Identification of quantitative trait loci for resistance to shoot fly in sorghum [Sorghum bicolor (L.) Moench]

Abstract

The shoot fly is one of the most destructive insect pests of sorghum at the seedling stage. Deployment of cultivars with improved shoot fly resistance would be facilitated by the use of molecular markers linked to QTL. The objective of this study was to dissect the genetic basis of resistance into QTL, using replicated phenotypic data sets obtained from four test environments, and a 162 microsatellite marker-based linkage map constructed using 168 RILs of the cross 296B (susceptible) x IS18551 (resistant). Considering five component traits and four environments, a total of 29 QTL were detected by multiple QTL mapping (MQM) viz., four each for leaf glossiness and seedling vigor, seven for oviposition, six for deadhearts, two for adaxial trichome density and six for abaxial trichome density. The LOD and R (2) (%) values of QTL ranged from 2.6 to 15.0 and 5.0 to 33%, respectively. For most of the QTL, IS18551 contributed resistance alleles; however, at six QTL, alleles from 296B also contributed to resistance. QTL of the related component traits were co-localized, suggesting pleiotropy or tight linkage of genes. The new morphological marker Trit for trichome type was associated with the major QTL for component traits of resistance. Interestingly, QTL identified in this study correspond to QTL/genes for insect resistance at the syntenic maize genomic regions, suggesting the conservation of insect resistance loci between these crops. For majority of the QTL, possible candidate genes lie within or very near the ascribed confidence intervals in sorghum. Finally, the QTL identified in the study should provide a foundation for marker-assisted selection (MAS) programs for improving shoot fly resistance in sorghum.

Recent Advances in Sorghum Genetic Enhancement Research at ICRISAT

“…The need for having shoot fly resistance in both female and male parents for producing shoot fly resistant high yielding hybrids was demonstrated [27]. In sorghum, quantitative trait loci (QTL) governing various component traits contributing for shoot fly resistance have been identified and mapped in the parent IS 18551 [28] and CT Hash, ICRISAT, Personal communication). The QTL have been transferred to two cultivated backgrounds namely, BTx623 and 296B at ICRISAT (Hash CT, ICRISAT, Personal communication).…”

Sorghum

“…Consequently, pests and pathogens of reproductive growth are much less important. If grain is important, then breeding for resistance to midge and shoot fly are important because these pests reduce grain yield [100][101][102][103].…”

- Energy Savings by Adopting Precision Agriculture in Rural Usa

“…Several studies have implied that pesticides and other agricultural chemicals can affect the epicuticular lipid composition, reducing the ability of the crop to resist insect attack [92,93]. To date, multiple genes have been identified for the gloss leaf trait in cabbage, and 18 loci have been mapped using mutants of maize and sorghum [88,94,95]. Although leaf waxes can vary with crop age and be influenced by the production environment, they provide an avenue for breeders to develop varieties that are suited for specific agroecosystems while improving pest resistance, yield loss, and overall sustainability of low-input systems.…”

“…In addition, trichome morphology has also been shown to play an important role in limiting pest establishment within a crop. Sorghum genotypes with unicellular pointed trichomes were less susceptible to insect damage than genotypes possessing bicellular blunt trichomes [94]. Satish et al [94] identified eight QTLs (quantitative trait loci) for trichome density using sorghum, two of which were specific for upper leaf surface, the remaining six specific to the lower leaf surface.…”

“…Sorghum genotypes with unicellular pointed trichomes were less susceptible to insect damage than genotypes possessing bicellular blunt trichomes [94]. Satish et al [94] identified eight QTLs (quantitative trait loci) for trichome density using sorghum, two of which were specific for upper leaf surface, the remaining six specific to the lower leaf surface. Four QTL were identified in maize for trichome density by Lauter et al [98], several of which were syntenic to those determined in sorghum.…”