progress in evaluating converted cotton race stocks for resistance to whiteflies and aphids
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Progress in evaluating converted cotton race
stocks for resistance to whiteflies and aphids
Mary M. ToothakerDr. Marvin Harris
Dr. C. Wayne SmithTexas A&M University
Why is this necessary? With the eradication of the boll weevil,
secondary pests such as whiteflies and aphids have become important pests
Honeydew from excessive whitefly and aphid populations affect ginning and reduce quality of the fiber
Feeding by excessive populations of aphids and whiteflies can decrease nutrient availability
(Photo: Richard Sequeira)
Aphids and whiteflies are also known vectors of many plant viruses
Aphids becoming an increasing problem with use of Bt cotton
Aphid populations have been shown to be higher in Bt fields than non-Bt fields, probably because of a decreased use of insecticides
Cotton Leaf Crumple Virus, transmitted by Bemisia tabaci
Selecting for Resistance Research done in 2003 - 2004
confirmed that 6 cotton race stocks (CRS) out of a selection of 116 photoperiod-insensitive race stocks showed resistance to whitefly
TX0154 TX0156 TX0188
TX0195 TX0221 TX0242
Selecting for Resistance
TX0154 and TX0156 were shown to be significantly lower in percent survival
TX0188, TX0195, TX0221, TX0242 were shown to be significantly longer in developmental time
Selecting for Resistance
Goal: Do plants within one CRS show variability in resistance characteristics compared to a known susceptible
Selection criteria - whitefly survival and developmental time: Which is better?
Selecting for Resistance - Whitefly
4 plants of each CRS, 3 leaves per plant
Excised leaf technique
Ten adult whiteflies were placed and contained on each leaf
Selecting for Resistance - Whitefly
Whiteflies removed after 24 hours and clip cages placed on same area
Number of eggs laid were counted and recorded
Nymphs allowed to hatch and develop for 14 days
After 14 days, the number of each instar was counted every 24 hours until all had completed development or died
Mean number of days to adulthood and percent mortality were calculated for each plant within each race stock
Mean Days to Adulthood
05
1015202530
A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D
DP PSC355 TX0154 TX0156 TX0188 TX0195 TX0221 TX0242
CRS/Plant Number
Percent Mortality
05
10152025303540
A B C D A B C D A B C D A B C D A B C D A B C D A B C D A B C D
DP PSC355 TX0154 TX0156 TX0188 TX0195 TX0221 TX0242
CRS/Plant Number
Current Research 20 whole plants
(6-8 leaf stage) of each CRS and a susceptible control (DP or PSC355)
Three cages per plant
7-8 adult whiteflies per cage
ResultsTX0188 Percent Mortality
0
0.2
0.4
0.6
0.8
1
1.2
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot 10
Plant
% M
orta
lity
TX0188 - Mean Days to Adulthood
0
5
10
15
20
25
30
35
40
Pot 1Plant 1
Pot 1Plant 2
Pot 3Plant 1
Pot 3Plant 2
Pot 4Plant 1
Pot 4Plant 2
Pot 6Plant 2
Pot 7Plant 1
Pot 7Plant 2
Pot 8Plant 1
Pot 10Plant 1
Plant
Days
PSC355(1) - Percent Mortality
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot 10
Plant
% M
orta
lity
PSC355(1) - Mean Days to Adulthood
0
5
10
15
20
25
30
Pot 1Plant 2
Pot 2Plant 1
Pot 3Plant 1
Pot 3Plant 2
Pot 4Plant 1
Pot 4Plant 2
Pot 5Plant 2
Pot 6Plant 1
Pot 7Plant 1
Pot 7Plant 2
Pot 8Plant 1
Pot 8Plant 2
Pot 9Plant 1
Pot 10Plant 1
Pot 10Plant 2
ResultsTX0221 Mean Percent Mortality
0.000.200.400.600.801.001.20
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot10
Plant
% M
orta
lity
TX0221 - Mean Days to Adulthood
05
101520253035
Pot 3Plant 2
Pot 4Plant 1
Pot 4Plant 2
Pot 5Plant 2
Pot 7Plant 2
Pot 9Plant 1
Pot 9Plant 2
Plant
Days
DP(2) - Mean Percent Mortality
0
0.2
0.4
0.6
0.8
1
1.2
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot 10
Plant
% M
orta
lity
DP(2) - Mean Days to Adulthood
0
5
10
15
20
25
30
35
Pot 1Plant 1
Pot 3Plant 2
Pot 4Plant 2
Pot 5Plant 1
Pot 5Plant 2
Pot 6Plant 1
Pot 6Plant 2
Pot 8Plant 1
Pot 8Plant 2
Pot 9Plant 1
Pot 9Plant 2
Pot 10Plant 1
Plant
Days
ResultsTX0195 - Percent Mortality
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot 10
% M
orta
lity
PSC355(2) - Percent Mortality
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot 10
Plant
% M
orta
lity
TX0195 - Mean Days to Adulthood
0
5
10
15
20
25
30
35
40
45
Pot 1 Plant 1
Pot 1 Plant 2
Pot 2Plant 1
Pot 2 Plant 2
Pot 3Plant 1
Pot 4Plant 2
Pot 5 Plant 1
Pot 5Plant 2
Pot 6 Plant 1
Pot 6 Plant 2
Pot 9 Plant 1
Pot 10 Plant 1
Pot 10 Plant 2
Days
to A
dulth
ood
PSC355(2) - Mean Days to Adulthood
29
30
31
32
33
3435
36
37
38
39
40
Pot 1 Plant 1
Pot 3 Plant 1
Pot 5 Plant 1
Pot 6 Plant 1
Pot 6 Plant 2
Pot 8 Plant 1
Pot 8 Plant 2
Pot 9 Plant 1
Mea
n D
ays
to A
dulth
ood
Discussion Mortality appears to be the better
selection criteria
Much more variation within each CRS in percent mortality than the controls using excised leaf technique
Days to adulthood appear to be slightly higher in the test groups than the controls
Breeding By using whole plants, individual plant
selections (IPS) can be made within each CRS using this selection criteria
TX0195 - Percent Mortality
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2
Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6 Pot 7 Pot 8 Pot 9 Pot 10
% M
orta
lity
Other Projects Use water-sensitive paper to
measure honeydew production
• Quantify amount of honeydew produced per acre over time
• Could determine aphid numbers in a field by measuring the honeydew produced
*in conjunction with USDA
Honeydew production by pecan aphid on a known susceptible variety of pecan
Honeydew production on a suspected resistant variety of pecan
Proof of Concept:
Acknowledgements Cotton, Inc. Texas A&M University – Department of
Entomology• Alexandra Gomezplata• Jessica Honaker• Robert Puckett• Allen Dean• Sarah Skrivanek
Texas A&M University – Plant Growth Facilities• Roger Horn
Texas A&M University – Department of Soil & Crop Sciences• Kasi Clay• Dawn Deno
USDA-ARS-SPARC• Dr. Juan Lopez • Dr. Dan Martin
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