The Selection Of Chrysanthemum Cultivars Resistant To Continuous Cropping Obstacle And Study On Its Mechanism

Chrysanthemum(Chrysanthemum morifolium),a perennial herb,is one of the top ten traditional flowers in China and one of the four cut flowers in the world.It has a long history of cultivation and has high ornamental and economic value.In recent years,the increasing demand for cut chrysanthemum in domestic and foreign markets has made the planting mode of cut chrysanthemum change rapidly to intensive and large-scale,resulting in the increasingly prominent obstacles of continuous cropping of cut chrysanthemum.Continuous cropping obstacles lead to the quality decline of cut chrysanthemum,plant short,cut chrysanthemum production in a large area,and even lead to flower farmers.Continuous cropping obstacle has seriously restricted the sustainable and healthy development of cut chrysanthemum industry in China,which is called the problem to be solved urgently.In this experiment,55 varieties of cut chrysanthemum were selected and tested in Nine-year continuous cultivation border.The survival rate of the selected varieties in different growth periods was investigated.The resistance evaluation and resistance classification of the selected varieties were carried out to screen four varieties with different resistance levels.Four representative varieties with different resistances were selected(high resistant variety‘Chenganna’,resistant variety‘Feeling sunny’ The differences of appearance and quality between ’Nannong huangfengwo’ and huangpingpang were compared,and the activities of leaf tissue enzymes,including peroxidase,were measured at different growth stages(growth stage,budding stage and flowering stage)under the conditions of continuous cropping of four different resistance representative varieties of cut chrysanthemum,for short,PPO,PAL,POD,and soil enzyme activities in root zone,including Soil urease(S-UE),Soil sucrase(S-SC),Soil catalase(Soil catalase,S-CAT)activity is aimed to lay a theoretical foundation for the selection of resistance varieties and the study of resistance mechanism of cut chrysanthemum continuous cropping.The main results are as follows:(1)The resistance of 55 cut chrysanthemum varieties to continuous cropping obstacles was evaluated.The results showed that the resistance of different cut chrysanthemum varieties to continuous cropping obstacles was significantly different.Among them,there are three high resistant materials of continuous cropping obstacle,namely ’Cheng Anna’,’Nannong Libai’ and ’Nannong Jidian’,three middle resistant materials,namely ’Nannong Fenying’ and ’Feeling sunny’.There were 25 susceptible materials such as ’Nannong Huangfengwo’,’Baianna’,’Guangyu’ and ’Laikesi’;25 susceptible materials such as’Huangpingpang’,’Nannong Xuanlv’ and ’Nannong Songmang’.(2)According to the results of resistance evaluation,four representative cultivars of cut chrysanthemum with different resistance were selected synthetically:’Chenganna’(high resistance),’Feeling sunny’,the changes of appearance quality of different resistant varieties under continuous cropping and healthy soil were studied.The results showed that the appearance qualities of different resistant varieties(plant height,stem diameter,leaf length,leaf width and flower diameter)was lower than that of healthy soil growth conditions,and the susceptible variety ’Huangpingpang’ was the most decreased,which was significantly higher than that of high resistant varieties.The results showed that under the condition of continuous cropping,the varieties with high resistance could maintain a more stable growth state,and the appearance quality was affected by the external factors.The enzyme activities in leaves of four varieties with different resistance grades were studied.The results showed that polyphenol oxidase,phenylalanine ammonia lyase and peroxidase in leaves of high resistant varieties also changed with the change of growth period,and the activities of phenylalanine ammonia lyase and polyphenol oxidase showed that the higher the resistance level,the higher the enzyme activity.(3)In three different growth periods,soil enzyme(Urease,Sucrase,Catalase)activities of four representative cultivars of cut chrysanthemum with different resistances changed significantly,which was positively correlated with their resistance levels as a whole,among which urease and sucrase activities increased first and then decreased from growth period,budding period to flowering period,while catalase activity always increased.The activities of soil urease,sucrase and catalase of high resistant cultivar ’Chenganna’ were significantly higher than those of susceptible cultivar ’Huangpingpang’.The results showed that the high resistant varieties could stabilize the soil enzyme activity and maintain the relatively healthy growth state of plants under the stress of continuous cropping obstacles.