Biological Control of Lasiodiplodia Rot of Mango Fruits by Yeasts

Abstract

Ninety nine yeast isolates were isolated from surface of mango fruits and were tested in vivo in preliminary study for biocontrol potential of Lasiodiplodia rot of mango fruits. According to primary screening, nine isolates were selected to continue the secondary screening using different concentrations of the washed yeast cells in water suspension to study their biocontrol efficacy at 16±1°C. It was found that using washed cells of yeast isolate Mg 147 (Candida multisgemmis) at 1x10 9 , 5x10 8 and 2x10 8 CFU/ml produced complete protection for 14 days to wounds of mango fruit inoculated with spore suspension of the fungus Lasiodiplodia theobromae 1x10 5 conidia/ml. Meantime, no lesion developed on the mango fruit treated with the isolates Mg 39 (Pichia guilliermondii strain A) at the highest tested colony forming unit (CFU) levels, i.e. 1x10 9 and 5x10 8 CFU/ml. Supernatant of the yeast cultures, tested in secondary screening, did not prevent spore germination of L. theobromae or decay of wounded mango fruit but had inhibitory effect. However, 1-Methylcyclopropene (1-MCP) treatment significantly reduced the infected area mm 2 on mango fruit inoculated with L. theobromae (1x10 5 conidia/ml) during the 14 days of storage at 16±1°C and improved efficacy of isolates Mg147 and Mg39. When applied as combined treatments between 1-MCP and biocontrol agents, no lesion developed on the fruit treated with the isolate Mg 147 at 1x 10 8 CFU/ml or higher. Meanwhile, no lesion developed on the fruit treated with the isolate Mg 39 at 2x 10 8 CFU/ml or higher while, the percentages of rot reduction were ranged between 94.1%-81.3% for concentrations 1x10 8 and 6.6x10 7 CFU/ml respectively.