ศักยภาพของราเอนโดไฟต์และแอคติโนมัยซีทจากดินรอบรากยูคาลิปตัสในการเป็นตัวควบคุมทางชีวภาพของ Cylindrocladium สาเหตุโรคใบไหม้ใน Eucalyptus camaldulensis

Abstract

Eucalyptus is one of the most important economic plants because it can bring many advantages, especially wood. It was be required in the paper industry in many countries. Leaf blight disease in Eucalyptus seedling caused by Cylindrocladium sp. was often epidemic in the wet reason and lead to defoliation and easy to death. The aim of this research was to selected endophytic fungi or rhizosphere actinomycetes which produce compounds to inhibit the growth of Cylindrocladium sp., the causal agent of leaves blight disease in Eucalyptus camaldulensis seedlings. Eucalyptus leaf blight samples were collected from Chiang Mai and Prachin Buri provinces. Three isolates of fungal pathogen, C. colhounii CMU 115, C. reteaudii TTCC02 and C. reteaudii TTCC06 were isolated. Two hundred and nine of endophytic fungi were isolated from leaves and branches of healthy eucalyptus. Moreover, 121 isolates of rhizospheric actinomycetes were obtained from soil samples around eucalyptus tree. The dual culture method was used for screening of antifungal activity. The result indicated that ten isolates of endophytic fungi showed the antifungal activity more than 65% inhibition and 16 isolates of actinomycetes showed the percentage of inhibition more than 80% inhibition. Culture filtrate of rhizospheric actinomycetes isolate PG4-36 showed the largest of clear zone with C. colhounii CMU115, C. reteaudii TTCC02 and C. reteaudii TTCC06 was 15.0 ± 0.8, 18.33 ± 1.2 and 16.67 ± 0.6 mm, respectively. Bennett's medium and potato dextrose broth were the suitable media for antifungal compound production. Crude extract of Streptomyces sioyaensis PG4-36 in Bennett’s medium was applied to control leaf blight disease in eucalyptus seedling. The disease rating in eucalyptus leaf was evaluated for in 5 treatments, Treatment 1: positive control, Treatment 2: negative control, Treatment 3: inoculation pathogen before 24 hours, then spray crude extract, Treatments 4: spraying crude extract prior to 24 hours before inoculation pathogen and Treatment 5: inoculation pathogen and spray crude extract simultaneously. It was found that the ratting of the disease in Treatment 4 : spraying crude extract prior to 24 hours before inoculation pathogen. This treatment is the most effective in controlling the leaf blight disease.