Isolation and identification of pathogens causing pineapple fruitlet core rot and screening of control agent

Objective To isolate and identify the pathogen responsible for Pineapple (Ananas comosu) fruitlet core rot (FCR), and screen control agents and field-based combination treatments, thereby providing a basis for studying the disease pattern and mechanism as well as green prevention and control.

Method Pathogens were isolated and purified, and the pathogenicity was verified using Koch’s law. The species of pathogens were determined according to the morphological characteristics of the strains and multi-gene sequence analysis. The inhibitory effects of the pathogen on five single agents and eight compound agents were determined using the mycelial growth rate method.

Result Nine genera of fungal strains were obtained by isolation and purification, among which two strains could infect pineapple fruitlets and cause brown spots. Combining morphological characterization with multi-gene sequence analysis, the pathogenic fungi that caused FCR were identified as Fusarium verticillioides LDL-3 and Talaromyces funiculosus LL-3, with LDL-3 being more pathogenic than LL-3. The results of fungicide virulence tests showed that flucytosine, feniconazole, pyraclostrobin, imidacloprid manganese salts and compound formulations had effects on the growth of the pathogens. Among these agents, imidacloprid manganese salts had a better inhibitory effect on LDL-3 with an EC₅₀ of 0.009 μg/mL, while pyraclostrobin showed a better inhibitory effect on LL-3 with an EC₅₀ of 0.134 μg/mL. Among eight compound formulations, benzyl · pyraclostrobin (volume ratio of difenoconazole and pyraclostrobin was 3∶1) inhibited both pathogens effectively with EC₅₀ less than 0.2 μg/mL. When insecticide, fungicide and growth regulator were used in combination, it still could effectively inhibit the pathogen growth with EC₅₀ less than 0.2 μg/mL.

Conclusion The FCR is mainly caused by Fusarium sp. and Talaromyces sp.. Benzyl · pyraclostrobin (3∶1, v/v) effectively inhibits these pathogens and offers a simplified and efficient solution for field control during flower induction and fruit expansion.