Alternaria spp. causing postharvest decay on apple fruit in Nigde province, Turkey

Abstract

Postharvest rots caused by Alternaria spp. result from infections occurring in the apple orchard at or before harvest and these may remain quiescent during the growing phase and only result in decay during postharvest cold storage. Therefore, the objective of this study was to identify and characterize Alternaria spp. associated with apple black spot and/ or decay during cold storage in Nigde, Turkey. Isolates of Alternaria spp. were obtained from apple fruit (cvs Fuji, Golden Delicious, Granny Smith, Red Delicious, and Starking Delicious) with dark, dry, spongy lesions. The symptomatic fruits were sampled from 18 commercial cold storages in the Nigde Province, Turkey, during the 2020/21 storage period. Decayed fruits were transferred to the laboratory for isolation of the fungi from the lesions. In total, 75 Alternaria isolates were characterized morphologically and were differentiated into 5 phenotypic groups based on their colony morphology, and characteristics of their conidiophores and conidia. At least 5 representative isolates were randomly chosen from each group for the pathogenicity tests. All Alternaria spp. isolates caused round, dry, dark, spongy lesions on/in the inoculated fruits and re-isolates from the inoculated apples of each phenotypic groups were similar to the initial isolates of each group in morphological characteristics. Molecular characterization of isolates is in progress. Since mycotoxin produced by Alternaria spp. in fruits is of unavoidable risk to human health, special care should be given in regards to the need to reduce widespread postharvest losses caused by Alternaria spp. in the cold storages of Niğde, which is the most important apple producer province of the country.