Igor Henrique de Lima Costa, Gloria Emperatriz Suqui Carchi, Isabela Schneid Kroning, Maria Fernanda Fernandes Siqueira, Frederico Schmitt Kremer, Wladimir Padilha da Silva, Cândida Renata Jacobsen de Farias, Alvaro Renato Guerra Dias
Abstract
This study reports the first case of Alternaria alternata causing soft rot in pitaya (Hylocereus polyrhizus) fruits in Rio Grande do Sul, Brazil. Symptomatic fruits were collected from a commercial orchard, and the pathogen was isolated, characterized both morphologically and molecularly (using ITS, GAPDH, and TEF-1α loci), and tested for pathogenicity. The colonies exhibited mycelial growth of 5.24 ± 0.35 cm after 7 days and 8.08 ± 0.37 cm after 14 days, with olive gray centers and light brown edges. The obclavate or obpyriform conidia had transverse (1–6) and longitudinal (0–3) septa, with a short apical tip (5–22.5 μm). Molecular analysis revealed 100 % similarity with A. alternata sequences in GenBank, confirming the pathogen via phylogenetic analysis. Pathogenicity tests produced dark brown, depressed lesions with a clear halo, characteristic of the disease, confirming Koch’s postulates. The 100 % incidence in commercial fruit crops resulted in significant economic losses, exacerbated by favorable weather conditions. Thus, this study presents the first evidence of A. alternata associated with post-harvest soft rot in pitaya fruits in Brazil, underscoring the need for management strategies to reduce waste and economic losses along the production chain.