Induction of defense mechanisms in greengram leaves and suspension-cultured cells by Macrophomina phaseolina and its elicitors

When greengram (Vigna radiata) leaves were inoculated with Macrophomina pha seolina, activities of phenylalanine ammonia-lyase (PAL) and peroxidase act ivities increased several fold. Synthesis of phenolics and lignin were also induced in the inoculated leaves. A glycoprotein elicitor was isolated fro m cell walls of M. phaseolina. Another proteinaceous elicitor with xylanase activin was isolated from culture filtrate of the fungus. When the trifoli ate leaves with petiols were dipped in either of these elicitors, similar i ncreases in PAL and peroxidase and their metabolic products phenolics and l ignin were observed. Suspension-cultured cells of greengram, which responde d to the fungal elicitors, were established. When the suspension-cultured c ells were treated with either of these elicitors, a sharp increase in PAL a nd peroxidase activities and several fold increases in the synthesis of phe nolics and lignin were observed. Thus, cultured greengram cells mimic the r eaction of the greengrarn leaves and the fungal elicitors mimic the true fu ngal infection process.