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Title: MOLECULAR ANALYSIS OF SORGHUM RESISTANCE TO GREENBUG (HOMOPTERA: APHIDIDAE)

Author
item KATSAR, CATHERINE
item PATERSON, ANDREW - UNIVERSITY OF GEORGIA
item TEETES, GEORGE - TEXAS A&M UNIVERSITY
item PETERSON, GARY - TEXAS A&M UNIVERSITY

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The greenbug is a key insect pest of sorghum, causing more than $30 million in losses annually. Plant resistance has been used to reduce economic losses from a variety of agricultural pests, including the greenbug. However, the use of plant resistance as a pest management strategy is complicated by the greenbug's capacity to rapidly adapt to and overcome plant resistance. Resistance gene deployment strategies that increase the efficacy and durability of genes for greenbug resistance are needed. This research was undertaken to determine the degree of genetic variability within the U.S. sorghum gene pool through the use of DNA probes. DNA probes diagnostic of resistance to the four main greenbug strains damaging sorghum were identified and used to distinguish resistance genes from one another. Previously, resistance to greenbug was thought to be controlled by 1 or 2 genes. However, these experiments indicated that resistance to greenbug in sorghum is the result of the coordinated action of multiple genes. Breeding for multigenic resistance via traditional breeding methodology is difficult and often not possible. Biotechniques such as marker-assisted selection may help expedite the transfer of multiple genes into a single plant variety. This information betters our understanding of plant-pest interactions and yields more insight into breeding for resistance to greenbug.

Technical Abstract: Chromosomal regions of sorghum, Sorghum bicolor (L.) Moench, conferring resistance to greenbug, Schizaphis graminum (Rondani), biotypes C, E, I and K from 4 resistance sources were evaluated by RFLP analysis. At least 9 loci, dispersed on 8 linkage groups, were implicated as affecting levels of sorghum resistance to greenbug. The 9 loci were been named according to the genus of the host plant and greenbug. Most loci for resistance to greenbug were additive or incompletely dominant. Several digenic interactions were identified, and in each case, these non-additive interactions accounted for a greater portion of the resistance phenotype than did independently acting loci. One locus in 3 of the 4 sorghum crosses seemed to be responsible for a large portion of resistance to greenbug biotypes C and E. None of the loci identified was effective against all biotypes studied. Correspondingly, the RFLP results obtained indicate resistance from disparate sorghums may be a consequence of alleli variation at particular loci. To prove this, it will be necessary to fine map and clone from various sorghum sources genes for resistance to greenbug.