Genetic Variation for Dinitrogen Fixation in Soybean of Maturity Group 00 and 0
- S. L. Neuhausen,
- P. H. Graham and
- J. H. Orf
Because soybean [Glycine max (L.) Merr.] are generally assumed to be active in N, fixation, their genetic variation in this trait has not been studied to the extent found in other crop legumes. In the few studies undertaken, local cultivars of limited genetic diversity have dominated. This study considered the genetic variation in N2 fixation of 21 Group 00 and 27 Group 0 soybean plant introductions over 2 yr at two Minnesota locations [Hubbard loamy sand (sandy, mixed Udorthetic Haploborall) and Waukegan silt loam (fine-silty over sandy, mixed, mesic Typic Hapludoll)] differing in available soil N. Traits measured were total N2 fixed (estimated by the difference method using a Clay Maturity Group 0 non-nodulating line), shoot dry weight at R2 and R6, plant N concentration at R6, the proportion of plant N derived from fixation, and seed yield. All traits except N concentration were positively and highly correlated with total N2 fixed, and therefore have the potential to be used as indirect estimates of N2 fixation for field screening under low to moderate soil N conditions. There were significant differences within both maturity groups for all traits. Some Group 00 lines fixed more N, than ‘McCall’ and as much N, as high N2-fixing Maturity Group 0 lines. There was sufficient genetic variation to suggest that breeding for improved N2 fixation is feasible in both maturity groups.
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