Physiological and N2-fixation-related traits for tolerance to drought in soybean progenies

Abstract: The objective of this work was to evaluate six soybean (Glycine max) genotypes for physiological traits and biological nitrogen fixation in drought conditions, and their capacity for recovery after rewetting, based on yield components. The genotypes evaluated in a greenhouse were the following: 'BRS 317', susceptible to drought; R01-581F and R02-1325, which show biological nitrogen fixation tolerant to drought; and the BRB14-207525, BRB14-207526, BRB14-207527 breed lines resulting from crossings between commercial genotypes and PI 471938, which shows a slow-wilting phenotype under drought. Drought conditions were applied to the genotypes at the full-flowering stage (R2) for ten days, whereas control plants were kept well-watered. Photosynthetic rate and gas exchanges under drought were more stable in the BRB14-207526 genotype. Root biomass increased 3.5 times in R02-1325 as an adaptive response to drought. In addition, leaf ureides - a trait related to biological nitrogen fixation in plants tolerant to drought - remained stable in genotypes R02-1325 and R01-581F exposed to drought, but decreased in BRB14-207527. Genotypes BRB14-207526, BRB14-207527, and R02-1325 show more favorable physiological performances and a lower accumulation of ureides under drought, besides a higher grain yield after rehydration. The BRB14-207526 and BRB14-207527 progenies show drought-tolerance traits from PI 471938, whereas R02-1325 is a promising source of tolerance to drought for soybean breeding.

摘要（Abstract）：本研究旨在基于产量构成要素，评估6个大豆（Glycine max）基因型在干旱胁迫下的生理性状、生物固氮（biological nitrogen fixation）能力，以及复水后的恢复能力。本试验于温室中对以下6个基因型进行了评估：抗旱敏感型大豆基因型‘BRS 317’；耐旱生物固氮型基因型R01-581F与R02-1325；以及由商业化基因型与干旱下表现为慢萎蔫表型（slow-wilting phenotype）的PI 471938杂交选育的BRB14-207525、BRB14-207526、BRB14-207527三个育种品系。供试基因型于全花期（R2）阶段接受为期10天的干旱胁迫，对照组植株则保持充分供水。干旱胁迫下，BRB14-207526基因型的光合速率（photosynthetic rate）与气体交换（gas exchanges）参数更为稳定。作为对干旱胁迫的适应性响应，R02-1325的根系生物量（root biomass）提升了3.5倍。此外，叶片脲酰类物质（ureides）——这一与耐旱植物生物固氮相关的性状——在干旱胁迫下的R02-1325与R01-581F基因型中保持稳定，但在BRB14-207527中出现下降。BRB14-207526、BRB14-207527与R02-1325基因型在干旱胁迫下表现出更优异的生理性状、更低的脲酰类物质积累，且复水（rehydration）后籽粒产量更高。BRB14-207526与BRB14-207527品系携带PI 471938的耐旱性状（drought-tolerance traits），而R02-1325则是大豆育种（soybean breeding）中极具潜力的耐旱种质资源。