การควบคุมโรค Dieback ของสตรอว์เบอร์รีที่เกิดจาก Lasiodiplodia theorbomae โดยการใช้ Bacillus spp.

Abstract

The objectives of this studied were to identify the Lasiodiplodia theobromae causal pathogen of strawberry dieback disease and evaluated the biological control efficiency of four antagonistic bacteria consisting of Bacillus subtilis S93, B. siamensis RFCD306, B. velezensis NK-CSL02 and B. amyloliquefaciens PD-VVL01 under in vitro and in vivo conditions. A total of three fungal isolates from infected tissues by tissue transplanting method. The result after 7 days of inoculation, all isolates caused dieback. All inoculated strawberry showed wilt symptom on the shoot followed by black necrotic leaves. Rot symptom was observed on the root and crown then the crown became brown to black color. Fungal pathogen was identified based on morphological characteristics and analysis of the internal transcribed spacer (ITS) and large subunit of the nuclear ribosomal RNA (LSU) sequences and constructed the phylogenetic tree. Three fungal isolates were identified as Lasiodiplodia theobromae. Evaluation of the biological control efficiency of antagonistic bacteria to inhibit mycelium growth of L. theobromae isolate LSS-1, LSR-2 and LSC-3 was conducted by dual technique on PDA. The result showed that B. subtilis S93, B. siamensis RFCD306, B. amyloliquefaciens PD-VVL01 and B. velenzensis NK-CSL02 inhibited mycelial growth with percentage of inhibition ranging from 82.07%-100.00%. The inhibition of spore germination by slide culture technique showed that all antagonistic bacteria inhibited spore germination ranging from 64.00-89.34%. In addition, the microscopic observation revealed the morphology change of hyphal and spore structure of L. theobromae with abnormal growth and swelling. The efficacy of

B. subtilis S93 to control strawberry dieback disease inoculated by L. theobromae isolate LSS-1 was evaluated under greenhouse condition. The result showed that spraying with B. subtilis S93 for 3 days before fungal inoculation had the best control efficacy with 78.33%.