فهرست مطالب علیرضا معرفت

Bacterial stripe caused by Xanthomonas translucens is one of the most important diseases of wheat worldwide. The disease was first reported on barley in America in 1917. In Iran, it was reported for the first time on wheat and barley in Kerman province in 1987. Based on the standards for naming pathovars, the currently accepted pathovars as pathogens infecting cereals include pv. cerealis, pv. translucens, pv. undulosa, and pv. secalis. Following climate changes, especially heavy rainfalls in recent years, and probably the transmission of infected seeds, the disease has shown significant outbreaks and damages on wheat in Kermanshah province, Iran. The present study was performed to (I) characterize the pathogen in Kermanshah province, (II) determine pathogen distribution, and (III) assess the genetic diversity of the strains.

Wheat seeds and leaves showing symptoms of the disease were collected from major wheat-growing areas in Kermanshah province during 2019 and 2020. In the laboratory, samples were rinsed with tap water and were macerated into a few drops of sterile distilled water. Two loops full of the resulting suspension were streaked on the nutrient agar medium. Plates were incubated at 25°C and pale yellowish colonies were purified. Physiological and biochemical tests were performed to identify and characterize 140 isolates. To determine the pathovar(s) of the pathogen, the pathogenicity of the strains was tested on wheat, barley, rye, and triticale in the greenhouse. Nearly complete 16S rRNA sequences were determined for two strains representatives of two pathovars distinguished by pathogenicity test using 27F and 1492R primers. Genetic diversity among the isolates was evaluated in rep-PCR utilizing BOX and ERIC primers.ResultsBased on physiological and biochemical tests, Xanthomonas strains from wheat in Kermanshah province were identified as X. translucens. Pathogenicity tests revealed two groups among the strains. Members of the first group induced disease symptoms on wheat and triticale exclusively and were identified as pv. undulosa, while the strains belonging to the second group infected wheat, barley, rye, and triticale, and were identified as pv. cerealis. The rep-PCR using ERIC and BOX primers demonstrated genetic variation among the strains. However, there was no significant difference between the results obtained by ERIC- and BOX-PCR. Nearly complete 16S rRNA sequences were determined as the representative strains of two pathovars distinguished by pathogenicity test and based on the comparison of sequences with the GenBank database. The two strains matched X. translucens with 100% similarity. The nucleotide sequences of the pathogen strains were deposited in the GenBank database under the accession numbers MW173461 and MW193070.

According to the findings of this study, X. translucens strains collected from wheat in Kermanshah province belonged to pathovars undulosa and cerealis. Considering the wide host range of these pathovars, the disease could be found on other cereals and grasses belonging to the Poaceae in the province and this subject must be taken into consideration in future studies. Although rep-PCR showed significant diversity among the strains, there was no correlation between the rep-PCR groups and the pathovars identified in the pathogenicity test or the geographic origin of the strains. Biochemical and physiological tests, as well as rep-PCR and 16S rRNA sequencing, could not distinguish the two pathovars. This confirms that pathogenicity tests and host range are still the main methods for determining pathogen pathovar(s).

Bacterial wilt disease caused by Ralstonia solanacearum is one of the most destructive diseases in the world, including Kurdistan province of Iran. Using the endophytic bacteria is one of the most effective and applicable methods to control of the disease. In this study, Bacillus sp. Bp91 which was isolated from potato fields in Kurdistan province was used as a superior antagonist against R. solanacearum. The results of the supplementary tests showed that the production of protease in the mentioned strain is positive. This was negative and relatively weak for hydrogen cyanide and siderophore production, respectively. The phylogenetic tree derived from 16S rRNA gene sequence showed the stain belongs to the genus Bacillus sharing the highest level of sequence homology with to B. pumilus. Metabolic studies by GC-mass were also indicated that the two metabolites Eicosane and Dibutyl phthalate are the most prominent antimicrobial metabolites produced by the bacterium.

Oak dieback is one of the most important diseases that presently affects the Zagros oak forests (Northwest to Southeast of Iran). The presence of Paecilomyces formosus, Biscogniauxia mediterranea and Neoscytalidium novaehollandiae associated with oak trees that show dieback and declining symptoms in the forests of Kermanshah province and the molecular and pathogenic characteristics of these pathogenic isolates were investigated. In molecular analysis using blast search tools, all three pathogens showed homology of 100% with the mentioned species in the GenBank. Pathogenicity test revealed that all isolates of these three pathogens were capable of producing cancers on detached branches and inoculated seedlings of oak trees. Our results showed that all three species obtained from oak trees could produce cankers on excised branches of other trees. In comparison with pathogenicity on two-years-old seedlings under drought stress, there was a significant difference between the three species in terms of the rate of disease progression, so that B. mediterranea caused symptoms on seedlings inoculated under drought stress in a shorter time. P. formosus caused symptoms in longer period on the inoculated seedlings than the other two species. After inoculation, all cankers that extended upward and downward from the point of inoculation were evident on stems of all inoculated seedlings. Re-isolation was performed, and isolates were compared to original cultures providing evidence for fulfilling Koch’s postulates. Investigation of the effect of temperature on radial growth of pathogenic species showed that all three species are thermophilic fungi, which may be related to warming and drought.

