【作者】 周新刚；

【导师】 吴凤芝；

【作者基本信息】 东北农业大学 ， 蔬菜学， 2011， 博士

【摘要】 黄瓜(Cucumis sativus L.)是一种世界性蔬菜,同时作为我国设施园艺栽培的第一大蔬菜作物,在蔬菜产业中地位均十分重要。随着设施栽种面积的逐年增加,其生产趋于规模化发展,然而由于生产栽培条件的限制及经济利益的驱使,设施内种植蔬菜种类单一,黄瓜连作现象普遍存在,严重制约了设施的可持续利用,成为亟待解决的问题,黄瓜连作障碍问题越来越多的得到了人们的重视。本文以不同黄瓜连作茬次土壤为研究对象,结合地上部黄瓜的生长状况,全面研究了黄瓜自然连作状态下不同连作茬次土壤中酚酸类物质含量、土壤营养状况、主要土壤微生物菌群、土传病原菌群落结构及大小的变化,以进一步揭示设施黄瓜连作障碍的产生的规律和机理,为采取相应的农业措施来有效地减轻连作障碍、提高黄瓜产量和品质、保持土地的可持续利用提供理论依据。所得主要结果如下：1.盆栽黄瓜连作第7茬表现出明显的生理障碍,黄瓜的叶面积、根体积、植株干重、根系活力、净光合速率等指标均低于其它各茬次。连作第9茬黄瓜生长状况比第7茬又有所好转。2.连作黄瓜土壤pH值从第1茬到第7茬逐渐降低,第9茬比第7茬又有所升高。连作黄瓜土壤EC值从第1茬到第7茬逐渐升高,第9茬比第7茬又有所降低。3.连作黄瓜土壤从第1茬到第7茬呈现富营养化的趋势。土壤碱解氮和速效磷含量从第1茬到第7茬逐渐升高,第9茬比第7茬有所降低。土壤有机质含量变化不明显。4.土壤脲酶、中性磷酸酶和过氧化氢酶活性均在第7茬最低,第9茬高于第7茬。土壤中性磷酸酶活性从第1茬到第5茬逐渐升高,土壤脲酶和过氧化氢酶活性在其它茬次间变化规律不明显。各茬次间土壤多酚氧化酶活性变化不明显。5. PCR-DGGE结果表明,连作改变了土壤细菌和真菌群落结构。连作对黄瓜土壤活性细菌和真菌群落结构比对总细菌和真菌群落结构有更大的影响,采用基于RNA的方法更容易了解土壤微生物群落的变化。同时,生长时期对土壤细菌和真菌群落结构的影响要大于连作茬次对土壤细菌和真菌群落结构的影响。6. qPCR结果表明,黄瓜连作第3茬土壤细菌16S rRNA拷贝数显著高于第1茬p<0.05),土壤细菌16S rRNA拷贝数从连作第3茬到第9茬呈降低的趋势；黄瓜土壤真菌ITS rRNA拷贝数从第1茬到第7茬随着连作茬次的增加逐渐增加,第9茬黄瓜土壤真菌ITS rRNA拷贝数比第7茬显著下降(p<0.05)。7.连作改变了土壤Fusarium菌群落结构。Fusarium菌群在连作第3茬减小,从第3茬到第7茬随连作茬次的增加逐渐增大,第7茬达到最多,在第9茬又减小。8.用HPLC法在连作黄瓜土壤中共检测到6种酚类化合物,对羟基苯甲酸、丁香酸、香草酸、香草醛、p-香豆酸和阿魏酸。其中p-香豆酸的含量在各茬次均为最高。土壤总酚含量随着连作茬次的增加从第1茬到第5茬有增加的趋势,第7茬均显著下降,第9茬含量比第7茬又显著增加p<0.05)。9.不同酚类化合物处理均在不同程度上均抑制了黄瓜种子胚根伸长和黄瓜幼苗生长；同时提高了黄瓜幼苗土壤脱氢酶活性、土壤微生物生物量碳含量以及细菌和真菌群落大小,改变了土壤微生物群落结构,降低了土壤细菌DGGE图谱条带数和多样性指数,提高了土壤真菌DGGE图谱条带数和多样性指数。综上,黄瓜在连作第7茬表现出明显的生理障碍,黄瓜连作障碍的发生与土壤pH值的降低、EC值的升高、土壤养分含量的增加以及土壤生物学性状的变化紧密相关。连作第9茬黄瓜生长状况以及土壤质量状况比第7茬又有所好转。PCR-DGGE结果表明黄瓜连作对土壤总细菌和真菌、活性细菌、真菌、Fusarium菌群落结构产生了影响。在RNA水平比在DNA水平更能反映连作对土壤微生物群落结构的影响。qPCR结果表明黄瓜连作影响了土壤细菌、真菌和Fusarium菌群落大小。酚类化合物可以直接对黄瓜产生毒害作用,也可以通过改变土壤生物学性状来影响黄瓜生长。更多还原

