Research On The Mechanism Of Oxalic Acid Affecting The Interaction Between Ralstonia Solanacearum And Tobacco

Tobacco bacterial wilt is a typical vascular disease that occurs during tobacco planting,which seriously affects the quality of tobacco.As a typical soil-borne disease,the occurrence of tobacco bacterial wilt is closely related to the soil environment.During the growth process,plants continuously secrete a large amount of root exudates to the rhizosphere,regulating the complex interaction between plants and microorganisms.Plants can transmit matter and energy through root exudates and soil microorganisms,and form complex interactions such as parasitism and infection,which constitute a special rhizosphere micro-ecological environment mediated by root exudates.Affect the occurrence of soil-borne diseases.The oxalic acid released from the plant during the growth process is one of the most acidic organic acids secreted by the roots.Recent studies have shown that oxalic acid can promote the growth of R.solanacearum and promote the transcriptional expression of R.solanacearum pathogenic genes.However,there is no relevant research on how oxalic acid affects the interaction between R.solanacearum and the host.In this paper,tobacco is used as a model crop.This paper intends to systematically study the interaction between oxalic acid and R.solanacearum and tobacco,and the role of oxalic acid in the occurrence of bacterial wilt.In the regulation of tobacco bacterial wilt,it provides new ways to regulate the occurrence of bacterial wilt,and provides theoretical support for further research on the mechanism of bacterial wilt.The main findings of this dissertation are as follows:1 Different tobacco varieties secrete different amounts of oxalic acidThe resistance of Yunyan 87 and PVH1452 were identified by pot experiment.The resistance of PVH1452 was better than Yunyan 87.The oxalic acid content of Yunyan 87 was higher than that of PVH1452,and the oxalic acid content of Yunyan 87 was 135.65±4.3 ?g/g dry root weight,which was significantly higher than that 29.98±19.02 ?g/g dry root weight of PVH1452.2 Oxalic acid can reduce the pH of the medium,but not affect the growth of R.solanacearumThe growth of R.solanacearum was slightly advanced in the B medium,indicating that oxalic acid did not affect R.solanacearum in B medium.At the same time,the pH test showed that the addition of oxalic acid would decrease the pH of the medium.But With the increase of incubation time,the pH values gradually converged.This also indicates that the pH reduction caused by the addition ofoxalic acid has no effect on the growth of R.solanacearum.Under the condition of M63 medium,oxalic acid could not stimulate the growth of R.solanacearum,indicating that oxalic acid could not be used as a nutrient carbon source for R.solanacearum growth.Oxalic acid was added to the NA medium,and it was found that the morphology of the bacteria was decreased at a concentration of 200 ?g/mL oxalic acid,but R.solanacearum can grow normally.In general,oxalic acid did not affect the growth of R.solanacearum in media.3 Oxalic acid can significantly stimulate the biofilm formation and colonization of R.solanacearum,but does not affect the transcriptional expression of pathogenic genesFurthermore,the effect of oxalic acid on the biofilm formation of R.solanacearum was detected by crystal violet staining.The results showed that different concentrations of oxalic acid could promote the biofilm formation of R.solanacearum.Among them,the oxalic acid treatment of 200 ?g/mL compared with the control,the increase rate reached 16.4%.Hydroponics colonization experiments showed that 100-200 ?g/mL oxalic acid could significantly promote the colonization of R.solanacearum in tobacco roots.In addition,the transcriptional expression of pathogenic genes was determined by RT-PCR.Different concentrations of oxalic acid had no significant effect on the expression of pathogenic genes of R.solanacearum.It is indicated that oxalic acid can stimulate the biofilm formation of R.solanacearum and induce the colonization of R.solanacearum in tobacco roots.4 Oxalic acid does not affect the growth of tobacco,and it can aggravate the occurrence of tobacco bacterial wilt in hydroponic and potting environments.Oxalic acid had not effect on the growth of tobacco under hydroponic conditions.At the same time,it was found in both hydroponics and pot experiments that oxalic acid can promote the infection of tobacco by R.solanacearum and aggravate the occurrence of tobacco bacterial wilt.Among them,in the hydroponic environment,on the 21 st day after inoculation,the disease index of 100-200 ?g/mL oxalic acid treatment was 75,72.5 and 90,respectively,while the index was only 60 under control treatment.In the potting environment,on the 15 th day after inoculation,the disease index of 150 ?g/mL and 200 ?g/mL oxalic acid treatment was 95 and 86.25,respectively,while the index was only 72.5 under control treatment.5 Oyster powder mixed soil application is beneficial to improve soil acidity,reduce oxalic acid content,and increase the activity of oxalate oxidase,thereby reducing the severity of tobacco bacterial wiltThe soil amendments(oyster powder,quicklime,grass ash)can significantly reduce the oxalic acid content in the rhizosphere soil and increase the pH of the acidic soil.After 10 days of transplanting,the oxalic acid content of the oyster powder treatment was 140.39 ?g/g dry soil,which was significantly lower than the control of 649.91 ?g/g dry soil.On the 8th day after transplanting,the pH of oyster powder and ash treatment was 7 and 7.11,respectively,which was significantly higher than the control of 5.54.The soil amendments also enhanced the activity of oxalate oxidase.The correlation between oxalic acid content and oxalate oxidase showed that the addition of soilamendments was mainly to regulate the oxalic acid content by oxalate oxidase degradation of oxalic acid.In addition,pot experiment showed that soil amendments can reduce the incidence of tobacco bacterial wilt.Among them,oyster powder has good control effect on tobacco bacterial wilt,and the control effect can reach 80.06%.In summary,oxalic acid is mainly due to its acidity affecting the interaction between R.solanacearum and the host.First,oxalic acid does not affect the growth of R.solanacearum and the expression of pathogenic genes,but decrease the pH of the medium,and then oxalic acid can promote the biofilm formation of R.solanacearum and the colonization of R.solanacearum in tobacco roots.At the same time,applying soil amendments can reduce the secretion of oxalic acid,increase the pH of tobacco rhizosphere,and reduce tobacco.The occurrence of bacterial wilt.Based on the above three aspects,it is proved that the large amount of oxalic acid secretion mainly affects the occurrence of tobacco bacterial wilt by its acidity.