzed. Adjust the fertilizer
rate to be used based on the recommended rate of 45-45-45 kg/ha of N, P2O5 and K2O.
Apply fertilizer basally on a per row plot basis at 10 cm from the base of the ridge at
planting time. Fertilizer should be applied only during the dry season, none during the
wet season.
Irrigation. Where irrigation water is available, irrigate whenever necessary.
Pest Control. To control insect pests and diseases, spray when necessary.
However, be sure to obtain the incidence and severity ratings before applying any
pesticide.
Hilling-up and Weeding. Hill-up and off-bar 3-4 weeks after planting. Weed
within the row whenever necessary.
Harvesting. Exclude two end hills per row. Hence the effective harvestable area
is only 10.8 sq. m. containing 18 hills per row. Record the actual number of hills
harvested per row. Results from an entry with more than 1 missing plot must be excluded
in the analysis. Harvest the individual hill using a spanding fork. Record the yield per
area basis.
Seasonal harvesting is as follows:
Low elevation sites:
Dry season - 105 days after planting
Wet season - 120 days after planting
High elevation sites:
Dry season - 120 days after planting
Wet season - 150 days after planting
Data to be gathered:
1. Field Stand – Record the number of plants for each entry at harvest.
2. Dry Matter Content – Determine for selected stations only (refer to page ____ ).
3. Starch Content – Determine for selected stations only (refer to page _____ ).
4. Pest and Disease Rating – Indicate the pests or disease rated. Use the 1 to 9
scale (refer to pages ____ & ____ ).
15
5. Shape of Storage Roots – Use the IPGRI identification system (Fig. 8).
6. Sensory Evaluation – Do this for table types only.
7. Marketable Yield – Consider only roots with diameter of at least 2.5 cm.
a. Number – Count the storage roots and record.
b. Weight – Weigh all storage roots and record. Express weight in kilogram.
8. Non-marketable Yield – Consider roots with a diameter of less than 2.5 cm.
9. Total Yield – Add the figures from 7 and 8 to get total number and weight of
roots.
10. Remarks – Record any other pertinent observation such as climatic and soil data.
Yield Calculation:
Plots with more than 30% missing hills will be excluded in the analysis.
The formula in converting yield from kg/plot to tons/ha is:
Yield (tons/ha) = Yield (kg/plot) x 0.92592
Figure 6. Field layout for one replication of a 16-entry sweetpotato trial
5.7 m
5.7 m
Sub-block I
(8 plots)
Sub-block II
(8 plots)
16
Figure 7. Suggested field layout for a 16-entry sweetpotato trial with 4 replications.
BR BR
Sub-block I, Rep. 1
BR BR
Sub-block I, Rep. 1
Sub-block I, Rep. 3
Sub-block I, Rep. 3
Border Rows (BR)
BR BR
Sub-block I, Rep. 2
Sub-block I, Rep. 4
BR BR
Sub-block I, Rep. 2
Sub-block I, Rep. 4
Border Rows (BR)
17
Figure 8. How a plot should look. In harvesting, exclude two end-hills per row.
(Effective harvestable area will be 10.8 sq. m.)
5.7 m
2 m
* *
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
* *
SUB-BLOCK OF
REPLICATION
1m
1m
18
Types of storage root shape
round elliptic round elliptic
ovate oblong obovate
long oblong long irregular
or curved
long elliptic
19
NRCCTP Form No. 3
NATIONAL ROOT CROP COOPERATIVE TESTING PROGRAM
SWEETPOTATO REGIONAL TRIAL
LOCATION: ________________________________ PLANTING DATE: _____________
SEASON: ________________________________ HARVEST DATE: _____________
Plot
No.
Entry
Name
No. of
Olants Harvested
Dry
Matter Content
Maturity Survival
Rate
Shape
of Roots
Skin
Color
Flesh
Color
Texture Eating
Quality
Pest & Diseases Weight & Number Remarks
Weevil Scab Marketable Non-
Marketable
Total
%
infestation
No. Wt. No. Wt. No. Wt.
20
PROCEDURE FOR GABI EVALUATION TRIALS
General Procedure
Choice of Land. Select an area which is well drained and more or less uniform in
fertility and slope. Ideally, use an area for one gabi cropping only. However, if land is
limited, at most two cropping evaluations may be done in the same area for as long as the
area will be fallowed for 2-3 months. An area previously used for other trials can only be
used for varietal evaluation if the previous trial imposed uniform cultural management.
Soil fertility variation must be controlled to the minimum.
Land Preparation. Plow the area twice when using a carabao-drawn implement.
Two harrowings at one week interval should be done after. One plowing and one
harrowing maybe sufficient when tractor-drawn plow and harrow are used.
Experimental Design. Use the randomized complete block design (RCBD) with
four replications.
Size of Plot. An entry will occupy a four row plot, 4 m x 3 m, with 0.75 m
distance between rows and 0.50 m spacing between hills.
Field Layout. Make each replication or block as square possible. Examples of
field layouts using sixteen (16) and eight (8) entries are shown in Figures 10 and 11.
Planting Materials. For planting materials, use suckers but remove the lower
portion of the corm or cormel. Remove all the leaves; leave only 3-4 petioles per sett
(part of the stem and upper portion of the corm). Use planting materials of the same size
per replication.
New entries for evaluation will be provided by the breeder and shall be
propagated in the different stations at least 6 months before the start of the new set of
trials.
Planting Method. Furrow planting is required. Follow the spacing of 75 cm
between furrows and 50 cm between pplants in the furrow. Bury or insert the planting
materials within the furrow up to a depth of 10 cm, then cover with soil.
Fertilizer Application. Have the soil in each site analyzed. Adjust the rate of
fertilizer to be applied based on the recommended rate of 30-30-30 kg N, P2O5, K2O. At
planting, apply half of the whole amount basally on a per hill basis. Apply the other half
at 2 months after planting.
Irrigation. Irrigate as often as necessary.
21
Pest Control. Apply pesticide when necessary. Rate the incidence and severity of
the pest before pesticide application.
Hilling-up and Weeding. Weed within the first 2 months after planting and later
whenever necessary.
Harvesting. At 8 months after planting, harvest all plants in each plot for yield
estimation. Record the actual number of hills harvested per plot. Exclude plots with more
than 30% missing hills and entries with more than one missing plot in the analysis.
Data to be gathered:
1. Field Stand – Record the number of plants harvested for each entry.
2. Dry Matter Content – Analyze in all stations by replications.
3. Starch Content – Determine in selected stations only.
4. Pest Rating – Use the 1 to 9 scale. (refer to p. ____ )
5. Disease Rating – Use the 1 to 9 scale. (refer to p. ____ )
6. Sensory Evaluation – Follow the standard procedure discussed in p. ____
7. Yield – Adjust main corm yield to tons per hectare using the formula below:
Yield (tons/ha) = Plot Yield (kg) x 0.8333
8. Remarks – Specify other observations obtained.
22
Figure 10. Suggested field layout for a 16-entry gabi trial with four replications.
