การควบคุมโรคถอดฝักดาบข้าวด้วยเชื้อแบคทีเรียปฏิปักษ์ที่อยู่ในดินบริเวณรอบรากข้าว

Abstract

Isolation of Fusarium sp. causing bakanae disease of rice was made from diseased plants, 58 isolates were obtained. The fungal isolates were pathogenicity tested and the isolate CRFuRD-7 was found causing most severe symptom. Molecular identification of this fungal isolate was made by sequencing nucleotide at ITS region by using 2 primers e.g. ITS5 and ITS4. It was found that this Fusarium isolate can be identified as Fusarium fujikuroi by comparing with the database of Genbank (NCBI). Isolation of bacteria from rhizoshere soil, 104 isolates were obtained. Primary selection of the bacterial isolates on antagonistic type, 14 isolates were obtained. The antagonistic bacterial isolates were then tested on growth inhibition of the fungus F. fujikuroi isolate CRFuRD-7 on PDA, using dual culture technique. Result showed that isolates RC-1, RR-51 and SR-31 gave highest of percent growth inhibition at 51.63, 53.73 and 51.63 respectively. The test on resistance of the pathogen to mancozeb fungicide on PDA, using poison medium technique, no resistance was found; all concentrations tested showed growth inhibition; at highest concentration, 1200 ppm could have 100 percent inhibition. Testing efficacy of the three bacterial isolate in production of metabolites. It was found that they could produce cellulase and amylase enzymes and siderophore. Molecular identification of the three of the three isolates bacteria was made by sequencing nucleotide at 16S rDNA region by PCR compared with database in Genbank (NCBI) and could be identified as Bacillus amyoliquefaciens. Comparative efficacy test of the three bacterial isolates with mancozeb fungicide in controlling bakanae disease of rice was conducted by soaking the seeds with the bacteria and macozeb solutions before inoculation or spraying the seeds with the solutions after inoculation which was done by mixing the rice seeds with the fungal pathogen. Result showed that soaking the rice seeds with the three bacterial isolates before inoculation had lower percentage of diseased seedlings than spraying the solution after. But soaking seeds with mancozeb before inoculation and spraying it after inoculation gave lower percentage of diseased seedlings, but not much, about 10 percent compared with bacteria treatment. However, when compared the results with control treatment the bacterial isolates could reduce percentage of diseased seedlings at high percentage.