Objective Freshwater shortages pose a serious threat to the development of rice production, leading to yield losses. This study aims to comprehensively evaluate the drought resistance of core rice germplasm, identify morphological and physiological differences in how different rice accessions respond to drought stress, helps provide a theoretical basis for the screening and breeding of drought-resistant rice varieties.

Method Fourteen typical rice germplasm accessions were used as test materials. Their agronomic traits were assessed under drought stress, with conventional paddy field cultivation serving as the control. Fifteen agronomic traits were measured during the tillering stage, grain-filling stage, maturity stage, and a drought resistance index and coefficients were calculated. A comprehensive array of physiological indicators was measured at the boosting stage, encompassing CAT activity, MDA, soluble sugar, and proline (Pro) contents. The physiological differences among different rice germplasms were analyzed using variance analysis, and their drought resistance was comprehensively evaluated using correlation analysis, principal component analysis, membership function analysis, and cluster analysis.

Result Drought stress inhibited rice growth, with yield traits being the most sensitive to drought (drought resistance index 0.20-0.27). Plant height, leaf area, panicle length, panicle formation rate, filled grain number, thousand-grain weight, and grain-setting rate showed extremely significant positive correlations with the drought resistance coefficient, while tillers number showed a significant negative correlation with the drought resistance coefficient. Principal component analysis identified three principal components with a cumulative contribution of 83.207%. Comprehensive evaluation screened out 3 highly drought-resistant accessions ('Kao deng', 'Kao kao', and 'Xilu 53', with a comprehensive drought resistance value of D ≥ 0.790), 10 moderately drought-resistant accessions, and 1 drought-sensitive accession ('Azucena'). The MDA content and CAT activity of highly drought-resistant rice accessions were both significantly lower than those of the drought-sensitive accession; soluble sugar content decreased in a gradient as drought resistance increased, with highly significant differences observed among the different drought resistance types; there were no significant differences in Pro content.

Conclusion Plant height, leaf area, number of tillers, and panicle length can serve as simple auxiliary indicators for the preliminary evaluation of rice drought resistance. The synergistic maintenance of panicle formation rate, grain-setting rate, and thousand-grain weight are the core indicators of drought resistance and stable yields. Three highly drought-resistant germplasm accessions were identified; under drought stress, they primarily rely on membrane protection mechanisms to withstand adverse conditions, rather than achieving drought resistance through the massive accumulation of osmoregulatory substances.