青稞根腐病对根际土壤微生物及酶活性的影响

选取甘肃省卓尼县青稞种植区为研究地点,调查青稞根腐病的发病情况,并分别采集其健康植株和发病株根际的土壤,对比分析其土壤微生物生物量(碳、氮、磷)、微生物数量(细菌、真菌、放线菌)以及过氧化氢酶、蔗糖酶、脲酶、碱性磷酸酶、纤维素酶5种酶活性。结果发现,研究区10个采样点均有青稞根腐病的发生,发病率在5%—20%之间,不同地点发病率不同。根腐病的发生,会显著影响青稞根际微生物生物量,导致微生物生物量碳、氮、磷的含量发生变化,其中微生物生物量氮和磷含量整体降低,且不同采样点微生物量不同。土壤微生物数量总体呈现细菌放线菌真菌的趋势,但不同微生物对根腐病发病的响应不同,细菌和放线菌数量因根腐病的发生而减少,真菌的数量则增多;不同采样点土壤微生物数量不相同,细菌和真菌呈现区域性特征,放线菌的数量不呈现地域性。根腐病的发生还造成土壤酶活性的改变,其中蔗糖酶、脲酶、磷酸酶的含量因根腐病的发生而降低,而纤维素酶则升高,过氧化氢酶的变化没有规律。总而言之,根腐病的发生会使青稞根际土壤微生物组成发生改变,碳、氮、磷等物质代谢受到抑制,而能量代谢发生紊乱。因此,研究和防治青稞根腐病就必须重视土壤微生物及土壤酶的作用。

Effects of naked barley root rot on rhizosphere soil microorganisms and enzyme activity

Naked barley is one of the major crops of western China. Root rot causes a serious reduction in naked barley. However, study of the rhizosphere soil microorganisms and enzyme activity of naked barley experiencing root rot may yet find ways to mitigate the damage. This study selected a naked barley growing area in Zhuoni county of the Gannan state in Gansu Province as its research site. Naked barley root rot was chosen as the object of study. Rhizosphere soil samples from healthy naked barley and naked barley infected with root rot were collected separately. Then microbial (bacteria, actinomyces, fungi) quantity was determined using the plate count method. Microbial biomass carbon was determined using the potassium dichromate sulfuric acid heating method. Microbial biomass nitrogen was determined using the Kjeldahl method. Microbial biomass phosphorus was determined using the molybdenum blue colorimetric method. Catalase activity was determined using the volumetry method. Sucrase and cellulase activity were determined using 3, 5-dinitrosalicylic acid colorimetry. Urease activity was determined using the indophenol blue colorimetric method. Alkaline phosphatase was determined using the phenyl phosphate disodium colorimetric method. Finally, we analyzed rhizosphere soil sampled from healthy naked barley and from naked barley infected with root rot to compare microbial biomass, microbial numbers in soil, and soil enzyme activity. The results showed that root rot occurred in naked barley at all 10 of the sampled areas with an incidence of 5% to 20%, though the morbidity differed between plots. The presence of root rot dramatically affected the microbial biomass of naked barley rhizosphere soil, which led to changes in the carbon, nitrogen, and phosphorus levels of the microbial biomass. The reduction in microbial biomass nitrogen and phosphorus levels and in microbial biomass differed between sampling sites. The total number of microorganisms varied, but showed a general population trend of bacteria > actinomyces > fungi. Different microorganisms have different responses to naked barley root rot, as the number of bacteria and actinomyces decreased when root rot was present, while the number of fungi increased. The total number of microorganisms varied between different sample areas, with bacteria and fungi showing rationality, while actinomyces did not. The presence of naked barley root rot also changed the enzyme activity of rhizosphere soil. Enzyme activity around sucrose, urease, and alkaline phosphatase decreased in the presence of root rot, while enzyme activity around cellulose increased. Changes in catalase activity did not appear to be correlated with the presence of root rot. Enzyme activity differed between samples of naked barley rhizosphere soil different samples to a significant degree. Correlation analysis showed a significant positive correlation between soil microbial biomass carbon and soil microbial biomass nitrogen levels. The number of soil bacteria and actinomyces showed a significant positive correlation with both soil microbial biomass carbon and biomass nitrogen levels. Soil fungi numbers showed significant positive correlation with both soil microbial biomass phosphorus and sucrose levels, and with enzyme activity around cellulose. Alkaline phosphatase activity showed significant positive correlation with both soil microbial biomass carbon and actinomyces numbers, but also showed significant negative correlation with catalase activity. In general, the presence of naked barley root rot was found to influence various factors of rhizosphere soil. These various factors are connected to and influence each other. The root rot changed the soil microbial flora composition of naked barley rhizosphere soil by restricting the presence of materials such as carbon, nitrogen, and phosphorus, and by disrupting energy metabolism. Therefore, research into the control of naked barley root rot must take the role of soil microorganisms and enzymes into account.