Abstract
Emmer wheat (Triticum turgidum ssp. dicoccum) represents the primitive situation in the domestication of AABB tetraploid wheat. As one of the earliest domesticated grain species, it was a principal crop in the development and spread of Neolithic agriculture in the Old World. Grain weight and dimension (size and shape) have been major targets of selection since the beginning of agriculture. To clarify the genetic mechanism (s) affecting grain weight and dimension, we utilized 92 backcross recombinant inbred lines (BRILs) derived from a cross between a domesticated emmer wheat and a wild emmer wheat (T. turgidum ssp. dicoccoides). Weight, grain dimensions (width, length, and height), ratios of dimensions (shape), and correlations between traits were evaluated for two consecutive years, 2015 and 2016. All grain dimension components showed strong positive correlation with grain weight. Among them, the highest correlation coefficient (r=0.822) was observed between the grain weight and width, suggesting that grain width was a main target of selection for increasing grain weight during emmer wheat domestication. In addition, both the grain length/width ratio and the length/height ratio showed negative correlation with grain weight. These results indicate that a transition from slender to round grain shape was advantageous in the early stage of wheat domestication.
