7

REVIEW OF LITERATURE

Medicinal plant cultivation is becoming a tool for diversification of Indian

agriculture as many farmers have been looking for some better alternative to diversify

from traditional agriculture due to gradual reduction in profit, decline in productivity

and increased incidence of diseases and pests. Cultivation of medicinal plants,

especially high value medicinal plants is creating new dimension in the field of

agriculture. The need for developing countries to acquire technologies and techniques

for programmed cultivation of medicinal plants is a current issue. Various aspects of

medicinal plant cultivation include old philosophies, modern impact of traditional

medicines, and methods of assessing the spontaneous flora for industrial utilization,

climatic variations, biological assessment, formulation, process technologies,

phytochemical research and information sources. There is a need for a scientific

approach for propagation of medicinal plants and to collect relevant information

regarding agro-technology, genuine planting material, economics of field cultivation,

high yielding varieties etc. Indian farmers are facing various problems in cultivation of

medicinal plants because lack of reliable and standardized technology package, lack of

planting materials, market potential and system, cultivated vs. wild plants, organic

farming techniques, and high fees for packages developed by various organizations etc.

Literature pertaining to agro-techniques for cultivation and other seed quality

parameters in both the experimental systems chosen for study is meagre. Some

information was available in medicinal plants or in other related crop systems is

presented, as under:

8

I. Agro-techniques for Cultivation

Cultivation of medicinal plants is gaining popularity among Indian farmers

because of higher return than the traditional crops and also as a tool for the

diversification of Indian agriculture. Due to the increasing depletion of natural resource

base, the cultivation of medicinal plant is an important strategy for meeting the ever-

increasing demand of medicinal plants. National Medicinal Plant Board as well as State

Medicinal Plant Boards are providing incentive for cultivation of medicinal plants.

Tiwari (1999) reported over 800 species of medicinal plants used by various

industries, whereas, less than 20 per cent species of medicinal plants are under

commercial cultivation.

Efforts were focused on the development of agro-technology, including

propagation methods for medicinal and aromatic plants. Central Institute of Medicinal

and Aromatic Plants (CIMAP) in Lucknow is a nodal institute focusing on agro-

technology as well as basic studies of plants of medicinal value.

In India, an area of 208,000 ha is estimated under cultivation of medicinal and

aromatic plants (Times News Network, 15 July 2003). Isabgol (Plantago ovata)

occupies the largest area of 50,000 ha in parts of Gujarat and Rajasthan followed by

senna (Cassia angustifolia) which occupies an area of about 25,000 ha in Tamil Nadu,

Maharashtra, Gujarat, Rajasthan and Delhi. Ashwagandha is cultivated in an area of

about 4,000 ha in India, mainly in the drier parts of Manasa, Neemuch and Jawad

tehsils of the Mandsaur district of Madhya Pradesh, and other parts of Punjab,

Rajasthan and South India. During 2001 cultivation of safed musli (Chlorophyton

borivilianum) gave a net profit of Rs. 7,00,000/ha. Karki et al. (2003) showed that

cultivation of Aconitum heterophyllum and Aconitum atrox gave three and eight times

more return respectively, than the traditional crop potato.

9

World Health Organization (WHO) has estimated that at least 80 per cent of the

world population relies on traditional systems of medicine for their primary health

needs. These systems are largely plant based. According to WHO over 21,000 plant

species are useful in the preparation of medicines. Due to the side effects and

complications of chemical and synthetic medicines, cosmetics and health supplements,

usage of herbal products has gained importance both in the eastern and western worlds.

Herbal plants have global market worth about US$ 62 billion per annum where Indian

share is only 0.2 per cent. This market will grow up to 15 per cent in near future.

Demand for a wide variety of wild species of medicinal plants is increasing with

growth in human needs, and commercial trade. With the increased realization, some wild

species are being over-exploited, a number of agencies are recommending that wild

species be brought into cultivation systems (Lambert et al., 1997; WHO, IUCN and

WWF, 1993). Cultivation has conservation impacts, however, and these need to be better

understood. Medicinal plant production through cultivation, reduce the extent to which

wild populations are harvested, but may also lead to environmental degradation and loss

of genetic diversity as well as loss of incentives to conserve wild populations (Anon.,

2002a).

Many medicinal plants, especially the aromatic herbs, are grown in home gardens,

some are cultivated as field crops, either in sole cropping or in inter-cropping systems

and rarely as plantation crops (Padua et al., 1999).

In a survey carried out for the rainforest alliance, companies involved in trade and

production of herbal remedies and other botanical products were asked what percentage

of their material is from cultivated sources and what percentage is from the wild. On an

average, 60–90 per cent of material was cultivated, with the remainder harvested wild.

However, when asked about species numbers rather than volume of material, the figures

are generally inverted (Laird and Pierce, 2002). Lange and Schippmann (1997) reported

10

that of the 1543 species traded in Germany, only 50–100 species (3–6 %) were under

cultivation.

Of more than 400 plant species used for production of medicine by the Indian

herbal industry, less than 20 species are currently under cultivation in different parts of

the country (Uniyal et al., 2000). In China, about 5,000 medicinal plants have been

identified and about 1,000 are commonly used, but only 100–250 species are cultivated

(Xiao Pei-Gen, 1991; He Shan-An and Ning Sheng, 1997). In Hungary, a country with a

long tradition of Medicinal and Aromatic Plants (MAP) cultivation, only 40 species are

cultivated for commercial production (Bernáth, 1999; Palevitch, 1991). In Europe as a

whole, only 130–140 medicinal plant species are cultivated (Verlet and Leclercq, 1999).

Based on these figures, we assume that the number of medicinal plant species

currently in formal cultivation for commercial production does not exceed a few hundred

world-wide. A global survey on the extent of medicinal plant cultivation in terms of

species, volumes and values would be highly desirable. On the other hand, however, we

recognize that many more medicinal plant species are cultivated on a small-scale in home

gardens, either as home remedies or by herbalists or that cultivation by local people can

take place as enrichment planting.

Given the demand for a continuous and uniform supply of medicinal plants and

the accelerating depletion of forest resources, increasing the number of medicinal plant

species in cultivation would appear to be an important strategy for meeting a growing

demand (Uniyal et al., 2000). Canter et al. (2005) emphasized that consumption of herbal

medicines is widespread and increasing. Harvesting from the wild, the main source of

raw material, is causing loss of genetic diversity and habitat destruction. In general, in all

countries, the trend is towards a greater proportion of cultivated material. The majority of

companies, the mass-market, over-the-counter pharmaceutical companies, as well as the

larger herb companies, prefer cultivated material, particularly since cultivated material

can be certified as biodynamic or organic (Laird and Pierce, 2002).

11

From the perspective of the market, domestication and cultivation provide a

number of advantages over wild harvest for production of plant-based medicines:

i. Wild collection often offers material adulterated with other unwanted,

sometimes harmful plant species, cultivation provides reliable botanical

identification.

ii. Wild harvest volumes are dependent on many factors that cannot be controlled

and the irregularity of supply is a common feature. Cultivation guarantees a

steady source of raw material.

iii. Wholesalers and pharmaceutical companies can agree on volumes and prices

over time with the grower.

iv. The selection and development of genotypes with commercially desirable

traits from the wild or managed populations may offer opportunities for the

economic development of the medicinal plant species as a crop.

v. Cultivation allows controlled post-harvest handling and therefore

a. Quality controls can be assured, and

b. Product standards can be adjusted to regulations and consumer

preferences.

vi. Cultivated material can be easily certified as organic or biodynamic although

certifiers are also presently developing wildcrafting standards (Leaman, 2002;

Palevitch, 1991; Pierce et al., 2002).

