Identification of a microsatellite on chromosomes 6B and a STS on 7D of bread wheat showing an association with preharvest sprouting tolerance
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In bread wheat, the transfer of tolerance to preharvest sprouting (PHS) that is associated with genotypes having red kernel colour to genotypes with amber kernels is difficult using conventional methods of plant breeding. The study here was undertaken to identify DNA markers linked with tolerance to PHS as these would allow indirect marker-assisted selection of PHS-tolerant genotypes with amber kernels. For this purpose, a set of 100 recombinant inbred lines (RILs) was developed using a cross between a PHS-tolerant genotype, SPR8198, with red kernels and a PHS-susceptible cultivar, ‘HD2329’, with white kernels. The two parents were analysed with 232 STMS (sequence-tagged microsatellite site) and 138 STS (sequence-tagged site) primer pairs. A total of 300 (167 STMSs and 133 STSs) primer pairs proved functional by giving scorable PCR products. Of these, 57 (34%) STMS and 30 (23%) STS primer pairs detected reproducible polymorphism between the parent genotypes. Using these primer pairs, we carried out bulked segregant analysis on 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. Two molecular markers, 1 STMS primer pair for the locus wmc104 anda STS primer pair for the locus MST101, showed apparent linkage with tolerance to PHS. This was confirmed following selective genotyping of individual RILs included in the bulks. Chi-square contingency tests for independence were conducted on the cosegregation data collected on 100 RILs involving each of the two molecular markers (wmc104 and MST101) and PHS. The tests revealed a strong association between each of the markers and tolerance to PHS. Using nullisomic-tetrasomic lines, we were able to assign wmc104 and MST101 to chromosomes 6B and 7D, respectively. The results also indicated that the tolerance to PHS in SPR8198 is perhaps governed by two genes (linked with two molecular markers) exhibiting complementary interaction.
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