The role of chlorogenic acid in the resistance of apples to apple scab (Venturia inaequalis (Cooke) G. Wind. Aderh.)

The content of chlorogenic acid was studied in three scab resistant apple cultivars (‘Topaz’, ‘Gold Rush’, ‘Goldstar’) and two scab susceptible ones (‘Golden Delicious Weinsberg’, ‘Golden Delicious Clone B’) growing in Laboratory Field of the Biotechnical Faculty in Ljubljana. The leaf samples were collected four times in 30 day intervals between 12 June and 10 September 2001 and analysed using the system of high pressure liquid chromatography (HPLC). The content of chlorogenic acid was determined by means of a standard. It did not differ statistically significantly between the resistant cultivars and the two susceptible ones. At all four dates, leaves of the cultivar ‘Goldrush’ contained statistically significantly larger quantities of chlorogenic acid than leaves of the remaining scab resistant and scab susceptible cultivars. The content of chlorogenic acid changed during the growing period: it was the highest in July or August while in September it declined. The scab infection of the leaves of scab susceptible cultivars affected the accumulation of chlorogenic acid in the way that its content increased with the degree of infection. Greater amount of chlorogenic acid was contained in the leaves of the cultivar ‘Golden Delicious Weinsberg’ than in the leaves of the cultivar ‘Golden Delicious Clone B’.