اصول کخ

Grapevine decline disease (GDD) complex is a major global viticulture problem associated with a multi-year decrease in plant productivity and an increase in vine mortality, resulting in important economic losses to the viticulture industry. More than 35 fungal genera have been involved in the GDD complex, and the genus Cytospora has also been reported as one of the genera included in the disease-causing complex. This study aimed to identify Cytospora species involved in GDD complex in the vineyards of Miyandoab (West Azarbaijan province) and Malekan (East Azarbaijan province) Counties. So, during the summer and autumn of 2020-2021, sampling was done from the diseased plants showing symptoms of shoot wilting and die-back, bark and wood discoloration, brown to black discoloration of vascular tissues, and wood canker. The fungal isolation was done based on common phytopathological methods, and 78 isolates with the common characteristics of the genus Cytospora were isolated and purified. Based on the results combining morphological characteristics and sequence data obtained from three genomic regions, ITS-rDNA, TUB2, and RPB2, four species viz., C. chrysosperma (15 isolates), C. ershadii (24 isolates), C. salicina (28 isolates), and C. viticola (11 isolates) were identified. Cytospora viticola is a new species for the fungal biota of Iran, and grapevine is reported as a new host (matrix nova) for C. ershadii in Iran and the world. Pathogenicity of the selected fungal isolates from the identified species was confirmed on shoots of the Thompson seedless cultivar based on Koch's postulates.