ABSTRACT

Knowledge on the existing root diversity in germplasms has been emphasized for soybean breeding to improve drought resistance. Yet, evaluation of root diversity for vast genotypes still remains challenging. Here we investigated the contribution of different genotypic roots to drought resistance by a grafting experiment. A total of 22 cultivars were used as rootstocks to graft with scions of drought-sensitive cultivar L21. Water withholding was imposed during 15 days at podding stage in pot-culture experiments. The root-related traits were measured under well-watered (WW) and water-stressed (WS) conditions. At maturity, the drought-resistance coefficient (DRC) was calculated as the yield under WS condition relative to WW yield. The DRC varied from 0.56 to 0.85 among grafts; thus, the rootstocks were categorized as drought-sensitive (DS), moderate (M) and drought-resistant (DR) types. The L21 scion grafted onto DR rootstocks resulted in higher DRC and greater drought resistance than those self-grafts. There were also significant interactions between water stress and genotype for root-related traits. With the increase of DRC, the plants showed linear increases in root length, root surface area, and root volume, but had linear decreases in root dry mass, root–shoot ratio and root tissue density under WS rather than WW conditions. We suggested that developed rooting with a low investment on dry matter identified by grafting experiments should be selected to improve drought resistance in soybean breeding.

摘要

在大豆育种中强调了对现有种质根系多样性的了解，以提高抗旱性。然而，评估大量基因型的根多样性仍然具有挑战性。在这里，我们通过嫁接实验研究了不同基因型根对抗旱性的贡献。共有22个品种作为砧木与干旱敏感品种L21的接穗嫁接。在盆栽实验中，在结荚阶段的 15 天内进行了停水。在充分浇水（WW）和水分胁迫（WS）条件下测量与根相关的性状。成熟时，抗旱系数 (DRC) 计算为 WS 条件下相对于 WW 产量的产量。移植物之间的 DRC 从 0.56 到 0.85 不等；因此，砧木被归类为干旱敏感（DS），中度 (M) 和抗旱 (DR) 类型。嫁接到 DR 砧木上的 L21 接穗比那些自嫁接穗具有更高的 DRC 和更强的抗旱性。水分胁迫与根相关性状的基因型之间也存在显着的相互作用。随着DRC的增加，植物的根长、根表面积和根体积呈线性增加，但在WS而不是WW条件下，根干质量、根冠比和根组织密度呈线性下降。我们建议应选择嫁接试验确定的干物质投资低的发达生根，以提高大豆育种的抗旱性。水分胁迫与根相关性状的基因型之间也存在显着的相互作用。随着DRC的增加，植物的根长、根表面积和根体积呈线性增加，但在WS而不是WW条件下，根干质量、根冠比和根组织密度呈线性下降。我们建议应选择嫁接试验确定的干物质投资低的发达生根，以提高大豆育种的抗旱性。水分胁迫与根相关性状的基因型之间也存在显着的相互作用。随着DRC的增加，植物的根长、根表面积和根体积呈线性增加，但在WS而不是WW条件下，根干质量、根冠比和根组织密度呈线性下降。我们建议应选择嫁接试验确定的干物质投资低的发达生根，以提高大豆育种的抗旱性。