Genetic Determinants of Grain Yield in Wheat Revealed By Assimilate Partitioning

Increasing the sink strength of the spike is crucial for wheat breeding, so manipulating assimilate partitioning is an important strategy for improving grain yield of wheat. We carried out cluster analysis of 54 yield-related traits from competing plant parts of wheat at harvest to investigate their phenotypic relationship. Competing plant parts or organs include pairs of: tiller:main shoot, spike: stem, spikelets within spikes, florets within spikelets, spike chaff-grains. Generally, we found that traits obtained from the same pair of competing plant organs show higher similarity (e.g. 5 traits measured for spike and stem) and clustered together. By using genome-wide association mapping (GWAS), we mapped these 54 traits in 200 genotypes to genetically dissect assimilate partitioning between competing plant parts of wheat. For example, the GWAS results obtained for tiller number, tiller dry weight (DW), main shoot DW and ratio of tiller DW/main shoot DW were used to genetically demonstrate to what portion assimilates were allocated between tiller and main shoot. Overall, GWAS results showed that traits belonging to the same pair of competing plant organs often shared the same quantitative loci (QTL). In addition, we found a large percentage of QTLs that were shared among the five competing pairs mentioned above, but more QTLs were only specific for one pair of competing plant parts. GWAS results further suggested that VRN, Ppd, FT, Rht, and Q genes are involved in the regulation of assimilate distribution between competing plant parts.