Marker assisted introgression of strigaresistance into Farmer preferred Sorghum variety (ochuti)

Abstract

Sorghum is the second most important cereal crop in East Africa and the 4th most important cereal crop worldwide. Striga is the key biotic constraint of sorghum and millet in this region with reported yield reductions of up to 100%. Efforts to control Striga through agronomic practices such as mechanical weeding, use of cover crops and trap crops, use of chemicals, early planting have proved futile. Breeding for resistance using conventional methods has also been used with limited success. There have been advances in breeding with the utilization of molecular markers tightly linked to Striga resistance quantitative trait loci (QTL) in marker assisted selection (MAS). In this study, Striga resistance was introgressed from a resistant sorghum variety, N13 into a farmer preferred sorghum variety in Kenya, Ochuti. This was introgressed into two backcross line 11 and 34 of BC2F3 generation. Nine plants were identified having one QTL in BC2F3, these materials were advanced to BC3F1 through MAS and four plants were identified each having one QTL. The number of plants advanced from one generation into the next was considerably low. This may have been the reason why there were fewer plants being identified with the Striga resistance. On station trials were carried out in Alupe and Kibos which are the hot spots for Striga in Kenya. Area under Striga Number progressive Count (AUSNPC) was used as a measure of resistance. The backcross genotypes gave lower Striga scores as compared to the susceptible check Ochuti. Line 34 however performed better than line 11. Yield was negatively correlated with AUSNPC. This correlation however was of -0.4 to -0.5. Of interest were factors such as stand count, host damage rate, plant height and plant tillering which varied significantly between the genotypes and the locations.