However, domestication of the resource through farming is not always technically

possible. Many species are difficult to cultivate because of certain biological features or

ecological requirements (slow growth rate, special soil requirements, low germination

rates, susceptibility to pests, etc.).

12

There is a world-wide trend of increasing demand for many popular, effective

species in Europe, North America and Asia, growing between 8–15 per cent per year

(Grünwald and Büttel, 1996). Rapid urbanization and the importance of herbal medicines

in African health care systems stimulated a growing national and regional trade in Africa

(Cunningham, 1993). Demand for medicinal plants also reflects distinct cultural

preferences. In USA, for example, only three per cent of people surveyed had used herbal

medicine in the past year (Eisenberg et al., 1993), whereas in Germany, with a strong

tradition of medicinal plant use, 31 per cent of the over-the-counter products in

pharmacies in 2001 were phyto-pharmaceutical preparations.

Socially disadvantaged groups who actually depend on gathering medicinal plants

for their survival and cash income may not have access to farmland at all and are

therefore not able to compete with large-scale production of medicinal plants by well-

established farmers (Anon., 2002b). Other limitations to the domestication approach

include boom-bust and fickle markets that let farmers down when consumers turn their

attention elsewhere (Laird and Pierce, 2002).

Date of sowing has a profound influence on the crop performance because it

determines the kind of environmental conditions to which the various phenological stages

of the crop are exposed. For quicker emergence, better growth and higher yield, crop

growth should synchronize with optimum weather conditions like temperature, rainfall,

light and relative humidity. Hormonous balance of vegetative and reproductive phases for

successful crop production has been stressed by Brown and Ware (1958). Though the

ashwagandha is drought hardy, the winter temperatures favour root development and

improves the withanolide content in the roots (Kahar et al., 1991). In an experiment,

Agarwal et al. (2004) at Jobner (Rajasthan) found that ashwagandha sown on 20th July

recorded significantly higher root length (147.5 cm) and root diameter (8.5 mm)

compared to other dates of sowing. The results of an experiment conducted at MPKV,

Rahuri on sandy loam soils during kharif season on the effect of planting dates on growth

and yield of ashwagandha indicated no significant influence on 100-seed weight, dry

13

weight of seedlings, number of primary and secondary branches per plant. However, the

number of capsules per plant (154.0) and vigour index (385.81) were significantly higher

at 15th July planting of ashwagandha (Desai et al., 2004). A field experiment was

conducted at Lucknow to study the effect of planting date on plant survival, tuber

development and tuber yield of a two years crop of medicinal yam (Dioscorea

floribunda) by Singh et al. (1990). They reported that planting during January, February

and March, using seed tubers dug out on the same day, produced 35-40 per cent of plant

survival at harvest, tuber growth of 350-410 mg per plant per day (DW basis) and dry

tuber yield of 60-65 q per ha, compared to 25 per cent surviving plants, tuber growth rate

of 365-425 mg per plant per day and a tuber yield of 35-42 q per ha when planted during

June or July. May planting produced the lowest percentage of plant survival (8.9%) and

the lowest tuber yield (9.3 q ha-1

). The influence of time of sowing, variety and their

interaction on the yield of ashwagandha was studied on medium black soils at Mandsuar

(UP) by Kahar et al. (1991). They reported that the crop sown in August gave

significantly higher root yield (801 kg ha-1

). The crop sowed earlier or later showed

reduction in root yield. The variety WS-22 produced more root yield than WS-20. In

another study, Farooqui and Sreenivas (2001) at Bengaluru found that the optimum dates

of sowing and harvesting for higher root yield (3 to 5 q ha-1

) of ashwagandha were July

and January respectively. Agarwal et al. (2004) in a study conducted on slightly alkaline

soil at Jobner, reported that ashwagandha sown on 20th July with 20 cm x 7.5 cm spacing

(6.66 lakh plants ha-1

) produced the highest root yield (8.2 q ha-1

) and seed yield (2.88 q

ha-1

) compared to other treatments. In a field experiment conducted on sandy loam soils

of MPKVV, Rahuri, Desai et al. (2004) reported that planting on 15th July recorded

significantly higher seed yield (164.79 kg ha-1

) and vigour index (385.81) in

ashwagandha compared to others. Agarwal et al. (2003) conducted a field experiment on

sowing time and spacing at Jobner (Rajasthan) on slightly alkaline soil and reported that

sowing ashwagandha on 20th July with 6.66 lakh plants per ha at 20 cm x 7.5 cm spacing

recorded the highest gross returns (Rs. 72,228 ha-1

), net profit (Rs. 56,098 ha-1

) and B:C

ratio (3.46) compared to other treatments. The stage of harvesting in any crop is most

14

important and plays a vital role in harvesting maximum yield and also good quality

products. If not harvested timely, the yield losses are to the great extent. The crop whose

economic parts (roots) are below the ground, it is difficult to decide the right stage of

harvesting though yellowing and leaf senescence may indicate to some extent, but these

changes could also be due to biotic and abiotic factors. In ashwagandha, the maturity of

the crop is judged by drying out of leaves and yellow-red berries. The crop is ready for

harvest at 150-180 days after sowing depending on soil moisture status. It requires dry

climate for better root growth but winters are known to improve the root quality

(withanolide content) and root yield (Kahar et al., 1991). In a study conducted on sandy

loam soils at Hyderabad (Andhra Pradesh) to study the effect of genotype and time of

harvesting on yield and quality of periwinkle under irrigation recorded the highest

number of leaves per plant at 10 months after planting (Rao et al., 1993). An experiment

was conducted on loamy sandy soils during late kharif at GAU, Anand to study the effect

of N levels and stages of harvesting on growth and yield of ashwagandha. The results

indicated that shoot length, root: shoot ratio, root diameter and dry matter production

were not affected by stages of harvesting (Patel, 2001). Jayalakshmi (2003) at

Coimbatore reported higher growth (plant height, plant spread number of laterals, leaf

area per plant) and yield attributes (number of tuberous roots, length). The effect of

planting material and time of harvesting on tuber yield in medicinal yam under irrigation

was studied by Hegde et al. (1981) at Bengaluru. Harvesting of tubers earlier than 15th

February reduced the tuber yields and harvesting much later than 15th February had no

additional advantage on yield. In another study at Hyderabad, Rao et al. (1993) observed

that there was no significant effect of time of harvesting on root yield of periwinkle. A

study was conducted to evaluate the effect of N levels and stage of harvesting on growth

and yield of ashwagandha at GAU, Anand on loamy-sandy soils by Patel (2001). He

found that the root and seed yields of ashwagandha were not significantly affected by

stage of harvesting. The results of an experiment to study the effect of seed rate and crop

duration on root yield and quality of ashwagandha at GAU, Anand, indicated a

significant increase in the yield of both thin and thick roots (from 92.0 to 171.0 kg ha-1

