Biological control of Rhizoctonia solani AG2-2 IIIB on creeping bentgrass using an antifungal Pseudomonas fluorescens HP72 and its monitoring in fileds
1997
Murakami, K. (Nisshin Flour Milling Co. Ltd., Tsukuba, Ibaraki (Japan). Tsukuba Lab.) | Kanzaki, K. | Okada, K. | Matsumoto, S. | Oyaizu, H.
Bacteria which show antifungal activity were isolated from roots of turfgrass and associated soil. Among the bacteria, a fluorescent pseudomonad (strain HP72) which was identified as Pseudomonas fluorescens showed strong antifungal activity and was selected as a candidate for biological control of golf course turfgrass pathogens. Enumeration methods, established to monitor the bacteria in soil, were based on the detection of a DNA fragment (ca. 800 base pairs) which was very specific to strain PH72. The methods called FIA-PCR and MPN-PCR gave very good results in a model inoculation test and were applied to laboratory sod and field survival experiments. Because a background of indigenous bacteria having the same DNA fragment as strain HP72 was not detected in soils used for these experiments, strain HP72 was easily enumerated. When soil temperature was lower than 35 degrees C, the bacteria survived for at least 20 days (ca. 10(5) cfu per gram soil and roots). However, if soil temperature rose higher than 43 degrees C for 2 hr per day, the bacteria died completely within 76 days. The ratio of strain HP72 to the total fluorescent pseudomonads on turfgrass roots increased up to 5 days after inoculation and was higher than 80% of total fluorescent pseudomonads for at least 20 days. In each greenhouse experiment, creeping bentgrass developed significantly less disease when inoculated with PH72 before inoculation with Rhizoctonia solani than when inoculated with the pathogen alone. The level of control provided by HP72 was as good as that by a widely used isoprothiolane-flutolanil fungicide
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