Mechanisms On Nursery Cultivation Arbuscular Mycorrhizal Watermelon Seedling Improving Phosphorus Absorption And Restraining Wilt Disease

Watermelon is a popular fruit in summer.It has to be continuous cropped since the inceasing requirement and plant area.Watermelon is susceptible to succession cropping obstacles in continuous cropping system.Wilt disease is the most serious symptom of the obstacles,which make the decline of yield and quality of watermelon.At present,there is no satisfying method to control watermelon wilt disease caused by continuous monocropping.Many researches reported that arbuscular mycorrhizal(AM)colonization can promote the absorption and utilization of nutrients,and effectively prevent the occurrence of fusarium wilt,but the mechanism of its action is less studied.This thesis will study the mechanism of arbuscular mycorrhization on watermelon resistance to wilt disease and its effects in the field from two pot trials and one field trial.The main results are showed as follows:1.Cultivating arbuscular mycorrhizal seedling improved acid phosphatase activity of watermelon root,as well as increased phosphorus concentration in shoot and root.2.Mycorrhizal seedlings of watermelon arbuscular mycorrhizal fungi can reduce the incidence of wilt disease and disease index,effectively prevent the occurrence of soil-borne diseases,and promote the growth of watermelon.When exploring the mechanism of its influence,it was found that arbuscular mycorrhizal seedlings on the one hand can effectively inhibit the propagation of Fusarium oxysporum in the rhizosphere soil environment,and on the other hand,arbuscular mycorrhizal seedlings can improve disease resistance.Related enzyme activities improve self-resistance.When the FON pathogen was not inoculated,the activity of phenylalanine ammonia-lyase(PAL)in leaves of watermelon inoculated with AMF was significantly higher than that in non-mycorrhizal seedlings;in the case of pathogen inoculation in watermelon rhizosphere,AMF treatment was not applied.The chitinase activity of the leaves was significantly higher than that of the AMF treatment.At the same time,theβ-1,3-glucanase in the leaves was not increased by 27.3%when the AMF was inoculated,and the root PAL enzyme activity was 1.2 times that of the non-inoculated FON.3.When pathogenic bacteria were inoculated,the Cla004921 and Cla004920 genes encoding chitinase,Cla009588,Cla16465 genes encoding β-1,3 glucanase,and Cla18298 gene encoding PAL enzyme were used to improve the watermelon wilt when accessing pathogenic bacteria.The ability to respond to high levels;when inoculated with FON,the arbuscular mycorrhizal seedlings induced the relative expression of Cla004 921,Cla004920 gene coding for chitinase,Cla16465 and Cla009588 genes encoding glucanase,and relative expression of Cla18298 gene encoding PAL enzyme.The amount increased the watermelon’s ability to resist the continuous wilt disease.4.Compared with the control,the arbuscular mycorrhizal seedlings enhanced the acid phosphatase activity in the root surface and rhizosphere of the watermelon,increased the phosphorus content in the shoot and underground of the watermelon,and the biomass of the shoot and the underground.The percentages increased by 54.7%and 19.9%respectively,indicating that watermelon arbuscular mycorrhizal seedlings can promote the absorption and utilization of phosphorus by watermelon,and increase its biomass and yield.