Root biomass explains genotypic differences in phosphorus uptake of rainfed rice subjected to water and phosphorus stresses

Aims Rainfed rice in subSaharan Africa suffers from combined drought and phosphorus (P) deficiency stresses. Enhanced root development under water stress may counteract the physical effects of drought lowering soil P bioavailability. This study was set up to evaluate how rice genotypes respond differently to variable water stress in P deficient conditions. Methods A greenhouse study was conducted with a full factorial combination of six genotypes, two soil P treatments (strong to moderate P deficiency) and two irrigation (W) regimes (rainfed limited and adequate). Plants were grown for 49 days and root traits were measured. Results The overall effects of P supply on shoot weight were larger than overall effects of water supply, water stress effects were most pronounced at highest P supply because of the higher transpiration in larger plants. Reduced water supply did not enhance P stress, and the stress antagonisms were genotype dependent. There was no genotypic variation in the increased root development in response to drought that would lead to increased P uptake. Root weight and root efficiency mainly explained shoot P content across all water treatments and genotypes with marginal effects of root architectural traits. Conclusion This study illustrates the importance of root biomass production and root efficiency under the combined stresses of water and P and corroborated the superior performance of genotypes Chhomrong Dhan and FOFIFA 172 that was found in the field.

Automated summary

Rainfed rice in sub-Saharan Africa faces the challenges of drought and phosphorus deficiency. This study examined the response of different rice genotypes to variable water stress under conditions of phosphorus deficiency. The results showed that the effects of phosphorus supply on shoot weight were greater than the effects of water supply. Reduced water supply did not enhance phosphorus stress, and the stress response varied among genotypes. Root biomass production and root efficiency were found to be important factors in combating the combined stresses of water and phosphorus. The study confirmed the superior performance of the genotypes Chhomrong Dhan and FOFIFA 172 found in the field.