Genetic Variation in Drought Resistance of Rice (Oryza sativa L.) at the Germination Stage

Drought stress is a major abiotic factor limiting rice growth and productivity. Establishing scientifically screening methods at the germination stage is critical for identifying superior drought-adapted genotypes. This study aimed to develop a novel discriminant equation for evaluating drought resistance in rice at the germination stage, with field yield data used as a benchmark to calibrate laboratory-based assessments. Seventy-six rice accessions from southern China were used as experimental materials. Drought resistance during germination was assessed using nine key physiological indicators, including vigor index and root length. Three statistical methods—Membership Function Comprehensive Evaluation Value (MFSV), Principal Component Analysis Comprehensive Evaluation Value (PCASV), and Grading Coefficient (GC)—were applied to classify drought resistance levels from different analytical perspectives. Field drought treatment was conducted throughout the growth period, and final grain yield was used to represent the comprehensive drought resistance (CDR) of each accession. Results showed that the nine indicators responded variably to drought stress. Drought resistance from the three statistical methods were inconsistent, with only 45% of accessions showing consistent classification across all methods, indicating that the choice of analytical approach influences the outcome. Correlation analysis revealed that MFSV, PCASV, and GC were all positively correlated with CDR, supporting the use of CDR as a reliable reference factor for integrating laboratory-based evaluations. Finally, a Fisher discriminant function was established using MFSV, PCASV, and GC as independent variables (X) and CDR as the dependent variable (Y), providing a more comprehensive and scientifically grounded method for assessing drought resistance during rice germination.