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Title: EFFICACY OF PYRAMIDING GREENBUG (HOMOPTERA: APHIDIDAE) RESISTANCE GENES IN WHEAT

Author
item Porter, David
item Burd, John
item Shufran, Kevin
item Webster, James

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2000
Publication Date: 8/1/2000
Citation: Porter, D.R., Burd, J.D., Shufran, K.A., Webster, J.A. 2000. Efficacy of pyramiding greenbug (Homoptera: Aphididae) resistance genes in wheat. Journal of Economic Entomology.93(4):1315-1318.

Interpretive Summary: Plant breeders have worked under the premise that pyramiding resistance genes, or combining two or more genes in the same cultivar, provides more durable resistance than when single resistance genes are released sequentially. In this study, we examined the scientific basis for this claim, and determined the potential benefits of pyramiding greenbug resistance genes in winter wheat. Resistance genes Gb2, Gb3, and Gb6, and pyramided genes Gb2/Gb3, Gb2/Gb6, and Gb3/Gb6 were tested for effectiveness against biotypes E, F, G, H, and I. By comparing the reactions of plants with pyramided genes with those with single resistance genes, we found that pyramiding provided no additional protection over that conferred by the single resistance genes. In other words, pyramiding greenbug resistance genes in wheat did not provide durable resistance, contrary to the popular theory mentioned above. Pyramiding resistance genes is a very costly approach to managing resistance because of the extra time and effort involved, compared with developing wheats with single resistance genes. Therefore, we recommend using single genes when developing greenbug- resistant wheat.

Technical Abstract: Durable resistance to greenbug, Schizaphis graminum (Rondani), in wheat is a goal of wheat improvement teams, and one that has been complicated by the regular occurrence of new damaging biotypes. Simulation modeling studies suggest that pyramiding resistance genes, i.e., combining more than one resistance gene in a single cultivar or hybrid, provides more durable resistance than sequential release of single genes. We examined this theor by pyramiding genes in wheat and testing with greenbug biotypes that were identified in the field. Resistance genes Gb2, Gb3, and Gb6, and pyramided genes Gb2/Gb3, Gb2/Gb6, and Gb3/Gb6 were tested for effectiveness against biotypes E, F, G, H, and I. By comparing reactions of plants with pyramided genes with those with single resistance genes, we found that pyramiding provided no additional protection over that conferred by the single resistance genes. Based on the results of this test, we concluded that the sequential release of single resistance genes, combined with careful monitoring of greenbug population genetics, is the most effective resistance deployment strategy.