Determination of Phosphorous-deficient Tolerance in Thai Lowland Rice Cultivars Based on Pup1-K46 Marker

Abstract

Phosphorus (P) deficiency is one of the major constraints for rice production due to its natural availability. The low P stress affects rice growth and yield, thereby food security. Using genetic markers to determine P-deficient tolerance is a promising tool to improve rice for sustainable production. Phosphate uptake 1 (Pupl-K46) is a diagnostic gene-based marker to confer the P-deficient tolerance in rice. This marker is dominantly conserved in upland ecotypes, but its presence in lowland rice cultivars has not yet been well-understood. In this study, thirty-one of the 61 Thai lowland rice cultivars were detected with the Pup/ region. Twenty to 21 lowland rice cultivars with and without the Pupl-K46 region were then selected and grown under half- or full- strength low P (0.25 or 0.5 mg/l) and high P (5 or 10 mg/l) Yoshida solutions for three or four weeks to determine the P-deficient tolerance, respectively. Results showed that the low P (LP) condition reduced rice biomass, total P concentration, P uptake, and Pi content in the rice tissues, except for chlorophyll content. Interestingly, the Pupl-K46+ cultivars maintained less shoot mass reduction and higher relative efficiency of P use (REP) than the Pupl-K46" cultivars under both LP conditions. Additionally, the Pupl- K46* cultivars accumulated higher root P concentration and P uptake as well as greater amount of Pi content in their shoot and root than the Pupl-K46 cultivars. These suggested that the Pupl-K46+ cultivars were more tolerant to the P starvation by holding superior shoot growth and accumulating higher P uptake and total P concentration via their roots. The Pupl-K46+ cultivars also maintained soluble Pi against low P availability by storing it in cytoplasm. It is therefore confirmed that the Pupl-K46 region empowers lowland rice cultivars to withstand the P deficiency like the upland rice ecotype.