Objective The goal was to identify the aerobic adaptation of early seedlings of upland rice germplasm resources, screen out the superior germplasm resources with the abilities of seed germination under low water stress and seedling emergence from deep soil, and provide genetic materials and valuable guidance for breeding new viarieties with excellent aerobic adaptation.

Method Under the conditions of 150 g/L polyethylene glycol (PEG6000) mimicking low water stress and 8 cm soil deep-seeding, 24 lowland rice (including ‘Huanghuazhan’, ‘longjing39’ and ‘jingyue1’) and 24 improved upland rice (including ‘Luying46’,‘IRAT318’ and ‘IRAT11’) varieties were used to evaluate the aerobic adaptability indicators. In addition, these indicators were assessed for 246 upland rice landraces. The principal component analysis, membership function and comprehensive evaluation value of aerobic adaptation were used to evaluate these germplasms, and they were classified by cluster analysis.

Result The relative germination potential, germination rate, root length, bud length and root number between lowland and upland rice varieties under low water stress were significantly different, and could be used as indicators for identifying aerobic adaptation at the early seedling stage. Under deep-seeding condition, root length, shoot length, mesocotyl length and coleoptile length were mainly responsible for seedling emergence. According to their differences in aerobic adaptability, the germplasms could be divided into five types, including highly strong type (type Ⅰ), strong type (type Ⅱ), intermediate type (type Ⅲ), weak type (type Ⅳ) and extremely weak type (type Ⅴ). Finally, seven varieties with elite aerobic adaptability were obtained.

Conclusion This study identified the indicators of aerobic adaptation and comprehensively assessed the upland rice landraces in Yunan, which could provide a basis for fostering dry direct-seeding rice varieties.