15

and 25.9 to 43.6 kg ha-1

respectively) with the increase in days of harvesting from 90 to

210 DAS (Patel et al., 2003). Patel et al. (2004) studied the effect of time of sowing, time

of harvesting and N application on dry root yield of ashwagandha at GAU, Anand. He

observed no significant effect of time of harvesting on root yield of ashwagandha. A

study conducted at Gujarat Agricultural University, Anand on the effect of stage of

harvesting and N levels on nutrient uptake by ashwagandha indicated that N content of

plant was significantly higher at 150 DAS (1.91%) compared to 210 DAS. Whereas the

uptake of N was significantly higher at 210 DAS (65.3 kg ha-1

) and P and K uptake were

unaffected by stage of harvesting (Patel, 2001). Kiruthikadevi (2002) reported decrease in

N and P content of leaf with increase in age of ashwagandha. Whereas, the K content of

leaf found to be increased with increase in age at 150 DAP. The uptake of N, P and K

increased with increase in age of the crop. Jayalakshmi (2003) at Coimbatore observed

the higher N and P content at 150 DAP and K at 180 DAP in Coleus whereas the uptake

of N, P and K was found to be highest at 180 DAP. Hegde et al. (1981) studied the effect

of planting materials and time of harvesting on diosgenin content in Dioscorea floribunda

under irrigated conditions at Bengaluru (Karnataka). They found that harvesting of tubers

earlier than 15th February, reduced the diosgenin yields whereas harvesting later than

15th February had no effect on diosgenin content (2.81 – 3.75%). In another experiment,

Celyan and Kaya (1983) found that the alkaloid content in ashwagandha roots was

highest at the beginning of flowering (0.132%) followed by post flowering (0.123%)

compared to full bloom and fruiting stages. Rao et al. (1993) reported the highest root

alkaloid yield (141.5 mg plant-1

) of periwinkle at 10 months after sowing. A field

experiment was conducted to study the effect of different seed rates with harvesting

periods on yield and quality of ashwagandha at Anand (Gujarat). The results revealed that

the maximum amount of alkaloids in roots was recorded at 4 kg seeds per ha when

harvested at the end of May (Anon., 2000). Karthik Kumar (2000) observed higher

alkaloid content in the roots of ashwagandha at fruiting stage followed by flowering

stage. Patel (2001) conducted an experiment to study the effect of N levels and stage of

harvesting on ashwagandha at GAU, Anand. The results revealed no significant effect on

16

total withanolides content and starch content in roots of ashwagandha due to stage of

harvesting. Patel et al. (2003) studied the effect of rate and crop duration on root and

quality of ashwagandha at GAU, Anand. They found that the alkaloid content was more

in late harvested crop (210 DAS) compared to early harvested crop (90 and 150 DAS).

There was a significant negative correlation between alkaloid and starch content

(-0.4874). Further alkaloid content was more in roots of different grades at a seed rate of

4 kg per ha. Variation in alkaloid content with age of the crop was also reported by

Baraiya et al. (2005) in ashwagandha. A field experiment conducted on sandy loam soils

of Anand during late kharif revealed that physical characters and dry root yield of

ashwagandha in general were not significantly affected due to different seed rates (plant

densities) and harvesting time, except total dry root yield which was the highest (227 kg

ha-1

) when crop was harvested by May end (Anon., 2000). The results of the experiment

on method of sowing, harvesting time and N levels on yield and economics of

ashwagandha indicated that harvesting the crop at 210 DAS recorded the highest gross

returns (Rs. 65,940 ha-1

), net returns (Rs. 56,237 ha-1

) and B:C ratio (6.80) compared to

harvesting at 150 DAS (Patel, 2001). A plant would perform better only when it is

provided with optimum environmental conditions. The establishment of adequate plant

population per unit area is most important to realize the full yield potential of a genotype.

Variation in plant population has been found to affect growth and dry matter

accumulation due to differential availability of light, moisture and nutrients. Higher plant

densities restrict the growth of branches per plant and number of reproductive parts per

plant but may be compensated by increased population densities. In ashwagandha, roots

are the economic part of the plant. The agronomic manipulations and practices aimed at

improving the yield of roots through optimizing source-sink ratio are of more practical

significance. The line sowing provides space for easy interculturing, weeding, fertilizer

application and other inputs apart from uniform plant stand ultimately resulting in better

growth and development of crop compared to broadcasting method of sowing (Nigam

and Kandalkar, 1995). The plant density to be used may depend on nature and fertility of

soil. On the marginal land, the population is kept high [Misra et al. (1997)].

17

Veeraragavathatham et al. (1988) conducted a spacing trial at Coimbatore in Coleus and

reported that shoot weight per plant and tuber yield per plant were higher at wider

spacing (60 cm x 30 cm) compared to closer spacing (60 cm x 20 cm). Shankargouda and

Hulamani (1999) studied the effect of plant densities on growth and yield of Coleus at

Arabhavi (Karnataka). They found that, plant height, plant spread in North- South and

East-West directions, branches per plant, leaves per plant, lamina length and breadth of

Coleus were affected significantly by different plant densities. Performance of diploid

and induced autotetraploid Solanum viarum at varying plant densities was studied by

Srinivasappa et al. (1999) at Bengaluru (Karnataka). They reported that number of berries

per plant had inverse relation with plant densities but dry weight per plant was

unaffected. Diploid and autotetraploid responded differently to varying plant densities for

plant height, leaf length and breadth, petiole length, fruits per node and internodal length.

Jayalakshmi (2003) in a field experiment on Coleus at Coimbatore under red sandy

loamy soil, observed that all the growth parameters (plant spread, branches, leaf area,

stem girth) and yield parameters (number of tuberous roots per plant, length and

diameter) were found higher at wider spacing (60 cm x 60 cm) and lower at closer

spacing (45 cm x 30 cm). The optimum spacing requirement for ashwagandha was

studied by Agarwal et al. (2004) at Jobner on loamy sand soil. They reported the longest

roots at closer spacing (20 cm x 5 cm) compared to wider spacing (25 cm x 7.5 cm). Rao

et al. (1981) carried out an investigation on the spacing requirement of medicinal yam

(Dioscorea floribunda) at Bengaluru (Karnataka) and reported that a spacing of 45 cm x

30 cm for one year crop and 60 cm x 45 cm for two years crop gave the highest tuber

yield under irrigation. In an experiment conducted on clayey alkaline soils of JNKVV,

Mandsaur, Nigam et al. (1984) observed significant increase in root yield of

ashwagandha at higher plant density of 6.6 lakh per ha (30 cm x 10 cm) compared to 4.4

lakh per ha (45 cm x 5 cm) and 2.2 lakh per ha (45 cm x 10 cm). The optimum spacing

requirement for periwinkle was studied by Hegde (1985) at Bengaluru (Karnataka). A

spacing of 45 cm x 15 cm recorded the highest root, leaf and stem yields. Wider spacing

gave significantly lower yields. Whereas, in another experiment at Bhubaneshwar, the

