Exploring the genetic variability and diversity of pearl millet core collection germplasm for grain nutritional traits improvement.

Improving essential nutrient content in staple food crops through biofortification breeding can overcome the micronutrient malnutrition problem. Genetic improvement depends on the availability of genetic variability in the primary gene pool. This study was aimed to ascertain the magnitude of variability in a core germplasm collection of diverse origin and predict pearl millet biofortification prospects for essential micronutrients. Germplasm accessions were evaluated in field trials at ICRISAT, India. The accessions differed significantly for all micronutrients with over two-fold variation for Fe (34-90 mg kg-1), Zn (30-74 mg kg-1), and Ca (85-249 mg kg-1). High estimates of heritability (> 0.81) were observed for Fe, Zn, Ca, P, Mo, and Mg. The lower magnitude of genotype (G) × environment (E) interaction observed for most of the traits implies strong genetic control for grain nutrients. The top-10 accessions for each nutrient and 15 accessions, from five countries for multiple nutrients were identified. For Fe and Zn, 39 accessions, including 15 with multiple nutrients, exceeded the Indian cultivars and 17 of them exceeded the biofortification breeding target for Fe (72 mg kg-1). These 39 accessions were grouped into 5 clusters. Most of these nutrients were positively and significantly associated among themselves and with days to 50% flowering and 1000-grain weight (TGW) indicating the possibility of their simultaneous improvement in superior agronomic background. The identified core collection accessions rich in specific and multiple-nutrients would be useful as the key genetic resources for developing biofortified and agronomically superior cultivars.

Grain iron and zinc density in pearl millet: combining ability, heterosis and association with grain yield and grain size.

Genetics of micronutrients and their relationships with grain yield and other traits have a direct bearing on devising effective strategies for breeding biofortified crop cultivars. A line × tester study of 196 hybrids and their 28 parental lines of pearl millet (Pennisetum glaucum (L.) R.Br.) showed large genetic variability for Fe and Zn densities with predominantly additive gene action and no better-parent heterosis. Hybrids with high levels of Fe and Zn densities, involved both parental lines having significant positive general combining ability (GCA), and there were highly significant and high positive correlations between performance per se of parental lines and their GCAs. There was highly significant and high positive correlation between the Fe and Zn densities, both for performance per se and GCA. Fe and Zn densities had highly significant and negative, albeit weak, correlations with grain yield and highly significant and moderate positive correlation with grain weight in hybrids. These correlations, however, were non-significant in the parental lines. Thus, to breed hybrids with high Fe and Zn densities would require incorporating these micronutrients in both parental lines. Also, simultaneous selection for Fe and Zn densities based on performance per se would be highly effective in selecting for GCA. Breeding for high Fe and Zn densities with large grain size will be highly effective. However, combining high levels of these micronutrients with high grain yield would require growing larger breeding populations and progenies than breeding for grain yield alone, to make effective selection for desirable recombinants.

Population biology of Avena : IX. Gene flow and neighborhood size in relation to microgeographic variation in Avena barbata.

Pollen and seed dispersal patterns were analyzed in both natural and experimental populations of Avena barbata. Localized estimates of gene flow rates and plant densities gave estimates of neighborhood size in the range of 40 to 400 plants; the estimates of mean rate and distance of gene flow seemed to vary widely due to variable wind direction, rodent activity, microsite heterogeneity, etc. The relative sizes of neighborhoods in several populations were correlated with the patchy distribution of different genotypes (scored for lemma color and leaf sheath hairiness) within short distances, but patch sizes had a wide range among different sites. Highly localized gene flow patterns seemed to account for the observed pattern of highly patchy variation even when the dispersal curves for both pollen and seed were platykurtic in many cases. Measures of the stability of patches in terms of their size, dispersion in space and genetic structure in time are needed in order to sort out the relative roles of founder effects, random drift (due to small neighborhood size), and highly localized selection. However, our observations suggest that many variables and stochastic processes are involved in such studies so as to allow only weak inference about the underlying role of natural selection, drift and factors of population regulatien.