IRANIAN JOURNAL OF PLANT PATHOLOGY
Year:2019 | Volume:55 | Issue:3|Papers Count:6

Beet black scorch virus (BBSV) is a soil-borne virus infecting sugar beet. In order to construct an infectious full-length cDNA clone of Mashhad isolate (IR-Mash1), Iran (GenBank Accession no. MK092329), and studying reaction of some sugar beet cultivars, sugar beet roots with beard lateral root growth were collected from Mashhad field and subjected to total RNA extraction and then cDNA synthesis. PCR reaction was performed to amplify the whole genome of the virus were cloned to pDrive Cloning Vector. DNA was extracted from the plasmid vector. It was used as templates for run-off transcription in vitro by use of a T7 RNA polymerase. Chenopodium quinoa was inoculated under greenhouse conditions. Necrotic local lesions formed on C. quinoa (5 dpi) leaves were used as inoculation material for inoculation of the leaves of different sugar beet cultivars grown in the greenhouse. BBSV was inoculated by rubbing the sugar beet seedling leaves. Iranian cultivar including Sharif (susceptible check), Aria, Shokoufa and foreign cultivar including Pauletta KWS (tolerant to Rhizomania and sugarbeet cyst nematode), Isabella KWS (Double Resistant to Rhizomania) and Dorothea (tolerant to Rhizoctonia) cultivars were inoculated under greenhouse conditions. Pinpoint Symptoms appeared on the leaves of all cultivars after twenty days. The result showed that the virus produces similar symptoms on leaves of susceptible and resistant cultivars to Rhizomania. So, using infectious clone, possible to screening sugar beet germplasms as part of pre-breeding programs under greenhouse conditions and to find sources of resistance to the virus in sugar beet and wild beets.

The fungal infection of rice seeds with Fusarium species, is a major problem for farmers in Iran and the world. Determining the pathogenicity of Fusarium species in rice fields might be helpful in development of strategies for management of the relevant diseases. In this research, the pathogenicity of forty seven isolates of Fusarium belonged to Fusarium fujikuroi, F. incarnatum, F. prolifratum, F. thapsinum, F. andyazi, F. oxysporum, F. graminearum and F. merismides obtained from rice seeds in Mazandaran, Guilan, Golestan, Khuzestan and Fars provinces were investigated. The pathogenicity test was performed by rice seed dressing method using spore suspension as inoculum in invitro, nursery and the paddy field. Percentage of healthy, unhealthy and dead seedlings recorded and percentage of disease incidence was determined. Also, the transmission rate of bakanae disease by seeds from the laboratory to the nursery and the paddy was determined. The results showed that all isolates were pathogenic on rice seedling and reduced germination percentage compared to control, and only one isolate of F. merismoides was non-pathogenic. F. fujikuroi isolates had the highest disease incidence rate. In addition, there was a significant difference among Fusarium species, isolates of each species and the five provinces in terms of disease incidence. Based on the disease incidence, 2. 1% of the isolates placed in the non-pathogenic group, 25. 6% of the isolates were in the moderate pathogenic, 34. 1% of the isolates were pathogenic and 38. 2% considered as severe pathogenic group. In this research, the rate of disease transmission from contaminated seeds to the nursery was 38%., but after seed disinfection, with fungicide, the transmission rate of the disease dropped from 38% to 3. 6%. These results show the importance of rice seed treatment with fungicides for the control of bakanae disease.

Bacterial canker caused by Clavibacter michiganensis subsp. michiganensis is an economically important disease of tomato. In this study after isolation and characterization of the pathogen, effects of tomato pretreatment with DL-β-aminobutyric acid (BABA) on bacterial canker was investigated under laboratory conditions. BABA is known as a powerful chemical resistance inducer in plants against diverse pathogens. In this study, tomato plants were treated with a 0. 2 mM concentration of BABA and distilled water served as control. The plants were subsequently challenged with a 1×108 CFU ml− 1 bacterial suspension. The results of experiments in different time intervals showed that BABA pre-treatment resulted in a significant reduction of bacterial population and symptoms severity of inoculated plants as compared to their controls. Furthermore, late appearance of disease symptoms indicated longer incubation periods for BABA treated plants. Also, a significant increase was observed in the expression of PR1 and catalase genes in treated plants. Based on our results and regarding the lack of proper management options against the disease, application of BABA as an environmentally safe agent is recommended as a valuable contribution to disease management.

Cereal yellow dwarf viruses are among the most destructive cereal viruses worldwide. In this study, subcellular localizations of silencing suppressor proteins ( P0) from two cereal yellow dwarf viruses, Cereal yellow dwarf virus-RPV (CYDV-RPV) and Cereal yellow dwarf virus-RPS (CYDV-RPS), were examined via confocal microscopy. To do so, P0 genes were synthesized by polymerase chain reaction (PCR) and were cloned through Gateway cloning system. Agrobacterium. tumefaciens clones harboring GFP: P0 constructs were infiltrated into Nicotiana benthamiana plants. Transient expression of P0 proteins with N-terminal GPF fusion enabled us to examine their subcellular localizations in plant cells, 24 hours post infiltration. Results showed that both proteins are nuclear-cytoplasmic but different tendencies were observed in their localizations. In other words, P0 of CYDV-RPS was more nuclear oriented than P0 of CYDV-RPV. In the Western blot analysis using GFP polyclonal antibody only GFP: P0 proteins but no free GFP, were detected indicating that localizations were related to GFP: P0 proteins.

In this study survivability, morphological characteristics and pathogenicity of 12 isolates of Ophiognomonia leptostyla, which is known as causal agent of walnut anthracnose, have been evaluated after 13-years of storage on filter paper in oat meal agar (OMA) and-20° C. The recovery rate varied from 0 to 89 percent and seventy-five percent of stored isolates were shown to be viable. In macroscopic and microscopic studies of revived cultures, the morphology of colonies was uniform for all isolates. Production of asexual bodies (acervular conidiomata) was preserved by all isolates. Fertile perithecia with asci and ascospores were not detected in pure fungal cultures after three months incubation at 8-10° C in darkness. In pathogenicity experiments, there was not a significant variability in infection severity for different isolates, and the first symptoms were observed on leaves 12-16 days after inoculation. Stability of morphological characteristics, ability to sporulation and retaining the pathogenicity of isolates confirmed that transferring of acervuli on filter paper in OMA medium could be a suitable, safe, simple and cost-effective tool to preserve O. leptostyla isolates in a viable state.

Phytophthora erythroseptica, the causal agent of potato pink rot, is one of the oomycete plant pathogens that causes significant losses in field and storage. In order to develop a sensitive and rapid method for detection and identification of P. erythroseptica, six nuclear and mitochondrial gene regions were investigated to design species-specific primers. Due to the high similarity of P. erythroseptica sequences to its closely related species, only one nuclear region, TigA, was appropriate to design specific primers. Using specific primers, a simple as well as a nested-PCR based method was developed for the identification and detection of P. erythroseptica. The specificity of designed primers was examined using a collection of Phytophthora species from different phylogenetic clades as well as close relatives of P. erythroseptica. In addition to pure DNA, designed primers detected P. erythroseptica in infected plant tissues including potato, tomato and spinach. Specific primers detected 10 pg of P. erythroseptica pure DNA, however, nested PCR increased primers sensitivity at least 100 times. Moreover, specific primers designed in this study were able to detect P. erythroseptica as the maternal or paternal parent species in hybrid isolates that would make a significant help to recognize one of the parental species in hybrids of P. erythroseptica.