Antagonistic Effects of Trichoderma Species in Biocontrol of Armillaria Mellea in Fruit Trees in Iran

Antagonistic Effects ofTrichodermaSpecies in Biocontrol ofArmillaria Melleain Fruit Trees in Iran Root and butt rot caused by species ofArmillariais one of the most serious diseases of fruit and forest trees in Iran. In this study, antagonistic effects ofTrichodermain biocontrol ofArmillariawere investigated.Armillaria melleawas isolated from infected roots and butts of cherry and almond trees and identified with pairing tests method.Trichodermaspecies were recovered from rhizomorphs and around soil ofArmillariainfected roots.Trichodermaspecies identified wereT. virens(nine isolates) andT. harzianum(three isolates).Trichodermadiscs were placed onto cultures ofArmillariato study antagonistic effects. All isolates ofTrichodermacolonizedArmillariacolonies within 5-7 days. Volatile compounds ofTrichodermaisolates inhibitedArmillariacolony growth and rhizomorph formation. Mechanisms of biocontrol were investigated by light and scanning electron microscopy, these included penetration ofTrichodermahyphae in rhizomorphs, colonization of rhizomorphs byTrichodermamycelia, colonization of apex meristemic center and apical buds of rhizomorphs, sporulation ofTrichodermain outer and inner surface of rhizomorphs, degeneration and lysis of rhizomorph tissue, and discharge of rhizomorph content.