Phosphate Solubilizing Endophytic Yeasts of Soursop and its Suppressive Effect on Aflatoxigenic Aspergillus flavus

Background: Many microorganisms isolated from plant surfaces and inside tissues are ecofriendly and beneficial for biofertilizer and biopesticides. Recent studies showed that colonization of plants by endophytic yeast have been studied due to their capacity to solubilize phosphate and produce organic acids that may be used to control toxigenic fungi. The aim this research was to investigate endophytic yeasts of soursop fruit to solubilize phosphate and their organic acid against toxigenic A. flavus. Methods: The fresh healthy ripe fruit were harvested and followed by surface sterilization. The inner tissue was homogenized and a serial dilution up to 10-11 CFU/ml. All dilution were pour plated with malt extract agar medium (MEA). Three replications were made for each dilution. All plates were incubated for 7 days at 29oC. Each yeast isolate was initially enumerated, isolated and examined for morphological characteristics. The potential of endophytic yeast to dissolve phosphate was observed in Pikovskaya’s medium. Coconut agar medium contain 30% organic acid produced by each isolate was used to determine mycelial growth and aflatoxin production of Aspergillus flavus. Result: Showed four endophytic yeasts were isolated and Rhodotorula sp. was the most dominant species (27´1011 CFU/ml), whereas. Candida sp. was the highest P solubilization index (7.71), organic acid producer (0,00354%) and inhibit mycelial growth and aflatoxin production of A. flavus.