Dwivedi Sharad K, Kumar Santosh, Natividad Mignon A, Quintana Marinell R, Chinnusamy Viswanathan, Henry Amelia
ICAR - Research Complex for Eastern Region, Patna, Bihar, 800014, India.
ICAR - Central Institute for Subtropical Horticulture, Lucknow, 226101, India.
Rice (N Y). 2023 Mar 17;16(1):14. doi: 10.1186/s12284-023-00631-6.
Harvest index is an important component of grain yield and is typically reduced by reproductive stage drought stress in rice. Multiple drought response mechanisms can affect harvest index including plant water status and the degree of stem carbohydrate mobilization during grain filling. In this study, we aimed to dissect the contributions of plant water status and stem carbohydrate mobilization to harvest index. Pairs of genotypes selected for contrasting harvest index but similar biomass and days to flowering were characterized at ICAR-RCER, Patna, India and at IRRI, Philippines.
Multiple traits were related with harvest index across experiments, including mobilization efficiency at both sites as indicated by groupings in principal component analysis, and plant water status as indicated by direct correlations. Biomass-related traits were positively correlated with harvest index at IRRI but biomass was negatively correlated with harvest index at ICER-RCER, Patna. We observed that some pairs of genotypes showed differences in harvest index across environments, whereas other showed differences in harvest index only under drought. Of all time points measured when all genotypes were considered together, the stem carbohydrate levels at maturity were most consistently (negatively) correlated with harvest index under drought, but not under well-watered conditions. However, in the pairs of genotypes grouped as those whose differences in harvest index were stable across environments, improved plant water status resulted in a greater ability to both accumulate and remobilize stored carbohydrate, i.e. starch.
By distinguishing between genotypes whose harvest index was improved across conditions as opposed to specifically under drought, we can attribute the mechanisms behind the stable high-harvest index genotypes to be more related to stem carbohydrate remobilization than to plant water status. The stable high-harvest index lines in this study (Aus 257 and Wanni Dahanala) may confer mechanisms to improve harvest index that are independent of drought response and therefore may be useful for breeding improved rice varieties.
收获指数是谷物产量的重要组成部分，在水稻生殖阶段通常会因干旱胁迫而降低。多种干旱响应机制会影响收获指数，包括植物水分状况以及灌浆期茎中碳水化合物的调动程度。在本研究中，我们旨在剖析植物水分状况和茎中碳水化合物调动对收获指数的贡献。在印度巴特那的印度农业研究理事会-水稻研究中心（ICAR-RCER）和菲律宾的国际水稻研究所（IRRI），对选择的收获指数不同但生物量和开花天数相似的基因型对进行了表征。
在各项实验中，多个性状与收获指数相关，包括主成分分析分组所示的两个地点的调动效率，以及直接相关性所示的植物水分状况。在国际水稻研究所，与生物量相关的性状与收获指数呈正相关，但在巴特那的ICER-RCER，生物量与收获指数呈负相关。我们观察到，一些基因型对在不同环境下收获指数存在差异，而其他基因型对仅在干旱条件下收获指数存在差异。在考虑所有基因型的所有测量时间点中，成熟时茎中碳水化合物水平在干旱条件下与收获指数最一致地（呈负）相关，但在水分充足条件下并非如此。然而，在收获指数差异在不同环境下稳定的基因型对中，改善的植物水分状况导致积累和调动储存碳水化合物（即淀粉）的能力更强。
通过区分收获指数在各种条件下（而非仅在干旱条件下）得到改善的基因型，我们可以将稳定的高收获指数基因型背后的机制归因于与茎中碳水化合物调动的关系比与植物水分状况的关系更大。本研究中的稳定高收获指数品系（Aus 257和Wanni Dahanala）可能具有独立于干旱响应来提高收获指数的机制，因此可能有助于培育改良水稻品种。
