Alternative breeding strategies for the improvement of iron efficiency in soybean

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Abstract
The potential production loss attributable to Fe‐deficiency chlorosis in soybean [Glycine max (L.) Merr.] grown on calcareous soil is sufficient to justify the development of high‐yielding, Fe‐efficient soybean cultivars in several states. Alternative breeding methods and screening techniques for the development of high‐yielding, Fe‐efficient cultivars and parental germplasm were studied. In the breeding methodology studies, populations derived from crosses of lower yielding, Fe‐efficient X high‐yielding, Fe‐inefficient parents had lower mean yields but greater average Fe‐efficiency than populations derived by backcrossing to the high‐yielding parent. Phenotypic correlations between the yield of breeding lines on noncalcareous soil and their Fe‐efficiency on calcareous soil were positive or not significant, indicating that selection of high‐yielding, Fe‐efficient cultivars should be possible. In a recurrent selection program to improve the Fe‐efficiency of a population, a nutrient solution system is used to obtain adequate chlorosis for the selection of superior lines for recombination. Correlations between field chlorosis ratings and those obtained in nutrient solution were highly favorable. Lines superior to the highly Fe‐efficient genotype A7 have been identified and released to research scientists.