Molecular Mapping of Sorghum Genes Expressing Tolerance to Damage by Greenbug (Homoptera: Aphididae)

Abstract

Genetic linkage maps are fundamental for the localization of genes conferring tolerance to greenbug, Schizaphis graminum (Rondani), feeding damage in sorghum, Sorghum bicolor (L.) Moench. Thirteen linkage groups (LGs) containing 60 simple sequence repeat (SSR) loci were mapped by using a set of sorghum recombinant inbred lines (RILs) obtained from the cross '96-4121' (greenbug-tolerant parent) x Redlan (greenbug-susceptible parent). The LG spanned a distance of 603.5 cM, with the number of loci per LG varying from 2 to 14. Seventeen additional SSR loci were unlinked at a log of odds value of 3.0. Based on chlorophyll loss occurring after greenbug feeding, visual damage ratings, and soil plant analysis development (SPAD), chlorophyll-loss indices were recorded for each RIL and for the parents used in the cross. Composite-interval mapping identified three quantitative trait loci (QTLs) associated with biotype I and five QTLs associated with biotype K. The amount of phenotypic variation explained by these QTLs ranged from 9 to 19.6%. The identification of QTLs that influence greenbug tolerance will not only facilitate the use of marker-assisted selection in sorghum breeding programs but also will provide a solid foundation for detailed characterization of individual loci implicated in greenbug tolerance in sorghum.

Identification and confirmation of greenbug resistance loci in an advanced mapping population of sorghum

“…Out of the nine sorghum loci detected for all four biotypes (C, E, I and K), three loci conferred resistance for biotype I. These loci were located on SBI05(LGH), SBI06(LG D), SBI07(LGJ) for biotype I and one loci on SBI09(LG G) accounted for resistance to biotypes C and E. Nagaraj et al (2005) identified three QTLs for biotype I resistance and five QTLs for biotype K resistance. For the biotype I, there were two QTLs present on chromosomes SBI01(LG5) and one on SBI04 (LG 3).…”

“…Furthermore, linkage maps allow researchers to identify and tag significant genomic regions affecting traits such as insect resistance and disease resistance (Mohan et al 1997; Yencho et al 2000; Reddy et al 2008). Several linkage maps developed in sorghum have facilitated tagging of greenbug resistance (Agrama et al 2002; Katsar et al 2002; Nagaraj et al 2005; Wu et al 2007; Wu & Huang 2008; Punnuri et al 2013). The alleles accounting for sorghum biotype I resistance have been documented through quantitative trait loci (QTL) studies, which support the involvement of multiple regions of the sorghum genome in greenbug resistance (Agrama et al 2002; Katsar et al 2002; Nagaraj et al 2005; Wu & Huang 2008; Punnuri et al 2013).…”

Application of Markers Assisted Selection for Striga Hermonthica Resistance on Sorghum (Sorghum bicolor (L.) Moench

“…Molecular markers have been used to identify and characterize QTL associated with many different traits in sorghum, including plant height and maturity [57], traits associated with domestication [58], disease resistance, insect resistance [59], and drought tolerance. Identification of QTL often leads to further investigations to identify the underlying gene or genes through fine mapping and map-based cloning.…”

Correlation study of traits associated with shoot fly resistance in recombinant inbred lines (RILs) population of sorghum [Sorghum bicolor (L.) Moench]

“…However, concerted efforts toward breeding for shoot fly resistance have resulted in some progress, and a number of genotypes with resistance to shoot fly have been identified (Sharma et al, 2003). The economic impact of shoot fly, the improvement of genetic resistance to this pest is one of the major goals of sorghum breeding programs in India (Nagaraj et al, 2005). The shoot fly resistance in sorghum appears to be a complex trait and depends upon the interaction of a number of component traits, which finally sum up in the expression of shoot fly resistance (Dhillon, 2005).…”