susceptibility to laurel wilt related to physiology of three clonal ... · randy ploetz lab...
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![Page 1: Susceptibility to Laurel Wilt Related to Physiology of Three Clonal ... · Randy Ploetz Lab Technician Randy Fernandez Biologist II Josh Konkol Biologist III Ana Vargas Collaborator](https://reader033.vdocuments.us/reader033/viewer/2022050105/5f43d03c12283d0a742459da/html5/thumbnails/1.jpg)
Laurel Wilt Susceptibility of Avocado Scions and Rootstocks In Relation to
Physiology and Stem Anatomy
Bruce Schaffer
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What we know about physiological responses to laurel wiltSusceptibility varies among cultivars with West Indian cvs. most susceptible
Hypothesis
• The higher the sap flow rate, the greater the susceptibility to laurel wilt
• This is related to the size of xylem vessels
• Size of xylem vessels differs among WI, M and G races
Preliminary EvidenceWI cvs. (the most susceptible) have the largest xylem vessels and highest sap flow
One More ThingGrafting can significantly affect the xylem sap flow rate
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‘Nabal’ (G)
‘Egas’(M)
‘Simmonds’(WI)
Xylem vessel size of avocado races
R. Ploetz, R. Blanchette & G. Beier, Unpublished data
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Specific Objectives
• To compare laurel wilt susceptibility among combinations of Mexican (M), West Indian (WI) and Guatemalan (G) rootstocks and scion/rootstock combinations using clonal plant material
• To relate laurel wilt susceptibility among the 3 races (rootstocks and scion/rootstock combinations) to whole plant physiology and xylem anatomy
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Clonal Plants From Brokaw Nursery, CA
• Cultivars of Different Races
• ‘Waldin’ (WI)
• ‘Simmonds’ (WI)
• ‘Duke-7’ (M)
• ‘Zutano’ (M)
• ‘Reed’ (G)
• ‘Nabal’ (G)
Non-grafted and grafted combinations WI/WI, WI/M, WI/G etc.
Phytophthora Tolerant Roostocks from CADuke-7 (M)Dusa (G x M)Toro Canyon (M)
Non-grafted & grafted with ‘Hass’ (G x M) and with ‘Simmonds’ (WI) scions
We are testing plants as soon as the reach adequate size for inoculation and physiological measurements
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Methodology
Inoculation with 3,000 conidia per plant
Control plants - inoculated with deionized water
Daily symptom assessment –
visual rating scale (0-10)
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Leaf gas exchange (photosynthesis, transpiration, stomatal conductance)
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Xylem sap flow
Rate of water movement up the plant stem
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Anatomical Measurements
Tyloses formation
Number and size of xylem vessels
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Root and Stem Hydraulic Conductivity
High pressure flow meter Calculated from xylem vessel anatomy
• Vessel frequency and diameter
• Relative hydraulic conductivity, RC=r4VF
• Vulnerability index, V=VD/VF
• % Vessel occlusion
• (# vessel tyloses / Total # vessels) x 100
Calculated from xylem vessel anatomy
• Vessel frequency and diameter
• Relative hydraulic conductivity, RC=r4VF
• Vulnerability index, V=VD/VF
• % Vessel occlusion
• 100
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• Internal LW Symptom Rating (0-10)
Based on the amount of vascular staining
• Recover the L.W. fungus (R. lauricola)
Plate stem segments on selective medium
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Example 1
Grafted clonal scions and clonal rootstocks
• ‘Simmonds’ (WI) scion / Waldin (WI) rootstock• ‘Simmonds’ (WI) scion / Reed (G) rootstock• ‘Simmonds’ (WI) scion / Duke-7 (M) rootstock• ‘Duke-7’ (M) scion / Waldin (WI) rootstock
Results – 3 Examples of Cultivar Comparisons
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Photosynthesis
‘Simmonds’ (WI) scion on Waldin (WI) rootstock
