LAUSR

A two-year comprehensive field survey was conducted across major tomato growing areas of Iran. Two hundred and thirty-four tomato fields and six tomato-producing greenhouses were surveyed for the potential presence of bacterial spot disease. Five hundred ninety-six symptomatic and asymptomatic tomato samples were analyzed. While Xanthomonas sp. were found in association with both symptomatic and asymptomatic tomato plants from five surveyed counties, the bacterial spot disease was observed only from three of them. Only strains isolated from symptomatic plants induced disease symptoms on tomato while those isolated from asymptomatic plants caused symptoms only on cabbage and common bean. None of the strains caused disease symptoms on pepper and eggplant. Phylogenetic analyses showed that X. perforans is the causal agent of tomato bacterial spot in Iran although X. campestris and X. axonopodis were also associated with asymptomatic tomato plants. All X. perforans strains isolated in this study were sensitive to streptomycin, copper sulfate and copper oxychloride at concentrations of 50 mg/l, 200 mg/l of, and 0.8 g/l, respectively. Unlike type strain of X. perforans, strains isolated in this study did not produce bacteriocin against other Xanthomnas spp. nor were they detected using the usual species-specific primer pair Bs-XpF/Bs-XpR. This suggests an atypical nature of X. perforans strains in Iran, which leads to hypothesize that X. perforans strains isolated in Iran may have a separate origin than those causing disease epidemics elsewhere. Aggregated dispersal pattern of the diseased tomato fields signifies the seed-borne introduction of the pathogen into the country. This article is protected by copyright. All rights reserved.