A phytotoxic activity in extracts of broth cultures of Mycosphaerella fijiensis var. difformis and its use to evaluate host resistance to black Sigatoka

Crude extracts from 28-day-old coconut (Cocos nucifera) and soybean (Glycine max) broth cultures of Mycosphaerella fijiensis var. difformis caused tissue necrosis on treated banana (Musa acuminata) and plantain (Musa acuminea×M. balbisiana) plants. The phytotoxic activity could be extracted by either chloroform or ethyl acetate. Phytotoxic activity was evaluated by either dipping cut leaf tips of banana and plantain plants developed from meristem cultures into a 1:10 aqueous dilution of the extract or by puncturing the leaf with a sharp needle through a 20-μl droplet of the diluted extract placed on the leaf surface. (…)