Characterization and pathogenicity of fungal trunk pathogens associated with declining of neem (Azadirachta indica A. Juss) trees in Iran

Abstract

Neem (Azadirachta indica A. Juss.) tree is an important and valuable forestry species and is also ideal for reforesting programs in some countries. Several field surveys were conducted on neem trees in different landscapes in Bandar Abbas (Hormozgan province, southern coast of Iran) to determine fungal species associated with trunk diseases. Wood samples were collected from branches of trees planted in boulevards, public parks, local streets, sidewalks and roadsides with yellowing, defoliation, dieback, canker, gummosis and internal wood discoloration. Fungal isolations were made from discolored wood tissues on potato-dextrose agar supplemented with 0.5 g/L of streptomycin sulphate. Fungal isolates obtained from neem trees, were identified based on morphological characteristics and DNA sequence comparisons. Curvularia hawaiiensis, Neoscytalidium hyalinum, Lasiodiplodia theobromae, Paecilomyces formosus, Paecilomyces dactylethromorphus, Phaeoacremonium venezuelense, P. angustius, P. minimum, P. rubrigenum, P. parasiticum and Pleurostoma richardsiae were the main fungal species recovered from neem trees showing disease symptoms. Pathogenicity of selected species was verified by inoculation of shoots of neem trees under controlled conditions. Neoscytalidium hyalinum was the most aggressive species based on the length of vascular necrosis in the wood. All fungal species, with exception of L. theobromae, are reported here for the first time on neem trees.