Effect Of Chloropicrin Disinfection On Soil Microbial Communities Of Panax Notoginseng

Panax notoginseng(Burk.)F.H.Chen belonging to Araliaceae family,is a unique Chinese herbal medicine,and it's efficacy could be summarized in the following six words:hemostasis,scattered stasis,and relieving pain.The P.notoginseng preference for warm,light shade and humid environment was an important factor in the formation of root rot,which thus has outstanding plant disease,especially the root rot that has not been solved effectively yet.The study showed that soil disinfection treatment is an effective measure of soil-borne disease controlling,P.notoginseng cultivation in disinfectant soil.The investigation on the composition and diversity of microbial communities in rhizosphere soil will contribute to develop effective methods in prevention and control of the soil borne disease and to slow continuous cropping obstacle of P.notoginseng.In this study,high-throughput sequencing was used to investigate the composition and diversity of fungus and bacterial communities in disinfectant rhizosphere soil under different doses of chloropicrin across various life stages of P.notoginseng.In addition to above mentioned study,growth traits,yield and saponin content of P.notoginseng were also analyzed preliminarily.The results obtained are as follows.1.Soil was disinfected with disinfection doses of 28kg,30kg,32kg and 40kg chloropicrin per mu respectively.After 25 days,the diversity of microbial communities in the disinfected soil was reduced to varying degrees comparing with nondisinfected soil.as well as beneficial fungi and bacteria remain highly abundant in both treated and control soil,while harmful those are relatively lower.2.P.notoginseng was transplanted to the above-disinfected plots for one year.The pathogenic fungi detected in the rhizosphere soil were Fusarium,Ilyonectria.Phorma and Botryotinia;the pathogenic bacteria were Pseudomonas,Sphingomonas,Stenotrophomonas;beneficial fungi were Trichoderma,Mortierella;beneficial bacteria were Bacillus,Burkholderia,Arthorbacter,but beneficial fungi and bacteria were in dominant position approximately.The measurement of the growth status of P.notoginseng,indicating that the average seedling survival rate in the disinfected plot by half and one year reached 95%and 92%respectively,by contrast,only that of 82%and 18%in nondisinfected plots.30-32kg per mu was considered comprehensively as the optimal disinfection dose.3.30kg per mu of chloropicrin was used as a disinfectant to study the effect of disinfection days on the microbial community structure in soil.The results showed that the soil samples in 0 day post-disinfection(0 dpd)have a higher microbial diversity and relative abundance.In 15 dpd,a decreased microbial diversity was detected,and a increased relative abundance of some bacteria genus in soil samples.The diversity and relative abundance of microorganisms were greatly reduced in the 25 dpd soil samples.After disinfection,the microbial community in the soil was greatly decreased,as well as most of the harmful microorganisms were killed,which laid the foundation for the growth of beneficial microorganisms.The beneficial microorganisms occupied the advantage in the soil microbial community.4.After transplantation of P.notoginseng for two years in disinfected plots,the diversity of the soil microbial communities in the rhizosphere had been reduced to varying degrees.Annual P.notoginseng was transplanted to a disinfected plot for one year.The relative abundance of the pathogenic fungus Fusarium was increased from 0.02%to 0.050%.The relative abundance of the pathogenic bacteria Sphingomonas was increased from 1.700%to 2.75%;the relative abundance of beneficial microorganisms Trichoderma was increased from 4.18%to 61.36%;the relative abundance of Bacillus was increased slightly from 0.46%to 0.52%;the relative abundance of Burkholderia was increased from 0.36%to 2.53%;the relative abundance of Arthorbacter was increased from 0.26%to 2.01%.From one to two years post-transplantation(ypt),the relative abundance of microbial communities was changed:the relative abundance of the pathogenic fungus Fusarium was increased from 0.05%to 0.16%.The relative abundance of pathogenic bacteria Sphingomonas was decreased from 2.75%to 1.14%;the relative abundance of beneficial microorganisms Trichoderma was decreased from 61.36%to 15.61%;the relative abundance of Bacillus was decreased from 0.52%to 0.41%;the relative abundance of Burkholderia was decreased from 2.53%to 0.47%;the relative abundance of Arthorbacter was decreased from 2.01%to 0.67%.The growth level of these pathogenic bacteria was relatively low after transplanting for two years,while that of beneficial bacteria was higher.5.The agronomic traits,yield and the saponin content were measured in the three-year-old P.notoginseng planted in the above plots.The results showed that the yield of P.notoginseng reached 150-200 kg yield per mu(dry weight),and the mean values of active saponin ingredients R1,Rg1,Re,Rbl and Rd were 0.46,3.02,0.17,1.65 and 0.64,respectively,which there was no significant difference by comparing with those of the newly planted three-year-old P.notoginseng.In summary,the soil disinfection could reduce the abundance of harmful microbial communities,allowing beneficial microbial communities to occupy sufficient growth space,and then resulting in decreasing of the soil-borne diseases.Therefore,Disinfecting the soil with disinfection could not only greatly shorten the time for crop rotation of P.notoginseng and overcome the continuous cropping obstacle,but also ensure the yield and quality of P.notoginseng.It is worthiness to extend more.