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Isolation, identification, and evaluation of the most aggressive fungi isolated from yellow pitahaya (Selenicereus megalanthus) in postharvest period

Abstract:

Background: The production and export of yellow pitahaya (Selenicereus megalanthus) in Ecuador has increased during the last decade. However, the presence of pathogens that cause decay in this fruit is a risk factor for the export and marketing of this product. Objectives: To isolate and identify fungal strains in fruits of yellow pitaya, and to assess the severity caused by pathogenic fungi in whole pitahayas during the postharvest period. Methods: The isolation was performed in fruits which exhibited signs and symptoms of fungal diseases (40 fruits were used, with one repetition). The identification of each strain was performed by macro and microscopic analysis of the pathogen grown in PDA (Potato Dextrose Agar) at 25 ° C, then were compared with mycological keys. The assessment of severity in the fruits was performed with selected fungi. The fruits were artificially inoculated with two different spore concentrations (103 and 105 conidia mL-1) by a wound in the equatorial zone of the sterile fruit. The disease severity was evaluated by determining the rot diameter (cm) for 21 days at 12 °C and 90% relative humidity (RH). 20 fruits, for each studied strain and for each inoculum concentration were used. An analysis of variance (ANOVA) was performed, the differences between averages and least significant difference (LSD) test at 95% confidence level were determined. Results: Strains of the genera: Alternaria, Aspergillus, Fusarium, Mucor, Penicillium and Rhizopus were identified as pathogens agents in postharvest of yellow pitahaya. Alternaria fungal genus was the most aggressive in the fruits of pitahaya, reaching a value of 4.44 cm at a concentration of 105 conidia mL-1 at 21 days of refrigerated storage. Conclusions: Of the six pathogens identified in the yellow pitahaya postharvest, Alternaria sp. was determined as the most aggressive pathogen.