First report of Alternaria arborescens causing leaf spot in manzano pepper (Capsicum pubescens)

Abstract

In Mexico, manzano pepper (Capsicum pubescens) is a crop of economic importance. In 2022, in the municipality of Taxco de Alarcon, Guerrero, Mexico, leaf spots were observed in the mazano pepper crop. The fungus Alternaria spp., was consistently isolated from symptomatic leaf of manzano pepper. A molecular characterization was carried out by amplification and sequencing of the internal transcribed spacer (ITS) region of ribosomal DNA, major allergen (Alt a 1), and anonymous gene region (OPA10-2). BLAST analysis indicated similarity that varied from 99.5 to 100% with Alternaria arborescens sequences in GenBank. A phylogenetic analysis was carried out using the Maximum Likelihood method of two isolates of Alternaria sp., obtained from manzano pepper, and indicated that they were clustered with A. arborescens sequences (CBS 115189 and CBS 112749). Using uninjured two month-old plants grown in greenhouse conditions, Koch’s postulates were verified and fulfilled. To our knowledge, this is the first report of Alternaria arborescens as a caused leaf spot in manzano pepper in Mexico and in the world.