18

highest tuber yield (501.61 q ha-1

) was obtained at 40 cm x 45 cm spacing though the

tuber weight per plant was more at wider spacings (Saxena and Dutta, 1985). At

Mandsaur on medium black soils, Nigam and Kandalkar (1985) found that the population

of 8.0 lakh per ha (25 cm x 5 cm) was optimum for higher root yield of ashwagandha

compared to wider spacings. In another study, the response of ashwagandha to plant

density was found up to 15 lakh plants per ha (Nigam, 1985). Reddy et al. (1991)

conducted an experiment on planting density and spacing arrangement for higher berry

yield in Solanum viarum at Bengaluru (Karnataka). A linear relationship was found

between planting density (up to 49,000 plants ha-1

) and berry yield in square spacing. The

plant population within a range of 6,900 to 28,000 plants per ha with rectangular spacing

(East to West) proved superior to square spacing for getting higher berry yields. Planting

in the direction of east to west helped in better light interception. The spacing

requirement for Solanum nigrum was studied by Reddy and Krishnan (1992) at

Bengaluru (Karnataka). They found that both diploids and tetraploids gave increased

berries yield (6216 kg ha-1

) at high plant density of 49,000 plants per ha compared to

lower plant densities of 18,000 and 28,000 per ha. The results of an experiment

conducted at Arabhavi (Karnataka) by Shankargouda and Hulamani (1999) on the effect

of different plant densities in Coleus indicated that the highest marketable tuber yield

(13.86 t ha-1

) was recorded at 1,11,111 plants per ha and the lowest (7.70 t ha-1

) at 27,778

plants per ha. Performance of diploid and induced autotetraploid Solanum viarum at

varying plant densities was studied by Srinivasappa et al. (1999) at Bengaluru

(Karnataka). They observed the highest berry yield (9.95 t ha-1

) at higher density

(1,11,000 plants ha-1

). In an experiment on sandy loam and light red soils at University of

Agricultural Sciences, Bengaluru, Farooqui and Sreenivas (2001) reported that the

optimum plant population was 20,000 to 25,000 per ha for harvesting higher root yield of

ashwagandha. At Coimbatore on red sandy loam soils, Jayalakshmi (2003) reported the

higher tuber yield of Coleus at closer spacing (45 cm x 30 cm) and lower yield at wider

spacing (60 cm x 60 cm). A field experiment conducted at Uttar Pradesh by Singh et al.

(2003) to evaluate the production potential of traditional monocropping systems vis-à-vis

19

monocropping of ashwagandha at low (100 x 103 plants ha-1

) and high (200 x 103 plants

ha-1

) plant density levels indicated 53.8 per cent and 66.7 to 73.3 per cent more roots at

high plant density levels than grown at low plant density under monocropping and

overlapping systems respectively. They also reported that growing ashwagandha is more

economical at both population densities in monocropping systems under moisture

stressed rainfed conditions. Overlapping cropping of ashwagandha is suggested as a way

to improve the productivity and economic returns from resource constrained rainfed

agriculture in sub-tropical North India. In another spacing trial, Chandrashekhar et al.

(2007) also found the higher tuber yield of Coleus at closer spacing compared to wider

spacing. In ashwagandha var. WS-20, the dry root yield (426 kg ha-1

) and seed yield (260

kg ha-1

) were significantly higher at plant density of 8 lakh per ha whereas in

ashwagandha var. WS-22, the highest root yield (492 kg ha-1

) and seed yield(312 kg ha-1

)

were recorded at 6 lakh per ha (Mohd. Abbas et al., 1994). In a field experiment on clay

alkaline soils at JNKVV, Mandsaur, Nigam et al. (1984) reported that application of

higher fertilizer dose of 30:30 kg N and P2O5 per ha recorded significantly higher root

yield of ashwagandha (632 kg ha-1

) compared to 15:15 kg N and P2O5 per ha (570 kg

ha-1

). Jayalakshmi (2003) reported higher N, P and K content in tuberous roots of Coleus

in wider spacing (60 cm x 60 cm) than closer spacing (45 cm x 30 cm) whereas, closer

spacing recorded the higher uptake of N, P and K (kg ha-1

) at 180 days after planting. The

effect of spacing on solasodine in Solanum viarum was studied by Patil and Laloraya

(1981) at Indore (Madhya Pradesh). They observed the highest solasodine yield (106 kg

ha-1

) at 45 cm x 60 cm spacing and lowest (72.4 kg ha-1

) at 90 cm x 120 cm spacing. Rao

et al. (1981) studied the spacing requirement of medicinal yam (Dioscorea floribunda)

under irrigation at Bengaluru (Karnataka). They reported that a spacing of 45 cm x 30 cm

for one year crop and 60 cm x 45 cm for two year crop gave the highest diosgenin. In a

spacing trial at Jorhat, the maximum diosgenin yield (356.34 kg ha-1

) from Dioscorea

floribunda was obtained by planting at 30 cm x 30 cm spacing (1,11,000 plants ha- 1

) as

reported by Singh et al. (1981). In another trial at Bhubaneshwar, Saxena and Dutta

(1985) observed the highest diosgenin yield (528.70 kg ha-1

) at 40 cm x 45 cm spacing

20

whereas, diosgenin content remained unaffected by plant spacing. In a field experiment

on planting density, at Bengaluru (Karnataka), Reddy et al.(1991) reported that the plant

densities within the range of 6,900 to 28,000 plants per ha with rectangular spacing (east

to west) proved superior to square planting for obtaining higher solasodine yields. Reddy

and Krishnan (1992) in an experiment on effect of plant density on solasodine yields of

Solanum viarum at Bengaluru, reported the higher solasodine yield (155.7 kg ha-1

) at

higher plant density (49,000 plants ha-1

) compared to lower plant density of 18,000 plants

per ha (84.3 kg ha-1

). In a field trial conducted on the effect of plant densities at Arabhavi

(Karnataka), Shankargouda and Hulamani (1999) reported the highest essential oil yield

(12.10 lit ha-1

) at higher plant population (1,11,111 ha-1

) and lowest oil yield (8.67 l ha-1

)

at 27,778 plant per ha in Coleus forskohlii. The results of the experiment on effect of seed

rate and crop duration on root yield and quality of ashwagandha conducted at GAU,

Gujarat, by Patel et al. (2003) indicated that the seed rate of 4 kg per ha recorded

significantly higher total alkaloid content of 0.944 and 0.907% in thin and thick roots

respectively compared to seed rates of 6, 8 and 10 kg per ha. In an experiment at Jobner

(Madhya Pradesh), the highest net profit (Rs. 56,098 ha-1

) and benefit: cost ratio (3.46)

were obtained when ashwagandha was sown on 20th July at 20 cm x 7.5 cm spacing

compared to other treatment combinations (Agarwal et al., 2003). Jayalakshmi (2003) at

Coimbatore realized the highest net returns (Rs. 82,192 ha-1

) and benefit: cost ratio (4.27)

in closer spacing (45 cm x 30 cm) with 50 kg N per ha at 180 days after planting of

Coleus. Singh et al. (2003) reported that growing ashwagandha proved to be more

economical at high (200 x 103 plants ha-1

) and low (100 x 103 plants ha-1

) plant densities

under monocropping and it is an ideal crop for moisture stressed rainfed conditions in

subtropical North India. Among the essential nutrients, nitrogen is one of the most

important nutrient which influences the growth and yield of non-legumes considerably. It

has a great role in plant right from cell division to formation and development of

vegetative and reproductive organs. Phosphorus plays a vital role in growth and

development of plant roots as well as the maturity of crops. An adequate supply of

phosphorus in the early stages helps in initiating its reproductive parts. Ashwagandha is a

21

very low input requirement crop. Cultivators normally do not use any fertilizer to this

crop. This crop is raised on sub-marginal lands, where cultivation of any other kharif or

rabi crops is considered uneconomical. Research data generated at AICRP on MAP (All

India Coordinated Research Project on Medicinal and Aromatic Plants) at Mandsaur

indicated that neither nitrogen nor phosphorus had beneficial effects on root yield (Nigam

and Kandalkar, 1995) whereas, Garcia-Mateos et al. (1996) reported positive correlation

between nitrogen level and alkaloids. In another study, Maheshwari et al. (2000) reported

that the alkaloids and withanolides in roots of ashwagandha were affected due to

nutritional status of soil.

