Discovery of new genetic determinants of morphological plasticity in rice roots and shoots under phosphate starvation using GWAS

Phosphorus is an essential nutrient for plants that is often in short supply. In rice (Oryza sativa L.), inorganic phosphate (Pi) deficiency leads to various physiological disorders that consequently affect plant productivity. In this study, a large-scale phenotyping experiment using 160 Vietnamese rice landraces was performed under greenhouse conditions, by employing an alpha lattice design with three replicates, to identify quantitative trait loci (QTLs) associated with plant growth inhibition caused by Pi deficiency. Rice plantlets were grown for six weeks in the PVC sand column (16 cm diameter × 80 cm height) supplied with Pi-deficient medium (10 μM P) or full-Pi Yoshida medium (320 μM P). The effects of Pi deficiency on the number of crown roots, root length, shoot length, root weight, shoot weight and total weight were studied. From 36 significant markers identified using a genome-wide association study, 21 QTLs associated with plant growth inhibition under Pi starvation were defined. In total, 158 candidate genes co-located with the defined QTLs were identified. Interestingly, one QTL (qRST9.14) was associated with all three weight-traits. The co-located gene GLYCEROPHOSPHODIESTER PHOSPHODIESTERASE 13 was found to be potentially involved in Pi transport. Understanding the molecular mechanisms of Pi-starvation responses, and identifying the potential QTLs responsible for low-Pi stress tolerance, will provide valuable information for developing new varieties tolerant of low-Pi conditions.