Cultivar differences in antifungal activity and the resistance to postharvest anthracnose and stem-end rot in mango (Mangifera indica L.)

Abstract

The study investigated the possible role of the three classes of constitutive antifungal substances in mangoes in the differential cultivar resistance to anthracnose and stem-end rot (SER). Fruits of eleven mango cultivars were screened for anthracnose and SER development during ripening. Basal level of antifungal activity due to constitutive gallotannins, resorcinols and chitinase in the fruit peel/latex was determined in six of these cultivars. The results showed a clear variability in the resistance of fruits to anthracnose and SER among cultivars. The cultivars, ‘Gira’ and ‘Karutha Colomban’, were among the most resistant to anthracnose disease but were susceptible to SER. Gallotannin activity was high in unripe and ripe fruit peel of all except ‘Willard’, the cultivar most susceptible to anthracnose but resistant to SER. There was a significant negative correlation between the level of gallotannins in the fruit at ripe stage and anthracnose development among six cultivars tested. ‘Gira’ and ‘Karutha Colomban’ that are among the most resistant cultivars to anthracnose showed higher levels of total resorcinols in the latex and 5-(12-cis-heptadecenyl)resorcinol in the unripe fruit peel. Chitinase activity was highest in ‘Rata’ and ‘Kohu’ that are resistant to SER and lowest in cultivars ‘Gira’ and ‘Karutha Colomban’ that are susceptible to SER. The results suggest that mainly the gallotannins and also 5-(12-cis-heptadecenyl)resorcinol contribute to the cultivar resistance of mango fruit to anthracnose pathogen, Colletotrichum gloeosporioides, while chitinases appear to contribute more to the fruit resistance to the SER pathogen, Botryodiplodia theobromae.