Plant Genomics

Biography

Biography: Reshma Rizvi

Abstract

Pearl millet (Pennisetum glaucum) is a global hunger & climate-change solution crop grown in the hottest, driest areas where dryland, rainfed and irrigated agriculture are practiced. Its production is most limited by low soil fertility and drought, and their interactions. Evidence suggests that phosphorus (P) is even more limiting than water in drier semi-arid zones of Africa and the Indian sub-continent. Plant species have evolved several adaptations to acquire P from P-deficient environments. These include changes in root architecture and exudates … that allow plants to access water and soil nutrients from larger soil volumes. The first component of this strategy can include shifts in plant root architecture (e.g., root depth explored, degrees and angles of branching, and proportions of fine vs thick roots). A second component of this strategy can involve acidification of the rhizosphere to mobilize poorly-available soil P, Fe, Zn, …. A third possible component of this strategy uses root exudates to attract symbiotic actinomycetes, bacte-ria, and/or mycorrhizae, …; but, this risks stimulating seed germination of parasitic weeds like Striga, Allectra and Orobanche spp. In situations where total soil P is limited, the only option may be to apply P; however, much applied P will soon be fixed in the soil in plant-non-available form(s). Limited access to P fertilizers, their high costs, and the relatively in-efficient use of ap-plied P fertilizers by the standing crops, make this a less viable option for resource-poor farmers in developing countries, especially in land-locked countries of West Africa where high transport costs result in local fertilizer prices three times the global average. Rock phosphates are slow-release and low-cost forms of phosphorus fertilizer which offer cost-effective solutions for af-fordable P supply to improve crop-livestock system productivity and sustainability in Africa and elsewhere. However, rock phosphates differ dramatically in their solubilities, and plants differ in their abilities to access these different forms of soil phosphates. Pearl millet genomic regions contributing to its low-P tolerance and/or ability to acquire P from poorly-soluble soil forms, are not yet understood well enough for applied use in marker-assisted selection to improve genetic gain for these traits. However, studies that provide some initial ideas are underway for this crop, as well as for rice, maize, and sorghum, in which such research has advanced considerably. Once the genomic regions contributing to more efficient phosphorus acquisition and use are mapped, it will be possible to use genome-wide marker-assisted selection to improve crop nutrient uptake from various forms of phosphorus applied to low-fertility soils.