Asfaw Asrat, Ambachew Daniel, Shah Trushar, Blair Matthew W
International Institute of Tropical AgricultureAbuja, Nigeria.
South Agricultural Research InstituteHawassa, Ethiopia.
Front Plant Sci. 2017 May 9;8:733. doi: 10.3389/fpls.2017.00733. eCollection 2017.
Common beans are a warm-season, food legume cultivated in areas prone to water limitation throughout their growing season. This study assessed the magnitude and pattern of trait associations for a total of 202 common bean genotypes divided into panels of 81 Andean and 121 Mesoamerican gene pool accessions grown under contrasting treatments of well-watered, non-stress, and water-limited, terminal drought-stress conditions. Linear correlation, complex path coefficient, and genetic divergence analyses were used to dissect the relationship dynamics between traits and the relative contribution of adaptive traits to differentiation among gene pools and genotypes based on drought stress. Drought severity level for the trial was high and created the ideal condition to reveal genotypic differences, as seen by the differential response of the genotypes for the various traits measured. The value for phenotypic coefficients of variation for all traits was higher than the corresponding genotypic values. Seed yield had positive and strong genotypic and phenotypic correlation with pods per plant across gene pools and stress levels. The overall amount of genetic correlation was greater than the corresponding phenotypic correlation matrix for all the traits within the gene pool and across stress levels. Moreover, the results depicted the phenotypic correlation as equal or better than its genotypic counterpart in estimating drought tolerance in common bean plants. Clustering analysis with Mahanalobis's coefficient of generalized distance grouped genotypes with a differential level of drought adaptation into different classes within each panel. This indicates drought tolerance involves different mechanisms of plant response and is present separately in each gene pool panel. Pods per plant, seed weight, pod partitioning index, and harvest index are useful selection objectives to improve drought adaptation in common bean, but must be differentially weighted in each gene pool. The analysis of genetic variation and association between adaptive traits on the two panels provided useful insights on which traits could be used to improve common bean adaptation to low water availability during the growth season.
菜豆是一种喜温的食用豆类，在整个生长季节易受水分限制的地区种植。本研究评估了202个菜豆基因型的性状关联程度和模式，这些基因型分为两个小组，其中81个属于安第斯基因库种质，121个属于中美洲基因库种质，它们在充分供水的非胁迫条件和水分受限的终末期干旱胁迫条件这两种对比处理下生长。采用线性相关分析、复路径系数分析和遗传距离分析，剖析性状之间的关系动态，以及基于干旱胁迫的适应性性状对基因库和基因型分化的相对贡献。该试验的干旱严重程度较高，为揭示基因型差异创造了理想条件，从所测各种性状的基因型差异反应中可见一斑。所有性状的表型变异系数值均高于相应的基因型值。在所有基因库和胁迫水平下，种子产量与单株荚数呈显著正相关，且基因型相关性和表型相关性均很强。在基因库内和不同胁迫水平下，所有性状的遗传相关总量均大于相应的表型相关矩阵。此外，结果表明，在估计菜豆植株的耐旱性方面，表型相关性等同于或优于基因型相关性。利用马氏广义距离系数进行聚类分析，将具有不同干旱适应水平的基因型在每个小组内分为不同类别。这表明耐旱性涉及不同的植物反应机制，且在每个基因库小组中是独立存在的。单株荚数、种子重量、荚分配指数和收获指数是提高菜豆干旱适应性的有用选择指标，但在每个基因库中必须进行差异化加权。对两个小组适应性性状的遗传变异和关联分析，为哪些性状可用于提高菜豆在生长季节对低水分可用性的适应性提供了有用的见解。
