Identification of low phosphorus tolerant parental lines of hybrid rice based on stress indices and haplotype analysis using Pup1 linked markers

Phosphorus (P) stands as a crucial macronutrient, indispensable for a multitude of plant functions and a requisite for all crops, including rice. In Indian soil, the P content typically ranges from low to medium, dictating the application of P for targeted crop returns. The development of rice varieties resilient to low soil P has gained significance in ensuring future food security. To address this, 55 parental lines of rice hybrids were evaluated under both low and normal levels of soil P. The evaluation included identifying the presence or absence of the tolerant allele related to the major low soil P tolerance QTL, Pup1, using specific PCR-based markers-namely, K46-1, K46-2, K48 and K59. Stress indices were computed by comparing yields under low soil P (Ys) and normal soil P (Yp) conditions, revealing seven out of 55 parental lines to be categorized as low soil P tolerant. These lines demonstrated minimal yield reduction compared to the checks, with a majority carrying either the complete or partial Pup1 locus. Notably, the genotypes PSV-41 and Rasi, lacking the Pup1 locus, exhibited superior tolerance under low soil P conditions. Through biplot analysis utilizing Yp and Ys stress indices, promising genotypes such as AYT21, ATR-305, Rasi, RP bio 4919–50–13 and AR 19–42R were identified under low soil P conditions. These low soil P tolerant parental lines hold potential as donors and for generating low soil P tolerant rice hybrids in future breeding endeavors.