Optimization Of Regeneration System Of Main Sweet Potato Varieties In Hainan And Characteristics Of Microbial Community Associated With Explants

Sweet potato is an important root crop for grain,feed,industrial raw materials and new energy sources.In recent years,sweet potato industry has developed steadily in southern China.However,sweet potato virus disease seriously restricts the development of sweet potato industry.The annual lost in production due to viral disease is as high as 40%.It is an important guarantee for healthy and sustainable development of sweet potato industry to produce high-quality and non-toxic seedlings quickly by means of tissue culture technology.In tissue culture of sweet potato,the browning caused by oxidation of secondary metabolites and the pollution caused by microorganism are two serious problems in tissue culture of sweet potato.Microorganisms are found to have potential value in improving the yield of agroforestry and the resistance of plants to disease while some of them may cause tissue or seedling pollution.In this study,the main sweet potato varieties Xinxiang,Guangshu 87,Chuanshan Zi,Ning Zishu,Shulv 1,High Line 14 and Sanjiao Ning were used as raw materials.Firstly,the selection of explants and different disinfection schemes were carried out.Medium formulation and selection of anti-browning agent,The optimum regeneration system of virus-free and rapid propagation was established for the main sweet potato varieties planted in tropical areas.Secondly,the traditional isolation and culture techniques were combined with high-throughput sequencing technique to reveal the species composition of sweet potato stem tip microbial community,in order to determine the identification information of pathogen and beneficial microorganism carried by sweet potato explants.The main conclusions are as follows:1.The results showed that the proliferation rate and survival rate of lateral buds were the highest in different parts of explants.In different explant disinfection treatments,75%alcohol for 60 seconds,2%sodium hypochlorite for 15 minutes,and 0.1%mercury chloride for 15 minutes had the lowest contamination rate.The experiment of hormone proportion showed that the medium formula with the shortest rooting time was as follows.:MS+0.05mg/L NAA+Omg/L 6-BA+0.1 mg/L GA3;The medium formula with the fastest growth of stem length is as follows:MS+0.1mg/L NAA+1mg/L 6-BA+0.5mg/L GA3;The medium formula with the fastest growth of stem diameter is as follows:MS+0.1 mg/L NAA+1.5 mg/L 6-BA+O mg/L GA3;The medium formula with the fastest growth rate of fresh weight and dry weight is as follows:MS+0.1 mg/L NAA+1.5 mg/L 6-BA+0.5 mg/L GA3?Adding 5-6g/1 sodium thiosulfate and 1.25g/1 polyvinylpyrrolidone(pvp)to the medium could effectively inhibit the browning of explants.2.Six fungi of different genera were isolated from sweet potato tissue culture contaminated bacteria by traditional plate marking method.Among them,Cladosporium?Fusarium and Edenia were endophytic fungi carried in sweet potato seedlings.Colletotrichum?Bipolaris and Diaporthe are contaminated miscellaneous bacteria.3.The results of high-throughput sequencing showed that the species diversity of the core microbial community at the stem tip of sweet potato was extremely high,and the otus numbers of fungi,bacteria and palaea were 13423,733 and 9463,respectively.Among the core microbial communities,dominant fungi,fusarium,alternaria and acremonium,and dominant bacteria,sphingomonas,aureimonas,and curtobacterium,are widely reported pathogenic microorganisms.4.The species composition of shoot tip microbial community of sweet potato in Haikou area is obviously different.The dominant species of sweet potato stem tip fungi community in Haikou area are Fusarium,Edenia and Cladosporium.And in bridgehead area is Edenia.In the bacterial community of stem tip,the dominant species in Haikou area are rhizobium,methylobacterium and sphingomonas,while pantoea is in Haitou and Xinzhou regions.This study established a set of tissue culture regeneration system suitable for the main sweet potato cultivars planted in tropical area of Hainan Province,and revealed the species identity of the core microbial community of sweet potato stem tip on the basis of this system.For further specific pathogenic microorganisms to take precise,effective explants disinfection measures to lay the foundation;In addition,the detailed species composition of non-pathogenic microorganisms revealed in this study will lay a foundation for the efficient screening of beneficial symbiotic microorganisms in the subsequent cultivation and production of sweet potato,as well as the scientific and rational utilization.