OCCURRENCE OF XANTHOMONAS SPECIES CAUSING BACTERIAL SPOT IN FRESH MARKET TOMATO FIELDS IN BRAZIL

Abstract

Tomato bacterial spot is caused by four Xanthomonas species (X. euvesicatoria, X. vesicatoria, X. perforans and X. gardneri), and is one of the most important diseases of both processing and fresh market tomato crops in Brazil. From 2005 to 2009, 81 isolates were collected from 23 commercial fields, in 11 states located in the southern, southeastern, central-west and northeastern regions of the country. The isolates were identified through rep-PCR based fingerprinting analysis (BOX and REP-PCR), by PCR with species-specific primers and pathogenicity tests on tomato and pepper susceptible cultivars. The majority of isolates were either X. perforans (49.4%) or X. gardneri (40.7%), which showed the highest number of haplotypes. Only 2 were X. euvesicatoria and 6 were X. vesicatoria. Presence of all 4 species could only be detected in the southeastern states. 32 isolates were pathogenic to both tomato and pepper, while 49 were pathogenic only to tomato. Isolates were also classified in races by avrRxv gene (present in race T1) and avrXv3 (present in race T3) PCR amplification and by hypersensitive reaction on tomato genotype carrying the Xv3 gene. Among the 81 isolates, races T1, T2 and T3 were identified, while races T4 and T5 of X. perforans were not detected.