Relationship between QTL for grain shape, grain weight, test weight, milling yield, and plant height in the spring wheat cross RL4452/ ‘AC Domain’


Cabral, A.L., Jordan, M.C., Larson, G., Somers, D.J., Humphreys, D.G., McCartney, C.A. (2018). Relationship between QTL for grain shape, grain weight, test weight, milling yield, and plant height in the spring wheat cross RL4452/ ‘AC Domain’. PLoS ONE, [online] 13(1),

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This study investigated the inheritance of seed shape in Canadian spring wheat using digital image analysis of grain samples from field trials. DNA markers were identified that were associated with seed shape characteristics such as seed length, seed width, seed size, seed roundness, etc. These results were compared to plant height in the field trials and grain measurements such as average grain weight, test weight (i.e. weight of a specific volume of grain), and flour yield (i.e. grain milling yield). Test weight affects grain transportation costs and a predictor of grain quality. Flour yield is affects the profitability of grain milling. Farmers prefer to grow short wheat varieties because they tend to remain standing in the field after heavy rains and winds, which protects grain quality and speeds harvest. We identified a strong association between two plant height reducing genes, grain weight, test weight, and seed shape as determined by digital image analysis. When plant height decreased, grain weight, test weight, and flour yield decreased. However, one of these height reducing genes had no detectable effect on test weight which should be beneficial in wheat breeding. A number of chromosome regions were identified that affected seed shape, which will provide additional opportunities in wheat variety development.


Kernel morphology characteristics of wheat are complex and quantitatively inherited. A doubled haploid (DH) population of the cross RL4452/‘AC Domain’ was used to study the genetic basis of seed shape. Quantitative trait loci (QTL) analyses were conducted on a total of 18 traits: 14 grain shape traits, flour yield (Fyd), and three agronomic traits (Plant height [Plht], 1000 Grain weight [Gwt], Test weight [Twt]), using data from trial locations at Glenlea, Brandon, and Morden in Manitoba, Canada, between 1999 and 2004. Kernel shape was studied through digital image analysis with an Acurum® grain analyzer. Plht, Gwt, Twt, Fyd, and grain shape QTL were correlated with each other and QTL analysis revealed that QTL for these traits often mapped to the same genetic locations. The most significant QTL for the grain shape traits were located on chromosomes 4B and 4D, each accounting for up to 24.4% and 53.3% of the total phenotypic variation, respectively. In addition, the most significant QTL for Plht, Gwt, and Twt were all detected on chromosome 4D at the Rht-D1 locus. Rht-D1b decreased Plht, Gwt, Twt, and kernel width relative to the Rht-D1a allele. A narrow genetic interval on chromosome 4B contained significant QTL for grain shape, Gwt, and Plht. The ‘AC Domain’ allele reduced Plht, Gwt, kernel length and width traits, but had no detectable effect on Twt. The data indicated that this variation was inconsistent with segregation at Rht-B1. Numerous QTL were identified that control these traits in this population.

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