Root and crown rot of bean caused with Fusarium solani, Rhizoctonia solani and Fusarium oxysporum, is one of the important diseases of bean in Zanjan province. Using native biocontrol agents integrated with chemical agents is one of the effective management strategies. This is also important to choose control methods effective against all major fungal pathogens and mixed contamination of bean, with them. This research was conducted to study synergistic effect of three major fungal pathogens and biocontrol effects of some native rhizobacteria on disease. During the mid-summer of 2011, 46 bacterial isolates were obtained from bean rhizosphere in Zanjan bean fields. Two isolates of each three fungal species (pathogenic on bean) were also received from mycology collection of Zanjan University. Two isolates of Rhizobacteria were chosen as the best biocontrol agents against all three fungi in terms of production of antibiotic, volatile metabolites, HCN and protease and selected for in-vitro antagonistic experiments. Greenhouse results showed that, seed treatment of bean with bacteria, decreased the disease and increased some vegetative factors of the plant. There was synergistic effect among the fungal species.

Root and crown gall caused by Rhizobium vitis, is one of the most important diseases of grapevine worldwide. Although there is no efficient chemical control for the disease, various antagonistic bacteria have been studied for its biocontrol. This study was conducted to identify soil inhabiting bacteria in Qazvin province vineyards and to investigate their inhibitory effect on the pathogen. Samples were collected from soil, as well as grape root and crown in 22 areas over the province. Two hundred ten bacterial isolates, obtained from the samples, were grouped and 73 isolates were selected for further study. Identification of the isolates was performed using physiological and biochemical tests. Also, primers Bsub5F and Bsub3R were used to confirm identification of isolates resembling Bacillus subtilis. Ability of the isolates for antibiotic, siderophore, hydrogen cyanide and protease production was studied. Primer pairs PhI2a/PhI2b and PM2/PM7-26R were used to detect PhID and hcnABC genes respectively in fluorescent psuedomonds. Antagonistic effect of five strains, selected from the identified bacteria, on the pathogen was studied on carrot and turnip slices. Based on the results, antagonistic bacteria belonged to Pseudomonas fluorescens biovar I, III and IV, as well as B. subtilis. All strains produced antibiotic and inhibited growth of the pathogen. Also, strains identified as P. fluorescens biovar I، III and IV produced hydrogen cyanide and protease; however, it differed in siderophore production. PhID and hcnABC genes were detected in strains belonging to P. fluorescens biovar I and IV. Two strains belonging to P. fluorescens biovar I, one P. fluorescens biovar IV strain and two B. subtilis strains inhibited gal formation by Rh. vitis on carrot and turnip slices.

Walnut tree is one of the most important orchard and jungle trees in Iran. It's world cultivation is growing up due to its plentiful uses. Meanwhile, some pests and diseases are known as the major reasons of restriction in walnut cultivation. Among walnut diseases, anthracnose is the most destructive in Iran. In this study, the main area of walnut cultivation in Zanjan were surveyed, walnut's infected organs (sprouts, leaves and fruits) were sampled and the disease agent was isolated and identified using ordinary plant pathological methods. The results showed that Ophiognomonia leptostyla (Fr.) Sogonov contribute to the walnut anthracnose disease, and it is permanently scattered in all Zanjan walnut orchards. It's damage varies between15% to 67% in different regions. Our study on Telemorph and Anamorph phases of the fungus showed that there are no significant differences between isolates collected from Zanjan and those from other provinces in vicinity. Meantime, the results showed that the majority of the collected isolates were Heterothal. Study on partial resistance of three Iranian local genotypes (Z53, Z63 and 60) and six exotic cultivars (Sere, Lara, Franket, Pedro, RDM and B21) showed that local genotypes were more susceptible to walnut anthracnose in comparison to exotic varieties. Although none of the varieties and genotypes was totally resistant, in comparison to introduced interior superior genotypes, exotic varieties of Persian walnut were by far in better condition against anthracnose.