BR BR
Sub-block I, Rep. 1
BR BR
Sub-block II, Rep. 1
Sub-block II, Rep. 3
Sub-block I, Rep. 3
TWO ROWS OF GUARD PLANTS (TRGP)
BR BR
Sub-block I, Rep. 2
Sub-block I, Rep. 4
BR BR
Sub-block II, Rep. 2
Sub-block II, Rep.
TWO ROWS OF GUARD PLANTS (TRGP)
23
Figure 11A. Suggested field layout for an 8-entry gabi trial with four replications.
B. Sample of a whole plot which is also the effective harvestable area
4 m 4 m
P1
P3
P5
P7
P2
P4
P6
P8
Rep II
Rep III Rep IV
8 m
3 m
3 m
12 m
A
* * * * * * *
*
* * * * * * *
*
* * * * * * *
*
* * * * * * *
*
B
.5m
.75m
24
PROCEDURE FOR UBI AND TUGUI EVALUATION TRIALS
General Procedure:
Choice of Land. Select an area which is well drained and more or les uniform in
fertility and slope. Ideally, use an area for one ubi/tugui cropping only. However, if land
is limited, at most cropping evaluations may be done in the same area. An area previously
used for other trials can only be used for varietal evaluation if the previous trials imposed
uniform cultural management. Soil fertility variation must be controlled to the minimum.
Land Preparation. Plow the area twice when carabao drawn implement is used.
Two harrowings at one week interval should be done after. One plowing and one
harrowing maybe sufficient when tractor-drawn plow and harrow are used. After the last
harrowing, construct ridges 1.0 m apart.
Experimental Design. Use a randomized complete block design (RCBD) with
four replications.
Size of Plot. The entries should occupy 4-row plots measuring, 6 m x 4 m each, 1
meter between rows and 75 cm between hills replicated four times.
Field Layout. Make each replication as square as possible.
Preparation of planting materials. Use setts (portion of the tuber) as planting
materials. Prepare 200 gram setts for ubi and 100 gm for tugui. Treat them with wood ash
or fungicides after licing.
Planting. Plant the setts at a distance of 1 m between rows and 75 cm beween
hills, and at a depth of 10 cm from the top of the ridge.
Replanting. Plant all extra setts at the same time to enure germination. Use the
pregerminated setts to replace the missing hills. Replanting should be done 2 weeks after
planting.
Fertilizer Application. At planting, apply fertilizer basally at a rate of 30-30-30
kg NPK per hectare.
Weeding. Weed whenever necessary.
Staking. When plants start to emerge, place one stake per hill. The stakes should
extend 2 m above the ground.
Spraying. Spray the plants with fungicides (e.g. Benlate, Zineb) or insecticides as
the need arises.
25
Hilling-up. Hill-up ar 2 months after planting. When storage roots get exposed,
hill-up using shovels from time to time.
Harvesting. Harvest during or after senescence. Record the actual number of hills
harvested per plot. Exclude plots with more than 30% mising hills in the data analysis.
Harvest all rows for yield estimates.
Data to be gathered:
1. Percentage Germination – Observe this at one month after planting
2. Pests and Time of Occurrence – Determine these at 3, 4 and 5 months after
planting (MAP)
3. Date of Maturity (weeks) – This refers to the time from planting th senescence
4. Tuber Acceptibility
a. Appearance
b. Aroma
c. Taste
d. Texture
e. General Acceptability
5. Yield per Plot
a. Marketable – Determine weight and number of tubers which are at least 300
gm for ubi and 100 gm for tugui
b. Non-marketable – Determine weight and number of all other tubers
6. Dry Matter Content of Tubers – Analyze actul dry matter content for all stations
7. Remarks – Record other pertinent observations and other climatic data
26
Figure 12. Siggested field layout for a 16-entry ubi and tugui trial with four
replications.
BR BR
Sub-block I, Rep. 1
BR BR
Sub-block II, Rep. 1
Sub-block II, Rep. 3
Sub-block I, Rep. 3
Border Rows (BR)
BR BR
Sub-block I, Rep. 2
Sub-block I, Rep. 4
BR BR
Sub-block II, Rep. 2
Sub-block II, Rep. 4
Border Rows (BR)
27
Figure 13A. Suggested field layout for an 8-entry ubi and tugui trial with four
replications
B. Sample of a whole plot which is also the effective harvestable area
6 m 6 m
P1
P3
P5
P7
P2
P4
P6
P8
Rep II
Rep III Rep IV
12 m
4 m
4 m
16 m
A
* * * * * * *
*
* * * * * * *
*
* * * * * * *
*
* * * * * * *
*
B
.75m
1.0m
28
NRCCTP Form No. 4
NATINAL ROOT CROP COOPERATIVE TESTING PROGRAM
UBI AND TUGUI REGIONAL TRIAL
LOCATION: _________________________________ PLANTING DATE: ___________________
SEASON: _________________________________ HARVEST DATE: ___________________
Plot
No.
Rep.
No.
Entry
Name
No. of
Plants
Maturity Number of Tubers Weight of Tubers (kg) Tuber
Dry
Matter
Content
Disease Rating Remarks
Marketable Non-
Marketable
Marketable Non-
Marketable
Anthracnose Leaf
Rust
ETC
29
STANDARD PROCEDURE FOR POTATO EVALUATION TRIALS
General Procedure
Choice of Area. Select an area which is relatively free from bacterial wilt (BW),
with good drainage and uniform soil fertility. Ideally, andy loam loam to clay loam soils
with pH ranging from 5.6 to 6.5 and high organic matter content are preferred. The trials
shall be conducted for at least four (4) seasons (2 dry, 2 wet) in at least two sites per
elevation. In the lowlands however, the trials shall be conducted for two crop seasons
only in at least two sites.
If possible, collect soil samples for laboratory analysis of bacterial wilt and
nematode diseases before setting-up the trial.
Land Preparation. Prepare the land thorough by plowing and harrowing at the
right soil moisture. Do each operation at least twice.
Experimental Dasign. Use the randomized complete block design (RCBD) with
three to four replications depending on the available area and planting materials. Plant at
least 40 to 60 plants per plot (or 20 to 30 plants per row) for each entry. Plant one border
row on each side of the experimental area and at least two hills of border plants at both
ends of each plot.
Size of Plot. Each plot must have two rows (double row) measuring 6.6 m long.
Space the two furrows 40 cm apart in the double row. Double rows must be 90 cm apart.
See Figs. 13-14 for illustration.
Planting Distance. Space the plants at 30 cm between hills in each row.
Field Layout. Make each replication/block as square as possible. An example of
blocking for 10 entry trials is shown in Fig. 14.
Border Rows of the Experimental Area. Provide a double row around the
whole area, at least three border hills on each end of the area, and 50 cm space with a
length of 5 m between double rows.
