Early Vigor of a Pyramiding Line Containing Two Quantitative Trait Loci, Phosphorus Uptake 1 ( Pup1 ) and Anaerobic Germination 1 ( AG1 ) in Rice ( O. Sativa L.)

Direct-seeded rice is one of the solutions against the issues of limited labor and time in the rice cropping system. Improved useful traits, such as fertilizer uptake and anaerobic germination, are needed to increase yield and efficiency in the direct seeding system in rice. Pup1 ( Phosphorous uptake1 ) containing PSTOL1 is useful in improving the phosphate uptake under rainfed/upland conditions. OsTPP7 is the major gene of AG1 ( Anaerobic Germination ), which shows anaerobic germination. IR64-Pup1-AG1 (I-PA) was developed by pyramiding Pup1 and AG1 . Around 20% of the chromosomal segments from the donor remained in I-PA. Phenotypic analysis revealed that I-PA showed better phenotypic performance under low and normal P conditions by enhancing the root system and tiller numbers during the early stage. Significantly better P uptake capacity of I-PA was observed upon a P-supplied soil condition. The coleoptile length and germination rate of I-PA showed tolerance under anaerobic-germinated conditions. PSTOL1 and OsTPP7 were independently expressed under different P conditions of soils, as well as anaerobic conditions. The newly developed breeding lines, I-PA, showed early vigor capacity through a high number of tillers, better P uptake, and germination in low-oxygen conditions. It will be a useful and improved breeding line for direct seeding rice breeding programs.