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Leaf spot disease in potato is caused by Alternaria alternata (Fr.) Keissler, an opportunistic pathogen that infests many agricultural crops worldwide in the field and during postharvest storage of vegetables and fruits. Alternaria alternata is associated with leaf spot disease in potato in Iran. Thus, there is a need to investigate the virulence and genetic variability of Iranian A. alternata isolates to facilitate the development of appropriate management strategies. In the present study, we analyzed a total of 28 isolates obtained from the main potato-growing regions of Iran, including the Ardebil, Hamedan, Isfahan, and Fars provinces. The pathogens were characterized based on sequence analysis of the genes encoding glyceraldehyde-3-phosphate dehydrogenase (gpd), plasma membrane ATPase, Alternaria allergen a 1 (Alt a1), calmodulin, and actin. In addition, random amplified polymorphic DNA (RAPD), intersimple sequence repeat (ISSR), and virulence studies were performed. Phylogenetic analysis of the combined dataset indicated that the five representative isolates were grouped with the subcluster comprising A. alternata. RAPD and ISSR analyses clustered the 28 A. alternata isolates into different groups with no correlation with their corresponding geographical origins. Results of the pathogenicity assay indicated that all A. alternata isolates were pathogenic against potato. However, the A. alternata isolates showed high variability in terms of virulence.
Potato leaf blight disease caused by Ulocladium atrum (Syn. Stemphylium atrum) is an important and epidemic disease in potato-growing regions of Iran. In this study, 30 isolates of the disease were collected from the main potato-growing regions of Iran and were analyzed on the basis of morphological characterization and pathogenicity. Based on morphological characteristics, all isolates were identified as U. atrum. Pathogenicity studies indicated that all 30 isolates were pathogenic on potato “Agria” to varying degrees. Five U. atrum isolates causing potato leaf blight disease, obtained from the Plant Pathology Laboratory, Isfahan Research Center for Agriculture and Natural Resources, Isfahan, Iran, were also examined in this study. A total of 35 isolates were genetically analyzed using random amplified polymorphic DNA (RAPD) and inter-simple sequence repeats (ISSR) markers. Cluster analysis using the un-weighted pair group method with the arithmetic average (UPGMA) method for RAPD marker revealed no clear grouping of the isolates obtained from different geographical regions. The groupings, based on morphological characteristics, virulence variability and RAPD analysis, were not correlated. Cluster analysis using Jaccard’s coefficient for ISSR divided the U. atrum isolates into four main groups, in which there was no significant correlation between the isolate groupings regarding their geographic location and pathogenicity. Using molecular techniques genetic variability was detected among the accessions, with cophenetic correlation coefficients (CCC) of 0.80 for RAPDs and 0.89 for ISSRs. The RAPD and ISSR marker results corresponded well, with a correlation of 0.55.
Chickpea plants were inoculated with two strains of Mesorhizobium ciceri: local strain (C-15) and non-local strain (CP-36) in order to evaluate plant growth parameters, activities of nitrogenase and antioxidant enzymes under drought stress as well as control condition within 15 days of imposition of drought stress. Biomass production, nodulation, nitrogen fixation and antioxidant enzyme activities under drought condition were compared. Under control condition, symbiotic efficiency in symbiosis formed by C-15 was higher than that in symbiosis derived by CP-36. Although drought stress decreased shoot dry weight, root dry weight, nodule dry weight and nitrogen fixation in both symbioses, the rate of decline in plants inoculated with CP-36 was higher than that in symbiosis chickpea with C-15. Therefore, symbioses showed different tolerance level under drought condition which was essentially correlated with symbiotic performance at nonstressful conditions. Under drought stress, nodular peroxidase (POX) activity increased in both symbioses but was higher in nodules produced by C-15. Ascorbate peroxidase (APX) increased significantly in nodules of symbiosis of chickpea with C-15. Catalase (CAT) and glutation reductase (GR) declined in both symbioses which decline extent in symbiosis with C-15 was lower than that in the nodules of CP-36. These results suggested contribution of rhizobial partner in enhancing the tolerance of symbioses to drought stress, which was related with the increase of antioxidant enzyme activities (APX and POX) under drought conditions.
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