Introgression of String Resistance Genes into an Eritrean Sorghum Variety through Marker Assisted Breeding
Tadesse, Yohannes H
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Sorghum [S. bicolor (L.) Moench] is the most important cereal crop in Eritrea grown over 200,000 hectare annually. However, the parasitic weed Striga hermonthica is the major biotic constraint to production causing up to 50% yield loss. Striga is a highly variable obligate parasite, with the ability to adapt to various hosts and environments, which makes breeding for resistance against it using conventional approaches, difficult. The aim of this study was to identify back-cross genotypes with Striga resistance generated from a cross between a resistant source, N13 and a susceptible local variety, Hugurtay through marker assisted selection (MAS) followed by evaluation of the resistance in artificially Striga infested fields. A total of 341 BC3F1 progenies from a population between crosses of Hugurtay and N13 were genotyped for the presence of Striga resistance quantitative trait loci (QTL) using 11 SSR markers. Eighty four lines of BC3F1 which were found to have introgressed one to four Striga resistance QTL were selected for background screening and field evaluation in an artificially Striga infested field at Alupe, Kenya during April 2012 - August 2012 season. From this population, 30 genotypes with one to four Striga resistance QTL that also showed better performance in the field during April 2012 - August 2012 season were further evaluated again under artificial Striga infestation at Alupe and Kibos substations during September 2012 - February 2013 season using an alpha lattice design of three replications. The parental genotypes, N13 and Hugurtay were included as checks. Genotyping results revealed that 216 samples had up to 4 Striga resistance QTL introgressed and 77.4% of the 84 progenies genotyped for background screening had 52 -72% recurrent parent genome recovery at the SSR loci analysed. Field results also showed that majority of the genotypes with introgressed Striga resistance performed better than the recurrent parent. Genotypes L2P3-B, L1P5-A and L2P5P35 supported the lowest number of Striga plants and gave the highest grain yields. This study demonstrated that MAS is a useful tool for enhancement, expediency and precision for sorghum improvement for Striga resistance.