Abstract
Biological nitrogen fixation (BNF) in soybean is vulnerable to drought; however, there are genotypic variations among soybean cultivars regarding the ability to keep BNF under moderate water restriction. The aim of this study was to evaluate parameters related to gas exchanges and regulation of BNF in soybean genotypes BNF drought-tolerant (R01-581F and R01-416F), or drought-susceptible (CD 215 and BRS 317), submitted to adequate water supply or restriction between 45 and 55 days after emergence. We searched for traits associated with tolerance/susceptibility to drought, which might be useful in the selection of drought-tolerant soybean genotypes. Plant biomass was not affected under water restriction, but the number and dry weight of nodules reduced by 33% and 12%, respectively, in the average of genotypes. Drought-tolerant genotypes were more effective in maintaining gas exchanges under water restriction. Under water restriction, all genotypes increased the concentration of ureides in nodules, but only the susceptible genotypes showed that in leaves. The maintenance of gas exchanges and N metabolism regulation under water restriction in genotype R01-581F suggests that these parameters may be used to characterize soybean genotypes that can be sources of drought tolerance in genetic breeding programs.
Highlights
The aim of this study was to evaluate attributes related to gas exchanges and regulation of biological nitrogen fixation (BNF) of soybean genotypes under water restriction, to characterize phenotypic differences associated with tolerance/susceptibility to drought, which may be useful in the selection for breeding programs of soybean cultivars for drought tolerance
Data on temperature and solar radiation inside the greenhouse during the induction of drought are shown in Figure 1(f), inner graph
The hypothesis of regulation of BNF by N metabolism can be supported, since water restriction altered the concentrations of ureides in several plant parts, especially nodules, where they may act negatively on the BNF in a feedback effect
Summary
Merrill) is one of the most important agricultural crops with high economic importance worldwide, and Brazil stands as the second global producer. (2014) Gas Exchanges and Biological Nitrogen Fixation in Soybean under Water Restriction. American Journal of Plant Sciences, 5, 4011-4017. Soybean has high nitrogen (N) demand for growth, which can be mostly provided via biological nitrogen fixation (BNF). This process is essential for the economic viability of soybean crop in Brazil and is based on the symbiosis with bacteria belonging to the genus Bradyrhizobium, providing most N required by plant, making this crop independent of N-fertilizers, with economic and environmental benefits [2] [3]
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