II. Standards for Seed Quality Parameters

Seed quality consists of physical purity, germination, moisture content and seed

health. Physical purity from seed testing point of view refers to physical or mechanical

purity of a given seed lot. Germination testing is important for the planting value of

seed. In addition, the laboratory germination results are also required for comparing the

performance potential or superiority of different seed lot. Moisture content of the seed is

one of the most important factor influencing the seed vigour and viability. Seed health is

another important parameter, an integral part of Seed Bill 2010 (proposed Seed Bill

2004).

The general seed certification standards are applicable to all crops which are

eligible for certification, and with field and seed standards for the individual crops, shall

constitute the minimum seed certification standards (Tunwar and Singh, 1988). With the

increased awareness and global trade medicinal plants have become popular among the

farming community of India. In the absence of seed standards, correct assessment of seed

quality is difficult. Parihar and Kumar (2006) emphasized these seed quality parameters

(Seed Standards) need to be formulated in respect of medicinal plants. The literature

pertaining to seed standards is very meagre, with reference to medicinal and aromatic

plants. Although these seed standards are already in practice in more than 102 field crops

22

(Parihar, 2006). Medicinal plants also constitute an important natural resource base as

their demand is increasing. In order to fully convert the potential of our medicinal plants

into economic wealth, seed standards must be formulated (Parihar et al., 2006). The

labeling standards had been notified for 22 species of medicinal and aromatic plants by

National Medicinal Plant Board.

Dadlani and Parihar (2007) reported the certification procedure and

standardization of several quality seed materials in medicinal plants. Parihar et al.

(2005b) generated information for formulating seed standards for isabgol (Plantago

ovata). Seed standards and seed testing procedures had been developed for Sesbania and

Crotalaria (Vari et al., 2004). Germination protocol has been standardized in kalmegh

(Andrographis paniculata) using hot water treatment (Preeti et al., 2008). Tetrazolium

testing had been standardized in some of the medicinal plants (Dhasmana et al., 2008).

Seed storage behaviour plays an important role for cultivation and conservation of

medicinal plant wealth of India (Parihar et al., 2005a).

Seed being hygroscopic, simultaneously exhibits fluctuation in moisture

absorption, with increase in relative humidity (RH) causing increase in seed moisture

content hence drastically reduces its survival during storage (Justice and Bass, 1978).

Ellis and Roberts (1980) studied the influence of moisture and temperature on seed

viability period in barley (Hordeum distichum L.).

Agarwal (1993) emphasized the need to test the seed lots to measure the status of

its health in order to avoid problems in seed production and quality control. Infected seed

lots are also responsible for the spread of the disease in the disease-free areas. Standard

blotter method is used for routine testing of seeds for detection of wide range of fungi.

Mathur and Neergaard (1972) carried out seed health testing of rice for studying the

effect of light and temperature on seed-borne fungi in the blotter test. Chuaiprasit et al.

(1974) studied the effect of light in the blotter method and found that incubation for 7

days at 22°C under 12 hr alternating cycles of light and darkness is suitable.

23

Benoit and Mathur (1970) identified different species of Curvularia based on

their growth characters such as shape, size, colour of conidia and its arrangement on the

conidiophores. Using this method Chidambaram et al. (1973) studied diagnostic

characteristics of different species of Bipolaris and Drechslera. EI-Nagerab (2002)

studied seed-borne fungi in fenugreek seeds. He reported 59 species and 11 varieties

belonging to 21 genera of fungi on incubation of fenugreek (Trigonella foenum- graecum

L.) seeds on moist filter papers and potato dextrose agar at 28±2°C were determined as

seed-borne in fenugreek crops.

III. Physiological Maturity

Austin (1972) and Delouche (1980) stated that seed maturation refers to

morphological, physiological and functional changes that occur from the time of

fertilization until the seeds are ready for harvest. Full viability and germination of seed

cannot be attained until the seed reaches full maturity. Seed maturation is an important

phase which controls final seed quality.

Rao and Rao (1990) reported that chilli pods should be harvested 35-41 days

after anthesis for obtaining better seed quality. Delay in the harvest also leads to decline

in the seed quality. Doijode (1988) stated that in chilli, the seed quality is largely affected

by the stage of fruit maturity at harvest. Therefore, it is desirable to know at what stage of

fruit, seeds attain maximum longevity. Ganai and Nawchoo (2002) in Arnebia benthamii

and Shivkumar et al. (2006) in Strychnous nux-vomica reported that GA3 enhances the

germination of seeds exhibiting physiological, morphological or morpho-physiological

dormancy. Further their study suggested that the efficacy of GA3 treatment in breaking

dormancy depends on the concentration and length of incubation.

Bewley and Black (1985) reported that maturation drying is an integral part of

development in most of seeds and in fact development is considered to be complete when

the seed is dried. Abdul-Baki and Anderson (1973) considered maximization of fresh

weight and dry weight of seed as an index of seed maturation in soybean. Dharmalingam

24

and Basu (1988) reported that highest germination and vigour of seed is harvested at

physiological maturity than those harvested prematurely in mungbean.

Jayabharathi et al. (1990) stated that seeds have maximum viability and vigour at

the stage of physiological maturity in brinjal.

Cseresnyes (1979) reported that the degree of maturity in seed influenced the

duration of dormancy and usually seed become impermeable during later stages of

maturation in sunflower. Jaya Rami Reddy et al. (2001) studies in chilli indicated that

seeds attained physiological maturation on 49 DAA and was coincided with the

morphological indices of maximum size and dry weight accumulation, physiological

indices like maximum germination (92%) and vigour measurement and change of seed

coat colour from green to brown. Jerlin et al. (2001) expressed the reduction in fresh and

dry weight at later stages was not only due to desiccation but also due to further reduction

in accumulation of food reserves.

Harrington (1972) also revealed the faster rate of dehydration at later stages of

development due to higher rate of respiration after the attainment of maximum fresh

weight and the reduction was continued with the attainment of maximum dry weight at

the given ambient conditions.

IV. Seed Germination

The objective of the germination test is to determine the minimum germination

potential of a seed lot which can be used to compare the quality of different seed lots and

estimate the planting value (Anon., 2008). Germination tests are successful in two aspects

(Mathews, 1981); they are repeatable and they provide information about the potential of

a seed lot to germinate under optimal conditions. Germination of a seed lot in laboratory

is the emergence and development of the seedling to a stage where the aspect of its

essential structures indicate whether or not it is able to develop further into a satisfactory

plant under favourable conditions in soil ( Anon., 2008).

