Correlation analysis of amino acids components in cucumber root exudates and fusarium wilt resistance
枯萎病不同抗性黄瓜(Cucumis sativus L.)根系分泌物氨基酸组分与抗病的相关性

Root exudates have an important effect on the resistance to soil-borne disease in some crops. Free amino acids are important components of some crop root exudates. The cucumber (Cucumis sativus L.) is an economically important vegetable, and fusarium wilt (Fusarium oxysporum. f. sp. cucumerinum owen) infection in cucumber production can be severe. Rigorous investigation of root exudates requires the study of correlations between amino acids components and disease resistance. Therefore, an experiment was designed to investigate this correlation.Root exudates were collected from five cucumber cultivars possesing different fusarium wilt resistance reactions. Free amino acids from these root exudates were then detected using an Automatic Amino Acid Analyzer. Data indicate that the kinds and contents of amino acids examined were different in these root exudates. Sixteen kinds amino acids were detected in root exudates of intermediate-resistant cucumber cultivars (Jinchun 3# and Zhongnong 1101), toindicate aspartic acid, methionine, leucine, glycine, phenylalanine, histidine, arginine, serine, glutamic acid, lysine, tyrosine, cysteine, threonine, alanine, valine, and isoleucine. Arginine was not found in the root exudates of the susceptible cucumber cultivars (Jinyan 4# and Qiupeng), and histidine and arginine were not found in resistant cultivars (Zhongnong 13). The research conclusion moreover, general amino acid content increased with increased degree of susceptibility in these cucumber varieties. Correlations between root exudates and disease indices in these cultivars indicated that disease indices were positively correlated with arginine, serine, and lysine content. However, disease indices were negatively correlated with the contents of the other thirteen amino acids examined. The correlation between phenylalanine content and disease indices was significant (P<0.05) and positive (0.95). A significant (P<0.05) negative relationship was detected between the disease indices and the ratios of content of serine to the asparagines (-0.943), alanine (-0.956), and glycine(-0.902), respectively. The disease indices were highly negatively correlated (P<0.01) with the ratios of content of serine to phenylalanine (-0.959).