Manipulating assimilate availability provides insight into the genes controlling grain size in sorghum |
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Authors: | Yongfu Tao Yuri Trusov Xianrong Zhao Xuemin Wang Alan W Cruickshank Colleen Hunt Erik J van Oosterom Adrian Hathorn Guoquan Liu Ian D Godwin Jose R Botella Emma S Mace David R Jordan |
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Institution: | 1. Queensland Alliance for Agriculture and Food Innovation (QAAFI), Hermitage Research Facility, The University of Queensland, Warwick, Qld, 4370 Australia;2. School of Agriculture and Food Sciences, The University of Queensland, Brisbane, Qld, 4072 Australia;3. Department of Agriculture and Fisheries (DAF), Agri-Science Queensland, Hermitage Research Facility, Warwick, Qld, 4370 Australia;4. Queensland Alliance for Agriculture and Food Innovation (QAAFI), The University of Queensland, Brisbane, Qld, 4072 Australia |
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Abstract: | Variation in grain size, a major determinant of grain yield and quality in cereal crops, is determined by both the plant’s genetic potential and the available assimilate to fill the grain in the absence of stress. This study investigated grain size variation in response to variation in assimilate supply in sorghum using a diversity panel (n = 837) and a backcross-nested association mapping population (n = 1421) across four experiments. To explore the effects of genetic potential and assimilate availability on grain size, the top half of selected panicles was removed at anthesis. Results showed substantial variation in five grain size parameters with high heritability. Artificial reduction in grain number resulted in a general increase in grain weight, with the extent of the increase varying across genotypes. Genome-wide association studies identified 44 grain size quantitative trait locus (QTL) that were likely to act on assimilate availability and 50 QTL that were likely to act on genetic potential. This finding was further supported by functional enrichment analysis and co-location analysis with known grain number QTL and candidate genes. RNA interference and overexpression experiments were conducted to validate the function of one of the identified gene, SbDEP1, showing that SbDEP1 positively regulates grain number and negatively regulates grain size by controlling primary branching in sorghum. Haplotype analysis of SbDEP1 suggested a possible role in racial differentiation. The enhanced understanding of grain size variation in relation to assimilate availability presented in this study will benefit sorghum improvement and have implications for other cereal crops. |
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Keywords: | sorghum grain size QTL genetic potential assimilate availability grain number crop improvement |
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