设施番茄连作障碍与土壤芽孢杆菌和假单胞菌及微生物群落的关系分析

以山东寿光及禹城地区不同连作年限(1~21年)的54个设施番茄土壤为研究对象,研究芽孢杆菌(Bacillus spp.)和假单胞菌(Pseudomonas spp.)及土壤微生物群落随连作年限的变化及其与土壤养分的关系,进而分析土壤中芽孢杆菌和假单胞菌与连作障碍之间的关系。结果表明:土壤细菌随着连作年限的持续增加而逐渐减少,连作年限少于6~10年时芽孢杆菌和假单胞菌的数量为增加趋势,连作6~10年后表现为减少趋势;PCR-DGGE(变性浓度梯度凝胶电泳)结果显示,作为土壤优势种群的芽孢杆菌及假单胞菌也在连作4~5年后减少,均与连作障碍发生(集中于5~10年)的时间基本吻合。土壤微生物生物量氮、碳随着连作年限呈增加趋势,符合指数增长模型(R2分别为0.30及0.20,P0.001)。由于设施番茄土壤肥料投入量大,土壤有机碳、C/N随着连作年限的增加而增加,呈显著正相关关系;土壤细菌数量与土壤C/N呈极显著负相关关系。通过对设施连作番茄土壤分析可知,连作番茄土壤中土壤细菌数量随连作年限呈减少趋势,芽孢杆菌及假单胞菌数量随着连作年限的变化与土壤连作障碍出现的时间基本吻合,可能是导致连作土壤微生物群落发生变化的原因。

Soil Pseudomonas spp., Bacillus spp., and microbial communities under tomato continuous cropping in greenhouse production

Long-term continuous cropping is unsustainable for vegetable production, especially for greenhouse vegetables. Most researchers have attributed the harmful effects of continuous cropping to the changes in soil microbial ecology. However, soil Pseudomonas spp. and Bacillus spp., two most important PGPR(plant growth promoting rhizobacteria) and dominant bacteria, have seldom been examined in investigating the microbial processes of continuous cropping obstacles until now. In this study, we investigated changes in soil Pseudomonas spp. and Bacillus spp. populations under continuous cropping and their relationships with soil microbial community using samples from 54 greenhouse tomato fields across continuous cropping years of 1~21 in Shouguang County and Yucheng County, Shandong, China. Results show that the number of total soil bacteria decreased as continuous cropping years increased, whereas the populations of Bacillus spp. and Pseudomonas spp. increased when continuous cropping years were shorter than 6~10 and then decreased after that. Results from PCR-DGGE(Denaturing Gradient Gel Electrophoresis) profile and sequence showed that Bacillus spp. and Pseudomonas spp. decreased after 4~5-year continuous cropping, which was similar to the actual period during which continuous cropping obstacles commonly occur(mainly 5~10 years). Soil organic carbon and C/N ratio significantly increased with the extension of continuous cropping time, and soil microbial C and N were a logarithmic function of continuous cropping year(R² were 0.20 and 0.30, respectively, P<0.001). Soil bacteria were significantly negatively correlated to soil C/N. Our investigation indicates that the occurrence of continuous cropping obstacles closely relates to the dynamic changes in these two dominant populations, suggesting that soil Bacillus spp. and Pseudomonas spp. play vital roles in maintaining soil ecology and soil health under long-term continuous cropping.