Bacteria and actinomycetes were quantitatively isolated from a soil collected from Avon, South Australia, which is suppressive to wheat bare-patch disease caused by Rhizoctonia solani anastomosis group 8. The percentage of isolates antagonistic to R. solani AG-8 isolate 21 was measured from the total population of bacteria and actinomycetes. Heat treatment (60℃, 10min.), a process previously shown to remove the suppressive qualities of this soil, significantly reduced the counts of total bacteria and actinomycetes on agar plates, but did not reduce the percentage of antagonists. Nine isolates were chosen from 2700 isolates, based on their strong inhibition of R. solani AG-8 isolate 21, Gaeumannomyces graminis var. tritici (Ggt) isolate 8, Fusarium graminearum isolate Fg, Verticillium dahliae isolate Vd5, Bipolaris sorokiniana isolate Bs, Pythium irregulare isolate BH40, and Rhizoctonia solani AG-4 isolate 1664 causing damping-off of cotton. Seven of the nine antagonistic isolates were either chitinase-or endoglucanase-positive, with strong chitinase production appearing to be associated with strong biocontrol activity.The nine antagonistic isolates were identified as Bacillus megaterium (isolate Ap25), B. subtilis (isolate Ap113), Streptomyces spp. (isolate Ap117), Bacillus coagulans (isolate Ap123), Streptoverticillium reticulum (isolate Ap89), Cellulomonas flavigena (isolate Ap75) or were actinomycetes (isolates Ap116, Ap111 and Ap139).B. megaterium Ap25 and B. subtilis Ap113 were the most effective in disease reduction and seedling growth promotion.These two isolates were inhibitory in vitro to a beneficial Trichoderma pseudokoningii isolate A5MH, which was isolated from the same soil sample, but did not significantly reduce the efficacy of A5MH in disease control and seedling growth promotion.%从南澳大利亚埃文采集的土壤样品中计数分离了细菌和放线菌,该土壤对Rhizoctonia solani 融合群8引起的小麦根腐病具有抑制作用.统计了分离物中对R. solani AG-8菌株21有拮抗作用的百分比.热处理(60℃, 10min)能够消除土壤的抑病能力,可显著减少土壤中细菌和放线菌的数量,但是并不改变对病原菌有抑制作用的分离物的总体百分比.依据对R. solani AG-8 菌株21, Gaeumannomyces graminis var. tritici (Ggt) 菌株8, Fusarium graminearum菌株Fg, Verticillium dahliae菌株Vd5, Bipolaris sorokiniana菌株Bs, Pythium irregulare菌株BH40, 以及引起棉花猝倒病的Rhizoctonia solani AG-4 菌株1664的抑菌能力,自2700个菌株中筛选了9个最强拮抗菌株;其中7个菌株能够产生几丁质酶,或者产生内切葡聚糖酶,而几丁质酶活性与生物防治效果具有相关性.这9个菌株鉴定为Bacillus megaterium (菌株Ap25), B. subtilis (菌株Ap113), Streptomyces spp. (菌株Ap117), Bacillus coagulans (菌株Ap123), Streptoverticillium reticulum (菌株Ap89), Cellulomonas flavigena (菌株Ap75),以及放线菌 (菌株Ap116, Ap111和Ap139). B. megaterium Ap25 and B. subtilis Ap113对小麦根腐病及全蚀病的防治效果以及刺激小麦生长的作用最强.这两个菌株能够在平板上抑制一种分离自同一土样的有益菌Trichoderma pseudokoningii菌株A5MH的生长,但对该木霉菌的生物防治效果及其刺激植物生长的作用没有明显削弱.
展开▼
