دکتر صفرعلی مهدیان

Grape trunk diseases are critical problems for grapes from the time of planting to the harvest stage. Grapes are susceptible to 29 fungal diseases due to their perennial woody trunk, so identifying and managing them is crucial. Among the methods of controlling these diseases, feeding with mineral fertilizers to reduce leaf symptoms resulting from the toxic secretions of fungi living in the woody part of the tree is of great importance. To manage these diseases, a mixture of fertilizers including calcium chloride CaCl2, 466 g, magnesium nitrate Mg(NO3)2, 403 g, seaweed extract (75 ml) and sterile distilled water 466 ml per liter of foliar spraying on the selected treatments in Sohrabi’s garden were used once every 20 days. Guaiacol peroxidase, catalase and leaf area index were measured in Sohrabi’s garden during 2017 and 2018 and were compared with the control. In the treatments sprayed with the fertilizers, the average amount of guaiacol peroxidase enzyme was 12.72 µl compared to the control (10.6 µl) and the average amount of catalase enzyme was 83.68 µl compared to the control (31.85 µl). The average size of the leaf area in the foliar treatments in Sohrabi’s garden was 11564 mm2, compared to the control that was 4959 mm2. The severity of the disease in the sprayed treatments (19.95 %) was lower than the control (56.6 %). These results are due to the increase in the leaf surface, which increases the amount of photosynthesis, and the increase in guaiacol peroxidase and catalase, which reduce the oxidative stress resulting from fungal secretions, which resulted in decreasing symptoms in foliar treatments.

Grapevine trunk diseases (GTDs)are known as the most important factors in crop reduction and cause considerable economic problems in grapevines worldwide. During 2016 to 2018, several field surveys were conducted on numerous vineyards in Khorasan-Razavi province to study fungal species associated with grapevine trunk diseases. In this study, samples were collected from trunk and branches of trees showing yellowing, stunted growth, dieback and wood discoloration in cross sections. In this study, 258 fungal isolates were obtained and identified based on morphological characteristics and comparison of DNA sequence data (ITS-rDNA region and a part of β-tubulin gene). These isolates were identified as Phaeoacremonium minimum (75 isolates), P. parasiticum (19 isolates), P. iranianum (52 isolates), P. tuscanum (8 isolates), Fomitiporia mediterranea (56 isolates) and Seimatosporium vitis (48 isolates). Pathogenicity of the selected isolates was verified by inoculation of potted grapevines shoots under greenhouse conditions. Based on the mean length of wood discoloration in the wood, P. minimum and F. mediterranea were the most and least virulent species, respectively. Our findings indicated that known fungal trunk pathogens such as Phaeoacremonium species and F. mediterranea occur on grapevine in Khorasan-Razavi province. This study is the first report of S. vitis associated with grapevine decline in Iran.

The Phomopsis is a genus of imperfect plant pathogenic fungus whose hosts comprise several species in different regions of the world, such as grapes, soybean, acacia, hollyhock, velvetleaf, and several other plants. In this study, samples collected from hollyhock, velvetleaf, purple bauhinia, and acacia plants suspected to be infected with Phomopsis fungi. Samples were cultured and then subjected to the separation and purification steps and morphological characteristics of the obtained isolates were done. Among the isolates, five representatives (P1 to P5) from Mazandaran province selected and their DNA, extracted. TEF and ITS regions of DNA were amplified and sequenced. The ITS (4 and 5) region from ribosomal DNA and a part of TEF gene were amplified and sequenced. The nucleotide sequence of the isolates was compared with the corresponding sequences available in the Gen Bank and phylogenetic tree of the isolates was constructed. Results showed that the sequence of the isolates P1, P2, and P4 had the highest similarity with Phomopsis malvacearum species. The sequence of isolate P3 was very similar to Phomopsis loropetali, and the sequence of the isolate P5 was very similar to Phomopsis theicola. The average size of pycnidia produced on three culture media viz, CDA, CMA and PDA was measured 16 days after incubation at 20–25°C. Size were 256 × 85 in acacia, 230 × 68 in velvetleaf, 230 × 69 in hollyhock and 193 × 47 micrometers in purple bauhinia isolates, respectively. Morphological and molecular features of the identified species were matched. Identified species here are reported from Iran for the first time. Symptoms of Phomopsis infection was varied depending on different hosts and identified species.