Progress in evaluating converted cotton race stocks for resistance to whiteflies and aphids

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


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


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


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


% 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


Plant

% M

orta

lity


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


% 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

Progress in evaluating converted cotton race stocks for resistance to whiteflies and aphids

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