**4. Conclusions**

Conclusions from the research discussed in this chapter are: (1) soybean seed [Fe] and/or seed Fe content provide reliable and consistent measures of genetic differences in resistance to Fe deficiency; (2) seed [Fe] is tightly controlled genetically; (3) it is not likely that

Importance of Seed [Fe] for

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or a combination of hydrogen release and iron reduction for selecting iron-efficient

susceptible genotypes will accumulate high seed [Fe] even when excess Fe is available; (4) seed [Fe] or content at harvest, more so than VCS, can also reflect responses to management practices designed to reduce or alleviate Fe deficiency; (5) when soybean is grown on chlorosis-prone soils, increasing seeding density can markedly increase grain yield and seed [Fe] of both susceptible and resistant cultivars, whereas applying higher rates of Fe-EDDHA especially benefits susceptible cultivars; (6) increasing rates of added fertilizer nitrate have little influence on Fe deficiency of resistant cultivars, but severely depress plant height, grain yield and harvest seed [Fe] of susceptible cultivars; (7) genotypic rank correlations of visual chlorosis scores across locations within a year are reasonably consistent and reliable; however, rank correlations across years are not; (8) classifying genotypes using VCS can result in heterogeneous class variances indicating that VCSs may not be appropriate (consistent, reliable) measures of Fe efficiency; (9) measures of genetic resistance to Fe deficiency should include measures of seed [Fe] or content; and (10) the slow improvement in genotypic resistance to Fe deficiency may be related to the plant trait used to measure resistance.

Seed [Fe] is very useful for identifying superior genotypes in management and agronomic performance trials; it also provides a consistent, reliable estimate of resistance to Fe deficiency, thereby enhancing genotype selection.
