Genetic variation and diversity for grain iron, zinc, protein and agronomic traits in advanced breeding lines of pearl millet [Pennisetum glaucum (L.) R. Br.] for biofortification breeding

Genetic improvements of iron (Fe) and zinc (Zn) content in pearl millet [Pennisetum glaucum (L.) R. Br.] may reduce the problems of anemia and stunted growth among millet dependent staple food consumers. The availability of variation in diversebreeding lines is essential to improve grain micronutrients in high-yielding cultivars. This study aimed to determine the extent of variability, heritability and diversity for grain Fe, Zn and protein, along with key agronomic traits, in 281 advanced breeding lines bred at ICRISAT and evaluated across two seasons (environments). A pooled analysis of variance displayed significant variation for all these traits. Highest variability was recorded for Fe (35–116 mg kg-1), Zn (21–80 mg kg-1), and protein (6–18%), and a three-fold variation was observed for panicle length, panicle girth and 1000-grain-weight (TGW). Diversity analysis showed 10 clusters. Cluster-III had maximum lines (25%) and Cluster-V showed the highest mean values for Fe, Zn, protein and TGW. These results highlight the success of breeding program that aimed both the maintenance and creation of genetic variability and diversity. A significant positive correlation among Fe, Zn, protein and TGW indicated the potential for simultaneous improvement. Grain yield had a non-significant association with Fe and Zn, while protein showed a negative correlation. These results suggest that significant variability exists in elite-breeding lines, thus highlighting an opportunity to breed for biofortified varieties without compromising on the grain yield. The lines with high Fe, Zn and protein content can be used as hybrid parents and may also help in further genetic investigations

Terminal drought and a d 2 dwarfing gene affecting grain iron and zinc density in pearl millet

Pearl millet, predominantly a rainfed dryland crop, often encounters terminal drought in crop season. Grain hybrids grown in India are of medium to tall height, and majority of them are based on d2 dwarf seed-parents. Eight pairs of tall and d2 dwarf isogenic-lines, developed from two diverse composites, were evaluated under irrigated control and imposed terminal drought for two-years to examine the effect of d2 dwarfing gene and terminal drought on grain iron (Fe) and zinc (Zn) density. In general, terminal drought had a significant effect on increasing the Fe and Zn density, the d2 dwarfing gene or the linked gene block significantly decreased both micronutrients, with the magnitude of increase or decrease, respectively, dependent on the environment and genetic background of the isolines. Terminal drought has severe adverse impact on grain yield, but grains produced from such environments are likely to be more nutritious with respect to Fe and Zn density. The d2 dwarf hybrids are likely to be less nutritious than non-d2 hybrids with respect to Fe and Zn density. Whether the d2 dwarf seed parents with reduced Fe and Zn density presumably may adversely affect grain yield and micronutrient levels of even non-d2 hybrids developed on them, and this aspect merits further investigation

Energy-Dispersive X-ray Fluorescence Spectrometry for Cost-Effective and Rapid Screening of Pearl Millet Germplasm and Breeding Lines for Grain Iron and Zinc Density

Comparison of energy-dispersive X-ray fluorescence (XRF) and inductively coupled plasma-optical emission spectroscopy (ICP) for iron (Fe) and zinc (Zn) densities in pearl millet grain samples from 11 trials showed significant differences between these two methods for both micronutrients. XRF values were more often higher than the ICP values for both micronutrients, but the differences were significant in only 15–38% genotypes for Fe and in 7–25% genotypes for Zn across the trials. In 82% genotypes the differences between these two methods were ≤6 mg kg−1 for Fe; and in 88% genotypes, the differences were ≤4 mg kg−1for Zn. There were highly significant and high positive correlations between ICP and XRF for both micronutrients. Selection of genotypes above the XRF trial mean for Fe/Zn included at least 30% top-ranking genotypes based on ICP. Therefore, XRF can be used for cost-effective and rapid screening of a large number of grain samples in pearl millet biofortification programs

Association of Grain Iron and Zinc Content With Other Nutrients in Pearl Millet Germplasm, Breeding Lines, and Hybrids

