Differences in physiological responses of Brassica napus genotypes under water stress during seedling stage

Pot experiments were carried out to study the physiological responses and drought resistance variations in 17 rapeseed genotypes.The results showed that rapeseed genotypes had significant different responses to drought stress as indicating by 9 physiological characteristics.Leaf wilting index(WI) has the largest values for coefficient of variation and improvement potential.Average subordinate function(AS) values for 17 genotypes ranged from 0.12 to 0.94.The AS was significantly correlated with 9 physiological characteristics(especially WI and chlorophyll content).In addition,WI was closely associated with other eight physiological indexes.By using either subordinate function or clustering analysis,17 tested rapeseed genotypes could be classified into 4 distinct groups(i.e.no resistance to drought,low resistance to drought,medium resistance to drought,and high resistance to drought),and four genotypes(i.e.Huayouza 10,B108,Q2 and Zhongshuang 7) were identified as highly tolerant to drought stress with AS0.75.These genotypes could be used in drought breeding program.WI was recommended as a key index for drought resistance screening at seedling stage,in that it was highly correlated with all other AS and was very easy to measure.