ICRISAT's pearl millet (Pennisetum glaucum (L.) R. Br.) breeding program at Patancheru, India, has developed genetically diverse hybrid parents since 1980s. The present study investigated genetic diversity pattern between two groups of parents in this program, bred till 2004 and developed during 2004-2010. Combined analysis of 379 hybrid parents (current 166 parents and 213 previously developed hybrid parents) carried out using a set of highly polymorphic 28 SSRs detected 12.7 alleles per locus. An average of 8.5 and 8.7 SSR alleles per locus were found in previously developed and current parents, respectively, indicating marginal improvement in the levels of genetic diversity of hybrid parents in this program. Distance matrix differentiated these current and previously developed hybrid parents into 2 separate clusters, indicating infusion of new genetic variability over time as reflected by development of more genotype-specific alleles. Also, the seed and restorer parents were found clearly separated from each other in both the sets with few crossovers, indicating existence of two diverse and broad-based pools in hybrid parents of pearl millet. Restorer parents (R-lines) were found more diverse than seed parents (B-lines), as higher average gene diversity was detected among R-lines (0.70) than B-lines (0.56), though variation between Band R-lines was found reduced in newly developed lines to 9.22% from 16.98% in previously developed lines. Results suggested that newly developed lines were as much divergent when compared with previously developed lines, indicating that current ICRISAT pearl millet breeding program was moving towards development of diverse new hybrid parental lines. The study suggested use of trait-specific donors in Band R-lines separately to maintain sufficient genetic distance between seed and restorer breeding lines. It was pointed out to cross parents having higher genetic distance within the seed (B-lines) and restorer (R-lines) breeding programs to derive diverse and productive hybrid parental lines in future.

Micronutrient malnutrition, especially deficiency of two mineral elements, iron [Fe] and zinc [Zn] in the developing world needs urgent attention. Pearl millet is one of the best crops with many nutritional properties and is accessible to the poor. We report findings of the first attempt to mine favorable alleles for grain iron and zinc content through association mapping in pearl millet. An association mapping panel of 130 diverse lines was evaluated at Delhi, Jodhpur and Dharwad, representing all the three pearl millet growing agro-climatic zones of India, during 2014 and 2015. Wide range of variation was observed for grain iron (32.3–111.9 ppm) and zinc (26.6–73.7 ppm) content. Genotyping with 114 representative polymorphic SSRs revealed 0.35 mean gene diversity. STRUCTURE analysis revealed presence of three sub-populations which was further supported by Neighbor-Joining method of clustering and principal coordinate analysis (PCoA). Marker-trait associations (MTAs) were analyzed with 267 markers (250 SSRs and 17 genic markers) in both general linear model (GLM) and mixed linear model (MLM), however, MTAs resulting from MLM were considered for more robustness of the associations. After appropriate Bonferroni correction, Xpsmp 2261 (13.34% R2-value), Xipes 0180 (R2-value of 11.40%) and Xipes 0096 (R2-value of 11.38%) were consistently associated with grain iron and zinc content for all the three locations. Favorable alleles and promising lines were identified for across and specific environments. PPMI 1102 had highest number (7) of favorable alleles, followed by four each for PPMFeZMP 199 and PPMI 708 for across the environment performance for both grain Fe and Zn content, while PPMI 1104 had alleles specific to Dharwad for grain Fe and Zn content. When compared with the reference genome Tift 23D2B1-P1-P5, Xpsmp 2261 amplicon was identified in intergenic region on pseudomolecule 5, while the other marker, Xipes 0810 was observed to be overlapping with aspartic proteinase (Asp) gene on pseudomolecule 3. Thus, this study can help in breeding new lines with enhanced micronutrient content using marker-assisted selection (MAS) in pearl millet leading to improved well-being especially for women and children.

No abstract

Micronutrient malnutrition, especially the paucity of iron (Fe) and zinc (Zn) is posing a big threat to the world affecting nearly 25% of worldwide population. Pearl millet is endowed with huge amount of variability for micronutrients especially for grain Fe and Zn content. Micronutrient enrichment in pearl millet is possible by identifying stable genotypes for high levels of micronutrients and utilising them in breeding programme. In this context, a set of 40 pearl millet genotypes along with one check, Dhanshakti (G30), were evaluated at three different agro climatic zones during the year 2014 for grain iron (Fe) and zinc (Zn) contents using Atomic Absorption Spectrometry. The genotypes contributed 58.3% and 52.8% of the total variation for grain Fe and Zn content, respectively. The magnitude of variation contributed by interaction component was also relatively high (39.7% and 32.5% for grain Fe and Zn). Both AMMI and GGE biplot analysis identified desirable genotypes; PPMI 708 (G40), PPMI 1102 (G25) and PPMI 683 (G39) for grain Fe content, whereas PPMI 708 (G40), PPMI 1116 (G24) and PPMI 683 (G39) for grain Zn content. The Pearson correlation coefficient for grain Fe and Zn content showed that both traits are highly associated (r = 0.8, p <0.01) and these traits did not associate significantly with grain yield. Hence, there is possibility for simultaneous improvement of both grain Fe and Zn content without compromising for grain yield.

Biofortification of lines of pearl millet (Pennisetum glaucum (L.) R.Br.) with increased iron (Fe) and zinc (Zn) will have great impact because pearl millet is an indispensable component of food and nutritional security of inhabitants of arid and semi-arid regions. The aim of the present study was to assess the stability of Fe and Zn content in recombinant inbred lines (RILs) developed for grain Fe and Zn content, and to use these lines in developing micronutrient-rich pearl millet hybrids. A mapping population consisting of 210 RILs along, with parents and checks, was assessed in three consecutive years (2014–16) under rainfed conditions at the same experimental location in an alpha design with two repetitions. Significant differences were observed in genotype, environment and genotype × environment interaction mean squares for all variables, particularly grain micronutrients. The first two principal components of an interaction principal component analysis cumulatively explained 100% of the total variation; respective contributions of the first and second components were 64.0% and 36.0% for Fe, and 58.1% and 41.9% for Zn. A positive and moderately high correlation (0.696**) between Fe and Zn contents suggests good prospects of simultaneous improvement for both micronutrients. Among the 210 RILs, RIL 69, RIL 186, RIL 191, RIL 149 and RIL 45 were found to be more stable with higher mean micronutrient content, additive main effects and multiplicative interaction stability value (ASV) and genotype selection index (GSI) under rainfed condition. These RILs are promising and can be tested further for their combining ability for yield as well as grain micronutrient content for developing superior biofortified, heterotic pearl millet hybrids.