پراکنش و ارزیابی میزان خسارت بیماری پوسیدگی ریشه و طوقه آفتابگردان در استان گلستان

Agricultural sunflower with the scientific name Helianthus annuus L. is one of the most important oilseeds in the world, and its cultivated area and production in the world and Iran have been increasing in recent years. After soybean, rapeseed and peanuts, sunflower has taken the fourth place in the cultivation of oilseeds in the world, it has more than 40% oil. Many biotic and abiotic factors affect the production and quantitative and qualitative yield of sunflower in different regions. Sclerotinia rot disease (Sclerotinia spp.) and charcoal rot (Macrophomina phaseolina) are among the most destructive sunflower diseases in the world and Iran. In a survey, in order to investigate the distribution and assess the amount of damage caused by sunflower sclerotinia root rot and basal stalk rot disease, sampling was done from different regions of Golestan province. Isolation and purification of fungal isolates was done using common methods in plant pathology and mycology. In order to identify the isolates, morphological characteristics were evaluated and compared with the authentic keys and in order to confirm the identity of the isolates, the genomic region of ITS-rDNA and TEF gene were sequenced. By combining morphological and molecular data, all fungal isolates obtained from Golestan province (52 isolates) were identified as M. phaseolina species. Based on the results obtained, M. phaseolina was identified as the main cause of sunflower crown and root rot disease in sunflower fields of Golestan province, and the amount of damage in different sunflower fields in this province was estimated between 35 and 80%, so that some fields were practically unharvested. Also, in order to evaluate the resistance of different cultivars, an experiment was conducted in the form of a completely randomized design in four replications in the greenhouse using 9 sunflower cultivars named Hybrid, Chine dor sefid, Qoli, Qoli keshidah, Qoli motavasset ceyah, Shamshiri, Baran, Redet, Sarbazi The results showed that all investigated cultivars showed sensitivity to the disease agent and were attacked by the pathogen. However, the symptoms of the disease were less developed in the Sarbazi variety and in terms of growth characteristics of plant, it was in a better condition than the others.