Swamy B P Mallikarjuna, Shamsudin Noraziyah Abd Aziz, Rahman Site Noorzuraini Abd, Mauleon Ramil, Ratnam Wickneswari, Sta Cruz Ma Teressa, Kumar Arvind
Plant Breeding Division, International Rice Research Institute (IRRI), DAPO Box 7777, Metro Manila, Philippines.
Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600, Bangi, Selangor, Malaysia.
Rice (N Y). 2017 Dec;10(1):21. doi: 10.1186/s12284-017-0161-6. Epub 2017 May 18.
The identification and introgression of major-effect QTLs for grain yield under drought are some of the best and well-proven approaches for improving the drought tolerance of rice varieties. In the present study, we characterized Malaysian rice germplasm for yield and yield-related traits and identified significant trait marker associations by structured association mapping.
The drought screening was successful in screening germplasm with a yield reduction of up to 60% and heritability for grain yield under drought was up to 78%. There was a wider phenotypic and molecular diversity within the panel, indicating the suitability of the population for quantitative trait loci (QTL) mapping. Structure analyses clearly grouped the accessions into three subgroups with admixtures. Linkage disequilibrium (LD) analysis revealed that LD decreased with an increase in distance between marker pairs and the LD decay varied from 5-20 cM. The Mixed Linear model-based structured association mapping identified 80 marker trait associations (MTA) for grain yield (GY), plant height (PH) and days to flowering (DTF). Seven MTA were identified for GY under drought stress, four of these MTA were consistently identified in at least two of the three analyses. Most of these MTA identified were on chromosomes 2, 5, 10, 11 and 12, and their phenotypic variance (PV) varied from 5% to 19%. The in silico analysis of drought QTL regions revealed the association of several drought-responsive genes conferring drought tolerance. The major-effect QTLs are useful in marker-assisted QTL pyramiding to improve drought tolerance.
The results have clearly shown that structured association mapping is one of the feasible options to identify major-effect QTLs for drought tolerance-related traits in rice.
鉴定和导入干旱条件下影响水稻产量的主效QTL是提高水稻品种耐旱性的一些最佳且已得到充分验证的方法。在本研究中，我们对马来西亚水稻种质的产量及产量相关性状进行了表征，并通过结构化关联作图鉴定了显著的性状-标记关联。
干旱筛选成功筛选出了产量降低高达60%的种质，干旱条件下水稻产量的遗传力高达78%。该群体内存在更广泛的表型和分子多样性，表明该群体适用于数量性状位点（QTL）定位。结构分析清楚地将这些种质分为三个带有混合类型的亚组。连锁不平衡（LD）分析表明，LD随着标记对之间距离的增加而降低，LD衰减范围为5-20 cM。基于混合线性模型的结构化关联作图鉴定出了80个与籽粒产量（GY）、株高（PH）和抽穗天数（DTF）相关的标记-性状关联（MTA）。在干旱胁迫下鉴定出了7个与GY相关的MTA，其中4个MTA在三项分析中的至少两项中被一致鉴定出来。鉴定出的这些MTA大多位于第2、5、10、11和12号染色体上，它们的表型变异（PV）在5%至19%之间。对干旱QTL区域的电子分析揭示了几个赋予耐旱性的干旱响应基因之间的关联。主效QTL在标记辅助QTL聚合中有助于提高耐旱性。
结果清楚地表明，结构化关联作图是鉴定水稻耐旱相关性状主效QTL的可行方法之一。