Planting Materials. Select good seed tubers for planting, i.e. full in form and of
the right physiological age. The recommended seed tuber size is 30 to 50 mm in diameter
or 40 to 60 gm in weight with 2 to 4 sturdy green sprouts, measuring about 0.5 to 1.5 cm.
Make sure that that the seed tubers are free from insect pests and diseases
especially bacterial wilt (BW) and viruses. Never use cut tubers unless very necessary
and when there is no problem on soil-borne diseases in the area. keep the source, size and
age of the planting materials as uniform as possible. Classify seeds into large, medium
and small. Plant only seeds of similar size in each replication.
30
Include at least two highland recommend cultivars as local check. As much as
possible, seed tubers of these check cultivars should come from the same source as the
test entries. Use a maximum of 10 entries for each trial.
Pre-planting Treatments. Pre-planting treatment foreasy germination maybe
done whenever necessary.
Planting Method. Plant on ridges and follow the double-row method of planting.
Space the two furrows in the double row at 40 cm. Provide a space of 50 cm between
pairs of furrows or between double rows and 30 cm between hills within furrows. Plant
parallel within the double rows of the experimental unit. Provide a pathway of 1 meter
between replications.
Fertilization. If possible, fertilizer application should be based on soil analysis.
The usual recommendation is 140-140-140 NPK fertilizer is recommended. Chicken
manure (or any available organic matter) at 2 tons/ha must be incorporated into the soil
during land preparation. In the absence of soil analysis, additional nitrogen fertilizer (50
kg N/ha) may be sidedressed 25 to 30 days after planting or before hilling-up.
Irrigation. Water the plants as often as necessary. The first 4 to 5 weeks is the
most critical period, hence supply sufficient water at this time. If possible, do not employ
flood irrigation to minimize the possible spread of BW. If there is no rain, irrigate at 5 to
7 dys interval. Stop watering 15 days before harvest.
Pest Control. Spray pesticides as the need arises. Control weeds especially
during the first 4 to 6 weks of the growing period.
Hilling-up. Hill-up once at 25 to 30 days after planting or during the sidedresing
of the additional nitrogen fertilizer.
Harvesting. Before digging, record the number of hills to be harvested per plot.
Exclude the two ebd-hill per row, leaving 20 inner hillsto be harvesyed; effective
harvestable area is 7.8 sq. m. Exclude plots with more than 30% missing hills.
Grade harvested tubers according to size, following he size description in number
7 under data to be gathered.
For mid-highland evaluation, harvest at 90 to 150 days after planting. For lowland
evaluation, harvest 70 to 80 days after planting.
Storage of tubers. Store the seed tubers under diffused light condition to evaluate
dormancy and storability. Before storing, treat the tubers properly (they could be used in
subsequent trials) by dipping or dusting them with an insecticide-fungicide mix. Record
all data on dormancy, tuber number ad weight losses. At the end of the storage period (8
31
to 9 months after harvest), rate the tubers in terms of degree of shrivelling and sprouting.
Follow the rating scale of 1-5 for each parameter.
Data to be gathered:
1. Number of hills planted, plant emergence (number) at 30 DAP and number of
hills harvested
2. Days of Emergence – Observe this when 50% of the total plants/plot have
emerged
3. Plant Vigor – Record this at 30 to 45 days after emergence using the 1 to 5 rating
scale (1-highly vigorous, 3=medium, 5=very poor vigor)
4. Maturity/Senescence Rating – Determine this at 70 and 80 DAP before
dehaulming using the 1 to 5 rating scale. (1 – very early or no senescence; 5 –
very late or fully senesced)
5. Insect Rating – Do separate ratings for viruses, aphids and other specific major
insect pests. Use the rating scale of 1 to 9 in increasing order of severity.
6. Disease Rating – Do separate ratings for BW, late blight, scab or other specific
major diseases. Use the rating scale of 1 to 9 in increasing order of severity. For
BW, conduct a water test to verify and count the number of wilted plants. All
plants with BW must be rogued.
7. Yield and its Components – Separate marketable and non-marketable tubers. Get
their total weight and number.
Yield Calculation:
Get yield on per hill basis but later compute yield in tons/ha or per area
basis (approx. 50,000 plants/ha).
Convert yield per plot to per hectare basis as follows:
Yield (tons/ha) = Yield (kg)/plots x 1.28205
Classify tubers according to size as follows:
Size Grams
Extra Large More than 100 g
Large 80 to 99 g
Medium 50 to 79 g
Small 30 to 49 g
Marble-ize Less than 30 g
32
8. Analyze the tubers according to the solid (dry matter) and sugar contents.
Unmarkable tubers are those weighing less than 30 g. Record the
percentage of cracking and secondary growth for each size. Also record/rate the
occurance of tuber diseases.
Farmer’s Preference Rating
1. Encourage the farmer-partner and other farmers (at least 5 to 10 farmers) to
follow-up/ visit the trial regularly. Conduct farmer’s preference rating at:
a. 50 to 5 DAP using 1 to 5 rating scale 1 – highly preferred; 5 – not preferred).
b. at harvest using the same rating scale above for yield, tuber size and
appearance
Tuber Quality Evaluation
1. Evaluate processing quality for chips and fries. Private processing companies may
be invited to evaluate the clones for processing (chips).
2. Form a taste panel for boiled potato tubers.
33
Field Layout for Potato
Figure 14. Field layout for a single replication of potato evaluation trial showing
dimensions of double rows and plot.
Plot size – 6.6 x 1.3 m
Distance between double rows – 90 cm
Effective plot area – 0.195 sq. m.
Effective harvestable area – 7.8 sq. m.
No. of plants harvested/row – 20 inner plants
Border rows
25 cm 40 cm 40 cm
Border rows
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6.6 m 6.6 m
6 m
1.3 m
34
Figure 15. A detailed illustration of potato trial on a plot basis
Plot size – 6.6 x 1.3 m
Distance between double rows – 90 cm
Effective plot area – 0.195 sq. m.
Effective harvestable area – 7.8 sq. m.
No. of plants harvested/row – 20 inner plants
40 cm
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40 cm 25cm 25cm
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60 cm
60 cm 40 cm
35
NRCCTP Form No. 5
NATIONAL ROOT CROP COOPERATING PROGRAM
POTATO REGIONAL TRIAL
LOCATION: _______________________________ PLANTING DATE:
___________________
SEASON: _______________________________ HARVEST DATE:
___________________
Plot
No.
Rep.
No.
Entry
Name
No. of
Plants
Maturity Insect Pest Disease Rating Weight of Tubers (kg) Tuber
Dry
Remarks
Aphids Thrips Late
Blight
Bacterial
Wilt
Viruses Etc. Marketable Non-
Marketable
Matter
Content
36
PROCEDURE FOR RATING OF THE DIFFERENT
ROOT CROPS ARTHROPOD PESTS
Cassava
Rating for insect pest infestation must be done at monthly intervals from the third
month after planting until harvest.
