Evaluation of grain dimension and weight using backcross recombinant inbred lines (BRILs) between wild and domesticated emmer wheat

Authors: MIYAZAKI, YUKI - Kobe University; NGOC, PHAM MINH - Kobe University; Liberatore, Katie; Kianian, Shahryar; VLADUTU, CRISTIAN IOAN - Kobe University; MORI, NAOKI - Kobe University

Submitted to: Crop Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2017
Publication Date: 11/1/2017
Citation: Miyazaki, Y., Ngoc, P., Liberatore, K.L., Kianian, S., Vladutu, C., Mori, N. 2017. Evaluation of grain dimension and weight using backcross recombinant inbred lines (BRILs) between wild and domesticated emmer wheat. Crop Research. 62:31-36.

Interpretive Summary: We aim to understand the early steps of wheat domestication using a valuable population derived from a cross between domesticated and wild emmer wheat (the direct ancestor of modern tetraploid durum/pasta wheat). Early human selection focused on desirable traits such as reduced shattering (keeping grains from falling off the plant too early), providing easy access to grains (free-threshing), and improving grain yield. However, this process decreased the available genetic variation in populations, which had inadvertent consequences such as reduced disease resistance. With a better understanding of the domestication process, we can improve traits of interest in modern wheat cultivars. Many phenotypic differences are seen between the domesticated and wild forms of emmer wheat including plant stature (e.g. height, tiller number), inflorescence characteristics (e.g flower number, arrangement, size, and shattering), grain characteristics (e.g. free-threshing vs. hulled, size, and shape), and disease response (e.g. susceptibility to cereal rusts). This paper focuses on detailed characterization of grain weight and grain dimensions (height, width, and length) in a valuable set of backcross recombinant inbred lines. These traits are directly related to plant fitness and overall grain yield.

Technical 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 > 0.8) 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 elongated to rounded grain shape was advantageous in the early stage of wheat domestication.