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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 Pup1locus. Notably, the genotypes PSV-41 and Rasi, lacking the Pup1locus, 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.

Breeding for “weed competitive” cultivars is a prioritized goal under direct seeded rice (DSR) conditions for achieving higher grain yields. Early seedling vigour (ESV) is an imperative trait that imparts weed competitiveness through initial rapid growth and uniform crop establishment. African rice species Oryza glaberrimahas been recognised as potential donors for weed competitive traits due to their early vegetative vigour. In the present study, 29 accessions of O. glaberrimawere evaluated for early seedling vigour traits under laboratory and DSR conditions. Seedling vigour index-I and II estimated from the paper roll method under laboratory condition revealed that six O. glaberrimaaccessions (EC861796, EC861801, EC861804, EC861814, EC861819 and EC861820) had higher/similar seedling vigour indices than high vigour check Sabita. In addition, during Kharif2017 and Rabi2018, O. glaberrimaaccessions were phenotyped for nine ESV traits, e.g.seedling height, number of leaves/tillers, leaf area, shoot fresh/dry weight, absolute growth rate, specific leaf area and crop growth rate under DSR condition. Significant genetic variation and genotype × environment interaction was observed for ESV traits under DSR condition. The heritability estimates for ESV traits were ranging from low to high, indicating complex inheritance of the trait. The study identified six accessions of O. glaberrima(EC861787, EC861790, EC861792, EC861795, EC861819 and EC861820) as promising accessions with early seedling vigour based on mean performance in both seasons under direct seeded rice condition. Thus, our study demonstrated inherent nature of early seedling vigour in O. glaberrimaand these promising accessions could be exploited for breeding weed-competitive rice cultivars.