Latency of infection in unripe avocados by Colletotrichum gloeosporioides is not due to inadequate enzyme potential
1989
Sivanathan, S. (Peradeniya Univ. (Sri Lanka). Dept. of Botany) | Adikaram, N.K.B.
Colletotrichum gloeosporioides produced exo-pectin lyase and protease in a) liquid cultures with incorporated washed cell wall material from unripe or ripe avocado and b) autoclaved immature fruit. The activity of exo-pectin lyase and protease produced in liquid cultures incorporating washed cell walls from immature fruit was almost the same as when washed cell walls from ripe fruits were incorporated. Ripe fruit tissue rotted by the fungus contained exo-pectin lyase, endo-polygalacturonase (endo-PG) and protease. The endo-PG was found to be endogenous to avocado fruit, and had a pH optimum of 5.5. The pH optima of exo-pectin lyase and protease were 8.5 and 7.5 respectively in all three enzyme preparations. All these enzyme preparations completely macerated avocado fruit tissue discs in vitro in less than 3 h of incubation but not potato tuber disc. Neither immature nor ripe fruit contained substances, proteinaceous or otherwise, which could inhibit the exo-pectin lyase or protease activity of the preparations. The results indicated that C. gloeosporioides possesses sufficient enzyme potential to invade cell walls of unripe fruit and that the fruit tissue does not have a mechanism to inactivate such enzymes
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