施氮水平对蚕豆枯萎病和根际微生物代谢功能多样性的影响

Effects of nitrogen application rate on faba bean fusarium wilt and rhizospheric microbial metabolic functional diversity

研究不同氮肥用量对蚕豆根际微生物功能多样性的影响及其与蚕豆枯萎病发生的关系.通过田间小区试验,采用Biolog微平板分析法研究了4个施氮水平N0(0kg·hm-2)、N1(56.25kg·hm-2)、N2(112.5kg·hm-2)和N3(168.75kg·hm-2)对蚕豆枯萎病危害和根际微生物代谢功能多样性的影响.结果表明:施氮(N1、N2、N3)处理显著降低了蚕豆枯萎病的病情指数和根际镰刀菌的数量,显著增加了蚕豆根际的细菌、放线菌数量、细菌/真菌和放线菌/真菌.其中N2处理蚕豆枯萎病病情指数和镰刀菌数量最低,而细菌、放线菌数量、细菌/真菌和放线菌/真菌最高.与N0处理相比,N1、N2、N3处理均提高了根际微生物群落碳源利用率(AWCD),但对6类碳源的利用存在一定的差异.不同施氮水平下根际微生物群落对糖类、羧酸类和氨基酸类碳源利用程度较高.主成分分析表明,施氮明显改变了蚕豆根际微生物群落结构,糖类、羧酸类和氨基酸类碳源是区分施氮导致土壤微生物群落变化的敏感碳源.施氮抑制了根际微生物对部分糖类和羧酸类碳源的利用,而提高了对氨基酸和酚酸类碳源的利用,这可能是施氮减轻蚕豆枯萎病危害的重要原因之一.适量施氮能增加根际细菌、放线菌数量,改变微生物代谢功能,降低病原菌数量,是抑制蚕豆枯萎病发生的有效措施.

A field plot experiment was conducted to study the effects of different nitrogen （N） ap- plication rates on the microbial functional diversity in faba bean rhizosphere and the relationships between the microbial functional diversity and the occurrence of faba bean fusarium wilt. Four nitro- gen application rates were installed, i. e. , N0（0 kg·hm^-2） , N1（56.25 kg ·hm^-2） , N2（112.5 kg ·hm^-2） , and N3 （ 168.75 kg·hm^-2 ）, and Biolog microbial analysis system was applied to study the damage of faba bean fusarium wilt and the rhizospheric microbial metabolic functional di- versity. Applying N （ N1 , N2, and N3 ） decreased the disease index of faba bean fusarium wilt and the quantity of Fusarium oxyspontm significantly, and increased the quantities of bacteria and acti- nomyces and the ratios of bacteria/fungi and actinomyces/fungi significantly, with the peak values of bacteria and actinomyces, bacteria/fungi, and actinomyces/fungi, and the lowest disease index and F. oxysporum density in N2. As compared with No , applying N increased the AWCD value sig- nificantly, but the effects of different N application rates on the ability of rhizospheric microbes in utilizing six types of carbon sources had definite differences. Under the application of N, the utiliza- tion rates of carbohydrates, carboxvlic acids, and amino acids by the rhizosDheric microbes werehigher. Principal component analysis demonstrated that bial community composition obviously, and the carboh applying N changed the rhizospheric micro- ydrates , carboxylic acids, and amino acids were the sensitive carbon sources differentiating the changes of the microbial community induced by N application. Applying N inhibited the utilization of carbohydrates and carboxylic acids but im- proved the utilization of amino acids and phenolic acids by the rhizospheric microbes, which could be one of the main reasons of applying N being able to reduce the harm of faba bean fusarium wilt. It was suggested that rationally applying N could increase the quantities of rhizospheric bacteria and actinomyces, alter the microbial metabolic function, and decrease F. oxysporum density, being an effective measure to control the occurrence of faba bean fusarium wilt.