Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/30/2007
Publication Date: 11/1/2007
Citation: Wu, Y.Q., Huang, Y., Porter, D.R., Tauer, C.G., Hollaway, L. 2007. Identification of a major quantitative trait locus conditioning resistance to greenbug biotype E in sorghum PI 550610 using simple sequence repeat markers. Journal of Economic Entomology. 100(5):1672-1678. Interpretive Summary: Greenbug biotype E, one of the greenbug types, is a widespread pest throughout the sorghum growing area. Host-plant resistance has been used in many sorghum breeding programs for controlling the pest. The objective of this study was to develop DNA markers that are closely linked to the quantitative trait locus (QTL) of resistance to greenbug biotype E. Based on an genetic linkage map recently developed in the lab, we have identified several DNA (SSR) markers closely associated with a major QTL which conditions resistance to the greenbug. These DNA markers proved a useful tool for marker-assisted selection. The major QTL detected in this study and the tightly linked SSR markers will facilitate efficient development of resistant lines or hybrids in sorghum.
Technical Abstract: Greenbug, Schizaphis graminum Rondani, is highly diverse in nature and represents the most important pest insect of sorghum, Sorghum bicolor (L.) Moench in the Great Plains, USA. Biotype E is the most widespread and dominant type not only in sorghum and wheat fields, but also on many non-cultivated grass species. This study was to determine sorghum accession PI 550610 resistance to greenbug biotype E, to map the resistance QTLs using an established SSR linkage map, and to identify SSR markers closely linked to the major resistance QTLs. In greenhouse screening tests, seedlings of PI 550610 showed strong resistance to the greenbug at a level similar to resistant accession PI 550607. For QTL mapping, one F2 population containing 277 progeny and one population containing 233 F 2:3 families derived from Westland A line x PI 550610 were used to genotype 132 polymorphic SSR markers, and to phenotype seedling resistance to greenbug feeding. Phenotypic evaluation of sorghum seedling damage at 7, 12, 17 and 21 day post-infestation in the F 2:3 families revealed that resistance variation was normally distributed. Single marker analysis indicated 16 SSRs spread over five chromosomes were significant (P<0.05) for greenbug resistance. Composite interval and multiple interval mapping procedures indicated that a major QTL resided in the interval of 6.8 cM between SSR markers Xtxp358 and Xtxp289 on SBI-09. The results will be valuable in the development of new greenbug biotype E resistant sorghum cultivars and for the further characterization of major genes by map-based cloning.