แบคทีเรียปฏิปักษ์เพื่อควบคุมโรครากขาวของยางพารา (Hevea brasilieansis)

Abstract

Soil born fungus, Rigidoporus microporus cause of white root rot disease is one of the important problems in rubber producing countries including Thailand. To decrease of fungicide use, therefore, it needs to prevent the disease by biological control. Bacillus species show broad-spectrum antimicrobial activity and have been widely used as agricultural biocontrol agents. This study aims to screen Bacillus spp. which were effective in inhibiting R. microporus. Selection of 44 isolates of antagonist bacteria, 3 isolates were able to inhibit R. microporus more than 51 percent viz B. subtilis isolate SM1, isolate LPDD3-2 and B. amyloliquefaciens isolate PT7. B. subtilis isolates SM1 are more effective against in inhibiting R. microporus than the antagonist bacteria. B. subtilis isolates SM1 can produce sterile and non-sterile of supernatant and volatile, antagonisitic substance and volatile compound of Isolate SM1 inhibited mycelial growth of R. microporus with the rate of 96.67, 63.33 and 50.00 percent respectively and soil amended and rubber limb inhibited mycelial growth of R. microporus with the rate of 28.57 percent of soil amended and 19.00 percent of rubber limb compared with untreated controls 100 percent of soil amended and rubber limb. Mycelial deforminity of R. microporus was observed by microscopy and SEM confirmed the pored and wrinkle mycelia. R. microporus causes the rubber tree to show signs of disease on the lower leaves, yellow leaves, the edges of the burn and convert to black color then decomposed with percentage disease of root 93.78 percent and aerial stem 77.78 percent. While using B. subtilis isolate SM1 can decrese the incidence of white root disease aerial stem and root 72.22 and 65.22, respectively. The rubber tree grows close to the one without white root fungus. The aerial stem remains normal green leaves, normal root and increased root volume. Soil nutrients tend to increase, phosphorus and potassium concentrations tend to be higher as well. B. subtilis isolate SM1 was effective in controlling white root disease in laboratory and green house. Therefore, it should be in formulation for controlling white root disease of rubber tree and reduce the use of chemicals.