Objective The comprehensive evaluation and screening system of acid-tolerant rice was established to explore the acid resistance characteristics of rice.

Method In this study, 96 rice varieties were treated with acid and control treatments. Ten traits including plant height, total root length, aboveground fresh weight, root fresh weight, total fresh weight, aboveground dry weight, root dry weight, root shoot ratio, total root surface area and total root volume were measured at seedling stage. Then, correlation analysis, membership function analysis, descriptive analysis, principal component analysis, cluster analysis and stepwise regression analysis were used to comprehensively evaluate the acid tolerance of rice. The acid tolerance evaluation model of rice was established, and the acid-tolerant rice varieties were screened and verified under acidic soil conditions in the field.

Result The plant height, total root length and aboveground fresh weight of different rice varieties under acid treatment were significantly lower than those of the control treatment, and the coefficient of variation of each index ranged from 22% to 66%. Through principal component analysis, 10 single indicators are converted into 3 independent comprehensive indicators, which represent 88.8% of the original information. Subsequently, the comprehensive evaluation value (D value) of acid tolerance of different rice varieties was clustered, and 96 rice varieties were divided into four groups, which were extremely acid-resistant type, acid-resistant type, intermediate type and sensitive type. The optimal regression equation was constructed by using the D value of different varieties of rice, and the screening system of acid-tolerant rice varieties was established. In addition, the plant height, setting rate and 1000-grain weight of acid-tolerant rice varieties were significantly higher than those of acid-sensitive rice varieties under acidic soil conditions in the field. The average yield of acid-tolerant rice varieties was 3.5 times higher than that of acid-sensitive rice varieties.

Conclusion Rice total fresh weight, total root length, total root volume, plant height and root dry weight can be used as indicators to screen out acid-tolerant rice varieties.