Micronutrient deficiency is most prevalent in developing regions of the world, including Africa and Southeast Asia where pearl millet (Pennisetum glaucum L.) is a major crop. Increasing essential minerals in pearl millet through biofortification could reduce malnutrition caused by deficiency. This study evaluated the extent of variability of micronutrients (Fe, Zn, Mn, and Na) and macronutrients (P, K, Ca, and Mg) and their relationship with Fe and Zn content in 14 trials involving pearl millet hybrids, inbreds, and germplasm. Significant genetic variability ofmacronutrients andmicronutrients was found within and across the trials (Ca: 4.2–40.0mg 100 g−1, Fe: 24–145mg kg−1, Zn: 22– 96mg kg−1, and Na: 3.0–63mg kg−1). Parental lines showed significantly larger variation for nutrients than hybrids, indicating their potential for use in hybrid parent improvement through recurrent selection. Fe and Zn contents were positively correlated and highly significant (r=0.58–0.81; p<0.01). Fe and Zn were positively and significantly correlated with Ca (r = 0.26–0.61; p < 0.05) and Mn (r = 0.24–0.50; p < 0.05). The findings indicate that joint selection for Fe, Zn, and Ca will be effective. Substantial genetic variation and high heritability (>0.60) for multiple grain minerals provide good selection accuracy prospects for genetic enhancement. A highly positive significant correlation between Fe and Zn and the nonsignificant correlation of grain macronutrients and micronutrients with Fe and Zn suggest that there is scope to achieve higher levels of Fe/Zn simultaneously in current pearl millet biofortification efforts without affecting other grain nutrients. Results suggest major prospects for improving multiple nutrients in pearl millet

Breeding high-iron pearl millet cultivars: present status and future prospects

Micronutrient malnutrition, widespread in resource poor families in the developing world where large populations rely on cereals as staple food, has emerged as a major health challenge. Over 60% and 30% of the world’s populations are deficient in iron (Fe) and zinc (Zn), respectively1. About 80% of pregnant women and 70% children are reported to suffer from Fe deficiency, while 52% children (<5 years) have stunted growth in India2,3. Biofortification is a cost-effective and sustainable agricultural approach to deliver essential micronutrients through staple foods. Pearl millet is an important staple food in the arid and semi-arid regions of Asia and Africa. The primary focus of HarvestPlus-supported pearl millet biofortification research at ICRISAT is on improving Fe density with Zn density as an associated trait..

Effect of grain colour on iron and zinc density in pearl millet

Pearl millet (Pennisetum glaucum (L.) R. Br.) is a climate resilient crop with higher nutrition and serve as staple food for several million populations in semi-arid regions of India and Africa. To utilize the nutritional variability of this crop, biofortification research has been initiated to combat micronutrient malnutrition, chiefly iron (Fe) and zinc (Zn) deficiency. Large variability for grain Fe and Zn density has been reported in pearl millet and mostly the high-Fe lines had relatively dark grey grain colour. Therefore, this study was designed to investigate the effect of grain colour on grain Fe and Zn density in pearl millet. Two dark grey lines were crossed with five white grain colour lines to produce 10 hybrids. These hybrids were evaluated along with their parental lines for Fe and Zn density in two seasons. Highly significant Fe density differences observed for both parents and hybrids while significant Zn density differences observed only for hybrids. The significant genotype × environment (G × E) interaction observed for Fe and Zn density in hybrid trial. Interestingly, grain colour× environment variance was not significant for both micronutrients. Results indicate both micronutrients were not differed from white to grey grain lots among hybrids (70-103 mg kg-1 Fe density and 64-80 mg kg-1Zn density), implying the genetic improvement of grain Fe and Zn density in pearl millet is highly feasible without compromising the grain colour preference of the farmers and consumers. Further, highly positive and significant correlation between these two micronutrient density irrespective of the grain colour recommended increase in Zn density as an associated trait while breeding for high Fe density in pearl millet

Breeding Biofortified Pearl Millet Varieties and Hybrids to Enhance Millet Markets for Human Nutrition

