Molecular breeding for phosphorus-efficient rice

Abstract

Rice is the main staple food for more than half of the world’s population and the main source of calories in most Asian and many African countries. Since many rice-dependent countries are poor, it is critically important to keep rice prices low and increase productivity to provide sufficient food for a growing population. However, a sustainable increase in rice production is possible only if nutrients removed with the harvest are replaced by application of either mineral fertilizers or manure. Since fertilizer costs are rising, depletion of soil nutrients is an increasing problem, especially in the developing world where most farmers do not have the resources to purchase sufficient fertilizer or do not have access to fertilizer. In addition, the majority of rainfed rice in Asia is produced on poor quality and problem soils that are often low in nutrients or have properties, such as low pH or high aluminum and iron, that render phosphorus (P) unavailable to plants. On those soils, very high fertilizer doses have to be applied to provide sufficient plant-available P. Given that currently known rock phosphate reserves, the source of P fertilizer, are limited it can be expected that P deficiency will aggravate and will increasingly limit productivity, especially in poor countries. One way to address this problem is to develop crops that are more efficient in acquiring P from the soil and applied fertilizer, or crops with higher internal P-use efficiency, that is, with higher biomass production per unit P. In this paper, we provide a brief comprehensive overview on P-related aspects of rice production and highlight the potential of molecular breeding approaches to improve P-efficiency. As an example, we describe the major quantitative trait locus Phosphorus uptake 1 ( Pup1 ), which confers tolerance of P deficiency.