Kattimani and Reddy (1999) reported self-propagation of ashwagandha crop is

25

through seed. Seeds have been reported to have low germination potential (Vakeswaran

and Krishnasamy, 2003). Germination reported to be temperature and light dependent in

aswagandha and pre-chilling treatment reduced the germination of seeds, whereas,

exposure to constant temperatures of 25°C, 35°C, and 45°C in the dark completely

inhibited germination (Kambizi et al., 2005).

Vakeswaran and Krishnasamy (2003) reported that seed should be exposed to

alternating temperature 25~30°C and placed on Top of Paper (TP) for conducting the

laboratory germination. Germination under light and dark was significantly higher than

under continuous light or continuous darkness.

According to Godai and Takaki (2004), the requirement of alternating

temperatures to optimize seed germination is a common behaviour and has been observed

in many plant species. Ellis and Barrett (1994) suggested that this mechanism prevents

germination, when cool day time temperatures are followed by possible very cold nights,

this necessity, reflects an adaptation to natural fluctuation of the habitat or may be

associated with dormancy process, which most often confers an adaptive advantage on

the species. Similar observations were recorded by Schonbeck and Egley (1981) on red

root pigweed seeds (Amaranthus retroflexus).

Vakeswaran and Krishnasamy (2003) studied the influence of plant growth

regulators like gibberellic acid (GA3), indole butyric acid (IBA) and indole acetic acid

(IAA) on the ashwagandha [Withania somnifera (L). Dunal] seed germination. GA3 was

found to be more effective in improving the seed germination in ashwagandha than either

IBA or lAA.

Lakshmanan et al. (2007) worked on method to overcome the major practical

problem in the cultivation of ashwagandha i.e., the poor germination percentage and

establishment at field level. They studied efficiency of native diazotrophic bacteria such

as Azospirillum and Azotobacter on the seed germination and seedling parameters of

Withania somnifera. Significant difference in germination rate and percentage root

26

length, shoot length, dry matter production and vigour index between untreated seeds and

seeds treated with Azospirillum and Azotobacter was observed. The maximum rate of

germination (2.59) was noticed in Azotobacter treatment followed by Azospirillum (2.31).

Similarly, the native isolates of Azotobacter and Azospirillum significantly increased the

germination rate to 50 per cent as against 20 per cent registered by the untreated control.

The Azotobacter treatment also registered the maximum root length (15.2 cm), shoot

length (9.0 cm) and dry matter production (142 mg).

Horowitz and Givelberg (1982) conducted an experiment to show the effect of

high temperature on germination and dormancy of Solanum viarum seeds. Seeds do not

germinate in dark and are optimal in light at 25°C. Treatment for 120 or 240 hr at 35°C

induced 77 and 44 per cent germination, respectively; germination was reduced to 43 per

cent after 72 hr at 45°C; and to 13 per cent after 24 hr at 50°C. Suzuki and Takahashi

(1968) suggested that egg plant seeds require alternate temperatures for full germination.

Andersson and Yahya (2003) conducted an experiment on primary dormancy in

Solanum viarum and Solanum physalifolium. In this experiment seeds of Solanum viarum

(two populations), Solanum physalifolium type I (two populations) and type II (one

population) were collected on two occasions. Germination in light and darkness was

tested after cold wet stratification and dry after-ripening for 1, 4, 8 and 12 weeks. They

concluded that germination percentage before and after stratification were higher in

Solanum viarum than in both genotypes of Solanum physalifolium. They recommended

that stratification substantially decreased the level of dormancy in Solanum viarum

whereas after ripening had only a small effect.

Chauhan and Nautiyal (2007) experiments on Nardostachys jatamansi seeds

indicate that continuous light decreased percentage germination, onset of germination and

delayed final germination under 10, 15 and 25°C as compared to continuous dark. A

temperature of 15°C was found optimum and showed 83.33 per cent germination; it took

6 days for onset and 22 days for final germination under light condition. It was found

27

optimum even under dark and required 8 days for onset and 24 days for final germination

(81.66%). However, at 30°C seed germination considerably decreased and recorded 61.6

per cent in both light and dark condition. Alternate temperature (25°C in light for 12 hr

and 10°C in dark for another 12 hr) was suitable to achieve maximum (86.66%)

germination along with minimum time (18 days) for completion of germination.

According to Hartmann and Kester (2001), alternating day and night temperatures

for some plant species gave better germination results than constant temperatures.

Seed dormancy could be considered simply as a block to the completion of

germination of an intact viable seed under favourable conditions, but earlier reviews

concluded that it is one of the least understood phenomena in the field of seed biology

(Hilhorst, 1995; Bewley 1997; Finch-Savage and Leubner-Merzger, 2006).

Depending on species, dormancy can also be broken by scarification, after-

ripening in dry storage and cold or warm stratification. Vleeshouwers et al. (1995)

reported that temperature regulates both dormancy and germination; whereas light

regulates germination in weed seeds. Casal and Sanchez (1998) found that in seeds with

coat dormancy, it is thought that light and gibberellins (GA3) can both release (coat)

dormancy and promote germination.

Baskin and Baskin (1998) reported that completely non-dormant seed has the

capacity to germinate over the wider range of environment.

Hilhorst (1995) reported that freshly harvested mature water-permeable dormant

seeds are said to have primary dormancy, which has been induced with the involvement

of ABA during seed maturation on the mother plant. Krock et al. (2002) have

demonstrated the induction of secondary dormancy in Nicotiana attenuata seeds by a

naturally occurring chemical signal [abscisic acid (ABA) and four other terpenes] in

leachate from litter that covers the seeds in their habitat. Manjkhola et al. (2003)

reported the stimulatory effects of KNO3 on seed germination in the Himalayan

28

medicinal plant Arnebia benthamii.

Choudhary et al. (1996) in Podophyllum hexandrum and McIntyre et al. (1997) in

oat showed the effect of nitrogenous compounds in various forms, particularly nitrates

(e.g., KNO3), to stimulate seed germination, and influence germination through change

in water relationship by increasing the physiological efficiency. Batak et al. (2002) and

Aloresi et al. (2005) revealed that exogenous nitrate can affect the requirement for light

to promote seed germination and their dormancy is influenced by the nitrate fed to the

mother plant. Mustyatse (1983) reported both positive and detrimental results of thiourea

on seed germination in Hypericum perforatum.

The endosperm acts as a mechanical barrier to the germination of seeds in several

angiosperm seeds. A decline in this mechanical resistance of the micropylar endosperm

(the endosperm layer covering the radicle tip) appears to be a pre-requisite for radicle

protrusion during seed germination reported by several workers like Hihorst (1995),

Bewley (1997) and Kucera et al. (2005). This endosperm weakening can be promoted by

GA3 and at least in part inhibited by ABA. Solanaceous species such as tomato

(Lycopersicon esculentum), tobacco (Nicotiana spp.), pepper (Capsicum annuum) and

Datura have become model species for endosperm weakening.

