GENETIC IMPROVEMENT OF PEARL MILLET (Pennisetum glaucum): A FOCUS ON GRAIN QUALITY TRAITS

Pearl millet is a crop with the potential to meet important nutrition challenges and achieve sustainable agricultural systems. Its high content of macro and micronutrients, low vulnerability to pathogens, tolerance to drought and salinity, and short life cycle, make this crop ideal as staple crop for growing populations. However, its nutritional quality is hampered by the presence of antinutrient molecules such as phytic acid (PA), which limits the bio-availability of minerals and of the C-glucosylflavones (CGFs) which may cause goitrogenic effects to consumers, PA is the major source of phosphorous in seeds, but it forms mineral complexes with Fe, Zn, Ca, K and Mg in the gut, causing problems such as poor mineral bioavailability and eutrophication of waterways. CGFs, a specific class of polyphenols, are able to interfere with and impair the metabolism of thyroid hormones thus causing goiter in populations using millet as the staple food. Aiming at identifying pearl millet inbred lines with low content of phytic acid (leading to higher content of bioavailable iron and zinc), C-glycosyl flavones and high content of essential minerals (Fe and Zn) in the grains we phenotyped for these traits in a panel of 145 pearl millet international genome wide association mapping population derived from the genetically diverse West African pearl millet germplasm accessions (PMiGAP-WCA) (only 69 for CGFs). The aim of the developing PMIGAP-WCA is to map the genomic regions and to apply genomic selection for traits of economic importance in WCA (West and Central Africa), such as, downy mildew resistance, head miner resistance, drought tolerance and nutritional quality traits. Contrasting lines with reduced and high PA amount (RPA and HPA, respectively) and reduced and high CGFs amount (RCGF and HCGF, respectively) were identified and further analyzed. The expression profiles (qRT-PCR) of 11 genes involved in PA biosynthesis and of a putative C-GucosylTransferase (CGT) were analysed during early, middle and late phases of grain development. Among the investigated genes only MIPS (myo-inositol phosphate synthase - Pgl_GLEAN10001337) showed an expression pattern correlating with the phytic acid content of the contrasting lines (higher MIPS gene expression detected in the HPA line). This outcome is very interesting and significant since MIPS catalyses the rate-limiting step in the synthesis of all inositol-containing compounds. As regards the CGFs biosynthesis, a slight increase of CGT (C-glucosyl transferase - Pgl_GLEAN10014648) gene expression was detected during early seed development and its contribution to the observed differences in CGFs content is at present under evaluation.