Genotypic variations for photoassimilates partitioning to the grains during early development of endosperm in wheat: Association with grain weight

There is little information on genotype variations for photoassimilates partitioning to the grains during early development of endosperm in wheat. Eighty-one wheat cultivars were examined in the Moghan region of Iran during 2010-2011 and 2013-2014 growing seasons. The amount and rate of photoassimilates partitioning to the grains were measured in the tested cultivars during anthesis-16 days after anthesis (DAA) and 16 DAA-maturity phases using time dependent changes in spike dry weight. There were substantial genetic variations in the amount and rate of partitioned photoassimilates to the grains during anthesis-16 DAA and 16 DAA-maturity phases. Part of these variations could be attributed to cultivars differences in anthesis time, spike dry weight at anthesis, and grain number per spike. Taking them into accounts, there were some cultivars but they differed in partitioned photoassimilates toward grains during anthesis-16 DAA and 16 DAA-maturity phases, further supporting the idea that breeding for photoassimilates partitioning during these phases was a possibility. The results yielded for 2013-2014 showed that there is close association between photoassimilates partitioning to the grain during anthesis-16 DAA and individual grain weight. The results suggest that in case wheat breeders could improve photoassimilates partitioning to the grains during anthesis-16 DAA, it would result in increased grain size and weight in the wheat.