Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2008
Publication Date: 4/15/2008
Citation: Wu, Y.Q., Huang, Y. 2008. Molecular mapping of QTLs for resistance to the greenbug Schizaphis graminum (Rondani) in Sorghum bicolor (Moench). Theoretical and Applied Genetics. 117(1):117-124. Interpretive Summary: Greenbug, particularly biotype I, has been the most damaging insect pest of sorghum and the pest success in the greenbug management were depended on the crop improvement using resistant sorghum germplasm. Thus, there is a strong demand for development of DNA markers for sorghum, which enable us to use marker-assisted selection to facilitate the sorghum breeding program. In this study, ARS scientists developed a genotyping method for sorghum and identified several DNA (SSR) markers that are closely linked to the quantitative trait locus (QTL) of resistance to greenbug biotype I. These DNA markers proved a useful tool for marker-assisted selection for greenbug resistance in sorghum. This work is not only important for the ARS scientists but should make it easier for public as well as private sorghum researchers working on sorghum breeding to implement marker-assisted breeding.
Technical Abstract: Sorghum is a worldwide important cereal crop and widely cultivated for grain and forage production. Greenbug, Schizaphis graminum (Rondani) is one of the major insect pests of sorghum and can cause serious damage to sorghum plants, particularly in the US Great Plains. Identification of chromosomal regions responsible for greenbug resistance will facilitate both map-based cloning and marker-assisted breeding. Thus, a mapping experiment was conducted to dissect sorghum genetic resistance to greenbug biotype I into genomic regions. Two hundred and seventy-seven (277) F2 progeny and their F2:3 families from a cross between Westland A line (susceptible parent) and PI550610 (resistant parent) combined with 118 polymorphic simple sequence repeat (SSR) markers were used to map the greenbug resistance QTLs. Composite interval mapping (CIM) and multiple interval mapping (MIM) revealed two QTLs on sorghum chromosome nine (SBI-09) consistently conditioned the resistance of host plant to the greenbug. The two QTLs were designated as QSsgr-09-01 (major QTL) and QSsgr-09-02 (minor QTL), accounting for approximately 55–80%, and 1–6% of the phenotypic variation for the resistance to greenbug feeding, respectively. These resistance QTLs appeared to have additive and partially dominant effects. The markers Xtxp358, Xtxp289, Xtxp67, and Xtxp230 closely flanked the respective QTLs, and can be used in high-throughput marker-assisted selections (MAS) for breeding new resistant parents and producing commercial hybrids.