The effect of pathogen inoculation or chemical treatment on activities of chitinase and beta-1,3-glucanase and accumulation of salicylic acid in leaves of green bean, Phaseolus vulgaris L

Changes in activity of two pathogenesis-related (PR) proteins, beta-1,3-glucanase and chitinase, and in amounts of free and bound (glucosylated) salicylic acid (SA) were measured in extracts of leaves at different times after treatment of the unifoliate leaves with Colletotrichum lindemuthianum or 2,6-dichloro-isonicotinic acid (INA). There were no significant changes in beta-1,3-glucanase activity in extracts of unifoliate leaves 1 day after either treatment compared with controls. Chitinase activity had increased slightly at this time in response to both treatments. Substantial increases in the activities of both enzymes were observed in extracts of unifoliate leaves 5 days after they had been treated with C. lindemuthianum and lesser increases after INA treatment. Significant increases in enzyme activity were also detected in extracts of first and second trifoliate leaves harvested 9 and 13-14 days after treatment respectively. Increases following INA treatment were then greater than those after fungal inoculation except for chitinase activity in first trifoliates. Salicylic acid levels were not affected in unifoliate leaves 1 day after treatment with C. lindemuthianum or INA. However, C. lindemuthianum inoculation caused massive increases in the accumulation of free and glucosylated SA in first trifoliate leaves 7 days after treatment. The amount of free and bound SA was 10.8 times and 33.5 times higher, respectively, than in water controls. In second trifoliate leaves harvested 13 days after treatment, the greatest accumulation of total SA occurred in C. lindemuthianum-inoculated plants. INA treatment did not enhance the accumulation of SA. Bound SA accounted for the majority of total SA in each sample. (C) 1996 Academic Press Limited.