Early identification method of drought-tolerance of soybean cultivars.

A simple method of germination rate at 48hafterwaterabsorption was used and verified to investigate soybean drought-tolerance.The drought-tolerances of 109 soybean germplasms were graded according to seed germination rate at the germination stage,and then in pot watercontrol trails at vegetative growth (V3) stage and reproductive growth (R4) stage.Results indicated significant differences in droughttolerance of soybean materials.Water absorption made no difference to droughttolerance.However,germination rate of 48hafterwaterabsorption and droughttolerance were closely correlated.Seedling branch root number,main root length and root dry weight had significant (P0.05) positive correlation with droughttolerance.Under repeated stress of supplying water for 24h after germination and then no water for 24h,the survival rate of droughttolerant cultivars was higher than those of ordinary ones.At the vegetative growth stage (V3),temporary wilting (under soil moisture of 9% to 11%) treatment led to leaf wilting of ordinary cultivars,with reduced plant height,stem diameter and leaf area.Among the traits,the changes of stem diameter and leaf area were highly significant (P0.01).During the reproductive growth (R4) stage,temporary wilting led to significantly lower (P0.05) root biomass and branch biomass in ordinary cultivars.When moved to the seed filling (R6) stage,ordinary cultivars wilted without recovery.On the contrary,the droughttolerant cultivars still maintained ability to grow.These results indicated that 48hgerminationrate of soybean seeds could be used as a method in drought resistance identification and screening.They also showed that soybean plants at R6 stage were most sensitive to water stress.