Pearl millet is an important food crop in the arid and semi-arid tropical regions of Africa and Asia. Iron and zinc deficiencies are widespread and serious public health problems worldwide, including in India and Africa. Biofortification is a cost-effective and sustainable agricultural strategy to address this problem. The aim of this review is to provide the current biofortification breeding status and future directions of the pearl millet for growing nutrition markets. Research on the pearl millet has shown that a large genetic variability (30–140 mg kg−1 Fe and 20–90 mg kg−1 Zn) available in this crop can be effectively utilized to develop high-yielding cultivars with high iron and zinc densities. Open-pollinated varieties (Dhanashakti) and hybrids (ICMH 1202, ICMH 1203 and ICMH 1301) of pearl millet with a high grain yield and high levels of iron (70–75 mg kg−1) and zinc (35–40 mg kg−1) densities have been developed and released first in India. Currently, India is growing > 70,000 ha of biofortified pearl millet, and furthermore more pipeline cultivars are under various stages of testing at the national (India) and international (west Africa) trials for a possible release. Until today, no special markets existed to promote biofortified varieties and hybrids as no incentive price to products existed to address food and nutritional insecurity simultaneously. The market demand is likely to increase only after an investment in crop breeding and the integration into the public distribution system, nutritional intervention schemes, private seed and food companies with strong mainstreaming nutritional policies. The following sections describe various aspects of breeding and market opportunity for addressing micronutrient malnutrition

Inbreeding Effects on Grain Iron and Zinc Concentrations in Pearl Millet

The magnitude, direction, and pattern of inbreeding effects on trait expression in selfing generations have a direct bearing on single-plant and progeny-based selection efficiency. In the present study on a pearl millet [Pennisetum glaucum (L.) R. Br.] biofortification initiative, initial random mated S0 bulks of three diverse composites and their S1 to S4 population bulks derived from four generations of selfing were evaluated for 2 yr under irrigated and terminal drought stress for iron (Fe) and zinc (Zn) concentrations. Both Fe and Zn concentrations were higher under terminal drought than under irrigated condition. Inbreeding had no significant effect on Fe and Zn concentrations in one composite and showed significant though marginal increase of both micronutrients in two composites. This finding, not unexpected, was in conformity with the earlier reports of predominantly additive gene effects and marginal partial dominance of genes determining low concentrations of these micronutrients observed in a low frequency of hybrids. The patterns of genetic changes in Fe concentration due to inbreeding were highly significantly and positively correlated with those in Zn concentration in all three composites. These results indicate that simultaneous single-plant and progeny-based early generation selection for Fe and Zn concentrations is likely to be effective to enhance the breeding efficiency for these micronutrients in pearl millet

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

Nutritional Security in Drylands: Fast-Track Intra-Population Genetic Improvement for Grain Iron and Zinc Densities in Pearl Millet

Considering the pervasive malnutrition caused by micronutrients, particularly those arising from the deficiencies of iron (Fe) and zinc (Zn), the primary focus of research in pearl millet is on biofortifying the crop with these two minerals. Pearl millet is a highly cross-pollinated crop where open-pollinated varieties (OPVs) and hybrids are the two distinct cultivar types. In view of the severe deficiency of Fe and Zn in Asia and Africa where this crop is widely consumed, crop biofortification holds a key role in attenuating this crisis. The present study included three OPVs previously identified for high-Fe and Zn density to assess the magnitude of variability and test the effectiveness of intra-population improvement as a fast-track selection approach. Large variability among the S1 progenies was observed in all three OPVs, with the Fe varying from 31 to 143 mg kg−1 and Zn varying from 35 to 82 mg kg−1. Progeny selection was effective for Fe density in all three OPVs, with up to 21% selection response for Fe density, and up to 10% selection response in two OPVs for Zn density, for which selection was made as an associated trait. Selection for Fe density had no adverse effect on grain yield and other agronomic traits. These results suggest that effective selection for Fe density in OPVs and composites can be made for these micronutrients and selection for Fe density is highly associated with the improvement of Zn density as well. These genetic changes can be achieved without compromising on grain yield and agronomic traits. Such improved versions could serve as essentially-derived varieties for immediate cultivation and also serve as potential sources for the development of parental lines of hybrids with elevated levels of Fe and Zn density. Therefore, fast-track breeding is essential to produce biofortified breeding pipelines to address food-cum-nutritional security