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Distribution of TaCol5 in tetraploid and hexaploid wheat germplasm

Tapia, Jennifer
Grain number per spike is one of the critical components of grain yield, and modulating the spike architecture has been proposed as a major strategy for improving the yield potential of future wheat varieties. TaCol-B5, the dominant allele of the wheat Constans-like gene 5 on chromosome 7B, has been found to modify spike architecture and increase the number of spikelets per spike and spikes per plant in common wheat. Field trial experiments of transgenic plants overexpressing the dominant TaCol-B5 allele showed a 12% increase in yield, suggesting its potential use in wheat breeding. TaCol-B5 is a rare allele in only 2% of the global modern wheat collection. However, in our initial germplasm screening, this allele was absent in cultivars from several wheat-producing countries. Thus, it is critical to identify the TaCol-B5 allele in the locally adapted germplasm of those regions to use it in the breeding program as well as identify more alleles that can provide an opportunity to improve crop productivity. We developed a Kompetitive Allele Specific PCR (KASP) marker for detecting the Single Nucleotide Polymorphism (SNP), which causes the critical Ser²⁶⁹/Gly²⁶⁹ substitution between TaCol-B5 and Tacol-B5 proteins. We used the KASP marker to screen over 100 Triticum turgidum and 3,000 Triticum aestivum genetic materials collected from the global wheat accessions. These accessions are mainly composed of landraces and cultivars in different parts of the world. Among these accessions, we identified 106 carrying the TaCol-B5 allele, which was distributed across 23 countries, with a higher incidence observed in Africa and America. The prevalence of the dominant allele, TaCol-B5, was found to be higher in spring wheat when compared to winter wheat, and it was also more present in tetraploid wheat than in hexaploid wheat. Further studies are required to determine how TaCol-B5 is associated with any phenotypes in the wheat germplasm.