Comprehensive Evaluation of Cold and Anaerobic Tolerance in Rice <scp> <i>Oryza sativa</i> </scp> L. and Screening of Multistress‐Resistant Germplasm

ABSTRACT Rice, a globally important staple crop, faces significant yield instability in early and ratoon cropping systems in China due to the susceptibility of its bud burst and seedling stages to combined cold and anaerobic stresses. This study assessed 529 accessions from the global 3K core germplasm, alongside 84 leading Chinese cultivars and hybrid lines, under treatments for anaerobic tolerance (ATBS) and cold tolerance at both bud burst (CTBS) and seedling stages (CTSS). A comprehensive tolerance index ( D ‐value), rooted in post‐stress seedling recovery rates, enabled multistress resistance evaluation. Results revealed the Tej subgroup within the 3K germplasm excelled under all stress conditions; TrjB and TrjA subgroups exhibited notable CTBS and CTSS resistance; Indica II, Indadx and Aus groups showed ATBS advantages. Tropical and subtropical areas predominantly house anaerobic‐tolerant varieties, while cold‐tolerant accessions thrive in high‐latitude and altitude regions. D ‐value analysis identified three elite accessions (e.g., IRIS_313‐8658), with strong resistance across all stresses, 11 accessions (e.g., IRIS_313‐8982), with dual ATBS and CTBS tolerance and 35 accessions (e.g., IRIS_313‐11929), with robust CTBS and CTSS tolerance. Evaluations indicate inadequate ATBS in Chinese indica hybrids and insufficient CTSS in conventional indica varieties. We propose a ‘modular aggregation’ breeding strategy and model to enhance screening for combined stress resistance.