The Production of Certain Cell Wall-Degrading Enzymes by Leptosphaeria Maculans in Culture and in Stem Canker Lesions of Oilseed Rape

Leptosphaeria maculans causes stem canker on oilseed rape (Brassica napus). Studies using sodium polypectate and rape cell wall media show that the pathogen can produce a variety of cell wall-degrading enzymes in liquid culture. There is also an accumulation of cell wall-degrading enzymes in stem canker lesions. The levels of polygalacturonase, α- l -arabinanases, β- l -galactanases and carboxymethyl-cellulase were studied in three oilseed rape/L. maculans interactions up to 40 days after inoculation. The early accumulation of high levels of polygalacturonase in the most susceptible interaction indicates a probable role for this enzyme in severe canker formation, whereas high levels of the other enzymes monitored were only detected after the compatibility of the interaction had been established. The importance of regulation of cell wall-degrading enzyme activity in disease resistance is discussed.