Ninety-eight high-yielding recombinant inbred lines (RILs) of WAB638-1/PRIMAVERA rice were evaluated with the parents under reproductive stage drought stress. The study aimed at characterizing flowering time response under drought stress and consequently classifying the genetic resources for efficient use in breeding programmes. Two field trials were conducted during the 2016 and 2017 dry seasons using the randomized complete block design with two replications. In 2016, 12 RILs were evaluated with the parents for the rooting attributes under drought stress and well-watered treatments. Analysis of variance revealed a significant (P < 0.05) variation among the genotypes for the traits evaluated. Drought stress reduced most of the characters in this study, including grain yield. However, the inbred lines exhibited considerable tolerance to drought stress as indicated by yield-related stress indexes, including stress susceptibility and drought tolerance indexes. Delayed flowering (FD) was recorded in 75 genotypes (including WAB638-1), while 25 genotypes (including PRIMAVERA) had no delay under drought stress compared to the control. The genotypes were grouped into flowering delay (D) genotypes (FD > 1 d) and no delay (N) genotypes (FD < 1 d), which significantly differ (P ⩽ 0.05) for numbers of days to 50% flowering. The flowering delay genotypes may be suitable for intermittent drought, while genotypes with little or no delay may be selected for terminal drought conditions. There was a significant correlation (r > 0.5) between the root length and number of days to 50% flowering. The study indicated that root parameters, such as the root length, may contribute to the drought adaptation mechanisms of the RILs.

中文翻译：

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WAB638-1/PRIMAVERA水稻重组自交系在生殖期干旱胁迫下开花时间响应特征

对 98 个 WAB638-1/PRIMAVERA 水稻高产重组自交系 (RIL) 与亲本在生殖期干旱胁迫下进行了评估。该研究旨在表征干旱胁迫下的开花时间响应，从而对遗传资源进行分类，以便在育种计划中有效利用。在 2016 年和 2017 年旱季，使用具有两次重复的随机完整区组设计进行了两次田间试验。2016 年，与父母一起评估了 12 个 RIL 在干旱胁迫和充分浇水处理下的生根属性。方差分析显示显着 (磷< 0.05) 所评估性状的基因型之间的变异。干旱胁迫降低了本研究中的大部分特征，包括谷物产量。然而，自交系对干旱胁迫表现出相当大的耐受性，如与产量相关的胁迫指数（包括胁迫易感性和耐旱性指数）所示。75个基因型（包括WAB638-1）记录到延迟开花（FD），而与对照相比，25个基因型（包括PRIMAVERA）在干旱胁迫下没有延迟开花。基因型分为开花延迟 (D) 基因型 (FD > 1 d) 和无延迟 (N) 基因型 (FD < 1 d), 它们之间存在显着差异 (磷⩽ 0.05) 表示开花至 50% 的天数。开花延迟基因型可能适用于间歇性干旱，而延迟很少或没有延迟的基因型可以选择用于终末干旱条件。有显着相关性（r> 0.5) 在根长和天数之间达到 50%开花。该研究表明，根参数，如根长，可能有助于 RIL 的干旱适应机制。