Current status of greenbug biotypes in sorghum

J. Scott Armstrong USDA-ARS, Wheat, Peanut and other Field Crop

Research Unit, Stillwater, OK

Really no single definition for biotypes but three common traits;

First, biotypes are intraspecifc categories.

Second, biotypes are usually morphologically indistinguishable.

Third, biotypes differ in expressed biological attributes.

What is significantly important to us is that biotypes are an economic threat to sorghum, and this is differentiated by what “type” they are; deter-mined by observing the host reaction (e.g., live/dead,resistant/susceptible) to a preselected matrix of plant genotypes.

Consequently, the genetic basis for identification of greenbugbiotypes is plant based and not insect derived.

Journal of Insect Science: 2010, Vol. 10 | Article 176D. Downie

“Baubles, bangles, and biotypes: A critical review of the use and abuse of the biotype concept”

Department of Zoology and Entomology, Rhodes University, Grahamstown, 6140 South Africa

“It is argued here that the term ‘biotype’ and its applications are overly simplistic, confused, have not proved useful in current pest management, and lack predictive power for future management”

The keeper of the greenbug biotypes

Biotypes A, C, E, F, G, H, I, K,

Collections from: NY, FL, SC,TX, CO, WY, etc…..etc….

Approximately 50% of the recognized insect biotypes on agricultural crops are aphids (Saxena & Barrion 1987)

Collect form grasses or agricultural landscape

Watch for parasitic wasps and other problems

Isolate (clones)

Keep a steady supply of plants (usually barley)

Ship to Universities, Agencies and Institutes across the U.S. for research purposes.

Screen for phenotypic reaction to the plant (differentiate biotype)

“Typing greenbugs”

Colony Custer DS 28A Amigo CI 17882 CI 17959 Largo GRS 1201 Elbon Insave Rye Wintermalt Post 90 PI 426756 TX TX TX PI Selection (Gb1) (Gb2) (Gb5) (Gb4) (Gb3) (Gb6) Rye (Gb2, Gb6) Barley (Rsg1a) (Rsg2b) 7000 2737 2783 550607

B S S R S S S R S R S R R ?? ?? S RC S S R R R R R S R S R R S R R RE S S S R R R R S R S R R S S R RF S R S S S S S S S S R R ?? ?? S SG S S S S S S R S R R R R S S S RH S S S S S R S S S S S S ?? ?? ?? RI S S S R R R R S R S R R S S S RK S S S R R R R S R S R R S S S S

NY S R R S S S S S R S R R S S S RFL1 S R R S S S S S R S R R S S S S

Plant matrix wheat / rye / barley / sorghum - greenbug determination

Colony TX TX TX PI Selection 7000 2737 2783 550607

B ?? ?? S RC S R R RE S S R RF ?? ?? S SG S S S RH ?? ?? ?? RI S S S RK S S S S

NY S S S RFL1 S S S SSC

Plant matrix for sorghum/greenbug determination

Biotype “E”: TX 7000 and TX 2737 are susceptible, TX 2783 and PI 550607 are resistant

Biotype “I”: TX 7000, TX 2737 and TX 2783 are susceptible.PI 550607 is resistant;

Biotype “K”: PI 550607, TX 7000, TX 2737 and TX 2783 are all susceptible.

PI 550610

RRRSRRRSRS

Table 1. Total mean (± SE) number of nymphs (Md) produced by a female greenbug reared on different sorghum varieties that are designated as susceptible or resistant*.

*Model DF = 11, 71, F = 6.27, P> F=< 0.001, Sorghum type DF = 3, F = 11.1, P> F= < 0.001, Greenbug biotype DF = 2, F = 6.32, P> F=< 0.003, Sorghum by Biotype interaction DF = 6, F = 3.86, P> F=< 0.003.

Greenbug Biotype

Sorghum Variety Resistance

Status to E, I, KE I K

TX 7000 S, S, S 48.3 ± 5.9 A 48.5 ± 5.2 A 52.3 ± 4.9 AB

TX 2737 S, S, S 39.7± 4.9 AB 34.5 ± 6.4 AB 42.5 ± 3.8 BC

TX 2783 R, S, S 21.0 ± 3.7 C 46.2 ± 6.4 A 58.3 ± 5.0 A

PI 550607 R, R, S 28.2 ± 2.1. BC 25.5 ± 2.2 B 30.5 ± 2.6 C

EC

IK

TX 7000TX 2783PI 55 0607

PI 55 0610

Chlorosis

Plant Height

Leaf number

Are there other ways to determine difference in biotypes beside plant reaction?

Molecular means – but not by mitochondrial DNA.

RNA seq analysis to differentiate biotypes. (Just genes and relatively cheap).

Cuticular hydrocarbons – with Dr. Jack Dillwith, OSU Entomology Dept.

Salivary proteins – can be done but not easily used for everyday test.

Intrinsic rate of increase for GB on different lines – Female – has offspring – take that offspring and count how long she is in reproduction and how many offspring she has.

rm = 0.738 (log Md)/d.

What’s in the future in terms of biotypes ???????

Thank you!