Rating of cassava spider mite, scale insect and whiteflies infestation should start 3
months after planting and should be done monthly until harvest especially during the dry
season. During the wet season, rating maybe done only during the months when high
infestation occurs. Damage rating will be done on 10 randomly selected plants in the
inner rows per replicate. To determine percent infestation, consider all infested plants in
the inner rows over the total number of plants/hill in all inner rows.
Red spider mite
Tetranychus kansawai Kishida
Level of Damage Type of Damage and Level of Infestation
0 Plant without mites; no damage
2 Basal or mid-leaves with some light ellow speckles;
about 10-20 specks grouped or dispersed over each leaf
3 Basal or mid-leaves with definite or noticeable yellow
speckles, about 50-100 spots per leaf
5 Extensive damage on basal and middle leaves of plants;
leaves completely speckled; yellowing and necrosis of
basal leaves; webbing on some leaves
7 Plants with general yellow appearance; mites on all
leaves; basal and middle leaves mostly affetced;
webbing on some leaves
9 Plants severely defoliated; mites abundant on all parts
of the plants; leaf necrosis; plants may die
37
White peach scale
Psuedaulascaspis pentagona Targiona-Tozzetti
Level Damage Type of Damage and Level of Infestation
0 No scale prsent
1 Few scales found around lateral or terminal buds
3 Same as in 2; some internodes attacked
5 Scales completely covering growing points and 50% of
internodes; loss of lower leaves
7 Approximately 75% of stem and branches covered with
scales; loss of intermediate leaves
9 Scales completely covering stem and branches;
desiccation of terminal shoots
Mealybug
Ferrisiana virgata Cockerel
Phenococcus hirsitus Green
Pseudococcus elisae Borchsenius
Include rating of mealybug infestation of roots at harvest. Rate at monthly
intervals during both dry and wet seasons.
Level of Damage Type of Damage and Level of Infestation
0 No nymphal stages or adults present
1 Nymphs found on underside of lower leaves
3 Same as in 1; chlorotic pots begin to appear on these
leaves
5 Adults, nymphs and ovisacs present; partial chlorosis of
basal leaves
7 Adults, nymphs and ovisacs on petioles and or stems;
total chlorosis of lower leaves and/or necrosis of their
margins; sooty mold on petioles and leaves
9 Death of growing points and new lateral buds attacked;
leaf necrosis and leaves fall; desiccation of stem
38
Whiteflies
Bemisia tabaci Gennadius
Aleurodicus disperus Russel
Level of Damage Type of Damage and Level of Infestation
0 No infestation by adults/ no pupa on laf
1 Less than 20% infestation of leaves/ less than 5 pupae
per leaf
3 20-40% infestation of leaves/ 5-10 pipae per leaf
5 41-60% infstation of leaves/ 11-50 pupae per leaf
7 61-80% infestation of leaves/ 26-50 pupae per leaf
9 81-100% infestation of leaves/ more than 50 pupae per
leaf
39
NRCCTP Form No. 6
NATIONAL ROOT CROPS COOPERATIVE TESTING PROGRAM
EVALUATION FOR RESISTANCE TO CASSAVA PESTS
Entry
Spider Mite
Date of
Observation ___________________
Scale Insect
Date of
Obervation ____________________
Whiteflies
Date of
Observation _________________
%
Infestation
Damage
Rating
Reaction %
Infestation
Damage
Rating
Reaction %
Infestation
Damage
Rating
Reaction
40
Sweetpotato
Rating of other pests (e.g. grubs be included using a rating scale of 0-9.
For other pests/diseases encountered but not included in the manual, contact
PRCRTC for assistance and assesment. Illustrations/pictures should accompany the
disease description, rating and scale.
1. Sweetpotato Weevil
Cylas formicarius Fabr.
Rate sweetpotato weevil infestation at harvest. The criteria used in
evaluating resistance will be based on percent weevil infestation, surface area
damaged and number of tunnels.
To determine percent weevil infestation, consider all roots from all inner
rows per replication. For damage rating, take 15-20 infested roots from
replication of the three replications. Use the following rating scale.
Rating Scale for Sweetpotato weevil (Cylas formicarius Fabr.) Infestation
Rating Description
External Damage
1 1 to 10% of surface area damaged
3
11 to 20% of surface area damaged
5
21 ro 40% of surface area damaged
7
41 to 60% of surface area damaged
9
61% or more of surface area damaged
Internal Damage
1 No damage; No tunnels or weevil in root
3 1-2 tunnels or weevil per root
5 3-4 tunnels or weevil per root
7 5-6 tunnels pr weevil per root
9 7 or more tunnels or weevil per root
41
NRCCTP Form No. 7
NATIONAL ROOTCROP COOPERATIVE TESTING PROGRAM
EVALUATION FOR RESISTANCE TO SWEETPOTATO WEEVIL
Entry W E E V I L (Date of Observation)
% Infestation Damage Rating
(External & Internal)
Reaction
42
Taro
Rate taro spider mite, scale insect and whiteflies infestation monthly from 3
months after planting until harvest especially during the dry season. During the wet
season, rating may be done only during the months where high infestation occurs.
Damage rating will be done on 10 randomly selected plants in the inner rows per
replicate. To determine percent infestation, consider all infested plants in the inner rows
over the total number of plants/hill in all inner rows.
RATING SCALE FOR TARO ARTHROPOD PESTS
Hornworm (Hippotion celerio Linn.)
Grasshopper (Gesonula mundata zonocera Navas)
Cutworm (Spodoptera litura Fabr.)
