NONHOST RESISTANCE TO COLLETOTRICHUM-LAGENARIUM IN PUMPKIN AND SQUASHIS NOT PRIMARILY ASSOCIATED WITH BETA-1,3-GLUCANASE AND CHITINASE ACTIVITIES

Disease symptoms typical of anthracnose were observed in cucumber, pum pkin and squash after infiltrating leaves with a conidial suspension o f Colletotrichum lagenarium, but symptoms developed only in cucumber w hen droplets of the conidial suspension were applied to the leaf surfa ce. There was no difference in the germination of conidia or in appres sorium formation on leaf surfaces of cucumber, pumpkin or squash plant s; however, penetration was markedly reduced into pumpkin and squash w ith or without systemic acquired resistance (SAR) and into cucumber wi th SAR. Little beta-1,3-glucanase and chitinase activities were detect ed in challenged pumpkin and squash leaves without symptoms even 5 day s after inoculation in leaf surfaces. However, the enzymes were detect ed in pumpkin and squash leaves with symptoms, and activities of the e nzymes were greater than those in cucumber. These results suggest that beta-1,3-glucanase and chitinase activities are not primary initial d efence compounds associated with non-host resistance of pumpkin and sq uash to C. lagenarium. (C) 1997 Academic Press Limited.