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Title: GREENBUG (HOMOPTERA: APHIDIDAE) BIOTYPES: SELECTED BY RESISTANT CULTIVARS OR PREADAPTED OPPORTUNISTS? (CHANGE TITLE AND ADD ACCEPT. DATE)

Author
item Porter, David
item Burd, John
item Shufran, Kevin
item Webster, James
item TEETES, GEORGE - TEXAS A&M UNIV

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: If you plant a wheat cultivar or a sorghum hybrid that has a single major gene for an antibiotic property that makes the plant resistant to the greenbug, then you will force the greenbug population to change and develop a new, virulent greenbug race, called a biotype. At least that is what has been the common belief among plant scientists for many years. This misconception has altered the thinking of many plant breeders, leading to confusion as to how best to deploy greenbug resistance to provide optimum protection for their crops. To better understand the relationship between plant resistance and the development of new greenbug biotypes, we looked at the history of greenbug resistance efforts in wheat and sorghum and the impact these efforts had on greenbug populations. We concluded from this analysis that there was no way that greenbug-resistant wheat could have altered the greenbug population and caused new greenbug biotypes to develop. In sorghum, we found three examples out of eleven biotypes identified that could have been influenced by the release of greenbug-resistant sorghum hybrids. However, even in these cases no cause-and-effect relationship could be established. Based on a review of all available information, we concluded that greenbug biotypes are impacted little, if any, by the release of resistant wheat and sorghum. Therefore, plant breeders should not be concerned about the possible effects their resistant plants may have on the greenbug population, and should use the very best sources of resistance possible.

Technical Abstract: Future advances in wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench] resistance to greenbug [Schizaphis graminum (Rondani)] will likely come from the introduction of transgenes into high-performance cultivars. First-generation transgenes will likely be single genes that impart antibiosis traits to the host plant. This approach to pest management is incompatible with the time-honored interpretations of simulation models which imply that the deployment of single genes that impart antibiosis properties drives the development of new, virulent greenbug biotypes. To understand the relationship between the deployment of resistance genes and the development of new greenbug biotypes we examined the history of greenbug resistance efforts in wheat and sorghum and the corresponding impact these efforts had on the development of new biotypes. We concluded from this analysis that there was absolutely no relationship between the deployment of resistance genes in wheat and the development of new greenbug biotypes. For sorghum, only in the case of three of the eleven biotypes can there arguably be any linkage between the release of resistant sorghum hybrids and the development of new biotypes. Even in these three cases there were no clear cause-and-effect relationships established. Based on the analysis of these interactions, we propose that future host plant resistance efforts focus on the use of the most effective resistance genes, regardless of preconceived notions of what effect these genes may have on aphid population genetics.