Level of Damage Description
0 No damage
1 1 - 5% leaf area damage/defoliation
3 6 - 25% leaf area damage/defoliation
5 26 - 50% leaf area damage/defoliation
7 51 - 75% leaf area damage/defoliation
9 76 - 100% leaf area damage/defoliation; unopened leaves
and petioles attacked
43
Aphid (Aphis gossypii Glover)
Level of Damage Description
0 No aphids
1 Few adults and nymphs on nether surface of leaves
3 Several colonies on nether surface of leaves
5 Many distinct colonies on nether surface of leaves
7 Many distinct colonies on nether surface of leaves and
petioles
9 Many distinct colonies on nether surface of all opened
leaces, unoppened leaves and petioles
Taro green mite (Schizotetranychus lechrius Rimando)
Level of Damage Description
0 No mites or no damage
1 Few mites; initiation of silvery spots on some basal and/or
middle leaves
3 Many mites on some leaves; fairly abundant silvery spots
on basal and middle leaves; extensive damage
5 Many mites on some leaves; abundant silvery spots on
basal and middle leaves; fairly extensive damage
7 Many mites on all open leves; entire and intermediate
leaves appear silvery; moderate/severe damage
9 Many mites on all open and unopened leaves; all leaves
appear silvery; browning and cupping of leaves; plants
wilt; very severe damage
44
Whiteflies (Aleurodicus dispersus Russell)
Level of Damage Description
0 No infestation by adults/no pupa present
1 Less than 20% infestation of leaves/ less than 5 pupae per
leaf
3 20 – 40% infestation of leaves/ 5-10 pupae per leaf
5 41 – 60% infestation of leaves/ 11-25 pupae per leaf
7 61 – 80% infestation of leaves/ 26-50 pupae per leaf
9 81 – 100% infestation of leaves/ more than 50 pupae per
leaf
Mealybugs (Phenococcus gossypii)
Level of Damage Description
0 No nympal stage or adults present
1 Nymphs found on underside of lower basal leaves
3 Same as in 1; chlorotic spots begin to appear on these
leaves
5 Adults, nymphs and ovisac present; partial chlorosis of
basal leaves
7 Adults, nymphs and ovisac on leaves and petioles;
chlorosis of lower leaves and/or necrosis of their margins;
sooty molds on leaves and petioles
9 Death of growing points and new lateral buds attacked;
leaf necrosis; wilting of leaves and desiccation of petioles
45
NRCCTP Form No. 8
NATIONAL ROOTCROP COOPERATIVE TESTING PROGRAM
EVALUATION FOR RESISTANCE TO CASSAVA PESTS
Entry
Hornworm
Date of
Observation
Grasshopper
Date of
Observation
Aphids
Date of
Observation % Infes-
ation
Damage
Rating
Reaction % Infes-
ation
Damage
Rating
Reaction % Infes-
ation
Damage
Rating
Reaction
46
Potato
Aphids (Aphis gossypii Glover)
(Myzus persicae Sultzer)
Level of Damage Description
0 No aphids
1 Few adults and nymphs on nether surface of leaves
3 Several colonies on nether surface of leaves
5 Many distinct colonies on nether surface of leaves
7 Many distinct colonies on nether surface of leaves and
petioles
9 Many distinct colonies on nether surface of all opened
leaves, unopened leaves and petioles
Thrips (Thrips palmi)
(Thrips tabaci)
Level of Damage Description
0 No infestation by aults / no pupa on leaf
1 Less than 20% infestation of leaves / less than 5 pupae per
leaf
3 20 – 40% infestation of leaves / 5 – 10 pupae per leaf
5 41 – 60% infestation of leaves / 11 – 50 pupae per leaf
7 61 – 80% infestation of leaves / 26 – 50 pupae per leaf
9 81 – 100% infestation of leaves / more than 50 pupae per
leaf
47
PROCEDURE FOR RATING OF THE DIFFERENT ROOTCROP DISEASES
Cassava
Cassava Bacterial Blight (CBB) Xanthomonas manihotis
Scale Decription Reaction
1 No symptom Highly Resistant
(HR)
3 Angular spot 15%;
defoliation not more than 30%
Resistant
(R)
5 Angular spot and blighting;
more than 50% defoliation;
more than 30% with gum
exudation
on stem
Moderately Resistant
(MR)
7 Total defoliation; death of the
lower lignified portion of stem
Susceptible
(S)
9 Total death of plant Highly Susceptible
(HS)
*Frequency of rating – bimonthly
*Sample size – 10 plants/replication/entry
48
Leaf spot (Cercospora vicosae and Cercosporidium henningsii)
Scale Decription Reaction
1 0-20% of leaves are affected (foliar lession)
defoliation
HR
3 21-40% of leaves are affected (foliar lession)
defoliation
R
5 41-60% of leaves are affected (foliar lession)
defoliation
MR
7 61-80% of leaves are affected (foliar lession)
defoliation
S
9 81-100% of leaves are affected (foliar lession)
defoliation
HS
*Frequency of Rating – Bimothly
*Sample Size – 10 plants/replication/entry
Sweetpotato Stem and Foliage Scab
Disease rating of sweetpotato scab coulb be done either in the field or in the
screenhouse. When done in the field, gather the estimated of infections from 10 randomly
selected plants per variety per replication. For screenhouse evaluations 2 – 5 plants per
variety may be used.
For disease evaluation in the field, use 2 rows with 12 plants per row per
replication. The best sample size is 10 plants per entry. When artificial infection is done,
the initial rating should be done 7 – 14 days after inoculation and the final rating at one
month before harvest. In case of natural infection, the initial rating should be done 28 –
30 days after planting and at 28 – 30 days before harvest for the final rating.
49
Sweetpotato Scab
Screenhouse Experiment
Scale Decription Reaction
1 No symptom on leaf and stem HR
3 Occasional lesions on their the stem
or leaf, 10 lesions per 30 cm vine
R
5 Scattered lesions on stem and leaves;
10 – 20 lesions per 30 cm of vine
MR
7 More than 20 lesions per 30 cm of vine;
slight leaf deformation
S
9 Numerous lesions on both leaf and stem
with severe leaf deformation
HS
50
Sweetpotato Scab
Field Experiment
Scale Decription Reaction
1 No symptoms HR
3 Occasional lesions on leaf ans stem but
no leaf deformation
R
5 Slight deformation of leaves and petioles MR
7 Moderate leaf deformation accompanied by
cupping
S
9 Severe leaf deformation and cupping HS
Sample size = 10 plants/replication/entry (2 rows with 12 plants/row)
Frequency of Rating
Induced Infection: 7 – 14 days after inoculation (initial rating)
1 month before harvest (final rating)
Natural Infection: 1 month after planting (initial planting)
1 month before harvest (final rating)
51
Leaf Spots, Rust and Blight Diseases
Crops: Yam and Gabi
Scale Percent of Leaf Area Affected Reaction
1 Less than 1% HR
3 1 – 5% R
5 6 – 25% MR
7 26 – 50% S
9 Greater than 50% HS
*Sample size: 10 plants/replication/entry
*Frequency of Rating – 1 month after planting
1 month before planting
52
Potato
Bacterial Wilt (Psendomonas solanacearum)
Scale Description Reaction
1 One leaflet (or leaf) wilting HR
3 25% of plant wilting R
5 50% of plant wilting MR
7 Whole plant wilting S
9 All plant dead HS
Leaf blight (Phytophthora infestans)
Scale Percent of Leaf Area Affected Reaction
1 Lesions none or very few HR
3 2% but not more than 25%
infection
R
5 25% but not more than 50% of the
foliage destroyed
MR
7 50% but not more than 75% of the
foliage destroyed
S
9 75-100% or foliage completely
destroyed
HS
53
STANDARD METHOD OF PREPARING ROOTCROPS
SAMPLE FOR DRY MATTER AND STARCH DETERMINATION
The method of sample preparation which enormously affects the final result in an
analytical procedure but its importance is often overlooked. Plant materials should be
sampled immediately to avoid breakdown of the chemical constituents and to minimize
the effects of temperature, light and air. Sampling should be carried out very carefully
because analysis is useless if the results ontained do not adequately represent the
composition of the whole material from which the sample was drawn.
Sample preparation includes sampling, cleaning to avoid contamination, size
reduction, stabilization and storage. The greatest error usually arises during sampling and
errors associated with sample analysis itself.
