Abstract

Among Indonesia’s cultivated crops, tomatoes (including the smaller red cherry types) are popular. However, the production of red cherry tomatoes has failed to meet the demand, largely due to the significant impact of the fungal pathogen Fusarium oxysporum lycopersici, which has led to a decrease in tomato productivity by up to 40%. Addressing this issue is crucial for achieving sustainable red cherry tomato production. The use of synthetic fertilizers poses environmental concerns, including soil, water, and air pollution. Therefore, exploring yeast as a plant growth promoter in biofertilizers presents a promising alternative or partial substitution fertilizer opportunity. In this study, we characterized 63 yeast isolates based on their ability for phosphorus solubilization, ammonia production, hydrogen cyanide (HCN) production, indole-3-acetic acid (IAA) production, and antifungal activities against F. oxysporum, Cercospora beticola and Alternaria porri. Among the isolates, four showed the most promising characteristics and were further identified through molecular techniques. In vivo experiments were conducted utilizing red cherry tomatoes to evaluate the effectiveness of these isolates. The phosphate solubilization test revealed that 11 yeasts exhibited high solubilization index (SI) activity (SI > 2). None of the isolates tested positive for ammonia or HCN production, but two showed a positive result for the IAA production test. Antifungal activity assays demonstrated that 63 yeasts could inhibit F. oxysporum and C. beticola, while 62 yeasts inhibited Al. porri. Based on sequencing results of the ITS2 region, the four identified isolates were assigned as follows: C4 as Cyberlindnera fabianii, C7 as Cutaneotrichosporon mucoides, C10 as Yarrowia lipolytica and K2 as Aureobasidium melanogenum. In vivo experiments confirmed that all four isolates effectively reduced the presence of F. oxysporum. Notably, C. mucoides exhibited the strongest inhibition ability, as indicated by a disease incidence rate of 51.10%.