Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2005
Publication Date: 2/1/2006
Citation: Wu, Y., Huang, Y., Tauer, C.G., Porter, D.R. 2006. Genetic diversity of sorghum accessions resistant to greenbugs as assessed with AFLP markers. Genome. 49:143-149._handler_=HandleInitialGet&journal=gen&volume=49&calyLang=eng&articleFile=g05-095.pdf. Interpretive Summary: The use of pest-resistant cultivars and hybrids in an integrated pest management program is the most economical and environmentally sound method to reduce the negative economic impact of insect pests, such as greenbug, which has been a serious insect pest on small grains such as sorghum, wheat and barley. Continuous improvement in defense ability of sorghum is dependent on the availability of the diverse genetic resources and judicious use of effective sources of resistance. Indeed, sorghum has a rich resource of genetic diversity that can be used for plant breeding for resistance to insect pests. However, those genetic materials are of little value unless they are evaluated, documented and utilized. In this study, we used AFLP markers to quantify the genetic relatedness of different sorghum accessions resistant to greenbug biotype I, which is currently the most virulent form to grain sorghum. The data of DNA marker analysis indicated that relatively diverse greenbug biotype I resistant germplasm exists in the sorghum collection. These results suggest that the resistance from different geographic regions may be controlled by different loci or different alleles within the same locus. Therefore, integrating the genetic resistance from different sources and especially combining African and Asian genetic resistance into sorghum breeding programs should increase the genetic diversity of the greenbug resistance cultivars in US sorghum.
Technical Abstract: Sorghum, Sorghum bicolor (L.) Moench, is the fifth most important cereal crop grown worldwide and the fourth in the US. Greenbug, Schizaphis graminum Rondani, is a major insect pest of sorghum with several biotypes reported. Greenbug biotype I is prevalent attackers and most virulent on sorghum plants. Breeding for resistance is an effective way to control of greenbug damage. A successful breeding program relies in part upon a clear understanding of the origins of the diverse sources of breeding materials. However, the genetic diversity and relatedness among the greenbug biotype I resistant accessions collected from different geographic origins have not been well characterized, although a rich germplasm collection is available. In this study, twenty six sorghum accessions from twelve countries were evaluated for both resistance to greenbug biotype I and genetic diversity using florescence labeled amplified fragment length polymorphism (AFLP). Twenty six AFLP primer combinations produced 819 polymorphic fragments indicating a relatively high level of polymorphism among the accessions. Genetic similarity coefficients among the sorghum accessions ranged from 0.69 to 0.90. Cluster and principal component analyses indicated that there were two major groups based on polymorphic bands. This study has allowed the identification of new genetic sources of sorghum with substantial genetic variation and distinct groupings of resistant accessions that have the potential for the development of durable greenbug resistant sorghum.