Water restriction and physiological traits in soybean genotypes contrasting for nitrogen fixation drought tolerance

ABSTRACT Biological nitrogen fixation (BNF) is essential to the economic viability of the soybean [Glycine max (L.) Merrill] crop in Brazil, but drought may impair the BNF processes. We evaluated physiological traits of nitrogen fixation drought-tolerant (NFDT) (R01-581F, R01-416F and R02-1325) and drought-susceptible (CD 215 and BRS 317) genotypes of soybean subjected to drought or regular water supply between 45 and 55 days after emergence, in an experiment under greenhouse conditions in pots containing non-sterile soil. R01-581F had more stable photosynthetic and transpiration rates, and higher intercellular CO2 levels under drought. Drought reduced the chlorophyll concentration in all genotypes, but with less intensity in R01-581F and R02-1325. The NFDT genotypes generally showed higher concentrations of N, K and Mn in shoots, irrespective of the water condition. Exposure to drought increased total soluble sugars in nodules in all genotypes, as well as the concentrations of ureides in leaves and nodules, whereas ureides in petioles increased only in the susceptible genotypes. Drought negatively affected photosynthetic and BNF attributes; however, R01-581F showed the best performance, with potential for use in breeding programs aiming at drought-tolerant varieties.

摘要 生物固氮（Biological nitrogen fixation, BNF）对巴西大豆[Glycine max (L.) Merrill]种植的经济可行性至关重要，但干旱会损害该固氮过程。本研究于温室非灭菌土壤盆栽条件下开展试验，针对出苗后45~55天的大豆基因型，评估了固氮耐旱型（nitrogen fixation drought-tolerant, NFDT）（R01-581F、R01-416F及R02-1325）与干旱敏感型（CD 215、BRS 317）大豆在干旱与正常供水处理下的生理性状。干旱条件下，R01-581F的光合速率与蒸腾速率更为稳定，且胞间二氧化碳浓度更高。干旱会降低所有基因型的叶绿素浓度，但R01-581F与R02-1325的降幅更小。无论供水条件如何，NFDT型基因型的地上部氮（Nitrogen, N）、钾（Potassium, K）及锰（Manganese, Mn）浓度普遍更高。干旱胁迫会提升所有基因型根瘤中的总可溶性糖含量，以及叶片与根瘤中的酰脲浓度，但仅在敏感型基因型中，叶柄酰脲浓度出现上升。干旱对光合与固氮相关性状产生负面影响，但R01-581F表现最优，具备应用于耐旱品种育种项目的潜力。