New fungal canker pathogens of apple trees in Iran

Apples are the main horticultural crops grown in West Azarbaijan province of Iran. In recent surveys of apple orchards in Urmia and Miyandoab, West Azarbaijan Province, symptoms including branch and twig bark cracks, cankers, dieback and tree decline were commonly seen. Isolation of the fungi from cracked and cankered branches yielded fungal isolates with typical characteristics of the genera Paecilomyces and Paramyrothecium. Based on combination of morphological characteristics and sequence data obtained from ITS-rDNA and β-tubulin gene sequences for Paecilomyces isolates and ITS-rDNA region for Paramyrothecium isolates, they were identified as Paecilomyces formosus and Paramyrothecium foliicola. Results of the pathogenicity tests on detached shoots of ‘Golden Delicious’ and ‘Red Delicious’ cultivars showed that isolates of P. formosus were pathogenic only on ‘Red Delicious’ cultivar, but Pa. foliicola isolates were pathogenic on both cultivars and showed symptoms of infection. Re-isolation of the fungi from inoculated shoots confirmed Koch’s postulates. To the best of our knowledge, the involvement of P. formosus and Pa. foliicola in the development of canker disease of apple trees is reported for the first time. Also, Pa. foliicola is a new record to Iran mycobiota.