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Bacterial canker of stone fruit trees caused by Pseudomonas syringae pv. syringae (Pss) interacts with several factors such as ring nematodes. The effect of infection of Mesocriconema xenoplax (Mx) and Pss and co-infection in pot conditions in the greenhouse on peach bacterial canker was investigated on GN and GF677 rootstocks, tolerant and susceptible to Mx, respectively. One-year peach seedlings (cv. Zaafarani), susceptible to Pss, grafted on these rootstocks were used. Infection treatments included nematode inoculation, bacterial inoculation, and inoculation with both pathogens. The experiment was conducted as a factorial in a completely randomized design with five replications. The results were evaluated and compared statistically based on disease severity, bud death, seedling height, root weight, total plant weight, and population of Mx in soil. The results showed a significant difference between GN and GF677 in terms of response to pathogen inoculation (s) based on evaluation indexes. In both vegetative rootstocks, canker severity and dead bud in seedlings co-inoculated with Mx and Pss were more than those only inoculated with Pss alone. In seedlings with GF677 rootstock, in infection with both pathogens, the rate of canker progression up to about 30 cm was measured and dieback was observed. In inoculation with only Mx and Pss, there was a significant difference in plant growth indexes (in both treatments) and nematode population and disease severity between the two rootstocks for inoculation with nematode and bacteria. Therefore, it can be concluded that Mx is a synergistic factor for peach trees (especially at a susceptible rootstock) to aggravate bacterial canker disease caused by Pss. [ABSTRACT FROM AUTHOR]

In order to identify the bacterial canker of poplar, various poplar clones in Gilan, Zanjan, Markazi, Western Azerbaijan, Kermanshah and Hamedan provinces were visited. Branches of one to several years old and trunk with canker symptoms were collected. Samples of Zanjan (eight isolates) and Markazi (four isolates) provinces were isolated from yellow and mucoid bacteria. The pathogenicity of the isolates on young shoots of poplar and hypersensitivity reaction in tobacco was proved. All bacterial isolates were gram-negative, oxidase, arginine dehydrolase, gelatin hydrolysis, lecithinase and urease negative, but in catalase test, they were positive and able to hydrolyze scolin, twin 80, produce levan and produce H2S from cysteine and peptone. All strains used sucrose, fructose, inositol, trehalose, galactose, sodium fumarate and sodium succinate as the only carbon source, but did not use al-arabinose, lactose, disorbitol, alumenose, raffinose, maltose, di-ribose and mellibiose. Based on their bacteriological properties and pathogenicity, all isolates were identified as Xanthomonas populi. The percentage of poplar trunk contamination in Khosbijan station (Arak) was determined between 0.0 to 13.3%. Based on our results, the lowest infection was observed in clones of P. alba (P. a 49.39) and P. betulifolia (P. b 56.21 and P. b 72.13) and the highest infection was observed in clones of Populus nigra (P. n 56.52, P. n 56.21 and P. n 72.14). This bacterium was not isolated from P. a 72.7 colony in Khasbijan site, nor from different colonies in Urmia, Kermanshah, West Azerbaijan and Hamedan. [ABSTRACT FROM AUTHOR]

Canker is one of the most damaging diseases of stone fruit trees which incites depressed brown to black lesions, often accompanied by exudation of gum, on twigs, branches and trunk of affected trees. The disease has been reported from different areas of Iran and shown to becaused by Pseudomonas syringae pv. Syringae a few case by Xanthomonas arboricola pv. pruni. To assess the distribution of the causal organisms samples were taken from fruit orchards in these regions. The stem tissues with canker symptoms were surface-disinfected in sodium hypochlorite, washed with sterile distilled water minced in drops of SDW. The suspension was plated on sucrose nutrient agar. The predominant colonies appearing on SNA were grayish-white, round and pasty. Representative isolates were tested for pathogenicity on peach seedling. Genomic DNA was extracted and a fragment of the 26S rRNA of the representative isolates was amplified by PCR and sequenced. The nucleotide sequence of 26S rRNA gene of the representative isolates showed high homology with sequences of Cryptococcus species. Comparison of their sequences with those deposited in GenBank. Also 27 isolates along with reference strains of Cryptococcus adeliensis and C. magnus were genetically characterized by using ERIC, REP, and BOXAIR primers in PCR. Cluster analysis was performed using NTSYS program. The isolates were separated into 11 genotypic groups by the concatenated data of rep-PCR at 33 % similarity level. The results demonstrated the existence of a considerable genetic diversity among isolates causing canker of stone fruit trees in the central provinces of Iran. [ABSTRACT FROM AUTHOR]