Evaluation of arbuscular mycorrhizal fungus and Trichoderma harzianum against Armillaria species and growth response of Dombeya torrida seedlings

Abstract

PC Sitieneia IN Wagaraa, ST Kariukia, J Jefwab

Armillaria root rot is a fungal root rot caused by several different members of the genus Armillaria. It has an extremely broad host range and hundreds of trees and shrubs are susceptible to root rot to varying degrees. Arbuscular mycorrhizal fungi (AMF) and Trichoderma harzianum are known to affect plant growth and disease resistance through interaction with phytohormone synthesis or transport in the plant. In the present study, potential of AMF and T. harzianum were tested for the biocontrol of Armillaria species and growth response of Dombeya torrida seedlings. Armillaria species was isolated from a severely infected Dombeya torrida plant and mass cultivation was done in malt extract Agar. Each plant was inoculated after every 1 month of growth by placing four agar plugs from the 14-day Armillaria species. Inoculant of mycorrhizae comprised, hyphae and infected root systemsand T. harzianum were prepared according to manufacturer’s instructions. Single inoculation of arbuscular mycorrhizal fungi did not significantly change shoot fresh weight compared with control plants, while inoculation with T. harzianum alone significantly increased shoot fresh weight compared with control plants. Plants inoculated with T. harzianum alone had significantly. The presence of T. harzianum increased arbuscular mycorrhizal fungi root colonization compared to plants inoculated with the arbuscular mycorrhizal fungi alone, co-inoculation with arbuscular mycorrhizal fungi and T. harzianum producing a higher percentage of colonization than any other treatment. The study clearly demonstrated that inoculation of AMF and T. harzianum either individually or in combination enhanced plant growth response of Dombeya torrida seedlings. The inhibitory effects of the T. harzianumand AMF should be evaluated against Armillaria species under field growth conditions in order to explore their whole potential as biocontrol agents suppressing Armillaria root rot in the forest ecosystems.