| In recent years,China ’s tomato industry has continued to develop steadily,with its cultivated area and total output ranking first in the world,playing an important role in agricultural product supply,farmers 1 income increase and rural economic prosperity.However,in modern agricultural production,agricultural facilities have the characteristics of high intensification and high multiple cropping index.Especially in the process of tomato cultivation,the relatively closed high temperature and high humidity environment in the facility will cause a series of continuous cropping obstacles such as secondary salinization of the facility soil,imbalance of microbial flora,and accumulation of pests and diseases.Tomato Fusarium wilt caused by Fusarium oxysporum f.sp.Lycopersici(FOL)is one of the most serious soil-borne diseases in tomato production,which reduces the quality and yield of tomato and brings great economic losses to the global tomato industry.Therefore,biological control with high efficiency,green,environmental protection and sustainable development has become a research hotspot at home and abroad.In this study,the biocontrol strain Paenibacillus polymyxa NSY50 with the best control effect on tomato Fusarium wilt was screened by plate confrontation and pot experiment.The effects of NSY50 on the growth,photosynthesis and disease index of tomato seedlings under Fusarium wilt stress were analyzed.The mechanism of NSY50 enhancing tomato disease resistance was preliminarily explored by transcriptome sequencing.The specific research results are as follows:1 Fourteen strains with good antagonistic effect on tomato fusarium wilt were screened from 28 potential biocontrol strains by plate confrontation test.They were identified as Paenibacilhis peoriae,Paenibacillus terrae,Paenibacillus polymyxa,Paenibacillus maysiensis,Bacillus velezensis,Bacillus subtilis,Paenibacillus brasilensis and Paenibacillus kribbensis by 16S rDNA sequence analysis.Further pot experiments showed that Paenibacillus polymyxa NSY50 had the best biocontrol effect,up to 64.44%.2 Compared with the control,the plant height,dry and fresh weight and root volume of tomato seedlings decreased significantly under the stress of Fusarium oxysporum,and the photosynthesis of tomato seedlings was inhibited.After preinoculation with NSY50,the plant height,dry weight,fresh weight and root volume of tomato seedlings under Fusarium wilt stress were significantly increased,and the photo synthetic capacity of plants under Fusarium wilt stress was improved.The net photosynthetic efficiency(Pn),transpiration rate(Tr),intercellular CO2 concentration(Ci),stomatal conductance(Gs)and chlorophyll content of tomato leaves were significantly increased by 41.98%,81.77%,42.61%,257.14%and 78.25%,respectively.Paenibacillus polymyxa NSY50 could effectively alleviate the inhibitory effect of Fusarium oxysporum on the growth of tomato seedlings.3 Through transcriptomics analysis,it was found that after inoculation with NSY50,the response of tomato plants to Fusarium oxysporum at the level of gene transcription regulation was significantly changed,and the expression levels of defense-related genes such as PR and PAL in tomato plants were significantly increased.At the same time,sucrose metabolism,alkaloid biosynthesis and terpene biosynthesis were also significantly improved,which played a positive role in reducing the damage caused by FOL infection and enhancing the disease resistance of tomato seedlings,Thirty-three NAC transcription factors were screened to respond to NSY50 or FOL treatment,and SlNAP1(Solyc 05g007770.3)was strongly induced by NSY50+FOL,which was significantly higher than FOL treatment.Gene silencing experiments showed that the transcription factor SlNAP1 played an important role in the induction of tomato resistance to Fusarium wilt by Paenibacillus polymyxa NSY50. |
