Xie Jianyin, Li Fengmei, Khan Najeeb Ullah, Zhu Xiaoyang, Wang Xueqiang, Zhang Zhifang, Ma Xiaoqian, Zhao Yan, Zhang Quan, Zhang Shuyang, Zhang Zhanying, Li Jinjie, Li Zichao, Zhang Hongliang
Key Lab of Crop Heterosis and Utilization of Ministry of Education and Beijing Key Lab of Crop Genetic Improvement, China Agricultural University, Beijing, 100193, China.
Genes Genomics. 2019 Mar;41(3):283-295. doi: 10.1007/s13258-018-0758-1. Epub 2018 Nov 19.
As one of the main yield components, grain number per panicle (GNP) played critical role in the rice yield improvement. The identification of natural advantageous variations under different situations will promote the sustainable genetic improvement in rice yield.
This study was designed to identify natural genotypes in a rice mini-core collection, to examine the genotypic effects across the indica and japonica genetic background in different environments, and excavating the superior genotypes that had drove the modern genetic improvement.
The association mapping of GNP was carried out using a mini-core collection including 154 indica and 119 japonica accessions in seven different environments. Genotypic effects of each genotype for each QTL were calculated and genotype frequency distortion between the commercial rice cultivars and landraces was screened by χ-test.
In total, 74 QTLs containing stable and sensitive QTLs in various environments were detected. Within them, 20 positive and 24 negative genotypes in indica, and 24 positive and 16 negative genotypes in japonica were identified. When checking the accumulation of positive genotypes identified in indica across cultivars in each of the two subspecies, it indicated that increased number of positive genotypes identified in indica results in the substantially increased GNP in both indica and japonica across all of the environments, while this trend was not obvious for the positive genotypes identified in japonica especially in short day environments. Moreover, the positive and negative genotype frequency distortion between the landraces and commercial rice cultivars indicated that both positive selection of positive genotypes and negative selection of negative genotypes had driven the genetic improvement on GNP.
Our findings suggested that the accumulation of positive genotypes and purifying negative genotypes played equivalently important roles in the improvement of rice yield, but the efficient use for some QTLs or genotypes depends on the comprehensive evaluation of their effect under diverse genetic backgrounds and environments.
每穗粒数（GNP）作为主要产量构成因素之一，在水稻产量提升中发挥着关键作用。鉴定不同环境下的自然有利变异将促进水稻产量的可持续遗传改良。
本研究旨在鉴定水稻微核心种质中的自然基因型，考察不同环境下籼稻和粳稻遗传背景中的基因型效应，并挖掘推动现代遗传改良的优良基因型。
利用包含154份籼稻和119份粳稻种质的微核心种质在7种不同环境下开展GNP的关联分析。计算每个QTL的每个基因型的基因型效应，并通过χ检验筛选商业水稻品种和地方品种之间的基因型频率畸变。
共检测到74个在不同环境下包含稳定和敏感QTL的位点。其中，鉴定出籼稻中有20个正向基因型和24个负向基因型，粳稻中有24个正向基因型和16个负向基因型。在检查两个亚种中每个品种籼稻中鉴定出的正向基因型的积累情况时，结果表明，籼稻中鉴定出的正向基因型数量增加导致所有环境下籼稻和粳稻的GNP均大幅增加，而粳稻中鉴定出的正向基因型的这种趋势并不明显，尤其是在短日照环境中。此外，地方品种和商业水稻品种之间正负基因型频率畸变表明，正向基因型的正向选择和负向基因型的负向选择均推动了GNP的遗传改良。
我们的研究结果表明，正向基因型的积累和负向基因型的纯化在水稻产量提高中发挥着同等重要的作用，但某些QTL或基因型的有效利用取决于对其在不同遗传背景和环境下效应的综合评估。
