Effect Of Pesticides On Mortierella In Rhizospheric Soil Of Panax Notoginseng And Their Colonization Ability In The Field

Radix notoginseng is a tranditional Chinese medicine with high pharmaceutical and economical values.But the diseases with high incidence decrease the quality and the profit of notoginseng.Even more,the serious continuous-cropping obstacles limit the development of notoginseng planting in the same sites.The changes of microorganisms in the rhizospheric soil are considered as a primary cause of the high incident diseases of notoginseng,which resulting in the serious replanting obstacles of notoginseng.These variations include the composition and diversity in the microbiome,and the increasing of pathogenic fungi and bacteria.In the previous study,our research group found that the relative abundance of Mortierella in Panax notoginseng rhizosphere soil increased rapidly after transplanting,and decreased in the following growth stages.The decrease of Mortierella was not significantly correlatived with soil chemical properties.It is important to explicit what induce the decrease of Mortierella and whether can improve the microecological balance by adding Mortierella for controlling diseases and relieving replanting obstacles.In this study,the pure culture and charastication of Mortierella isolates were developed.We also investigated the effects of the common used fungicides in the management of P.notoginseng on the growth of Mortierella isolates.In vivo colonizing capacity of the Mortierella isolates was evaluated in the planting soil with 3-yr-old notoginseng plants.Culturable methods and polyphasic characteristic techniques were employed in our study.Six Mortierella isolates were obtained from rhizospheric soil of P.notoginseng.On the basis of characteristics of morphology(colony and microscopy)and phylogeny of ITS sequences,the isolates YIM PH30681,YIM PH30684 and YIM PH30689 were assigned as Mortierella alpine,the isolates YIM PH30686 and YIM PH30690 as M.amoeboidea,and YIM PH30682 as M.elongata.Eleven pesticides were evaluated on the growth of the Mertierella isolates.Mancozeb,thiophonate-methyl/thiram,thiophonate-methyl/mancozeb,and polyoxins presented inhibition the growth of all six Mertierella isolates with different degrees.The isolates YIM PH30691 ? YIM PH30682 could not grow with thiophonate-methyl/thiram at 100 ?g/mL.The isolates YIM PH30681 and YIM PH30689 could not grow with thiophonate-methyl/mancozeb at 150 ?g/mL,and the growth of YIM PH30682 and YIM PH30686 were inhibited with mancozeb at 150 ?g/mL.However,the growth of YIM PH30690 was promted with a certain centration of polyoxins.The in vivo soil-colonizing capacity of the Mortierella isolates was tested with the gene copy numbers of Mortierella on the basis of Q-PCR techiques with specific ITS sequence for Mortierella.In the 3-yr-old notoginseng soil,the gene copy numbers of the isolates YIM PH30681,YIM PH30689 and YIM PH30690 increased with time after root-irrigating treatment comparing to the control.The results infer that these isolates could well colonize in the soil with notoginseng plants.The other isolates,YIM PH30682,YIM PH30684 and YIM PH30686 could not colonize in the soil in this study.The results of the study solve the reasons in the P.notoginseng soil of Mortierella number changes and obtained in our study could supply guideline to the rational fungicidal use.Colonzing Mortierella isolates could change the fungal community in the rhizospheric soil of notoginseng,implying that root rot diseases could be prevented by manually adjusting the fungal microbiome with colonizing some beneficial microbial groups.