Mechanism Of Root Rot Resistance,Water Saving And Quality Improvement Of Panax Notoginseng Under Rain Shelter Cultivation And Micro-Sprinkler Irrigation

Excessive rainfall in the rainy season and over-irrigation in the dry season lead to high root rot incidence of Panax notoginseng in Yunnan.Reducing soil water content in the field and improving root rot incidence resistance of Panax notoginseng and irrigation water productivity are of great significance in promoting sustainable development of agriculture in seasonally dry areas.This study was conducted a three-year field experiment in Luxi County,Yunnan Province.Two planting patterns（Sr,rain-shelter planting pattern;NSr,unrain-shelter planting pattern）and three deficit irrigation levels[conventional irrigation（I₃=85%W）,mild deficit irrigation（I₂=75%W）and moderate deficit irrigation（I₁=65%W）,W is the irrigation quota,upper and lower limit of irrigation conditions（100%～40%）θ_FC].Combined with shading micro-sprinkler irrigation conditions,studied the effects of deficit irrigation and rain-shelter cultivation techniques on soil water and nutrients in the root zone,and the promotion of physiological growth characteristics,root rot incidence,yield,quality and economic benefits of Panax notoginseng.A technical model of synergetic root rot reduction was put forward,and the feedback mechanism between Panax notoginseng roots,rhizosphere microorganisms and rhizosphere soil were established through Illumina Nova Seq sequencing,GC-TOF-MS,and LC-MS/MS.The formation mechanism of resistance to root rot of Panax notoginseng under rain shelter cultivation and deficit irrigation technology was discussed,with a view to providing new technical support for the green development of agriculture in Yunnan.The main research results were as follows:（1）Rain-shelter cultivation combined with micro-sprinkler deficit irrigation significantly decreased the soil water content（SWC）in the 0-40 cm soil layer of Panax notoginseng,and the SWC in the root zone under the treatment with the lowest root rot incidence（Sr I₂）varied in the ranges of 21.7-29.3%,20.7-28%,and 22-28.3%;Rain-shelter cultivation and micro-sprinkler deficit irrigation increased the soil nutrient content of Panax notoginseng,and I₂ significantly increased the soil nutrient content of Panax notoginseng compared with I₁ and I₃,and I₂ significantly increased the soil nutrient content of Panax notoginseng compared with I₃.Compared with I₁and I₃,I₂ significantly improved the accumulation of soil nutrient contents in soil nutrient environment of Panax notoginseng.Based on DTOPSIS,the comprehensive evaluation model of soil nutrient environment of Panax notoginseng was constructed to propose that the optimal irrigation cultivation patterns for soil nutrient environment were Sr I₂ and Sr I₃.Compared with other treatments,Sr I₁ significantly increased the nutrient utilization efficiency of Panax notoginseng yield;the root rot incidence of Panax notoginseng was the lowest in Sr I₂,and the root rot incidence of Panax notoginseng in three-year,four-year and five-year old Panax notoginseng was decreased by 16.7%,17.4%,and 14.0%compared with that in NSr I₃ treatment respectively;and a comprehensive benefit evaluation model for Panax notoginseng yield nutrient utilization efficiency,irrigation water productivity,yield,and economic benefit under the irrigation cultivation was constructed,and the disease-resistant,water-saving and yield-increasing irrigation cultivation methods of Panax notoginseng were Sr I₁ and Sr I₂;It was revealed the mechanisms of the coupled conditions of rain-sheltered cultivation and micro-sprinkler deficit irrigation to improve the soil moisture environment in the root zone of Panax notoginseng,enhance the soil nutrient content in the root zone to promote the absorption and utilization of Panax notoginseng,reduce the root rot incidence,increased the yield and economic benefits of Panax notoginseng.（2）Plants can modify their growth environment;the soil microbiota was known to play a key role in the resulting plant-soil feedbacks.Illumina Nova Seq sequencing,GC-TOF-MS,and LC-MS/MS techniques were used compared and analyzed the differences in microbial diversity and community structure,rhizosphere soil metabolism,and root metabolism of healthy and root rot Panax notoginseng in the continuous cropping system.We found that a positive feedback regulation mechanism between root,rhizosphere microbial,and rhizosphere soil mediated by root secondary metabolites in the rhizosphere of Panax notoginseng.The root sends a metabolic signal Dihydroxyacetate Aceter（DPAE）to recruit beneficial bacteria（Nitrobacillu,Blastomona,and Chloroflexi）into the rhizosphere to inhibit the accumulation of harmful bacteria（Proteobacteria）in the rhizosphere soil and stabilize the predominant fungal（Ascomycota）.The rhizosphere soil cooperates with the root system to upregulate metabolism 3β-Cholestanol and threonine to enrich the Acidobacteria and Ascomycota in soil,increase microbial diversity in the rhizosphere soil,balance the microbial environment in the rhizosphere soil of Panax notoginseng,promote the propagation of beneficial bacteria in the rhizosphere,and address the challenge of root rot caused by the accumulation of pathogens in the continuous cropping system.Our results reveal a mechanism by which Panax notoginseng shaping the rhizosphere soil metabolites and the composition of rhizosphere microbiota,alleviate root rot stress in continuous cropping system.（3）The results indicated that:all of the rain-shelter cultivation with deficit irrigation amounts treatments significantly increased photosynthetic characteristics,plant hydraulic conductivity,root growth characteristics,canopy growth index,dry matter,yield and PNS;I₂treatments significantly increased Pn,kr,R_L,R_SA,R_D,R_V,SD,PH,LA,CDW,RDW,yield and PNS of Panax notoginseng in the shelter cultivation with micro-sprinkler irrigation cultivation compared with I₁and I₃;Sr I₂and Sr I₃were recommended as the most optimal field management measures of Panax notoginseng for improving yield,and quality of Panax notoginseng.Based on DTOPSIS,a comprehensive evaluation model of physiological growth characteristics,dry matter and quality of Panax notoginseng were constructed,and the optimal water supply cultivation method for Panax notoginseng,which is conducive to the abatement of root rot incidence and the improvement of quality and yield by wate r conservation,was proposed as Sr I₂.Including the water-saving benefit and root rot incidence rate into the comprehensive analysis,under the condition of not significantly reducing crop growth,the rain-shelter cultivation（Sr）,irrigation amount I₂（460mm-520mm）can achieve the best effect in four aspects of yield,root rot incidence,economy and water-saving benefit to the southwestern seasonal dry area Panax notoginseng root rot green prevention and control and high-quality cultivation to provide the theoretical basis and technical support,and to provide guidance for the improvement of product quality of Chinese herbal medicine production area in the practice of production.It also provides a theoretical basis and technical support for the green preve ntion and control of Panax notoginseng root rot incidence and high-quality cultivation in the seasonal dry area of southwest China,and has a guiding significance for the improvement of product quality in the production areas of Chinese medicine.