Genetic Variation and Postflowering Drought Effects on Seed Iron and Zinc in ICRISAT Sorghum Mini Core Collection

Drought stress invariably reduces yield and may alter seed chemistry. This experiment was initiated to characterize the sorghum [Sorghum bicolor (L.) Moench] mini core collection for genetic variation and to study the effect of postflowering drought on seed Fe and Zn concentrations. Accessions with similar maturity, together with controls, were evaluated in split-plot design under irrigated and drought-stressed environments for two postrainy seasons. Residual (or restricted) maximum likelihood (REML) analysis of data considering genotypes as random and drought and year as fixed indicated highly significant variance as a result of genotypes. Highly significant effects of drought (D), year (Y), and D x Y interaction emphasized need for multilocation evaluation of germplasm for agronomic and seed nutritional traits. About twofold variation in Fe (25.8–48.9 mg kg−1 seed) and threefold variation in Zn (13.5–42.6 mg kg−1 seed) concentrations was observed across environments. Eleven accessions with high seed Fe, 14 accessions with high Zn, and nine accessions high in both Fe and Zn were identified. These accessions, however, produced low seed yields. In addition, six and four accessions, respectively, showed 8 to 39% and 9 to 38% greater Fe and Zn over control IS 33844 and produced seed yields similar to that of IS 33844. Significant rank correlation (0.70) indicated that accessions with high Fe or Zn under irrigated environments are also expected to perform well under drought-stressed environments. Significantly positive correlation between Fe and Zn indicated simultaneous improvement as a realistic approach in breeding. The identified germplasm are ideal genetic resources for the development of Fe- and Zn-dense sorghum cultivars.