Pearl millet has recently emerged as a significant irrigated summer season cereal crop in northwestern India. But its flowering coincides with air temperatures of ≥40 • C, leading to reduced seed set and poor grain yield in most of the available hybrids, although a few hybrids with good seed set and high yield potential are widely cultivated. Under a recent initiative to diversify the genetic base of heat tolerant hybrids, field screening of 221 hybrid parental lines (both Band R-lines), 53 germplasm accessions and 4 improved populations over four-year period revealed large genetic variability in seed set at daily maximum air-temperature of ≥42 • C during flowering. Two locations data on 46 medium maturing genotypes screened during summer 2009 showed that seed set in pearl millet started declining when maximum air temperatures reached 42 • C and decreased in curvilinear fashion to 20 percent at 46 • C. Similar relationship of seed set with minimum and mean temperature was observed with threshold values of 26.4 • C and 34.2 • C, respectively. Similarly, the relationship of percent seed set with vapor pressure deficit (VPD) showed threshold value of 6.2 kPa for maximum VPD, 1.2 kPa for minimum VPD and 3.7 kPa for mean VPD. Seed set on 2 each of heat tolerant and susceptible genotypes fitted well on the seed set-temperature response curve for the maximum, minimum and mean air temperatures. Based on 3 to 4 year field screening (2009-2012), five hybrid seed parents (ICMB 92777, ICMB 05666, ICMB 00333, ICMB 02333 and ICMB 03555) and a germplasm accession IP 19877 with 61 to 69% seed set as compared to 71% seed set in a heat tolerant commercial hybrid 9444 (used as a control) was identified. Intra-population variability for heat tolerance was observed in four populations, and highly heat tolerant progenies from two of them were identified. Evaluation of six hybrid parents under controlled environment (maximum temperature of 43 • C and minimum temperature of 22 • C) revealed boot-leaf stage of pearl millet plant to be more heat sensitive than panicle-emergence stage, and investigations on 6 A-/B-pairs under controlled environment (max. temperature of 44 • C and min. temperature of 22 • C) revealed female reproductive system of pearl millet to be more heat sensitive than pollen. Comparison of 23 hybrids and their parents for seed set at high air temperature (>42 • C) showed heat tolerance as a dominant trait, implying heat tolerance in one parent would be adequate to produce heat tolerant hybrids in pearl millet. Heat tolerant composite developed using identified lines showed high mean seed set under high air temperatures during flowering.

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Pearl millet is an important food crop in the arid and semi-arid tropical regions of Africa and Asia. These regions are home to millions of poor smallholder's households living in harsh agroecology and reported higher prevalence of malnutrition. . Indeed, pearl millet is one of the food crops they continue to grow for their food and nutritional security. Considering inherent high nutritional values and climate resilient nature (drought and heat), demand for pearl millet as food, beside valued for its Stover as a source of livestock fodder, is projected to grow strongly in Asia (India) and Africa (West and Central Africa). Iron (cause anemia) and zinc (cause stunting) deficiencies are widespread and serious public health problems worldwide, including India and Africa. Biofortification is a cost-effective and sustainable agricultural strategy to address this problem. Aim of this review is to provide current status and future directions of pearl millet biofortification for growing nutrition markets. Research on pearl millet has shown that 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. Both Open -pollinated varieties (Dhanshakti and Chakti) and hybrids (ICMH 1202, ICMH 1203 and ICMH 1301) of pearl millet with high grain yield (>3.5 tons/ha in hybrids) and high levels of iron (70-75 mg kg −1 ) and zinc (35-40 mg kg −1 ) densities have been developed and released in India. Currently, India growing >70,000 ha of biofortified pearl millet, besides more pipeline hybrids and varieties are under various stage of testing at the national (India) and international (west Africa) trials for possible release. Biofortification program utilized the existing high-Fe lines identified from the mainstream program to serve the immediate objective of developing high-yielding and high-Fe hybrids. Genomic tools will be an integral part of biofortification breeding program particularly to use diagnostic markers and genomic selection for micronutrients. Several biofortified varieties and hybrids released in pearl millet. Till today, no markets to promote biofortified varieties and hybrids as no incentive price and such products aims to address food and nutritional security challenges simultaneously. The demand is likely to increase only after investment in crop breeding and integration into modern public distribution system, nutritional intervention schemes, private seed and food companies with strong mainstreaming nutritional policies. In the non-traditional regions, this will contribute to livestock and poultry feed industry as spill-over benefits to improve nutrition. The following sections of this review describing various aspects of breeding for increased market opportunity of this crop towards addressing micronutrient malnutrition.

Crop biofortification is increasingly being recognized as a cost-effective and sustainable approach to address the widespread micronutrient malnutrition arising from Fe and Zn deficiencies. Pearl millet as a cereal crop species has higher Fe density than all other major cereals. Earlier studies in pearl millet have shown that breeding lines, hybrid parents, improved populations and composites having high Fe and Zn densities were often based largely or entirely on iniadi pearl millet germplasm. In an attempt to identify additional sources of high Fe density in this group of germplasm, 297 accessions were screened using Perl's Prussian Blue staining, of which 191 accessions (118 from Togo, 62 from Ghana and 11 from Burkina Faso) were re-evaluated during the 2010 rainy and 2012 summer seasons using the inductively coupled plasma atomic emission spectroscopy method. On the basis of the mean performance over the two seasons (environments), large variability was observed for both Fe (51 -121 mg/kg) and Zn (46-87 mg/kg) densities. There was a highly significant and positive correlation between the two micronutrients (r ¼ 0.77, P , 0.01). Of these re-evaluated accessions, 49% had higher Fe density than the high-Fe control commercial cultivar ICTP 8203 (81 mg/kg), and most of these accessions also had Zn density $61 mg/kg (59 mg/kg for ICTP 8203). A total of 27 accessions (20 from Togo and seven from Ghana) having a Fe density of 95 -121 mg/kg (1 standard error of difference above that for ICTP 8203) and a Zn density of 59-87 mg/kg were selected as a valuable germplasm resource for genetic improvement of these two micronutrients in pearl millet.

We describe a program at ICRISAT, India, fo r breeding pearl, millet fo r disease-resistance and high grain yield. Large-scale, reliable techniques for screening in the field for dow ny mildew, ergot and smut have been developed and are routinely being used. Since dow ny mildew is economically important, all breeding material passes through the downy mildew-screening nursery and resistant varieties and hybrids have been bred. Synthetic varieties have been produced which are also resistant to smut and are agronomically good. Variability from African germplasm material, particularly for disease resistance, head volume, and seed size, has been exploited in crosses with Indian material. African parent age occurs in nearly all o f the advanced breeding products o f the ICRISAT program. Recurrent selection has been used to produce open-pollinated varieties, one o f which (WC-C75) is the first to be released in India where it already occupies a considerable, hectarage. Conventional pedigree breeding has been used to produce synthetic parents, pollinators and seed parents. Several new seed parents have been released, and this broadens the genetic base o f the hybrid crop which previously relied heavily on a single malesterile line.