0
5
10
15
20
25
-4 -2 -1 1 3 5 8 10 12 13 15 17 19 23
A (
µm
ol C
O2
m-2
s-1
)
Days after Inoculation
C…
0
5
10
15
20
25
-4 -2 -1 1 3 5 8 10 12 13 15 17 19 23
A (
µm
ol C
O2
m-2
s-1
)
Days after Inoculation
'Simmonds' (WI) / Reed (G) rootstock
0
5
10
15
20
25
-4 -2 -1 1 3 5 8 10 12 13 15 17 19 23
A (
µm
ol C
O2
m-2
s-1)
Days after Inoculation
'Simmonds' (WI) scion / Duke 7 (M) rootstock
0
5
10
15
20
25
-4 -2 -1 1 3 5 8 10 12 13 15 17 19 23
A (
µm
ol C
O2
m-2
s-1)
Days after Inoculation
'Duke 7' (M) scion / Waldin (WI) rootstock
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'Simmonds' (WI) Scion / Reed (G) rootstock
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dai
ly S
ap F
low
Rat
e (K
g/d
ay)
Days after inoculation
Xylem Sap Flow Rate
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dai
ly S
ap F
low
Rat
e (K
g/d
ay)
Days after inoculation
'Simmonds' (WI) scion / Waldin (WI) rootstock
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dai
ly S
ap F
low
Rat
e (K
g/d
ay)
Days after inoculation
'Duke 7' (M) scion / Waldin (WI) rootstock
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dai
ly S
ap F
low
Rat
e (K
g/d
ay)
Days after inoculation
'Simmonds' (WI) scion / Duke 7 (M) rootstock
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Disease Severity Ratings
1
2
3
4
5
6
7
8
9
10
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dis
ease
Sev
eri
ty R
atin
g (1
-10)
Days after inoculation
'Simmonds' (WI) scion / Waldin (WI) rootstock
1
2
3
4
5
6
7
8
9
10
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dis
ease
Sev
eri
ty R
atin
g (1
-10)
Days after inoculation
'Simmonds' (WI) scion / Reed (G) rootstock
1
2
3
4
5
6
7
8
9
10
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dis
ease
Sev
eri
ty R
atin
g (1
-10)
Days after inoculation
'Simmonds' (WI) scion / Duke 7 (M) rootstock
1
2
3
4
5
6
7
8
9
10
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Dis
ease
Sev
erit
y R
atin
g (1
-10)
Days after inoculation
'Duke 7' (M) scion / Waldin (WI) rootstock
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Example 2
Non-grafted clonal rootstocks
• Toro Canyon rootstock
• Duke-7 rootstock
• Dusa rootstock
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Photosynthesis
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Xylem Sap Flow Rate
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Visible Symptom Rating
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Example 3: Most Recent Experiment • Waldin (WI) scion /Duke-7 (M) rootstock
• Simmonds (WI) scion / Duke-7 rootstock
• Duke-7 (M) scion / Duke-7 rootstock
• Reed (G) scion /Duke-7 rootstock
Preliminary Results (data not statistically analyzed yet)
• ‘Waldin’ and ‘Simmonds’ (WI) scions - most susceptible
• ‘Duke-7’ (M) scion – susceptible but much slower disease progression
• ‘Reed’ (G) scion – much slower disease progression that all others
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Conclusions (so far)
• Scion has more of an influence on LW susceptibility than rootstock
• Rootstock does have some influence on LW susceptibility
• There appears to be a race and a cultivar effect on LW disease progression
- This appears (at least partially) related to xylem anatomy and physiology
For You folks in California…
In non-grafted, clonal ‘Toro Canyon’, ‘Dusa’ and ‘Duke-7’, LW disease progression is relatively very slow, but they are susceptible
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Current Experiment
• ‘Hass’ scion on ‘Duke7’ rootstock
• ‘Hass’ scion on ‘Dusa’ rootstock
• ‘Hass’ scion on ‘Toro Canyon’ rootstock
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Co-PIRandy Ploetz
Lab TechnicianRandy Fernandez
Biologist IIJosh Konkol
Biologist IIIAna Vargas
CollaboratorEd Etxeberria
Bruce Schaffer, PI
PhD StudentRaiza Castillo
The Team
BiologistAime Vazquez
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Thank you for your attention!