Cell Wall Degrading Enzymes and Permeability Changes in Sunflower (Helianthus annuus) Infected with Alternaria helianthi

The inoculation of leaves of resistant (EC 68414) and susceptible (EC 68415 C) cultivars of sunflower with Altentaria helianthi evoked a differential response in activities of cell wall degrading enzymes. Polygalacturonase (PG) and cellulase activities increased progressively upon infection in leaves of susceptible (EC 68415 C) cultivar upto 7 and 9 days respectively. In contrast, a decline in activities of PG and cellulase was discerned in leaves of EC 68414 upto 9 days after inoculation (DAI). Although β 1,3 glucanase activity increased upon infection in both the cultivars, the magnitude of increase was much more in EC 68414 (142.7%) than that in the blight sensitive variety (41.0%) at 9 DAI stage. Electrolyte leakage also enhanced progressively throughout the duration of the infection from I DAI to 9 DAI stage in the susceptible cultivar to 2.6 folds over their uninoculated control plants while no change was recorded in membrane permeability of resistant cultivar (EC 68414). The results suggest that PG and cellulase may play a role in pathogenesis and β 1,3 glucanase in expression of resistance.