Genotypic variation for tolerance to phosphorus deficiency in rice and the potential for its exploitation in rice improvement

Deficiency in phosphorus (P) can severely limit rice yields. Developing cultivars with tolerance to P deficiency may represent a more sustainable solution than sole reliance on fertilizer application. To assess genotypic variation for tolerance to P deficiency the P uptake of 30 genotypes was measured on P-deficient soil. Variation for P uptake was high, ranging from 0.6 to 12.9 mg P/plant, Traditional varieties were superior to modern varieties. A major quantitative trait locus for P uptake had previously been identified in a population developed by crossing the modern variety 'Nipponbare' with the P deficiency-tolerant landrace 'Kasalath'. This quantitative trait locus was transferred to 'Nipponbare' by three backcrosses. Under P deficiency this improved line surpassed 'Nipponbare' in P uptake by 170% and in grain yield by 250%. These results show that the genotypic variation for tolerance to P deficiency in rice can be used successfully in rice improvement. By combining high P uptake of the donor variety 'Kasalath' with a high harvest-index characteristic of modern varieties it was possible to more than triple the grain yield of 'Nipponbare' under P deficiency.