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Microsphere stem blockage as a screen for nitrogen‐fixation drought tolerance in soybean
Author(s) -
Pradhan Deepti,
Bertin Diana,
Sinclair Thomas R.,
Nogueira Marco A.,
Livingston David,
Carter Thomas
Publication year - 2021
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/ppl.13281
Subject(s) - xylem , nitrogen fixation , transpiration , biology , population , drought tolerance , nitrogen , fixation (population genetics) , germplasm , agronomy , horticulture , botany , chemistry , photosynthesis , biochemistry , demography , organic chemistry , sociology , gene
Symbiotic nitrogen‐fixation of soybean ( Glycine max [Merr.] L) commonly decreases in response to soil drying in advance of other plant processes. While a few soybean lines express nitrogen‐fixation drought tolerance, breeding for genetic variation is hampered by laborious phenotyping procedures. The objective of this research was to explore the potential of an initial screen for nitrogen‐fixation drought‐tolerant genotypes based on a possible relationship with xylem‐vessel diameter. The hypothesis was that nitrogen‐fixation drought tolerance might result from fewer, large‐diameter xylem vessels in the stem that are vulnerable to disrupted flow as water deficit develops. The disrupted flow could cause nitrogen products to accumulate in nodules resulting in negative feedback on nitrogen‐fixation rate. The proposed screen involved exposing de‐rooted shoots to a suspension containing microspheres (45–53 μm diameter) and recording the decrease in transpiration rate as a result of microsphere xylem‐blockage. Two soybean populations were tested. One population was progeny derived from mating of two parents with high and low nitrogen‐fixation drought sensitivity. A high correlation ( R 2 = 0.68; P < 0.001) was found in this population between decreasing transpiration rate resulting from the microsphere treatment and increasing sensitivity of nitrogen‐fixation to soil drying. The second tested population consisted of 16 genotypes, most of which had been previously identified in germplasm screens as expressing nitrogen‐fixation drought tolerance. Nearly half of the lines in this second population were identified in the screen as showing minimum blockage of transpiration when exposed to the microspheres. Overall, these results showed the potential of using the microsphere screen to identify candidate genotypes expressing nitrogen‐fixation drought tolerance.