Increased drought tolerance and wider adaptability of qDTY 12.1 conferred by its interaction with qDTY 2.3 and qDTY 3.2

The genetic basis of high grain yield under reproductive-stage drought was studied using an F3-derived population generated from the cross of upland rice (Oryza sativa L.) cultivars Vandana and Way Rarem. Contributed by the susceptible parent Way Rarem, locus qDTY 12.1 was hypothesized to have interaction with loci from the Vandana genome to enhance the grain yield of tolerant line Vandana under drought. A test of the digenic interaction of qDTY 12.1 showed that two loci, qDTY 2.3 on chromosome 2 and qDTY 3.2 on chromosome 3, significantly increased the yield and harvest index of qDTY 12.1 -positive lines under severe upland and lowland drought conditions. qDTY 2.3 and qDTY 3.2 , in interaction with qDTY 12.1 , reduced days to flowering and plant height of qDTY 12.1 -positive lines under stress and non-stress conditions in upland. BC2F3-derived backcross inbred lines (BILs) were used to validate these results and identify new quantitative trait loci. Lines with qDTY 2.3 and qDTY 12.1 showed increased yield over Way Rarem under severe and moderate stress conditions, in upland. IR84996-50-4-B-4, a selection from one of the BILs, yielded more than the popular drought-tolerant cultivars Apo, UPLRi7, and IR74371-54-1-1 under severe stress conditions. Introgressed segments from Vandana also improved yield under non-stress conditions. The results indicate that digenic interactions can explain the genetic control of complex quantitative traits such as grain yield under drought, and a few interacting loci with large effects on grain yield or yield-related traits may enhance drought response across a wide range of genetic backgrounds and environments when introgressed together.

本研究以旱稻（Oryza sativa L.）品种Vandana与Way Rarem杂交获得的F3衍生群体为试验材料，探究了生殖生长期干旱胁迫下高籽粒产量的遗传基础。由感旱亲本Way Rarem所贡献的位点qDTY 12.1，被推测可与Vandana基因组内的其他位点产生互作，从而提升耐旱品种Vandana在干旱胁迫条件下的籽粒产量。针对qDTY 12.1的双基因互作验证结果显示，第2染色体上的qDTY 2.3与第3染色体上的qDTY 3.2这两个位点，可在重度旱作与水田干旱胁迫条件下，显著提升携带qDTY 12.1的株系的籽粒产量与收获指数。在旱作环境的胁迫与非胁迫条件下，qDTY 2.3、qDTY 3.2与qDTY 12.1共同形成的互作体系，可缩短携带qDTY 12.1株系的开花天数并降低其株高。研究采用BC2F3衍生回交自交系（backcross inbred lines, BILs）对上述结果进行验证，并挖掘新的数量性状位点（quantitative trait loci, QTLs）。在旱作环境的重度与中度干旱胁迫条件下，同时携带qDTY 2.3与qDTY 12.1的株系，其籽粒产量相较于Way Rarem显著提升。其中一份源自回交自交系的选育材料IR84996-50-4-B-4，在重度干旱胁迫条件下的籽粒产量高于主流耐旱品种Apo、UPLRi7以及IR74371-54-1-1。源自Vandana的染色体导入片段在非胁迫条件下同样可提升籽粒产量。本研究结果表明，双基因互作可解释干旱胁迫下籽粒产量这类复杂数量性状的遗传调控机制；若将少数对籽粒产量或产量相关性状具有显著效应的互作位点共同导入，即可在广泛的遗传背景与环境条件下提升作物的干旱响应能力。