V. Assessment of Genetic Variability

The first and foremost step for improvement in any crop is to study the variation

of different traits of its available germplasm. This emphasizes importance of variability in

relation to crop improvement. In order to understand the variability partitioning of

observed variation is pre-requisite. Genetic variability in relation to environmental

variability was first studied by Fisher (1918) who recognized the importance of genetic

variance and partitioned it into three components, namely additive, dominant and

epistatic. He suggested that genetic variance could be utilized for genetic advance

through judicious selection.

29

Ashwagandha displays an appreciable spectrum of variability in its morphometric

traits. Atal and Schwarting (1961) observed that the authentic root from commercial

plants differed from the commercial roots in certain external and internal characteristics

and suggested that commercial roots were derived from the cultivated plants. Atal and

Schwarting (1962) documented five different morphological forms of Withania

somnifera from different populations growing in varied regions of India. The pattern of

genetic variation in plant species is determined by its sexual system, which affects the

genetic structure and dynamics of populations within the species.

Beg et al. (1988) examined morphological diversification and genetic isolating

mechanism between some members of Solanum viarum complex. They reported that the

members of Solanum viarum complex differ from each other on such cytomorphological

characters as plant habit, fruit colour and chromosome number. Shahid and Khan (1996)

studied morphological account of some seeds of Solanaceae family. Macro and micro-

morphological studies were undertaken on 14 species of the family Solanaceae. Data

were tabulated on colour, shape, texture and size. Edmonds and Chewya (1997) studied

the morphology and distribution on black nightshades (Solanum viarum L.) and related

species. Dela-vinca et al. (1996) studied the morphology and cytology of indigenous wild

vegetable germplasm Solanum viarum L. 12 accessions of Solanum viarum collected

from Isabela and Ifugo provinces (Philippines) were characterized morphologically and

cytologically. The number of flowers per inflorescence ranged from 6 to 13. Khanna et

al. (2006) carried out seed protein characterization and identified five promising

germplasm lines in Withania somnifera (L.) Dunal. The ashwagandha accessions

categorized on the basis of location morphometric characteristics is presented below.

30

Kumar et al. (2007) collected twenty five accessions of ashwagandha from different

states of India (Jammu and Kashmir, Himachal Pradesh, Madhya Pradesh, Uttar Pradesh,

Punjab, Andhra Pradesh, Gujarat, Maharashtra and Rajasthan) evaluated in a randomized

block design in three replications in years 2002-2004. They studied morphological and

chemical variation in 20 elite accessions of wild and cultivated populations and their

spatial distribution throughout India. They also studied seven morphometric characters

namely, plant height, number of branches/plant, number of seeds/berry, root yield (g),

root length (cm), root diameter (cm) per plant and berry colour. Based on the D2 values

and PCA (Principal Component Analysis) of these phenotypic traits, 25 accessions were

grouped in five clusters. They suggested that height of the plant and colour of the berry is

Accessions Locations Morphometric Characteristics

AGB-002 Bikaner-Rajasthan Perennial, tall (l00-110 cm), 4-5

branches, root yield 21-23 g per

plant with red berry

AGB-009 Amritsar-Punjab Perennial, tall (100-120 cm), 4-5

branches, root yield 15-28 g per

plant with red berry

AGB-015 Ghaziabad-Uttar

Pradesh

Annual, dwarf (40-50 cm), 2-3

branches, root yield 3-6 g per plant

with orange berry

AGB-025 Neemuch-Madhya

Pradesh

Perennial, tall (100-110 cm), 4-5

branches, root yield 21-23 g per

plant with red berry

AGB-030 Bhopal-Madhya

Pradesh

Perennial, tall (100-120 cm), 4-5

branches, root yield 15-28 g per

plant with red berry

31

closely associated with root yield and withanolide content. They found that

morphological diversity is genetic.

At DMAPR, Anand a study was undertaken (Anon., 2008), to categorize the wild

plant type and the cultivated plant type (cv. JA-20) morphologically. Cultivated type was

shorter in height compared to wild type. Also the leaf size was smaller and narrower in

the cultivated type. Average leaf area in the cultivated type was 11.95 cm2 compared to

40.34 cm2 in the wild one. Leaf margin was wavy in the cultivated, whereas, it was

straight in the wild type. In the cultivated type, number of leaves ranged from 128 to 208

per plant whereas in the wild type it ranged from 346 to 711 at the harvesting stage (four

months from the seed planting). Photosynthetic rate was comparatively higher in the wild

type. However, chlorophyll contents were almost similar in both the plant types. In the

cultivated type, fresh weight at harvesting stage of root per plant ranged from 4.89 to

10.04 g whereas in the wild it ranged from 111.9 to 267.70 g. Root diameter was 8.52 cm

in the cultivated and 29.37 cm in the wild. The number of fruits per plant in cultivated

type ranged from 29 to 109 and 56 to 261 in the wild type at the harvesting stage. The

size of fruit with calyx was 1.73 x 1.06 cm in cultivated type, whereas in wild type it was

1.20 x 1.07 cm. Berry was orange to saffron colour in cultivated and red in wild type.

Seeds were larger in size in the cultivated type. Average test weight of the seeds in the

cultivated type was 224 mg, whereas, it was 135.1 mg in the wild type.

VI. Storage Behaviour of Seeds

Production and maintenance of high quality seed is the corner stone of agriculture

which lays the basis and foundation for a stable and sustainable crop production. A high

agronomic output can be guaranteed only if the seed that reaches the farmer, after its

production, handling and storage is of superior quality. Seeds are used for commercial

cultivation of the crop. They are also used in genetic conservation, owing to ease of

handling, are capable of maintaining genetic stability, and are inexpensive hence, high

quality seed is as important as an improved variety. However, like any other organism,

32

seeds too age and deteriorate with the passage of time. Therefore, the deterioration

process in seed is a continuous and irreversible and it varies not only from species to

species but also from variety to variety within a species (Agarwal, 1980). Roberts (1973)

based on seed storage behaviour classified the seeds into two major groups: orthodox

seeds and recalcitrant seeds. The young seed is rich in moisture content and dry matter

accumulation increase with advances in maturity. At the time of harvest, dry matter flow

ceases and moisture contents are fairly reduced. The process of seed deterioration begins

on the separation of seed from the mother plant.

Barton (1961) suggested that seed moisture content and storage temperature are

the two major factors which influence the rate of loss of seed viability during storage.

Harrington (1972) reported that seed life decreases by one-half when temperatures are

increased by 5°C in the temperature range 10°C to 50°C. Seeds of several species tolerate

freezing temperatures, especially at low levels of seed moisture, thereby enhancing seed

longevity. Roberts (1972) reported that low-temperature storage is advantageous for

maintenance of seed viability, with few exceptions. Seed storage at fluctuating

temperatures damages seed quality (McRostie, 1939). Horky (1991) noted that seeds of

certain vegetable crops having 5.6 to 7.5 per cent moisture content maintained their initial

viability (similar/closer to at start of seed storage) for seven years at 0°C, whereas high

moisture (22 % mc) causes injury to seeds if stored at -6°C (Agena, 1961). Low

temperature is effective in preserving seed quality, especially in moisture-proof

containers under humid conditions. Seeds of tomato, cucumber, and sweet pepper are

viable for 36 months at 20°C (Zhang and Kong, 1996). Stanwood and Sowa (1995)

preserved different types of seeds at -18°C and -196°C. Seed viability did not decline

over the ten years. The percentage of germination of seeds stored at 5°C dropped from 94

to 68 per cent, which is attributed to the variation in seed moisture contents. Seed deteri-

oration was more at 5°C than at -18°C and - 196°C.

