Three Strategies for Population Development in Breeding High-Yielding Soybean Cultivars with Improved Iron Efficiency
Improvement of yield and iron (Fe) efficiency in soybean [Glycine max (L.) Merr.] is important for cultivars grown on some calcareous soils. The objective of the study was to compare three-way cross populations with single-cross and backcross populations for selection of high-yielding soybean cultivars with improved Fe-efficiency. Three high-yielding, Fe-inefficient cultivars were crossed to a moderate-yielding Fe-efficient line to develop single-cross populations. F2-derived lines were evaluated for Fe efficiency in field tests on calcareous soil, and selected lines were crossed to their high-yielding Fe-inefficient recurrent parent to develop the backcross populations, and to the two other high-yielding Fe-inefficient parents to develop the three-way cross populations. F4-derived lines from the single-cross and three-way cross populations, BC1F3-derived lines from the backcross populations, the parents and a check cultivar were evaluated for seed yield on noncalcareous soils in replicated tests in three environments, and for Fe efficiency on calcareous soil in replicated tests in four environments. The backcross populations had the highest average seed yield not significantly different from the seed yield of the three-way cross populations, and the single-cross populations had the lowest average seed yields. The single-cross populations had the highest average Fe efficiency. Compared with a check cultivar that had high yield and adequate Fe efficiency, the average percentages of superior lines for both traits were 15% for the backcross, 9% for the three-way, and 5% for the single-cross populations. When an Fe-efficient genotype with moderate seed yield is used as a parent, a backcross or three-way cross are appropriate for development of cultivars with improved seed yield and adequate Fe efficiency. Single-crosses could also be considered if a high level of Fe efficiency is necessary. Phenotypic correlations for the mean of the populations and the mean performance of the parents of each population were significant for seed yield (r = 0.84), and for chlorosis ratings (r = 0.91), indicating that parent performance for these traits may be important in deciding the population type to use.
Copyright © 1994.