Involvement of epicatechin in cultivar susceptibility of avocado fruits to Colletotrichum gloeosporioides after harvest
1988
Prusky, D. (Volcani Center, Bet Dagan (Israel). Agricultural Research Organization) | Kobiler, I. | Jacoby, B.
Avocado cultivars were defined as susceptible and resistant to Colletotrichum gloeosporioides depending upon the length of the incubation period of the diesase after fruit softening. In the susceptible cultivars Fuerte, Horshim, Vurtz, Rincon and Benik, epicatechin concentration of the peel decreased to 69-130 mu.g(-1), fr. wt. at fruit softening and symptoms appeared on the same or one day later. In the resistant cultivars Hass, Nabal, Netaim and Pinkerton, epicatechin concentration was still 632-1740 mu.g(-1) fr. wt. when fruit softening and symptoms appeared only 4-10 days later. When susceptible Fuerte fruits became soft the - concentration of the antifungal compound 1-acetoxy-2-hydroxy-4-oxo-heneicosa-12,15 diene, had decreased to 120 mu.g(-1) fr. wt. and symptoms appeared. In resistant Hass fruits, the antifungal diene was still 238 mu.g(-1) fr. wt. at fruit softening, and it had further decreased to 159 mu.g(-1) fr. wt. when symptoms appeared, four days later. A modified atmosphere and 0.2 M CaCl2 infiltration both delayed softening of Fuerte fruits, but symptom appearance on these fruits was related to diene decrease and not to fruit softening. The results are discussed in relation to the hypothesis that the susceptibility of avocado cultivars to post-harvest decay by C. gloeosporioides is related to the degradation of the antifungal diene, catalyzed by avocado lipoxygenase, the activity of which is regulated by the decline of its inhibitor epicatechin
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