Size reduction is done by chopping and/or blending. Obviously, this process
should be carefully carried out so as to avoid the introduction of foreign materials into the
sample. Once broken down, the materials should be ove-dried to maintain the chemical
composition and to arrest biochemical reactions.
A. Sample Preparation for Chemical Analysis
Procedure:
1. Take three to five samples of small, medium and large tubers/roots/corms.
2. Wash to remove soil and adhering debris
3. Peel and remove any disease-infected part
4. Use whole tuber/root as sample if it is small. If the root/tuber is larger (for
sweetpotato, yam and taro), take two quarters then bulk them together. For
cassava roots, take three slices of about 50-100 g each (one from each end and
one slice from the middle) then bulk them together.
5. Cut the samples into 1 cm cubes and chop them using a blender.
54
6. Take a representative sample after mixing well the material. Dry samples in a
convection oven at 40-50ºC until constant weights are obtained or in a forced-
draft oven at 45ºC for 36 to 48 hours.
7. Grind dried samples finely using a Wiley mill and store in air-tight bottles.
This sample will be used in the analysis of starch, protein and other
constituents.
B. Sample Preparation for Moisture Analysis
Procedure:
1. Follow steps 1 – 5 of sample preparation for chemical analysis
2. Weigh about 15 – 20 g of the well mixed, freshly sliced sample and place in
aluminum foil boxes. Prepare two samples.
3. Dry the samples at 100ºC until constant dry weights are obtained (usually for
5 –6 hours), or in a forced-draft oven for 36 to 48 hours.
4. Take samples from the oven then cool the dired samples in a dessicator
5. Take the weight of the dried samples
6. Calculate % moisture using the formula:
%moisture = (fresh wt. – dry wt) / fresh wt. x 100
55
RAPID EVALUATION OF CYANIDE CONTENT OF CASSAVA ROOTS
Procedure:
1. Cut 1 x 6 cm strips of Whatman no. 1 filter paper.
2. Prepare alkaline picrate stock solution by dissolving 25 g anhydrous sodium
carbonate and 5 g moist picric acid in a liter of distilled water. This is
essentially a saturated solution and may be stored for several months..
3. Dil filter paper strips into picrate stock solution and drain free from excess
liquid just before use.
4. Place 1 g sample of cassava root in a test tube.
5. Add 5 drops of toluene.
6. Immediately suspend the filter paper strip saturated with alkaline picrate
above the sample and hold it in place with a cork or rubber stopper.
7. leave at room temperature for 24 hours.
8. Rate using 1 – 5 or 1 – 9 scale based on intensity of red color. (higher
intensity of red = higher HCN content of root sample.
56
TECHNIQUES IN SENSORY EVALUATION
Importance
The acceptability of a food product is ultimately judged by the consumers based
on its sensory properties. Sensory evaluation therefore is an important part of crop
evaluation and product development. Care must be observed to minimize errors
especially since sensory responses are greatly affected by many factors such as type of
individual acting as sensory evaluation methods to make them aware/updated of the
importance, procedure and technique used and to increase the reliability of sensory
evaluation results.
Aims of Sensory Evaluation
1. To evaluate the sensory characteristics of the different NCT entries
2. To determine the acceptability/preference of the different NCT entries
DO’s and DON’T’s in Sensory Evaluation
DO’s
1. Allow the panelists to rest before the test.
2. Wash hands with soap before the test.
3. Concentrate while doing the test.
4. Rinse your mouth between samples.
5. Ask help from person in-charge of the sensory evaluations.
6. Place each panelist in separate compartment or booth.
7. Make the size and shape of the sample uniform.
8. Control the number of samples per panelist.
9. Each panelist should evaluate one set of samples per session.
10. Employ at least 24 people per session/replication in an individual booth.
57
DON’T’s
1. Do not allow pregnant or lactating women to join sensory evaluation.
2. Do not do the following 30 minutes to 1 hour before the test.
take snacks
drink anything with lingering after taste
use strong smelling cosmetics
eat sucking candies and chewing gums
eat highly spiced foods
3. Do not make unnecessary noise during the test.
4. Do not converse with your neighbors during the test.
5. Do not let the panelist see the other sets of samples.
6. Do not let a panelist who has not slept to participate in the sensory evaluation
Procedure
A. Prepare a Master Sheet
1. Write all the necessary information about the test on the master sheet such as
name of the product, testing date, replication number, type of test, judges
random code, assignment of sample and order of serving (Appendix Form
Nos. 1 and 2).
2. Assign the random code number of each sample for each judge or set. Use 3-
digit random numbers which can be taken from the Table of Random
Numbers (Appendix Table 1). Skip double numbers such as 122, 333, 499 or
those with number 13 like 213, 313 or 413.
3. Carefully examine the code number of each sample for each judge so that no
two samples of the same code numbers appear for each judge.
4. Determine random order of presentation of samples for each judge employing
the Table of Random Numbers-Permutations of Nine (Appendix Table 2).
Make sure that this differs from one judge to the other so than each sample
has equal chances of being eaten first, mid or last. Write the order of serving
of the samples on the upper right hand corner of the 3-digit random code
number of the samples.
58
B. Prepare Score Sheet
1. Prepare a score sheet for each judge (Appendix Form No. 3). Fill up the
necessary information such as judge number, date of testing and code number
for each judge.
2. Copy the random code number assignment of the samples following sequence
of random order of presentation from the master sheet.
3. Accomplish all score sheets for each judge or set if the test calls for several.
C. Prepare Code Numbers and Containers
1. Mark the sample containers with the 3-digit random numbers copied from the
master sheet. Use a marking pen which does not impart odor to containers and
samples. The same ink color should be used in all samples for each judge and
among judges.
D. Prepare Samples
1. Cut samples into uniform sizes and shapes about 20 g each and place into
designated containers. If liquid, place aliquot samples about 15 – 20 ml into
the designated containers.
E. Set-up trays and serve
1. Arrange samples on the tray/plate according to random order of serving. Make
sure that this order tallies with the score and master sheets.
2. Place score sheet on each tray/plate.
3. Serve. Provide a glass of water for each tray/plate and advise the panelists to
thoroughly rinse their mouth with water before tasting the next sample.
F. Decode Score Sheets
With the master sheet as guide, convert back the code number into treatment or
sample number (Appendix Form No. 4).
G. Compute the date using ANOVA and DMRT.
59
IMPORTANCE OF UNIFORM FIELD PILOT TECHNIQUES
IN THE CONDUCT OF VARIETY TRIALS
In any crop variety trial, uniform methodology and strict adherence to the
principles of designing an experiment are necessary. Residual variation or experimental
error (as reflected by the coefficient of variation) must be minimized in each trial per
cropping season per location. The specific procedure for each crop is described in this
manual for easy implementation. This section aims to emphasize to project/study leaders
of the NRCCTP, (both old and new ones) the value of a carefully conducted research.
