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Angular leaf spots of sleepy mallow Malvaviscus penduliflorus have been observed in some areas of Mazandaran and Golestan provinces. The spots were angular, brown and necrotic. A levan positive and oxidase negative pseudomonad was isolated from the symptomatic leaves. The biochemical and physiological characteristics and profile of fatty acid methyl esters of the causal bacterium was very similar to Pseudomonas syringae pv. syringae. Pathogenicity of selected strains was confirmed by inoculation of sleepy mallow with bacterial suspension of several strains. PCR amplification using the syrB specific primer pairs yielded the expected 720 bp fragment from all strains. In rep-PCR, the fingerprints of the strains from sleepy mallow showed 28% similarity to those of the standard strains of P. s. pv. syringae. However, on the bases of difference in host specifity, some genotypic properties, sequencing of some highly conserved genes (rpoD and gyrB), the strains isolated from angular leaf spot on sleepy mallow just were similar to Pss but were genetically distinct from other groups and may represent a new pathovar of P. syringae belonged to another genemospecies. [ABSTRACT FROM AUTHOR]

Grapevine fanleaf virus (GFLV) is one of the most destructive grapevine viruses worldwide. The best strategy to control the virus is to cultivate virus free plant material in non-infested soils. Therefore, detection of the virus plays a key role in control of GFLV. To establish a reliable and sensitive technique for detection of GFLV in the stock grapevines or in preparation of virus free grapevines, samples from different vineyards of Iran were collected in 2009 and their infection by GFLV was assessed by DAS-ELISA. Fourteen ELISA positive samples were subjected to RT-PCR using GFLV published primers and the primers designed in this study. Most of the primers available in literature failed to detect GFLV in all 14 tested samples, whereas the primers designed in this study detected the virus in all mentioned samples. The efficacy of the designed primers in this study was confirmed by detection of the virus in further 35 ELISA positive samples collected from other provinces in 2010. Moreover, GFLV infectivity of grapevines for the first time was confirmed by green grafting. The results revealed that the combination of the green-grafting with RT-PCR method, using the introduced primers in this study, offers a reliable method for detection of GFLV isolates. [ABSTRACT FROM AUTHOR]

Cucurbit yellow stunting disorder virus (CYSDV), a member of the genus Crinivirus (family Closteroviridae), causes considerable losses in cucurbits. Using of the resistant cultivars is a potential option for control of the disease induced by CYSDV. In this research twenty five accessions of Cucumis melo, including local melons, collected from different regions in Iran, were evaluated under controlled conditions for their reaction to Iranian CYSDV isolate, (Bushehr). Inoculations were made at first true leaf-stage with Bemisia tabaci. Assays included mean of disease severity index 6 weeks after inoculation, time of symptoms development (infection percentages 20 days after inoculation) and virus concentration in plant (mean ELISA value 8 weeks after inoculation). Only two accessions Chorook zard and Til zard showed delay in symptom development, low disease severity index and low concentration of the virus. They were considered resistant to the virus and tolerant to the disease. The accessions Zard khareji, Zard moshabbak dorosht, Zard talaee and Sefid because of low concentration of the virus in ELISA and Sirjan and Kashefi because of delay in symptoms development were resistant to virus. Yazdi, Zard talaee, Sirjan, Zard moattar and Sefid had low disease severity index and rated tolerant. Other accessions were highly sensitive to the virus. [ABSTRACT FROM AUTHOR]

The shallow bark canker of Persian walnut (Juglans regia L.) trees incited by the bacterium Brenneria nigrifluens affects the bark of trunk and scaffold branches. Fifty-nine isolates of bacterium were isolated on the basis of disease symptoms from 114 plant samples, collected from Mazandaran, Golestan, Kerman and Kermanshah provinces. Furthermore, 10 isolates from Fars province, one isolate from Kohgiluyeh-va-Boyerahmad province and one isolate from Kurdistan province were received. Based on physiological and biochemical characters, bacterial isolates were divided into two groups and identified as Brenneria nigrifluens or strains close to B. nigrifluens. The electrophoretic profile of the strains cell proteins also confirmed this grouping. Isolates were assessed by polymerase chain reaction (PCR) using a specific primer pair for B. nigrifluens. Twenty four isolates produced the expected band of approximately 255 bp and were named PCR+ strains. Pathogenicity tests performed with one PCR+ isolate and three PCR- isolates showed that only PCR+ isolate was able to cause cankers in walnut seedlings. Eight weeks after inoculation of PCR+ isolates on Persian walnut seedlings, water-soaked cankers appeared around the inoculation sites. The bacterium was reisolated from the bark lesions of the inoculated seedling on EMB-agar medium. To investigate the certitude of the primer pair, one PCR+ isolate and three PCR isolates from different geographic locations were analyzed by sequencing 16S rDNA. The results revealed that PCR+ isolates were Brenneria nigrifluens. On the basis of this study, it can be concluded that general phenotypic tests are not reliable enough to identify B. nigrifluens isolates and that specific detection of the pathogen with pathogenicity test or PCR is necessary. [ABSTRACT FROM AUTHOR]

RNA directed RNA polymerase 1 (RDR1) expression is induced by virus infection and appears to be involved in resistance to infection by some viruses. In the present study, reactions of two transgenic tobacco (Nicotiana tabacum cv. Samsun NN) lines in which the expression of their RDR1 gene was silenced were assessed against several plant viruses under greenhouse conditions. Silencing the RDRI gene in tobacco led to no change in the response to virus infection but in others, as expected, an enhanced susceptibility to tobacco mosaic virus was observed. By contrast, lines of tobacco with silenced RDR1 gene showed enhanced resistance to infection by several viruses, viz., tobacco rattle virus (genus Tobravirus) and tomato bushy stunt virus (genus Tombusvirus). These results suggest that complex interactions occur between the innate resistance pathways, so inhibiting one component involved in resistance may show effects on other aspects of innate resistance. Nevertheless, suppressing RDRI gene expression may provide novel, broad-spectrum resistance to a range of viruses. [ABSTRACT FROM AUTHOR]