How constitutive defences affect the development of postharvest anthracnose and stem-end rot in mango fruit
Anthracnose disease caused by Colletotrichum species belonging to Colletotrichum gloeosporioides complex and the stem-end rot (SER) caused by Botryodiplodia theobromae are two major postharvest diseases in ripe mangoes. Unripe mango fruit are generally resistant to both these diseases and contain a formidable system of constitutive defences comprising antifungal resorcinols and chitinases in the latex and three closely related gallotannins in the peel tissue. On TLC bioassay, gallotannins were shown to be directly inhibitory to Colletotrichum isolates causing anthracnose but less inhibitory to B. thaeobromae causing SER. Conidia of both pathogens, when exposed to the aqueous phase of mango latex, became digested gradually. Retention of latex by keeping the pedicel intact in harvested fruits reduced both anthracnose and SER development during ripening. Eleven Sri Lankan mango cultivars screened showed varying resistance to anthracnose and SER. There was a positive correlation between the level of resorcinols and gallotannins in fruit peel and the degree of resistance to anthracnose. Mango cultivars more resistant to anthracnose showed greater levels of resorcinols in the latex while cultivars more resistant to SER had greater chitinase activity. These results suggest that the gallotannins and resorcinols contribute more towards the resistance of fruits to anthracnose whereas the chitinases appear to contribute more to the fruit resistance to SER.
Karunanayake, L.C., Sinniah, G.D., Adikaram, N.K.B. and Abayasekara, C.L. (2017). How constitutive defences affect the development of postharvest anthracnose and stem-end rot in mango fruit. Acta Hortic. 1183, 245-250
constitutive defences, resorcinols, antifungal compounds, fruit resistance, gallotannins, chitinase, mango diseases