Beno-Moualem, D., Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel
Vinokur, Y., Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel
Prusky, D., Department of Postharvest Science of Fresh Produce, Agricultural Research Organization, Volcani Center, Bet Dagan, 50250, Israel

Treatment of avocado callus originating from avocado mesocarp (MC-2) or pericarp (PC-1) with compounds mimicking cytokinin activity enhanced the level of epicatechin. Increasing thidiazuron (TDZ) in the medium (0.9 μM to 1.8 μM) tripled the epicatechin level of the mesocarp in cytokinin-dependent (MC-2) callus. TDZ also induced the level of epicatechin in the cytokinin-independent clone mesocarp (MC-1), but the overall level of epicatechin in this tissue was 12-fold lower than in the cytokinin-dependent callus. Preharvest spray of avocado cv. Fuerte fruits with TDZ (10 μM) or benzylaminopurine (BAP) (40 μM) increased activities of flavanone-3-hydroxylase (F3H) and dihydroflavanone reductase (DFR) at 2 weeks as well as levels of epicatechin and resistance to Colletotrichum gloeosporioides. Preharvest treatments of fruits of avocado cv. Ettinger with benzyl adenine delayed fruit softening and decay by 20%. It is suggested that compounds with cytokinin-like activity stimulate the flavonoid biosynthetic pathway in avocado tissue. This can lead to enhanced fruit resistance as shown by the delay in decay development due to C. gloeosporioides.