Abstract
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.
Highlights
There is an increasing global attention towards addressing micronutrient malnutrition as the health impairment caused due to poor quality diet is more wide spread than low energy intake (Murgia et al, 2012)
Pearl millet grain iron and zinc content were having a wide range of variation at all six environments studied showing significant differences between genotypes in the analysis of variance (Tables S4A–E)
On the basis of occurrence of favorable alleles for high grain iron and zinc content in the panel, we have suggested a set of lines (Table 4) which can be used in the crossing programs to accumulate favorable alleles together in the segregating generations, resulting in higher Fe and Zn content
Summary
There is an increasing global attention towards addressing micronutrient malnutrition as the health impairment caused due to poor quality diet is more wide spread than low energy intake (Murgia et al, 2012). One-third of its share is from India alone (Barthakur, 2010) It is more prominent in inhabitants of low income countries who depend on cereal based low quality staple food (Tiwari et al, 2016). One among successful approaches to alleviate hidden hunger is biofortification, so that micronutrients can be delivered effectively to rural poor residents who majorly depend on staple food crops (Bouis and Welch, 2010; Saltzman et al, 2013). This can be achieved through molecular breeding. The biofortified products are cost-effective, sustainable, and remain within the purchasing power of rural poor (Pfeiffer and McClafferty, 2007; Bouis and Welch, 2010)
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