| Chrysanthemum(Chrysanthemum morifolium)is a perennial plant,is one of the most important ornamental plants with high ornamental and economic values.In recent years,with the increase in the demand for cut chrysanthemum in the domestic and foreign markets,the cut chrysanthemum industry in China has developed rapidly.Due to the continuous expansion of the production area of cut chrysanthemum,the continuous continuous cropping obstacles of cut chrysanthemum becoming more and more serious.The quality of cut chrysanthemum is decreasing with the deterioration of soil physical and chemical properties,imbalanced nutrient ratio and soil microbial ecological environment,which is a bottle neck of cut chrysanthemum production.Considering the flower pattern and color,55 varieties of cut chrysanthemum were selected and then were tested in the field of continuous cultivation for many years.The incidence and disease index of the selected cut chrysanthemum were investigated.According to the resistance level of continuous cropping obstacles based on the membership function method,4 different resistant representative varieties(Chrysanthemum morifolium’Nannonglibai’,Chrysanthemum morifolium ’Nannongbingjie’,Chrysanthemum morifolium’Nannongdoulv’,Chrysanthemum morifolium‘Nannong fenying’)were selected.The content of organic matter,ammonium nitrogen content,available nutrients(available phosphorus and available potassium),conductivity,pH value,leaf enzyme(polyphenol oxidase,phenylalanine ammonia lyase,peroxidase)activity,soil enzyme(urease,sucrase,catalase)activity and the effects on rhizosphere soil microbes of the continuous cropping soil in four different resistant cut chrysanthemum varieties were determined.The aim is to provide a theoretical basis for screening and resistance mechanism analysis of cut chrysanthemum continuous cropping resistance varieties.The main findings are as follows:(1)The variation of resistance to continuous cropping in 55 cut chrysanthemum varieties was studied.The results showed that the resistance of different cut chrysanthemum varieties to continuous cropping obstacles was significantly different.According to the classification criteria of continuous resistance resistance evaluation,different resistant varieties were screened.The high resistant material is Chrysanthemum morifolium ’Nannonglibai’.The medium anti-materials are Chrysanthemum morifolium ’Nannongyuanlv’ and Chrysanthemum morifolium ’Nannongbingjie’.The susceptible materials are Chrysanthemum morifolium’Menghong’,Chrysanthemum morifolium ’Nannongdoulv’ and Chrysanthemum morifolium’Nannongdaixue’.The other 49 varieties are all high-sensitivity.(2)According to the results of resistance evaluation,four different resistance representative varieties Chrysanthemum morifolium‘Nannonglibai’(high resistance),Chrysanthemum morifolium ’Nannongb ingj ie’(medium resistance),Chrysanthemum morifolium‘Nannongdoulv’(susceptible)and Chrysanthemum morifolium ’Nannong fenying’(high sensitivity)were selected to study the continuous cropping soil physical and chemical properties,the enzymatic activity of cut chrysanthemum leaves and the difference in appearance quality respectively.The results showed that the content of organic matter and ammonium nitrogen in the high resistant varieties was the highest,and the content of available phosphorus and available potassium was the lowest.On the contrary,the content of organic matter and ammonium nitrogen in the high-sensitivity varieties was the lowest,and the content of available phosphorus and available potassium was the highest.There was no significant difference about the organic matter and ammonium nitrogen content between susceptible and high-sensitivity varieties,and the soil conductivity of the high-sensitivity varieties was the highest,and the soil pH of the high-resistance varieties was the lowest.Polyphenol oxidase,phenylalanine ammonia lyase,and peroxidase all showed higher resistance levels and higher enzyme activities.Comparing the appearance quality of cut chrysanthemum,it was found that the plant height,stem diameter,stem and fresh and dry weight of high-resistance varieties and medium-resistant varieties were significantly higher than those of susceptible and high-sensitivity varieties.(3)The activities of soil enzymes(Urease,Invertase,Catalase)and the number of rhizosphere microorganisms in the soils of four cut chrysanthemum varieties were significantly different.The enzyme activities of four different resistant varieties showed sequential and gradually decreasing from high resistance to high sensitivity.And the activities of sucrase and urease were not significantly different among the resistant and susceptible varieties.The catalase between the high and medium resistant varieties was no significant difference.The enzyme activity in turn showed:high resistance>medium resistance>susceptible>high sensitivity.Among the four different resistant varieties,the highest number of bacteria in the rhizosphere soil of high resistant varieties was 24.68×108copies g-1 soil,while the high-sensitivity variety had the least number of bacteria in the rhizosphere soil,which was 5.80×108 copies g-1 soil.The susceptible variety was 7.87×108copies g-1 soil,and the medium resistant variety was 13.50×108 copies g-1 soil.The continuous cropping rhizosphere soil of high resistant varieties had the least number of fungi,which was 9.73×106 copies g-1 soil.The number of fungi in the rhizosphere soil of the susceptible and high-sensitivity varieties was significantly higher than that of the high-resistance varieties.The ratio of bacterial/fungi in the rhizosphere soil of the high-resistance varieties was 252.80,and the bacterial/fungi value in the rhizosphere soil of the medium-resistant varieties was 64.45.The bacterial/fungi values in the rhizosphere soil of diseased and high-sensitivity varieties were 37.21and 38.52,respectively,indicating that there were significant differences in rhizosphere soil enzyme activities and rhizosphere soil microbial numbers in different resistant varieties of cut chrysanthemum. |
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