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Pistachio (Pistacia vera L.) is a perennial woody plant that produces edible seeds with a high nutritional value. Canker disease is one of the important diseases of pistachio, causing considerable loss globally. During 2019–2021, a series of symptoms, including tree weakness, brown to black lesions, canker, and exudation of black sap were observed on the trunk of pistachio trees from different regions of Lorestan province, western Iran. Bacterial isolation resulted in the development of uniform and yellow colonies on yeast-extract peptone glucose agar (YPGA) medium 24 hours post-inoculation (hpi). The colonies were then purified on YPGA and yeast-extract-dextrose-calcium-carbonate agar (YDC). Based on the analysis of morphological, biochemical, and molecular characteristics using nucleotide sequences of the gyrB, infB, atpD, and 16S rRNA, a putative pathogen was identified as Pantoea agglomerans (formerly Enterobacter agglomerans). To fulfill Koch's postulates, bacterial suspensions (107 CFU/ml) were inoculated to one-year-old pistachio seedlings. Thirty days after inoculation, small necrotic lesions developed on the bark in the vicinity of inoculation sites, followed by brown necrotic streaks in the inner bark. Subsequently, the bacterial strains exhibiting the characteristic colony morphology were retrieved from lesions on inoculated pistachio seedlings and verified as P. agglomerans. To the best of our knowledge, this is the first report on the occurrence of pistachio canker caused by P. agglomerans.

Mycopathogenic bacteria play a pivotal role in the productivity of edible mushrooms grown under controlled conditions. In this study, we carried out a comprehensive farm survey and sampling (2018 to 2021) on button mushroom ( Agaricus bisporus) farms in 15 provinces in Iran to monitor the status of bacterial pathogens infecting the crop. Mycopathogenic bacterial strains were isolated from pins, stems, and caps, as well as the casing layer on 38 mushroom farms. The bacterial strains incited symptoms on mushroom caps ranging from faint discoloration to dark brown and blotch of the inoculated surfaces. Among the bacterial strains inciting disease symptoms on bottom mushroom, 40 were identified as Ewingella americana based on biochemical assays and phylogeny of 16S rRNA and the gyrB gene. E. americana strains differed in their aggressiveness on mushroom caps and stipes, where the corresponding symptoms ranged from deep yellow to dark brown. In the phylogenetic analyses, all E. americana strains isolated in this study were clustered in a monophyletic clade closely related to the nonpathogenic and environmental strains of the species. BOX-PCR-based fingerprinting revealed intraspecific diversity. Using the cutoff level of 73 to 76% similarity, the strains formed six clusters. A chronological pattern was observed, where the strains isolated in 2018 were differentiated from those isolated in 2020 and 2021. Taken together, due to the multifaceted nature of the pathogen, such a widespread occurrence of E. americana on mushroom farms in Iran could be an emerging threat for the mushroom industry in the country.

International audience; In Iran, during 2013-16, 16 Gram-positive corynebacteria-like strains were recovered from the epiphytic parts of solanaceous vegetables including eggplant, pepper and tomato. The strains were recovered accidentally as a result of monitoring for other bacterial pathogens in solanaceous fields. The strains were phenotypically different from Clavibacter michiganensis strains. Although none of the strains were pathogenic on their host of isolation or on any other solanaceous plants, 12 out of 16 strains were pathogenic on common bean, cowpea, mung bean and soybean. Colonization by strains was observed on maize, zucchini, faba bean, honeydew melon, rapeseed, sugar beet and sunflower plants under greenhouse conditions. In PCR tests, the primer pair CffFOR2/CffREV4, specific for Curtobacterium flaccumfaciens pv. flaccumfaciens, enabled the amplification of the appropriately sized fragment in 12 out of 16 strains, and all 12 strains were pathogenic on dry beans. Phylogenetic analysis, using the gyrB and recA genes, showed all 16 bacterial strains clustered within several pathovars of C.flaccumfaciens. A nonpathogenic yellow-pigmented strain (Xeu15) was clustered with the type strains of C.flaccumfaciens pv.betae and C.flaccumfaciens pv.oortii. Bacteriocin profiling assays revealed no significant differences among the pathogenic and nonpathogenic strains. Host range and population dynamics of four representative strains on 17 plant species showed population build-up of the strains only on common bean, cowpea, wheat and red nightshade plants. The results provide important insights into the possible role of nonhost plants as reservoirs of plant pathogenic bacteria, which has important implications in plant disease epidemiology and management.

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.

International audience; Bacterial wilt of dry beans, caused by Curtobacterium flaccumfaciens pv.flaccumfaciens (Cff), is one of the most severe diseases affecting dry bean production worldwide. In Iran, the disease outbreak was first reported in 2012, which was limited only to some restricted areas of the country. Subsequently, Cff has rapidly spread and established itself across the major dry bean growing areas of Iran, and currently it represents a severe constraint for growers in terms of crop yield and quality. To better understand the spread of the disease and genetic and phenotypic diversity of the pathogen, including host range, we conducted a comprehensive survey across twelve Iranian provinces, where legume crops are widely grown. In addition, we performed isolations and characterizations of the causal agent. Our results showed that, besides previously reported disease outbreaks from East Azerbaijan and Markazi provinces, legumes cultivated across West Azerbaijan, Zanjan, Ghazvin, Alborz, Fars and Lorestan provinces were widely affected by the pathogen. cff strains with two different colony variants (yellow and orange) were isolated from the infected tissues which were different in terms of pathogenicity and host range. Ten out of eleven different legume species tested were infected by the pathogen and only yellow sweet clover did not show any symptoms. The yellow variant of the pathogen was more aggressive than the orange one on a number of hosts including cowpea, lima bean, broad bean and pea. Unlike the orange variant, the yellow variant of the pathogen caused disease on wild hairy vetch, a major weed in dry bean growing areas of Iran, thereby suggesting the role of weeds as a potential reservoir of the pathogen. It is concluded that, given the seed-borne nature of the pathogen, frequent phenotypic diversity observed, and a wide host range of the strains, an effective management of the disease requires the development and adoption of a number of tools, still poorly available. In particular, there is an immediate need to develop more sensitive and reliable detection methods (e.g. molecular seed screening techniques) that allow detection of the pathogen from seeds, and help reduce the risk of pathogen introduction into a given area.