Identification of a microsatellite on chromosomes 6B and a STS on 7D of bread wheat showing an association with preharvest sprouting tolerance

In bread wheat, the transfer of tolerance to preharvest sprouting (PI-IS) t hat is associated with genotypes having red kernel colour to genotypes with amber kernels is difficult using conventional methods of plant breeding. T he study here was undertaken to identify DNA markers linked with tolerance to PI-IS as these would allow indirect marker-assisted selection of PI-IS-t olerant genotypes with amber kernels. For this purpose, a set of 100 recomb inant inbred lines (RILs) was developed using a cross between a PI-IS-toler ant genotype, SPR8198, with red kernels and a PI-IS-susceptible cultivar,'H D2329', with white kernels. The two parents were analysed with 232 STMS (se quence-tagged microsatellite site) and 138 STS (sequence-tagged site) prime r pairs. A total of 300 (167 STMSs and 133 STSs) primer pairs proved functi onal by giving scorable PCR products. Of these, 57 (34%) STMS and 30 (23%) STS primer pairs detected reproducible polymorphism between the parent geno types. Using these primer pairs, we carried out bulked segregant analysis o n two bulked DNAs, one obtained by pooling DNA from 5 PHS-tolerant RILs and the other similarly derived by pooling DNA from 5 PHS-susceptible RILs. Tw o molecular markers, I STMS primer pair for the locus wmc104 and a STS prim er pair for the locus MST101. showed apparent linkage with tolerance to PI- IS. This was confirmed following selective genotyping of individual RILs in cluded in the bulks. Chi-square contingency tests for independence were con ducted on the cosegregation data collected on 100 RILs involving each of th e two molecular markers (wmc104 and MST101) and PHS. The tests revealed a s trong association between each of the markers and tolerance to PHS, Using n ullisomic-tetrasomic lines, we were able to assign wmc104 and MST101 to chr omosomes GB and 7D, respectively. The results also indicated that the toler ance to Pi-IS in SPR8198 is perhaps governed by two genes (linked with two molecular markers) exhibiting complementary interaction.