【Abstract】 As an economically important vegetable, cucumber (Cucumis sativus L.) is one of the most popular greenhouse plants. With the rapid development of horticulture in our country, the trend of a scale and specialization production in cucumber appears. Because of the restriction of plant condition and the urge of economic profits, soil sickness of cucumber is common, which severely restrichs the persistant use of horticulture and need to be solved urgently.In this paper, cucumber was continuously monocropped in pots for nine growing seasons. The growth condition of cucumber was observed. Soil phenolic compound contents, soil nutrient condition, soil bacterial, fungal and Fusarium community structures and sizes were also analyzed. Main results of this paper were as flowing:1. Cucumber of the seventh growing season showed an obvious retarded growth behavior. The leaf area, root volume and activity, and net photosynthetic rate of cucumber in the seventh growing were lower than in other growing seasons. The cucumber growth condition of the ninth growing turned better compared with the seventh growing season.2. In the continuously monocropped cucumber system, soil pH decreased from the first growing season to the seventh growing season, and increased in the ninth growing season. Soil EC increased from the first growing season to the seventh growing season, and decreased in the ninth growing season.3. The soil nutrient contents tended to increase from the first growing season to the seventh growing season. Contents of soil available nitrogen and phosphorous increase from the first growing season to the seventh growing season, and decreased in the ninth growing season. Changes of soil organic matter were not obvious in these different treatments.4. Activities of soil urease, neutral phosphatase and catalase were the lowest in the seventh growing season among these five treatments. Soil neutral phosphatase activity increased from the first growing season to the seventh growing season. Soil urease and catalase activities showed no obvious changes in the other four treatments. Soil polyphenol oxidase activity showed no obvious changes in all treatments.5. PCR-DGGE results showed that the continuous monocropping of cucumber changed soil bacterial and fungal community structures. The continuous monocropping of cucumber had stronger effects on active soil bacterial and fungal community than on total soil bacterial and fungal community, indicating that the RNA-based method was more efficient in soil community researches. The influence of the cucumber growth period on soil bacterial and fungal community structures was stronger than that of the continuous monocropping.6. Quantative PCR was used to measure the sizes of soil bacterial and fungal communities. Soil bacterial 16S rRNA gene copy numbers were significantly higher in the third growing season than that in the first growing season (p<0.05), and soil bacterial 16S rRNA gene copy numbers tended to decrease from the third growing season to the ninth growing season. Soil fungal ITS rRNA copy numbers increased with growing season from the first to the seventh growing season, and decreased in the ninth growth season.7. Continuous monocropping of cucumber changed the Fusarium community structhre. The Fusarium community size (Efla gene copy numbers) decreased in the third growing season, and increased from the third to the seventh growing season, finally decreased in the ninth growing season.8. Six kinds of phenolic compounds were detected in the soils under cucumber in the continuously monocropped system. p-coumaric acid content was the most abundant, followed by p-hydroxybenzoic acid> syringic acid> ferulic acid> vanillin> vanillic acid. The content of soil total phenolics increased with growing season from the first to the fifth growing season, and decreased in the seventh growth season, and increased in the ninth growing season.9. Amendments of phenolic compound suppressed cucumber radical elongation and seedling growth, increased soil dehydrogenase activity, microbial biomass C content, and bacterial and fungal abundances. Amendments of phenolic compound also changed soil bacterial and fungal community structures, decreased DGGE band numbers and diversity indices of the soil bacterial community structure, while increased that of the soil fungal community structure.Overall, Cucumber of the seventh growing season showed an obvious retarded growth behavior. The increase of soil EC and soil nutrient contents, decrease of soil pH, and changes of soil biological characters were closely related to the soil sickness of cucumber. Methods at the RNA level could reflect the effects of continuous monocropping of cucumber on soil microbial community composition better than at the DNA level. Phenolic compounds could directly affect the growth of cucumber, and indirectly by changing soil biological characters.更多还原