伴生分蘖洋葱改善番茄氮素吸收与氮转化微生物之间的关系研究

Long-term excessively nitrogen application would result in the decrease of tomato yield and quality, and increase of the incidence of plant diseases and insect pests, hence it has become the main issues of restricting the tomato production under greenhouse. Previous studies shown that companion cropping tomato with potato onion promoted nutrient absorption of tomato seedlings and increased tomato fruit yield, however, the mechanism by which companion cropping tomato with potato onion promotes nitrogen nutrient absorption keeps unclear. In present study, the rhizosphere soil and seedlings of tomatoes that are companioned by potato onion were used to to determine the total nitrogen content in tomato seedlings and the availability of nitrogen in the rhizosphere soils, for preliminary determining the effects of companion cropping with potato onion on tomato nitrogen absorption, as well the influence factors. Using GeoChip 4.2 and qRT-PCR to analysis the numbers and diversities of related genes involved in nitrogen cycle in the rhizosphere soils of tomato seedlings. The results would ascertain the molecular mechanism by which companion cropping tomato with potato onions improves yield of tomato and promotes nitrogen nutrition. Furthermore, the results would provide theoretical basis for application of tomato/potato onion companion cropping system, and ensure the sustainable development and reduce fertilizer application of tomato production under greenhouse.

设施栽培长期过量施用氮肥会使土壤养分失衡，致使番茄产量和品质下降，病虫害加重，已成为制约设施番茄生产的主要问题。申请者前期研究发现，伴生分蘖洋葱促进植株养分的吸收，提高了番茄产量，但伴生促进养分吸收的机理尚不明确。因此，本项目以分蘖洋葱伴生番茄的植株和根际土壤为研究目标，对番茄植株全氮含量和土壤氮有效性相关指标进行测定，初步明确伴生分蘖洋葱改善番茄氮吸收和土壤氮有效性的作用及影响因子。利用基因芯片技术 (GeoChip 4.2)和qRT-PCR技术分析伴生番茄根际土壤中氮循环相关功能基因数量及多样性变化。研究结果可望探明伴生分蘖洋葱改善番茄氮营养提高植株产量的分子机理，进而为分蘖洋葱/番茄伴生栽培模式的应用提供理论依据，为设施番茄减肥增效的可持续发展提供保障，具有重要的科学和现实意义。

本项目以分蘖洋葱伴生番茄的植株和根际土壤为研究目标，对番茄植株全氮含量和土壤氮有效性相关指标进行测定。试验结果显示，伴生两种分蘖洋葱均促进了番茄生物量积累和产量的提高，伴生降低了氮养分向叶中分配比例，增加了氮养分向根和花果中分配比例，改变了氮养分在番茄植株内分配规律，从而提高了伴生番茄对氮的利用率。伴生后番茄根际土壤中铵态氮含量显著增加，硝态氮含量显著降低，伴生改变土壤铵态氮和硝态氮比例，促进了番茄的氮吸收。伴生提高了番茄根际土壤脱氢酶和脲酶活性，土壤pH值、脱氢酶和脲酶是影响土壤氮素转化微生物功能基因的主要因素。伴生提高了番茄根际土壤芽孢杆菌属（Bacillus）、假单胞菌属（Pseudomonas）和鞘氨醇单胞菌属（Sphingomonas）等细菌的相对丰度；伴生提高了番茄根际土壤青霉菌属（Penicillium）、曲霉菌属（Aspergillus）和毛壳菌属（Chaetomium）等真菌的相对丰度，但却降低了散囊菌属（Eurotium）和梭孢壳属（Thielavia）的丰度，伴生番茄根际微生物菌群结构的改变可能是促进了番茄氮养分吸收的关键因素之一。伴生番茄根际土壤中氮循环功能基因数量及Simpson多样性指数显著高于单作，其中碳降解、氨氧化及芳香族化合物合成途径中关键功能基因探针强度显著高于单作番茄，而砷、碲及碳固定相关功能基因显著低于单作番茄。氨氧化细菌中亚硝化单胞菌属（Nitrosomonas）和假单胞菌属（Pseudomonas）丰度增加，亚硝化螺菌属（Nitrosospira）和弧菌属（Nitrosovibrio）等丰度降低，伴生番茄根际土壤中氨单加氧酶基因（amoB）Beta多样性显著高于单作，亚硝酸盐还原酶基因（nirS）Beta多样性显著低于单作。伴生显著提高了番茄根际土壤中amoB和一氧化二氮还原酶（nosZ）功能基因的表达量，而对nifH和nirS功能基因的表达量影响不显著。探明了伴生分蘖洋葱通过根际土壤中氨氧化微生物多样性及相关功能基因丰度变化是促进番茄根际土壤氮的转化主要环节，阐明了伴生改善植株氮素吸收与土壤氮转化微生物之间的关系，揭示了伴生分蘖洋葱提高番茄氮吸收的生物学机理。