In vitro screening of biological control agents on Lasiodiplodia theobromae of mango

Stem end rot of mango, caused by Lasiodiplodia theobromae, is a severe pathogen of the mango worldwide. Lasiodiplodia theobromae is ranked second to Colletotrichum gloeosporioides in postharvest diseases. Therefore, controlling its effects on the postharvest disorders of mango is a priority. The use of microorganisms as biological control agents is favoured over synthetic fungicides that leave toxic residues on the fruits and are environmental pollutants. This study evaluated the use of yeast and Bacillus species as potential biological control agents for the control of L. theobromae in vitro. The biological control agents were isolated from different fruits and plant parts and tested for their efficacy in inhibiting the growth of L. theobromae mycelia in vitro. A total of 45 yeast and 18 Bacillus isolates were isolated from avocado leaves and peels of mango, avocado, and apples for screening against L. theobromae on potato dextrose agar at 28°C in vitro. Nine of the 45 yeast isolates tested in primary and secondary screening inhibited the mycelial growth of L. theobromae by more than 50%, with isolate Pl21 showing 64.58% mycelial growth inhibition. Four Bacillus isolates (Bsc11, Bcs16, Bcs17 and Bcs18) of the 18 tested in primary and secondary screening inhibited the mycelial growth of L. theobromae by more than 50%; isolate Bcs17 exhibited 69.16% mycelial growth inhibition. In general, the results suggested that the Bacillus isolates more effectively controlled L. theobromae than yeast isolates, although they were all ranked similarly in inhibition efficacy.