Archivio Journal of Plant Pathology

Abstract:

During the summer of 2015, leaf deformations and chlorotic mosaic symptoms on leaves and unusual necrotic lesions on leaves, stems and fruits were observed on pepper (Capsicum annuum) plants grown in Almeria (Spain). Symptomatic leaf and fruit samples from eight collected plants, carrying L3 and L4 resistance against tobamovirus, were analyzed by ELISA specific for potyviruses, Cucumber mosaic virus and each of the following possible pepper-infecting viruses: Paprika mild mottle virus, Tobacco mosaic virus, Tomato mosaic virus, Tobacco mild green mosaic virus, and Pepper mild mottle virus (PMMoV). The eight plants tested negative for all viruses except for PMMoV. Mechanically inoculated extracts from two PMMoV-positive, singly infected symptomatic pepper plants systemically infected C. annuum cv Mazo (Unigenia), but not C. chinense PI159236, C. chacoense PI260429, four commercial L4, and two L3 resistant pepper plants, which exhibited local necrosis symptoms. Total RNAs from two plants inoculated with single infections were extracted, analyzed by reverse transcription PCR using primers designed to specifically amplify the coat protein gene (CP) of PMMoV (Antignus et al., 2008) and directly sequenced. Two independent samples yielded identical nt sequences (GenBank accession No. KT962848) and BLAST analysis showed the highest deduced aa identities of 99.4% with P1,2 isolates (M81413, AB000709, EF434393) of PMMoV. However, the predicted aa sequence possessed an Ala→Thr mutation at residue 66 of the CP. To our knowledge, although PMMoV has been shown to have variants that fail to infect L3 and L4 resistant pepper plants, based on unique CP coding sequences, this is the first report of a new P1,2 pathotype in Spain.