IRANIAN JOURNAL OF PLANT PATHOLOGY
Year:2009 | Volume:45 | Issue:3 (179)|Papers Count:7

The synthetic promoters can be very beneficial in order to decrease the complexity of natural promoters and are effective to improve the plant breeding programs. In this study two synthetic promoters SynP1 and MinP were constructed and fused with b-glucuronidase as reporter gene. Functional analysis showed SynP1 promoter significantly responds to salicylic acid, chitin and cell wall released elicitors of Rhizoctonia solani and Fusarium graminearum. Methyl jasmonate, wounding and environmental conditions (cold, heat and UV) did not induce the SynP1 promoter. The background expression of SynP1 promoter was approximately the same as minimal promoter (MinP) and wild type plants. These results showed that SynP1 promoter is related to salicylic acid defense signaling pathway.

Genetic structure of Fusarium solani isolates from four host populations was investigated. One hundred and forty-nine isolates were analyzed for their fluorescent amplified fragment length polymorphism (FAFLP) patterns. The isolates were obtained from four host populations including 60 isolates from potato, 30 isolates of F. solani f.sp. cucurbitae, 29 isolates of F. s. f.sp. phaseoli and 30 isolates of F. s. f.sp. pisi. After DNA extraction, digestion by EcoRI and MseI restriction enzymes, and ligation of adapters to DNA fragment, a preamplification PCR was done. Selective PCR amplification was performed using three primer combinations labeled with fluorescent dyes. The products were separated by capillary electrophoresis on an ABI PRISM 310 Genetic Analyzer. Analysis was performed based on 151 polymorphic markers. Polymorphic bands were analyzed by Popgen 32, GeneAlex 6.1 and NTsys-pc 2.0 software programs using UPGMA method and Nei coefficient. In general, 92% of observed molecular variance was related to within host populations and 8% variation was found among them. Genetic similarity between four mentioned host populations was more than 92%. In average genetic variation for host populations of potato, cucurbit, bean and chickpea were 0.3431, 0.3792, 0.3619 and 0.3606, respectively. In average genetic variation for all isolates was 0.3883 and this is not related to their host and geographical origin. The results indicated that the fungal isolates related to potato, cucurbits, bean and chickpea in this study, are one clonal lineage. High degree of similarity between populations may be due to gene flow among them.

Sclerotinia stem rot caused by Sclerotinia sclerotiorum, is one of the most important disease of canola in Iran. Regarding to importance of this disease and the lack of comprehensive knowledge on genetic diversity of this pathogen in Iran, mycelia compatibility groupings (MCGs) and genetic variation among MCGs from Golestan, Mazandaran and western Azarbaijan provinces were examined. Sixty-four isolates were selected respecting to geographic distribution and their MCGs were determined. Among these tested isolates, 38 MCGs were identified. Pathogenecity tests were carried out in greenhouse and analysis of resulting data (lesion phenotype+lesion length+girdling) categorized isolates into three groups with different range of virulence. Our data indicated that virulence of isolates varied within one MCG and also between MCGs. Study of genetic diversity among MCGs (38 isolates representative of 38 MCGs), using banding pattern of four rep-PCR primers categorized isolates into seven groups at the 64% similarity level. Accordingly, majority of isolates were separated based on their geographic origin. The discriminatory power of rep-PCR genotyping (D=0.993), which discriminated 37 different genotypes, was high, indicating that rep-PCR is a rapid, effective marker for genotyping S. sclerotiorum isolates.

To study the relationships among arginine dihydrolase and oxidase - positive strains of Pseudomonas associated with sheath rot of rice, the strains were characterized in parallel with three standard strains by using pathological and biochemical tests, protein fingerprints and PCR - RFLP of 16S rRNA. Cluster analysis of phenotypic characters grouped the strains into four main clusters and two single – membered groups. Comparison of fingerprints of each cluster as well as other characteristics including pathogenicity, type of tissues they were isolated from and geographical origin were used to select one or more representative strains from each clusters. Representative strains and three standard arginine dihydrolase and oxidase - positive strains of Pseudomonas were studied using the 16S rRNA - RFLP. Cluster analysis of the data produced by different restriction enzymes was used to group the strains into six distinct clusters (genotypes). Pathogenic strains were divided into four genotypes including P. marginalis and three other genotypes which were also distinct from standard strains, P. fuscovagina and P. fiuorescens. None of the strains was similar to the standard strain of P. fuscovaginae, wich is considered to be the main causal agent of sheath rot and grain discoloration of rice.

In order to identify plant-parasitic nematodes belonging to criconematids in Tabriz and its suburbs, 85 soil and root samples were collected from rhizosphere of vegetations during 2006-2007. The nematodes were recovered using the sieving and centrifugal-flotation technique and processed to anhydrous glycerin. The extracted nematodes were mounted in permanent microscopic slides. As a result, one species of Criconema, under the name of C. mutabile, seven species of Criconemoides, viz. C. antipolitanus, C. curvatus, C. informis, C. ornatus, C. parvus, C. pseudosolivagus and C. xenoplax; two species of Ogma, viz. O. civellae and O. fimbriatum; three species of Hemicycliophora,viz. H. poranga, H. sturhani and H. vaccinium were identified. H. vaccinium and O. fimbriatum are new records from Iran.

Rice blast isolates Magnapothe grisea from Guilan and Mazandaran provinces inoculated on eight international differential cultivars including Raminad str.3, Zenith, NP-125, Usen, Dular, Kanto 51, Sha-tiao-tsao-s, Calaro and five isogenic lines carrying major resistance genes to blast with their parents and the resistance or the susceptibility of the cultivars evaluated. Races IA-89, IA-90, IA-25 and IC-25 identified for Guilan province and IA-90 and IA-25 identified for Mazandaran province.