Several important factors which affect the shelf life of the seeds like seed-borne

fungi, high storage temperature and high seed moisture content not only increase the rate

33

of seed deterioration but also, results in drastic reduction and loss of viability. The seed

storage life is primarily dependent on genetic factors. Seed longevity differs among the

different cultivars during storage and is influenced by storage temperatures and

cultivation conditions (Passam et al., 1997). Some genotypes withstand ageing to a

certain extent and remain viable for relatively longer periods under ambient conditions

(Doijode, 1994). This was further evidenced by high permeability of membrane resulting

in excessive leaching of electrolytes (Doijode, 1990).

Seed deterioration is rapid in humid tropics owing to prevalence of high humidity

and high temperatures. Seed viability loses rapidly and cannot be preserved for longer

period under ambient conditions. Areas where dry and cool climate is prevalent are best

suited for seed storage. Agarwal (1976) identified Delhi, Ludhiana and Jaipur as good

places for seed storage; Indore, Coimbatore, Pune, Varanasi, Bareilly and Hyderabad as

moderate places for seed storage whereas Patna, Bengaluru, Mumbai, Cuttack and

Kolkata as poor and Trivandrum and Guwahati as very poor places for seed storage. The

seed certification standard with respect to germination was maintained for less than six

month in onion seeds in Delhi conditions (Agarwal, 1980). For safer seed storage, the

sum of temperature and relative humidity should not exceed hundred per cent

(Harrington, 1960a,b). Siddiqui (1976) also investigated the requirements for seed

storage in India and reported that the moisture content of seeds should be less than 12 per

cent; storage room temperature; 10°C; whereas, relative humidity should not exceed 70

per cent.

Seed moisture plays an important role in seed storage. Initially, the moisture

content is high which decreases on maturation and ripening of seeds. Seed moisture

content depends on the relative humidity of the atmosphere, air temperature and chemical

composition of seeds. At a given moisture content, viability and vigour decreases more

rapidly at higher temperatures. Seedling vigour showed an earlier and more rapid decline

than viability (Doijode, 1990). According to Harrington (1972) the seed longevity

doubles for every 1 per cent decrease in moisture content. Therefore, most of the

34

vegetable seeds are dried to 5-7 per cent moisture content for safer storage. Cromarty et

al. (1982) recommended seed drying at low temperature (15°C) and low humidity (15 %

RH) for safe seed storage. Zhang and Zhang (1994) reported that ultradrying of seeds

improves seed storability. Ultra dry (2.0 to 3.7 % mc) seeds preserve viability better than

dry (5.5 to 6.8 % mc) seeds at 20°C (Ellis et al., 1996). Minkov et al. (1974) also

reported that loss of seed viability was rapid between 13 and 15 % moisture as compared

to seeds with 11 % moisture content. Storage of seeds under reduced moisture has been

found to maintain seed viability for longer periods.

Several workers through a series of experiments showed that relative humidity

and temperature are the most important factors affecting maintenance of seed quality

during storage (Barton, 1961; Christensen and Kaufmann, 1969). Of these, relative

humidity is of crucial importance due to its role in equilibrating seed moisture content

(Delouche et al., 1973). Seed, being hygroscopic, simultaneously exhibits fluctuation in

moisture absorption, with increase in relative humidity causing a proportional increase in

seed moisture content. The storage life of seeds decreases with increase in storage

temperatures. According to Harrington (1972) the seed longevity doubles for every 5°C

decrease in storage temperature. The influence of temperature is expressed at varying

levels of seed moisture and these factors are interrelated.

According to Thulasidas et al. (1977), seeds of egg plant stored with silica gel in

aluminium foil under ambient conditions recorded 50 per cent germination on 30 months

from the start of seed storage, as compared to seeds stored without silica gel, which had

50 per cent germination on 12 months from the start of seed storage. Seed viability and

vigour preserve well under low temperatures. Seed viability declines rapidly under warm,

humid conditions. Seed deterioration is a gradual and irreversible process resulting in loss

of seed quality. Like other Solanaceous crops ashwagandha seeds are capable of

withstanding adverse storage conditions to a certain extent, show orthodox storage

behavior, wherein, desiccation of seeds and storage at low temperatures increase seed

longevity. Farmers prefer to preserve viable seeds until the immediate next growing

35

season, whereas breeders demand the fairly long storage for germplasm conservation.

Tomato seeds maintain their viability for long periods, and this is attributed to genetic

factors (James et al., 1964). Seed longevity differs within the genus among species and

cultivars. Seed germination percentage varies among different cultivars stored for four

years under ambient conditions (Doijode, 1987). Pre-germinated and germinated seeds

remain viable for shorter periods under ambient conditions. They retain their viability for

five days at 5°C. Further storage reduces viability and vigour due to the degradation of

enzymes and functional structures and an increase in free fatty acids (Sunil, 1991).

Tomato seeds preserve well under ambient conditions (Bosewell et al., 1940). Higher

temperatures and relative humidity are not favorable for storage. Seeds stored at 50°C

and 77 per cent RH showed slow and less germination (Harrington and Setyati-Harjadi,

1966). The optimum temperature and RH for seed storage are close to 0°C and not

exceeding 70 per cent, respectively (Kurdina, 1966). Low seed moisture, 5 to 7 per cent;

is ideal for longer seed storage, even if higher temperatures are maintained. Tomato seeds

survive in outer space conditions for several years without adverse effects on germina-

tion, emergence, and fruit yield (Khan and Stoffella, 1996). Seed vigour depends on

initial status of seed quality and the seed storage conditions. Tomato seeds retained high

seed viability and vigour for three years under ambient conditions. Thereafter, seed

viability decreased; however, the seeds were economically viable until the eighth year of

seed storage (Popovska, 1964). Barton and Garman (1946) reported that tomato seeds

maintain seed viability for 13 years at room temperatures and for 18 years at -5°C.

Sundstrom (1990) reported that 10 per cent moisture is optimum for better storage

of Capsicum frutescens seeds. Fischer (1980) showed that seeds remained viable for

seven years when packed and stored at 5°C to 10°C. However, seeds lost viability rapidly

under unsealed conditions. Under fluctuating temperatures from 2°C to 26°C, seed

viability decreased from 92 to 29 per cent during five years of seed storage (Thakur et al.,

1988). Ultra-low-temperature storage of seeds at -70°C did not improve the storability

over that of -12°C (Woodstock et al., 1983). The knowledge that seed longevity is better

36

at lower relative humidity has resulted in the development of moisture resistant

containers in seed storage. Thin gauges of polyethylene and similar materials do not

provide much protection as they are moisture pervious (Barton, 1953; Miyagi, 1966)

whereas, packaging material like aluminium foil pouches provides better protection

against moisture due to their moisture impervious nature (Harrington, 1960a). Harrison

and Carpenter (1977) reported that low moisture seeds stored in sealed containers extend

the viability.