Conventional and Molecular Breeding Approaches for Biofortification of Pearl Millet

Abstract

Pearl millet is an important nutri-rich cereal grown in Sub-Sahara Africa and Indian subcontinent. Shrinking of food basket to a few fine cereals like wheat and rice has contributed to inadequate intake of essential micronutrients such as iron (Fe) and Zinc (Zn). Pearl millet serves as a significant source of dietary energy and contributes to 19–63% of the Fe and 16–56% of the Zn intake from all food sources to a vast population in parts of the major pearl millet growing states of India. Genetic enhancement in pearl millet for increased micronutrients is a relatively new area and has focused so far on improving grain Fe and Zn contents since anemia and stunting are predominant across world. Significant progress has been achieved within short time. The area that have been addressed include (1) development of cost-effective screening protocol; (2) assessment of extent of genetic variation for grain Fe and Zn contents in available germplasm; (3) identification of elite genetic material with high Fe and Zn contents; (4) understanding nature of genotype × environment interaction and relationships between grain minerals and agronomic traits; and (5) genetic control of micronutrients. It has been established that iniadi germplasm from west and central Africa makes a valuable germplasm resource for genetic improvement of Fe and Zn contents in pearl millet and there also exists a large natural variation for grain Fe and Zn contents in elite breeding lines and commercial cultivars. Genetics of grain Fe and Zn contents have indicated a larger role of additive genetic variance in inheritance with little heterosis for higher Fe and Zn contents in hybrids. Simple selection has been shown to be effective in increasing the micronutrient contents in selected populations without any compromise in grain yield. Association studies between grain Fe and Zn contents showed highly positive and significant correlation between these two micronutrients indicating that improvement in Fe content may simultaneously improve the Zn content. On the other hand, variable results are available in association between grain yield and Fe and Zn contents. Nonetheless, commercial hybrids bred for higher yield and widely cultivated in India have been found to possess high Fe content showing the possibility of combining grain yield and micronutrient in cultivars. A high-yielding cultivar ‘Dhanashakti’ has been released for cultivation as a high-iron pearl millet variety for all India level in 2014 and has been adopted widely. A few other hybrids are in the process of testing and possible release. Efforts toward molecular breeding have only recently been initiated taking cognizance of development of molecular marker and availability of linkage maps. A few quantitative trait loci have been identified for higher Fe content and have been transferred in the genetic background of parental lines of commercial hybrid. The future prospects of biofortification breeding approaches in pearl millet are also discussed.