SATURATION OF STRIGA RESISTANCE QTLS IN SORGHUM (SORGHUM BICOLOR (L.) MOENCH)

Sorghum bicolor (L.) Moench is the 5th most important cereal crop worldwide. The main biotic constraint to sorghum production is the parasitic weed Striga hermonthica (Del.) Benth. Striga is controlled using a combination of cultural, chemical and bio-control measures which cannot be afforded by farmers. A cost-effective alternative is to breed varieties resistant to Striga. Previous studies involving development of a sorghum genetic linkage map and mapping genomic regions contributing to Striga resistance have shown that resistance is a complex trait controlled by at least five QTLs. Genetic linkage maps provide an important genomic resource for understanding genome organization and evolution, and genetic basis of quantitative traits, and provide useful information for identifying and isolating genes responsible for a given phenotype. Therefore there is need for identification of molecular markers closely linked to these resistance QTLs to improve efficiency of marker-assisted selection (MAS) to accelerate development of Striga-resistant varieties. The aim of this study was to saturate genomic regions of Striga resistance QTLs using SSRs and DArT markers. QTL regions associated with Striga resistance were well saturated and confidence intervals for these QTLs were reduced: 27 SSR markers, two morphological markers, along with 175 DArTs markers were added to the previously mapped skeleton linkage map on linkage groups SBI-01, SBI-02, SBI-05a, SBI-05b and SBI-06 at intervals of 3-5 cM. Identified markers would be useful in marker-assisted selection for Introgression of this trait into susceptible sorghum cultivars. Addition of markers tightly linked to Striga resistance QTLs are not only advantageous for MAS application, but also assisted in saturating the sorghum linkage map.