International Crops Research Institute for the Semi-Arid Tropics
Abstract
An experiment was conducted during the 1997/99 cropping seasons, in Mali, France, to study the inheritance for resistance to head bug (Eurystylus oldi) of sorghum progenies using quantitative trait loci (QTL) maps. Cultivars Malisor 84-7 (resistant) and S 34 (susceptible) were used as parents. To build the sorghum genetic map, 345 restriction fragment length polymorphism (RFLP) probes in combination with 6 restriction enzymes (BamHI, DraI, EcoRI, EcoRV, HindIII and SstI) were screened for their ability to reveal polymorphism. Thousand kernel weight (TKW) and germination rate at grain maturity were measured. Head bug damage was assessed visually on a 1 to 9 scale on the infested part of the panicle (NOTF2). Among the 345 RFLP probes, 81 revealed polymorphism between the parents. Additionally, 14 microsatellite markers gave amplification products. The genetic map based on Malisor 84-7 × S 34 includes 13 linkage groups (LGs) covering a total distance of 1160 cM. Three significant and 7 putative QTLs were detected. One QTL for TKW reduction that accounted for 13% of the phenotypic variation was detected on LG C2. For this QTL, resistance is conditioned by the Malisor 84-7 allele and is dominant. Two QTLs were detected on LG D and LG E for visual damage score under natural head bug infestation, explaining 16 and 26% of the phenotypic variation for this trait, respectively. Resistance from the QTL on LG D is conditioned by the S 34 allele, whereas resistance from the QTL on LG E is provided by the Malisor 84-7 allele. In both cases, resistance is recessive. No significant QTLs were detected for NOTF2 and germination rate, but co-localization of 2 putative QTLs for these traits was observed on LG G2, and in both cases, resistance is conditioned by the S 34 allele
