Pearl millet, known scientifically as Pennisetum glaucum and also called bajra across much of India, is a genuinely climate-resilient cereal. It thrives on sandy, low-fertility soils where wheat and rice fail, tolerates punishing heat, and produces grain with naturally elevated micronutrient levels compared with polished staples. Those qualities make it a priority crop for biofortification, the strategy of breeding staple foods to accumulate higher concentrations of minerals and vitamins in the edible portion. With anaemia and zinc deficiency still widespread across South Asia and sub-Saharan Africa, the prospect of a staple grain that combats hidden hunger simply by being eaten every day carries enormous public-health weight.

Yet breeding for both yield and nutrition simultaneously is not straightforward. Breeders need to know which traits are controlled by additive gene action, the cumulative effects of alleles that can be reliably fixed through selection, and which depend on non-additive effects such as dominance and epistasis, which are exploited best through hybridisation. The new study addressed exactly this question using a half-diallel crossing design. Ten genetically diverse inbred lines were crossed in all possible pairwise combinations without reciprocals, following Griffing’s Method 2 under a fixed-effect model, generating 45 F1 hybrids alongside their 10 parents, for a total of 55 entries.

The full set of entries was evaluated across two sowing-date environments at Jaipur in a randomised complete block design with three replications, allowing the team to estimate genotype-by-environment interaction alongside the classical combining-ability statistics. Grain yield per plant was recorded along with grain iron concentration, zinc concentration and protein content, with micronutrients quantified in a dedicated analytical laboratory. Statistical treatment included general combining ability (GCA), specific combining ability (SCA), Baker’s ratio for partitioning additive versus non-additive variance, heritability estimates, genetic correlation, and a multi-trait performance index that ranked genotypes under five different weighting schemes.

The central genetic finding is a clean division of labour between the two classes of traits. Biofortification traits, meaning grain iron, zinc and protein, were governed predominantly by additive gene action, with Baker’s ratios ranging from 0.71 to 0.91 and strikingly high heritability estimates between 0.90 and 0.94. In practical terms, micronutrient density behaves like a trait a breeder can simply select for and accumulate generation after generation, and selection in early generations will pay off. Genotype-by-environment interaction was statistically significant for iron and zinc, meaning sowing date or season shifted absolute concentrations somewhat, but the genotypic variance was substantially larger than the interaction variance, so heritability remained high and ranking of lines stayed meaningful. Protein content showed no significant interaction with environment at all, making it the most stable of the nutritional targets.

Grain yield told a different story. Yield was governed largely by non-additive gene action, with a Baker’s ratio of only 0.54 and significant genotype-by-environment interaction. This is the classic signature of heterosis, the hybrid vigour that arises when divergent parental lines are crossed and deleterious recessive alleles are masked while favourable dominance effects combine. The message for breeders is unambiguous: yield gains in pearl millet are best pursued through hybrid breeding programs, while micronutrient density is best pursued through recurrent population improvement that fixes favourable additive alleles in the parental pools. The authors therefore recommend an integrated strategy in which population improvement raises the nutritional baseline of breeding lines, and hybridisation then converts those improved lines into high-yielding commercial hybrids.

The combining-ability estimates identified standout parents for each nutritional target. Line RIB-9205 recorded the highest general combining ability for grain iron at 6.65, significant at P < 0.001, marking it as the donor of choice for iron-dense breeding material. RIB-9184 topped the GCA rankings for both zinc, at 3.85, and protein, at 0.78, both significant at P < 0.001, making it a dual-purpose nutritional donor. RIB-9185 emerged as a balanced combiner, contributing favourable additive effects to grain yield at 1.39 as well as to micronutrient concentrations, the kind of well-rounded parent that anchor-lines in breeding pipelines are built around.

When the hybrids themselves were ranked, one cross towered above the rest. RIB-9184 × RIB-15131 placed first under all five weighting schemes of the multi-trait performance index, scoring 1.31, an unusually robust result indicating its superiority does not depend on how yield and nutrition are weighted against each other. The hybrid produced a grain yield of 18.84 grams per plant while simultaneously delivering 46.16 milligrams of iron per kilogram of grain, 38.86 milligrams of zinc per kilogram, and 11.91 percent protein. For context, nutritionists have long targeted iron levels in the forties per kilogram of pearl millet grain as biologically meaningful for combating deficiency, and this hybrid achieves that benchmark without sacrificing productivity.

Perhaps the most consequential single number in the study is the genetic correlation between grain iron and zinc, estimated at rg = 0.82 and significant at P < 0.01. A correlation that strong means the two minerals are controlled largely by shared genetic machinery, so selecting lines for high iron will almost automatically raise zinc, and vice versa. This collapses a two-objective breeding problem into a single-objective one, accelerating progress and reducing screening costs. It also aligns with earlier quantitative trait locus mapping work in pearl millet, which has repeatedly found genomic regions harbouring QTL for both minerals, and with systematic reviews showing that high-iron millets measurably improve iron status and haemoglobin levels in human intervention trials. Randomised controlled trials have even demonstrated that biofortified pearl millet increases iron and zinc absorption above physiological requirements in young children.

The broader implications reach well beyond one experimental station. India’s National Family Health Survey documents a persistent double burden of malnutrition, with anaemia coexisting alongside other dietary deficits, and pearl millet is already grown by millions of smallholder farmers across the arid zones where nutritional deficiency bites hardest. A hybrid that raises yields for farmers while quietly enriching the grain for consumers embodies the double-win logic of biofortification at its most efficient. The study’s framework, a diallel analysis feeding directly into multi-trait ranking under realistic environmental variation, offers a template other national programs and international centres can replicate for sorghum, finger millet and other orphan cereals. If RIB-9184 × RIB-15131 or its descendants reach farmers’ fields, the arid belts of Rajasthan and beyond may soon grow a grain that pays its way in the market and in the bloodstream alike, a fitting legacy for the researcher whose vision the paper memorialises.

Subject of Research: Genetic analysis of combining ability and gene action for grain yield and iron, zinc and protein biofortification in pearl millet hybrids bred for arid regions.

Article Title: Combining ability and gene action for grain yield and biofortification traits in pearl millet [Pennisetum glaucum (L.) R. Br.]: implications for breeding high-yielding biofortified hybrids in arid regions

Article References: Punia, M., Sharma, L. D., Gothwal, D. K., Kajla, S. L., Rolaniya, L. K., Sharma, V., & Jat, R. L. (2026). Combining ability and gene action for grain yield and biofortification traits in pearl millet [Pennisetum glaucum (L.) R. Br.]: implications for breeding high-yielding biofortified hybrids in arid regions. Theoretical and Applied Genetics, 139(10), Article 265. https://doi.org/10.1007/s00122-026-05378-4

Image Credits: AI Generated

DOI: 10.1007/s00122-026-05378-4

Keywords: pearl millet, biofortification, combining ability, grain iron, grain zinc, hybrid breeding, diallel cross, gene action, genotype-by-environment interaction, heritability, hidden hunger, arid regions