PLFA方法研究连作对加工番茄根际土壤微生物群落结构的影响

Microbial community structure in rhizosphere soils of long-term continuously cropped processing tomato based on PLFA method

通过在石河子大学农学院试验站开展加工番茄连作定点微区试验,采用氯仿熏蒸和磷脂脂肪酸(PLFA)法相结合,研究了不同连作处理(种植1 a、连作3 a、5 a和7 a)对新疆加工番茄花果期和成熟期根际土壤微生物群落结构及土壤微生物量的影响。结果表明,连作导致土壤微生物量碳(SMBC)、微生物量氮(SMBN)和微生物熵(q MB)下降,SMBC/SMBN升高,而微生物量磷(SMBP)随连作年限和生育期的变化而不同。连作显著增加了真菌PLFAs含量,降低了细菌PLFAs含量、土壤PLFAs总量及细菌/真菌PLFAs的比值,而放线菌PLFAs含量变化无规律。连作7 a时,成熟期的细菌PLFAs含量、土壤PLFAs总量较对照分别减少62.9%、50.3%(P<0.05),而真菌PLFAs含量较对照升高60.2%(P<0.05)。从多样性指数分析看,Shannon-Wiener指数、Simpson指数、Brillouin指数和Pielou指数均随连作年限的延长呈先升后降的变化,其中连作3 a时各项指数最大,连作7 a时最小,表明在本试验年限范围内,连作使得微生物群落多样性与均匀程度皆出现了一定程度的降低。相关性分析表明,土壤微生物各类群PLFAs量、微生物量及土壤肥力之间存在相关性,说明土壤微生物量与土壤肥沃程度相关,可作为评价土壤肥力的生物学指标。可见,加工番茄连作改变了土壤微生物群落结构,降低了土壤微生物量,最终在根际土壤微生态系统和环境因子等因素的综合作用下产生连作障碍。

Xinjiang Uygur Autonomous Region is a major production base of processing tomato in China. In the effort to meet market demand for processing tomato, mono-cropping has been widely adopted. Unfortunately, this phenomenon has become the dominant factor limiting the stable production and yield of tomato in the region. Here, we conducted a field study to determine the impact of continuous cropping over the long-term on microbe community structure in rhizosphere soil of processing tomato using phospholipid fatty acid (PLFA) and chloroform fumigation extraction method. The mono-cropping field experiment started in 2007 at a station belonging to the College of Agriculture of Shihezi University. The processing tomato cultivar used in the experiment was ‘Ligeer 87-5’. Soil samples were collected for analysis from plots with different cultivation histories (3, 5 and 7 years of continuous cropping) and a control plot that was under fallow for 3 years. The results showed that soil microbial biomass C (SMBC), soil microbial biomass N (SMBN) and soil microbial biomass entropy (qMB)significantly decreased, while soil microbial biomass C/N increased with increasing duration of continuous cropping (P <0.05). However, soil microbial biomass P (SMBP) exhibited a different response to both continuous cropping and variousgrowth stages. PLFA analysis indicated that continuous cropping significantly increased fungal PLFAs, whereas the reversetrend was observed for bacterial PLFAs, total PLFAs and the ratio of bacterial PLFAs to fungal PLFAs. However,actinomycetous PLFAs had no regular change with increasing duration of continuous cropping. After 7 years of continuouscropping, bacterial PLFAs and total PLFAs amount decreased by 62.9% and 50.3% (P < 0.05), respectively, but fungal PLFAsamount significantly increased by 60.2% compared with control. Based on diversity index analysis, Shannon-Wiener index,Simpson index, Brillouin index and Pielou index all initially increased and then decreased with increasing years of continuouscropping of processing tomato. Soil microbial diversity index was highest in the treatment of 3 years continuous cropping and was lowest for the treatment of 7 years continuous cropping. It was concluded that microbial community diversity and uniformity decreased with increasing of continuous cropping years in this area. Correlation analysis showed significant correlation among PLFAs of bacteria, fungi and actinomycetes, total PLFAs, soil microbial biomass and soil fertility, which indicated that soil microbial biomass was highly related with soil fertility. Therefore, soil microbial biomass could be used as an available biological index for the evaluation of soil fertility. The results suggested that years of mono-cropping had a major influence on microbial community structure and soil microbial biomass in rhizosphere soil of processing tomato, which in turn limited sustainable development of processing tomato.