Bean root rot caused by plant pathogenic fungus، Fusarium solani، is considered one of the most important diseases of bean in the world and in Iran. Because of economic importance of bean and the lack of information on population diversity of the pathogen in Zanjan province، a research was conducted to study phenotypic، genotypic and pathogenicity variation of pathogen isolates and to assess pathogen host range among several commonly cultivated crops in the studied region. Plants with disease symptoms were sampled from 11 fields of province and totally 30 isolates of F. solani were obtained. After disease proving، host range experiment and phenotypic investigations، polymerase chain reaction (PCR) was conducted on total DNA by using RAPD and ERIC primers. The results showed no significant difference in pathogenicity of isolates، but there was phenotypic and genotypic diversity among them. Among 9 inoculated plants including wheat، alfalfa، white bean، red bean، pinto bean، sain foin، faba bean، lentils and chick pea، only wheat showed no disease symptoms. DNA fingerprinting patterns from both molecular markers demonstrated high genetic diversity of isolates on bean in Zanjan. However RAPD PCR based on using single primer (OPA 13) produced more reliable products، but grouping based on this marker was considerably consistent with grouping based on ERIC marker. There was no association between geographic regions and genetic groups. Also there was no consistency between phenotypic and genotypic diversity of isolates.

Crown and root gall caused by Rhizobium vitis, is one of the most important diseases of grapevine worldwide. In Iran٫ the disease has been reported in different areas such as Zanjan province. Despite the importance of the disease in the orchards٫ there is no an effective control measure for the disease. In this study the most important soil-inhabiting bacteria from vineyards in Zanjan province were isolated and were identified. Antagonistic effects of some isolates were investigated against the pathogen. For this mean٫ samples were collected from grapevine roots with surrounding soil in vineyards in different areas of the province. Based on morphological٫ physiological and biochemical characteristics٫ 200 isolates were selected and their inhibitory effects were investigated on the pathogen in vitro for antibiotic production. Fifty isolates with the most inhibitory-effect in the tests were identified to genus and species levels. Some isolates identified as Pseudomonas spp. were further studied for the hcnABC gene. Biochemical tests identified representatives as Pseudomonas fluorescens biovare I٫ III and V٫ P. putida٫ Basillus subtilis٫ Pseudomonas sp. ٫ and Bacillus sp. Identified Pseudomonads showed significant inhibitory effect on R. vitis on King-B medium also via HCN production. In the PCR٫ hcnABC gene was amplified from five Pseudomonas strains. Indeed, seven strains with the most inhibitory-effect in vitro were selected across identified Pseudomonas and Bacillus strains and their antagonistic effect on the pathogen population was studied in the soil environment. Based on the results, all tested bacteria showed significant inhibitory effect on the pathogen population. However٫ Pseudomonas fluorescens bv. V, III and Bacillus subtilis were more effective.

Wheat root and crown rot known as take-all disease caused by Gaeumannomyces graminis var. tritici is one of the most important diseases of wheat worldwide. In Iran,the disease has been reported from provinces such as Markazi and Golestan. In recent years, symptoms of the disease such as stunted and yellow plant, rotted roots and whitened/empty heads have been observed in wheat fields in various areas of Zanjan province. This study was conducted to probe the existence of the disease in the province, to identify its causal agent and to identify wheat rhizobacteria for possible use in the biocontrol of the disease. To this aim, 25 samples were collected from wheat roots and soil surrounding them in various areas of the province. Fungi were isolated on potato dextrose agar (PDA) and identification of Ggt was performed based on CMI Description. Pathogenicity of fungal isolates was proved on wheat in the greenhouse. Isolation and identification of rhizobacteria were performed based on conventional procedures. From 420 bacterial isolates, 140 isolates were selected based on preliminary grouping and were screened for their antagonistic effects in the lab. Thirty-four isolates with the most inhibitory power were selected for identification by biochemical tests. Results showed that antagonistic bacteria mainly belonged to Pseudomonas, Erwinia and Bacillus genera. Finally, three strains representing the three genera were selected and their capability for the control of the disease was studied under greenhouse conditions. Results revealed that bacteria belonging to the mentioned genera can be used for biocontrol of the disease.

Pectobacterium is one of the major destructive causal agents in most crop plants throughout the world. During the years 2007-2008, 38 isolate of soft rot pectobacteria were isolated from different hosts including: potato, onion, cabbage and carrot in Hamedan, Semnan, Hormozgan, Kerman, East Azarbaijan, Khuzestan, Zanjan, Tehran and Isfahan provinces. Phenotypic identification of the strains were performed using recommended biochemical and physiological tests. Also genetic diversity determined by BOX-PCR using BOX A1R primer. According to results, all strains identified as "Carotovora" group as Pectobacterium carotovorum subsp. carotovorum, P. atrosepticum and Dickeya chrysanthemi. Also some characteristics of the pathogen differ from those described for this bacterium isolated in some countries. The combined results of performed tests showed a high variability among pectolytic bacteria in Iran and there was no clear relationship between the resulting DNA fingerprints and geographical origins of isolates.