Expression of Drought‐Tolerant N₂ Fixation in Heterogeneous Inbred Families derived from PI471938 and Hutcheson Soybean

Abstract

Nitrogen fixation of soybean [Glycine max (L.) Merr.] is particularly vulnerable to drought, since, in most genotypes, N2 fixation activity decreases very early in the soil drying cycle. Although a few soybean genotypes, including ‘PI 471938’, have been identified that express N2 fixation tolerance of drought, it is unknown how readily this trait is transferred to progeny. Unfortunately, the techniques used to phenotype for the tolerance trait are either too crude or too labor‐intensive to allow the acquisition of data required for a classical inheritance assessment. In this study, a heterogeneous inbred family (HIF) population derived from PI 471938 × ‘Hutcheson’ was studied for its N2 fixation drought tolerance to obtain a preliminary indication of the expression of this trait in progeny genotypes. An in situ flow‐through acetylene reduction assay was used to track the N2 fixation rates of 13 HIFs over dry‐down periods lasting about 2 wk. There was a distinct segregation among the HIFs, with nine exhibiting tolerance equivalent to PI 471938 and four exhibiting sensitivity equal to or greater than Hutcheson. These results indicate that N2 fixation drought tolerance might be transferred to progeny lines fairly readily, or at least retained in a selected population such as these HIFs.

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

“…Yields undergone a reduction under drought exposure in both BRB and NFDT genotypes; notwithstanding, the grain yields of R02-1325 still kept similar to their best performing BRB progenies. Progenies originated from 'Jackson' and PI471938 have also been identified as showing different capacities to sustain the BNF under moderate drought (Chen et al, 2007;Cerezini et al, 2014;Riar et al, 2018), confirming that the slow-wilting trait can be transferred from a parental, as observed in the BRB progenies in this work. Maintenance or recovery of the BNF after drought stress is a desirable trait in soybean that might bring advantages for grain yield.…”

“…(1) Means followed by equal letters, uppercases in the lines and lowercases in the columns, do not differ by the Tukey's test, at 5% probability (n = 10). Sinclair, 2013), and the basis for drought tolerance in PI 471938 remains unknown (Riar et al, 2018). Plants under water restriction reduced the shoot dry matter by -37% in average, in comparison with the well-watered plants (Figure 1 A), whereas the root dry matter increased, but the increase intensity depended on the genotype (Figure 1 B).…”

Unraveling the genetic architecture for carbon and nitrogen related traits and leaf hydraulic conductance in soybean using genome-wide association analyses

“…A MG VI accession from China, PI 567377B, had the most negative (favorable) breeding value for N concentration using the sum across both individual environments (Additional file 1). PI 471938, which was previously identified as a genotype possessing nitrogen fixation drought tolerance [21, 33], had the 40th lowest breeding value for N concentration (Additional file 1). Only 20 of the genotypes tested had negative breeding values for N concentration.…”

Genome-Wide Association Analyses Reveal Genomic Regions Controlling Canopy Wilting in Soybean

“…PI 471938 was also previously identified as expressing N 2 fixation tolerance to soil drying (Sinclair et al 2000;Devi and Sinclair 2013;Riar et al 2018). These two plant introductions are being used as sources of slow wilting in applied breeding programs (Devi et al 2014;Carter et al 2016).…”