干旱是影响作物产量的主要非生物胁迫。定位水稻的数量性状基因座(QTLs)和挖掘耐旱性基因对于识别基因功能和分子育种靶标具有重要意义。这里,我们使用来自Jileng1(干旱敏感)和Milyang23(耐旱性)的重组自交系种群进行了耐旱性的连锁分析。超高密度遗传图谱,以前由我们的研究小组使用全基因组测序的基因型数据构建,与2017-2019年田间干旱胁迫条件下种植的水稻的表型数据结合使用。确定了39个与叶片滚动指数和叶片枯萎程度相关的QTL,和QTL在除6号、10号和11号染色体以外的所有染色体上发现。在2017年干旱胁迫32天和46天后检测到qLWD4-1,解释了7.07-8.19%的表型变异。两个基因座,qLRI2-2和qLWD4-2是在2018年干旱胁迫29、42和57天后鉴定的。这些基因座解释了表型变异的10.59-17.04%和5.14-5.71%,分别。QTL区间内有281个基因。通过基因功能注释和表达分析,两个候选基因,Os04g0574600和OsCHR731被发现。定量逆转录PCR分析表明,这些基因在干旱胁迫下的表达水平明显高于正常,表明积极的调节。值得注意的是,Os04g0574600是新发现的耐旱基因。单倍型分析表明,RIL群体携带两个基因的两种单倍型(Hap1和Hap2)。携带Hap2的品系表现出比携带Hap1的品系显著或极其强的耐旱性,表明Hap2是一种优异的单倍型。在水稻种质资源中,Os04g0574600和OsCHR731分别有两种和三种单倍型。四川地方水稻资源比例高,云南,安徽,广东和福建两省都有Hap基因。在野生稻,50%的种质含有Os04g0574600的Hap1,50%携带Hap4;13.51%,59.46%和27.03%的野生稻分别含有Hap1,Hap2和Hap3。在粳稻资源中发现了Os04g0574600的Hap2。因此,Hap2在未来的粳稻抗旱育种中具有更大的利用潜力。
Drought is a major abiotic stress affecting crop yields. Mapping quantitative trait loci (QTLs) and mining genes for drought tolerance in rice are important for identifying gene functions and targets for molecular breeding. Here, we performed linkage analysis of drought tolerance using a recombinant inbred line population derived from Jileng 1 (drought sensitive) and Milyang 23 (drought tolerant). An ultra-high-density genetic map, previously constructed by our research team using genotype data from whole-genome sequencing, was used in combination with phenotypic data for rice grown under drought stress conditions in the field in 2017-2019. Thirty-nine QTLs related to leaf rolling index and leaf withering degree were identified, and QTLs were found on all chromosomes except chromosomes 6, 10, and 11. qLWD4-1 was detected after 32 days and 46 days of drought stress in 2017 and explained 7.07-8.19% of the phenotypic variation. Two loci, qLRI2-2 and qLWD4-2, were identified after 29, 42, and 57 days of drought stress in 2018. These loci explained 10.59-17.04% and 5.14-5.71% of the phenotypic variation, respectively. There were 281 genes within the QTL interval. Through gene functional annotation and expression analysis, two candidate genes, Os04g0574600 and OsCHR731, were found. Quantitative reverse transcription PCR analysis showed that the expression levels of these genes were significantly higher under drought stress than under normal conditions, indicating positive regulation. Notably, Os04g0574600 was a newly discovered drought tolerance gene.
Haplotype analysis showed that the RIL population carried two haplotypes (Hap1 and Hap2) of both genes. Lines carrying Hap2 exhibited significantly or extremely stronger drought tolerance than those carrying Hap1, indicating that Hap2 is an excellent
haplotype. Among rice germplasm resources, there were two and three haplotypes of Os04g0574600 and OsCHR731, respectively. A high proportion of local rice resources in Sichuan, Yunnan, Anhui, Guangdong and Fujian provinces had Hap of both genes. In wild rice, 50% of accessions contained Hap1 of Os04g0574600 and 50% carried Hap4; 13.51%, 59.46% and 27.03% of wild rice accessions contained Hap1, Hap2, and Hap3, respectively. Hap2 of Os04g0574600 was found in more indica rice resources than in japonica rice. Therefore, Hap2 has more potential for utilization in future drought tolerance breeding of japonica rice.