Experimental Error
In statistics, experimental error refers to the variation (differences) among
experimental units which have been treated alike. In field trials, experimental error
should only be attributed to soil heterogeneity. Common mistakes commited in the
conduct of an experiment may inflate experimental error, hence reduce the accuracy or
results. Thus, it is imperative to put extra care in conducting an experiment. The
principles of experimental design i.e., randomization, replication and local control
(“Blocking”) must be applied to minimize experimental error.
Local Control
Soil heterogeneity is a common source of variability in field experiments.
Blocking is one way to minimize variability due to soil heterogeneity. Here, the
experimental area is divided into groups or blocks with relatively homogeneous
experimental units within them (e.g. more or less uniform soil fertility). Precision of the
experiment is enhanced since each treatment (variety) is compared with all other
treatments (varieties) in the same block. The differnce among blocks is segregated from
the random variation among plots in the experimental error.
Plots within each block are assumed to be uniformed in all soil factors. This
means that correlation of yields between plots of the same block is higher than that
between plots of different blocks.
60
It is better to choose an experimental area with known soil fertility. As much as
possible, the area must be uniform in slope. In the fertility status of the area is unknown,
heterogeneity is assumed and so the trial must be carefully laid out using some qualitative
indices of soil heterogeity such as slope of the area, growth of plants (weeds) or path of
water flow.
For a variety trial, the chosen area must not have been previously used for any
fertilizer trial using various fertilizer rates. Residuals of fertilizer treatments often
markedly affect yield of a variety. Ideally, a chosen area must have been used for an
experiment with uniform cultural management such as for seed production of a single
variety.
Labelling and tagging of plots can also reduce risk of unintentional mistakes
during data gathering. Correct tags and labels using durable material are necessary.
Careless labeling may lead to wrong identification and can distort the results. Some
researchers have the erroneous notion that results can be adjusted through statistical
methods. Statistics is just a tool to detect and separate differences among treatments. Any
mistake committed in the conduct of an experiment can never be corrected by any
statisrtical technique. A mistake may result in reduced precision and inaccurate results
often lead to wrong conclusions.
Randomization
The manner of randomization depends on the chosen experimental design. All
variety trials for rootcrops must use the randomized complete block design (RCBD).
Thus, randomization of treatment (varieties) must be within each block. Randomization
should be independent for each block, i.e. random assignment of varieties in one block
must differ from those in the other blocks.
Randomization requires that each treatment assignment does not depend on the
characteristic of the materials. Every entry must have the same probability (chance) to be
assigned to any plot in a block. This ensures the independence of experimental error.
Experimental error only measures the random extraneous source of variation that cannot
be controlled by a given experimental design.
61
Replication
It has been agreed that all rootcrop variety trial must have four replicates
(repetition) of each basic experiment unit. Four replications became the choice to give
sufficient confidence level in detecting significant differences and to make allowance for
missing plots. Although increasing the number of replicates may reduce experimental
error, the management of a uniform trial may be constrained by the size. This may also
increase human error in planting, harvesting and data gathering.
Each replicate in an expriment laid out in RCBD is also the block. Blocks
preferably should be contiguously located for easy management. However, they may be
separated from each other (see Fig. 3) if the areas available can not accommodate the
whole experiment, i.e. they are small and not side by side.
Shape and Orientatrion of Blocks and Plots in a Block
There are procedures to determine the optimum plot size and shape for a variety
trial of a given crop. The procedures presently used for rootcrops trials are based on
experiments conducted at UPLB, PRCRTC and at CIAT in the case of cassava.
If the extent and direction of heterogeneity of the area to be used for a variety trial
is not known, orient or distribute plots such that a more or less square block (replication)
will result. This also means that each block have to be divided into sub-blocks. If the area
has fertility gradient and its direction is known, the blocks could be reactangular or not
sub-blocked. Blocking must be perpendicular to the direction of the heterogeneity
(gradient).
Establishment of Border Rows Around the Experimental Area
Border rows around the experimental plots are necessary not only to protect the
experiment from grazing animals but more importantly, to remove any advantage or
disadvantage of the variety planted at the edge or end of an area over those found at the
middle of the block.
62
Border Plants or Guard Rows in a Plot
To minimize the effect of interplot competition, guard or extra rows must be
provided in each plot of a variety trial. These are outer rows that will not be included
during harvesting. Such guard rows are not necessary in sweetpotato trials where
interplot competition is insignificant with the row spacing used.
Data Gathering
1. Follow the field layout in data gathering.
2. Keep a permanent record book and write the data on it. Record books in the field
must be firm and water resistant. Use pencil or indelible pen. If a mistake has been
committed cancel the mistake by a single stroke (\) and not erase it completely.
Sometimes, changes in data entries lead to unnecessary errors.
3. Measure characters and attributes necessary and relevant to the objectives based on
the defined variables set in this manual.
4. Gather covariates if necessary to ensure correct measurements. Analysis of
covariance can help to increase precision of data/results.
5. Make sure you know how to use the measurement gadgets. Ensure the precision of
your weighing scales and other measuring devices. A good knowledge of the material
used in important.
6. Always provide a copy of the field lay-out in your report, together with the data
required written on prescribed data sheets. Also, fill up the information required in
the NRCCTP Form No. 8 and send to PRCRTC, LSU, Baybay, Leyte 6521-A.
63
NRCCTP Form No. 8
National Seed Industry Council Evaluation
__________________________________________
(specify name of crop)
1. Name of Cooperator (s): _____________________________________________
2. Institute and Address: _______________________________________________
3. Location of the Trial:
Place ___________________________ Latitude ______________________
Evaluation ______________________ Longitude _____________________
4. Date of Planting: ___________________________________________________
5. Date of Harvesting: _________________________________________________
6. Soil Type (if possible): Kind of Soil ____________________________________
Result of Soil Analysis (if available) ____________________________________
7. Fertilizer Used N_______kg/ha: P________kg/ha: K_______kg/ha
8. Irrigation Method and Frequency: ______________________________________
9. Meteorological Data during the Cropping season (from planting to harvesting)
64
Appendix Form No. 1
MASTER SHEET*
Name of Product: _______________
Date: _________________________
Replication No.: ________________
Judge
No.
T R E A T M E N T S Total
*Typical master sheet used for setting up a sensory test.
65
Appendix Form No. 2*
Name of Product: Boiled Sweetpotato
Date: June 14, 1994
Replication No.: 1
T R E A T M E N T S
JUDGE
NO. 1 2 3 4 5 6
1 5934 103
2 868
6 950
2 168
3 924
5
2 1562 716
5 405
3 751
6 803
1 574
4
3 7353 259
6 783
5 345
1 832
4 769
2
4 3704 837
3 202
2 742
1 640
5 056
6
5 2675 659
4 273
6 567
2 728
1 284
3
6 5804 763
6 975
1 195
5 245
2 472
3
7 6263 631
4 745
1 107
6 153
2 138
5
8 7314 510
2 304
5 026
3 602
6 395
1
9 6592 124
6 328
3 808
1 651
4 065
5
10 5681 615
4 498
2 758
5 749
6 728
3
T1 - VSP 6 T4 - VSP 4
T2 - VSP2 T5 - RED WONDER
T3 - VSP 5 T6 - VSP 3
* A properly accomplished Master Sheet
66
Appendix Form No. 3
Boiled Sweetpotato
Name of Product
Name _____________________________ Date ___________________
Judge No. 1
Direction: Please evaluate the samples presented to you for their sweetness, texture
and general acceptability. Kindly mark x the description that best
describes the samples and rate its acceptability using the scale below.
