青海高寒地区油菜地土壤中放线菌组成及拮抗性放线菌研究

Population and antimicrobial effects of soil actinomycetes from the rape field in alpine cold region of Qinghai Plateau

【目的】研究青海高寒生态区油菜地土壤中放线菌组成及其对油菜菌核病、黑斑病及软腐病的拮抗性,为克服青海油菜连作障碍提供放线菌生态依据及拮抗性生防放线菌菌株。【方法】以青海化隆县（2830 m）、门源县（2800 m）、互助县（2600 m）及青海农业科学院（2300 m）4个海拔高度不同的代表性地区采集的4个土样为研究对象,采用稀释平板法分离计数、皿内琼脂块法筛选拮抗放线菌及发酵滤液抑菌率测定法检测拮抗效果。【结果】①低海拔油菜田土壤中放线菌数量较多,在海拔2300 m的农科院油菜田土壤中,高氏1号培养基上分离的放线菌总数、小单孢菌数量及小单孢菌在放线菌中所占比例分别是高海拔地区（2600-2830 m）的1.5-2.7倍、3.4-6.2倍及1.4-2.5倍,而链霉菌所占比例为51.6%,在海拔较高的3个油菜田土壤中,链霉菌所占比例高达60.6%-75.0%,高海拔土壤中以腐殖酸为碳源能源的链霉菌数量约为低海拔土壤的2倍。②在91株分离自青海高寒地区油菜田土壤放线菌中,有58.2%的放线菌对油菜3种病原菌有抗菌活性;在海拔大于2 600 m的3个供试地区,随着海拔降低,对3种病原菌有拮抗性的放线菌的比例从53.8%提高到70.8%,对胡萝卜软腐欧文氏菌有抗性的放线菌的比例从21.4%降低到5.9%。③从青海高寒地区油菜田土壤中分离的53株拮抗性放线菌中,对芸苔链格孢菌、核盘菌及胡萝卜软腐欧文氏菌有拮抗性的放线菌分别占供试放线菌的59.3%,26.4%及13.2%,拮抗芸苔链格孢菌的放线菌比例最高。④青海高寒地区油菜田土壤中放线菌数量及拮抗性放线菌比例与土壤养分之间无规律性关系。⑤对核盘菌和芸苔链格孢菌有较强抑制作用的放线菌所占比例分别为14.3%和12.5%,尚未筛选到对胡萝卜软腐欧文氏菌有较强抑制作用的拮抗性放线菌;放线菌发酵滤液对核盘菌和芸苔链格孢菌的最高抑制率分别为51.7%和69.7%。【结论】青海高寒地区油菜田土壤中放线菌总量、拮抗性放线菌比例及对不同病原菌的抗性与土壤所处海拔高度有一定关系,与土壤养分之间无规律性关系,表明青海不同海拔高度油菜种植区的土壤微生态环境对3种油菜土传病害的潜在抗性不同。

[Objective] In order to probe into the actinomycetes ecological distribution in soil in the area of Qinghai Plateau,the antimicrobial effects of actinomycetes on Sclerotinia sclerotiorum （Lib.） de Bary,Alternaria brassicae （Berk.） Sacca,Erwinia carotovora subsp, carotovora （Jones） Bergey et al. subsp, carotovora of rape. [Method] Four soil samples were collected from Hualong County（2 830 m）, Menyuan County（2 800 m）, Huzhu County（2 600 m）, Academy of Agricultural Sciences in Qinghai（2 300 m）Province with different altitudes in different regions as the research object,dilution plate and agar block methods were used to isolate and screen antimicrobial actinomycetes and determination methods of inhibition rate of fermentation liquid for the strain of actinomycetes were used to test the antimicrobial effects of the actinomycetes. [Result] ①There were a large number of actinomycetes in the low-lying rape fields soil. In the rape fields of Academy of Agricultural and Forestry soil 2 300 meters above sea level, the total of actinomycetes,micromonospora and the percentage of micromonospora to total actinomycetes separated from GA approximately 1.5--2.7,3.4--6.2 and 1.4--2.5 times as much as those in the soil of high-lying rape fields. But the percentage of streptomycetes to total actinomycetes was just on the contrary trend. In the low-lying rape fields soil,the number of streptomycetes was accounted for 51.6 percent of the actinomycetes. In the three higher-lying rape fields,the percentage of streptomycetes was an high as 60.6%--75.0%. The number of streptomycetes, which was dependent on humic acid for energy,in high-lying rape fields was about 2 times as much as that in low-lying rape fields. ②58.2% of 91 actinomycetes had antimicrobial activity which were isolated from rape fields soil in the area of Qinghai Plateau. With the lower elevation,the percentage of actinomycetes had antimicrobial activity against three Pathogens rose from 53.8 % to 70.8 %. Actinomycetes rate down to 5.9% from 21.4 %,which had antimicrobial activity against Erwinia carotovora. ③59. 3% ,26.4% and 13.2% of fifty-three tested strains had antimicrobial activities against Sclerotinia sclerotiorum （Lib.） de Bary,Alternaria brassicae （Berk.） Sacca, Erwinia carotovora subsp, carotovora （Jones） Bergey et al. subsp carotovora respectively,which illustrated that the percentage of actinomycetes against Erwinia carotovora is higher than others. ④The percentage of antimicrobal aetinomycetes to total actinomycetes had irregular relations to their soil nutrients. ⑤The intensity of inhibition actinomycetes to S. sclerotiorurn and A. brassicae was 14.3% and 12.5%. We did not screen the antimicrobal actinomycetes which had strong inhibition against E. carotovora. The highest of the Inhibiting rate of ferment fluid of antagonistic actinomycetes to S. sclerotiorum and A. brassicae was 51. 7% and 69.7%. [Conclusion] The quantity of actinomycetes, the percentage of actinomycetes had antimicrobial activity and the antagonism of different pathogens in the area of Qinghai Plateau had relations to soils of different altitudes, which illustrated that micro-ecological environment in the soil of different altitudes had different potential resistance to these three pathogens.