IDENTIFICATION AND PHYTOTOXICITY OF 3-METHYLTHIOPROPANOIC AND TRANS-3-METHYLTHIOPROPENOIC ACIDS PRODUCED IN CULTURE BY XANTHOMONAS-CAMPESTRIS PV VITIANS

Two phytotoxic metabolites were isolated from culture filtrates of Xan thomonas campestris pv. vitians, the causal agent of lettuce leaf spot s and headrot. The two compounds were identified as 3-methylthiopropan oic (1) and trans-3-methylthiopropenoic (2) acids by chemical and spec troscopic methods. Toxic effects of the two compounds on leaf tissues and protoplasts of lettuce and cabbage were investigated. Solutions of 1 and 2 induced chlorosis and necrosis on lettuce leaves at minimum c oncentrations of 300 and 50 mu g/ml, respectively. Infiltration in cab bage leaves did not produce any symptoms. The LD(50) values for 1 and 2 against lettuce protoplasts were 15 and 16 mu g/ml, respectively. Ac tivity of the two metabolites against cabbage protoplasts was very low (LD(50) > 500 mu g/ml).