Please rinse your mouth with tap water before tasting easch sample. Thank
you.
SWEETNESS 103 950 168 593 896 868
5 – very sweet
4 – moderately sweet
3 – sweet
2 – slightly sweet
1 – not sweet
Acceptability Score
DRYNESS/MOISTNESS
7 – very dry
6 – moderately dry
5 – slightly dry
4 – neither dry nor moist
3 – slightly moist
2 – moderately moist
1 – very moist/watery
Acceptability Score
General Acceptability
Score
Acceptability/Gen. Acceptability Score
9 – like very much 4 – dislike slightly
8 – like very much 3 – dislike moderately
7 – like moderately 2 – dislike very much
6 – like slightly 1 – dislike very much
5 – neither like mor dislike
67
Appendix Form No. 4
Boiled Sweetpotato
Name of Product
Name _____________________________ Date ___________________
Judge No. 1
Direction: Please evaluate the samples presented to you for their sweetness, texture
and general acceptability. Kindly mark x the description that best
describes the samples and rate its acceptability using the scale below.
Please rinse your mouth with tap water before tasting easch sample. Thank
you.
Sample Code
T2 T4 T3 T1 T6 T3
SWEETNESS 103 950 168 593 896 868
5 – very sweet
4 – moderately sweet x x
3 – sweet x
2 – slightly sweet x x
1 – not sweet x
Acceptability Score 8 7 8 7 6 7
DRYNESS/MOISTNESS
7 – very dry x
6 – moderately dry x x
5 – slightly dry x x
4 – neither dry nor moist x
3 – slightly moist
2 – moderately moist
1 – very moist/watery
Acceptability Score 6 8 8 7 7 7
General Acceptability
Score
7 8 8 7 6 7
Acceptability/Gen. Acceptability Score
9 – like very much 4 – dislike slightly
8 – like very much 3 – dislike moderately
7 – like moderately 2 – dislike very much
6 – like slightly 1 – dislike very much
5 – neither like mor dislike
68
Appendix Table 1. Table of random numbers
59391
99567
10363
86859
11258
58030
76364
97518
19558
24591
52098
77204
64432
51400
36863
82718
14615
25670
16706
55368
87024
27062
98342
99612
37121
82848
43918
61891
59798
94335
04190
01896
27101
32803
34936
95068
54463
16874
92494
15669
88628
47237
62677
63157
56689
35911
73800
57412
76593
35682
14530
31017
13215
91326
40844
33020
36239
31389
03505
35256
80428
71824
62233
72389
81872
39936
83671
80827
96363
35213
00116
15696
97720
11666
71628
74586
10703
15369
13841
73130
84989
65178
51259
71681
78783
23476
90637
69620
98000
75691
67104
63110
03388
35979
41632
39495
17622
13699
39719
09847
39100
53988
33423
81899
61547
40501
22518
75112
80327
45548
51089
55576
30485
02671
60251
99943
98215
62173
98191
42146
91834
83068
02132
84242
05597
41995
10798
14878
90813
48822
88931
86211
92879
49269
81366
73631
36584
22281
95451
34598
57430
73528
25991
78388
34534
82270
39559
65959
16638
12477
10421
34434
70769
09134
09965
00541
88596
64721
59980
96657
43648
54086
86413
63806
57994
75888
71693
33475
48472
59439
55049
43132
42740
39318
76330
83266
76970
37074
83712
20287
32883
80876
65198
06514
56862
43451
10237
44785
30101
69717
15579
39515
68624
78295
94420
38155
79152
98336
54656
64936
29793
74798
84481
85417
03866
40914
39357
98710
43189
27227
74216
64081
56171
26793
65988
61592
49863
75818
74951
72850
86538
08479
47750
95466
47737
27041
96001
67814
74307
54719
65172
18888
29575
13330
52056
85532
14810
10526
42664
01596
07571
70745
66192
85515
03845
27366
56760
72880
79999
28440
42271
10909
43338
38100
07819
43001
98147
93643
08062
21580
73399
34736
58904
58103
51459
21105
33863
59543
47961
47971
03280
95256
32943
83841
29882
73457
12731
11231
25878
13990
69
Appendix Table 2. Table of random numbers – permutations of nine
98119
42293
71926
17455
66834
29662
35341
84787
53578
47634
62781
19563
58857
25245
83196
75918
96479
31322
62128
39637
58873
11765
27285
93516
44949
76491
85352
74824
56945
41611
19452
25299
32777
93188
68563
87336
26316
93661
12194
57975
71782
64843
85428
38259
49537
69967
35153
24228
47815
88679
92581
71742
16396
53434
99242
26837
17798
52523
34114
73375
58486
81659
45961
24814
52498
71675
98581
37137
63226
86349
19752
45963
99952
87383
78536
33164
45775
16691
64849
22217
51428
56378
22131
73495
49769
97913
38586
61622
85847
14254
32381
69919
27778
86257
51435
93122
15644
48893
74566
21148
15466
77622
88255
93913
54874
62331
46597
39789
97297
36866
55159
72928
14312
29581
63645
48774
81433
72848
98794
51263
85426
18975
44112
39681
63557
17339
35951
62737
93289
57693
74862
19174
86518
48456
21345
41886
28622
53491
75743
87515
39259
66168
14937
92374
65455
97774
21397
49661
54246
33113
12838
88522
76989
39863
94.34
16212
77747
43585
82151
25974
68628
51436
86891
65615
98532
54358
19779
47924
31147
73483
22266
26531
71386
12463
44121
87859
59624
93998
38217
65776
12772
36396
83527
59213
64959
75834
41141
97468
28685
46622
32234
25553
14871
91485
57997
78366
63140
29719
22565
77979
66127
33813
98384
15656
84292
49438
51741
57564
61291
89656
48879
23448
36185
74722
15937
92313
62716
19143
47931
33229
75582
56864
28657
81498
84375
48346
19222
84577
37769
95118
21884
76693
52455
63931
22575
98313
46781
79698
67862
53946
84137
31229
15454
78356
54127
43718
38599
82865
61484
99632
17273
25941
85392
72575
51457
96724
48683
64968
27846
19211
33139
17996
9477
72341
46815
28624
51183
64569
35232
83758
58885
91117
72394
23931
46578
64763
85256
19449
37622
38247
93856
47919
75785
52168
19332
81571
26624
64593
84138
77347
62519
95794
11983
33622
49461
58256
26875
71165
82872
34731
15923
99488
27299
58617
66356
43444
44772
29147
82898
57113
61586
73355
95634
18461
36979