Occurrence Of Bacterial Wilt Research Articles

Antibacterial Activity and Mechanism of Three Root Exudates from Mulberry Seedlings against Ralstonia pseudosolanacearum.

Bacterial wilt is a significant soil-borne disease that poses a threat to mulberry production yield and quality of agricultural production worldwide. However, the disease resistance mechanisms dependent on root exudates are not well understood. In this present study, we investigated the antibacterial mechanisms of the main active substances (erucamide, oleamide, and camphor bromide) present in mulberry root exudates (MRE) against Ralstonia pseudosolanacearum (Rp), the causal agent of bacterial wilt. Our findings revealed that these three active substances inhibited the growth activity of Rp by affecting the cell morphology and extracellular polysaccharide content, as well as triggering a burst of reactive oxygen species. The active substances induced oxidative stress, leading to a decrease in Rp growth. Additionally, the expression levels of key genes in the hrp gene cluster (hrpB, hrpX, and hrpF) and other virulence-related genes (such as ripAW, ripAE, Rs5-4819, Rs5-4374, ace, egl3, and pehB) were significantly reduced upon treatment with the active substances. Further pathogenicity experiments demonstrated that root exudates (at a concentration of 1.5 mg·mL-1) delayed or slowed down the occurrence of bacterial wilt in mulberry. These findings provide valuable insight into the antimicrobial mechanisms of MRE against Rp and lay a theoretical foundation for the development and application of biocontrol agents to control mulberry bacterial wilt.

Study on the relationship between bacterial wilt and rhizospheric microbial diversity of flue-cured tobacco cultivars

Bacterial wilt caused by Ralstonia solanacearum, is one of the serious soil-borne diseases in flue-cured tobacco production areas in China. However, it was found that the occurrence of bacterial wilt not only varied with different cultivars but also varied with various sites even under the condition of planting the same variety. It suggests that the occurrence of bacterial wilt could be controlled by regulating soil microorganism and the growth environment. Therefore, the relationship between microorganism’s diversity in the rhizosphere and actual incidences were evaluated on the number of symptomatic plants and the functional diversity of soil microorganisms in field trials on two sites. The results showed that the incidence of bacterial wilt in the same cultivar was varied between the two experimental sites. However, the same trend was found in the number of rhizospheric microbes among the three varieties except for fungi. Also, a good relationship was found between the number of pathogens, microbial functional diversity in the rhizosphere, and actual incidences. The utilization intensity of carbohydrates, amino acids, carboxylic acids, polymers, amines, and carbon utilization of rhizospheric soil microbial community was negatively related with the occurrence of bacterial wilt while it was on the opposite for the utilization intensity of phenolic acids. The results revealed that the mechanism for resistance in flue-cured tobacco was directly associated with the number of pathogenic microorganisms in rhizosphere and the diversity of rhizospheric microbes. By improving the diversity of rhizospheric microbes, the incidence of tobacco bacterial wilt disease can be reduced.

Bacillus amyloliquefaciens Strain PMB05 Intensifies Plant Immune Responses to Confer Resistance Against Bacterial Wilt of Tomato

Tomato is an economic crop worldwide. Many limiting factors reduce the production of tomato, with bacterial wilt caused by Ralstonia solanacearum being the most destructive disease. Our previous study showed that the disease resistance to bacterial soft rot is enhanced by Bacillus amyloliquefaciens strain PMB05. This enhanced resistance is associated with the intensification of pathogen-associated molecular patterns (PAMP)-triggered immunity (PTI). To determine whether the PTI-intensifying Bacillus spp. strains are able to confer disease resistance to bacterial wilt, their effects on PTI signals triggered by PAMP from R. solanacearum and on the occurrence of bacterial wilt were assayed. Before assay, a gene that encodes harpin from R. solanacearum, PopW, was applied as a PAMP. Results revealed that the B. amyloliquefaciens strain PMB05 was the one strain among 9 Bacillus rhizobacterial strains which could significantly intensify the PopW-induced hypersensitive response (HR) on Arabidopsis leaves. Moreover, we observed that the signals of PopW-induced reactive oxygen species generation and callose deposition were increased, confirming that the PTI was intensified by PMB05. The intensification of the PopW-triggered HR by PMB05 in Arabidopsis was reduced upon treatment with inhibitors in PTI pathways. Furthermore, the application of Bacillus spp. strains on tomato plants showed that only the use of PMB05 resulted in significantly increased resistance to bacterial wilt. Moreover, the PTI signals were also intensified in the tomato leaves. Taken together, we demonstrated that PMB05 is a PTI-intensifying bacterium that confers resistance to tomato bacterial wilt. Screening of plant immunity intensifying rhizobacteria is a possible strategy to control tomato bacterial wilt.[Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Feasibility of Delaying Removal of Row Covers to Suppress Bacterial Wilt of Muskmelon (Cucumis melo).

Bacterial wilt, caused by Erwinia tracheiphila, is a major disease of cucurbit crops in the United States. Management of the disease relies on controlling two vector species, striped (Acalymma vittatum) and spotted (Diabrotica undecimpunctata) cucumber beetles. Six field trials were conducted at Iowa State University research farms during 2007, 2008, and 2009 to assess the efficacy of delayed removal of spunbond polypropylene row covers to control bacterial wilt on muskmelon (Cucumis melo). Treatments were (i) row cover removed at anthesis (conventional timing of removal), (ii) covers removed 10 days after row cover ends were opened at anthesis, (iii) covers removed 10 days after bumble bee hives were inserted under row covers at anthesis, and (iv) a noncovered control. In two field trials during 2007 and 2008, the delayed-removal row-cover treatments significantly suppressed bacterial wilt throughout the growing season and enhanced yield compared with the noncovered and removal-at-anthesis controls. In Gilbert in 2008, however, bacterial wilt suppression was equivalent among all three row-cover treatments. No bacterial wilt was observed during three trials in 2009, and there was minimal difference in marketable yield among treatments. Net returns were compared using partial budget and sensitivity analyses. Melon prices and occurrence of bacterial wilt had a strong impact on net returns. Using row covers increased production costs by 45%. In site years in which bacterial wilt occurred, delaying removal of row covers resulted in the highest returns. When bacterial wilt was absent, however, the delayed-removal row-cover treatments had the lowest returns. Results of the sensitivity analysis indicated that delaying removal of row covers for 10 days could be a cost-effective component of an integrated bacterial wilt suppression strategy for muskmelon where bacterial wilt occurs ≥50% of production seasons.

Ralstonia solanacearum em viveiros clonais de eucalipto no Brasil

A incidência da murcha bacteriana, causada por Ralstonia solanacearum, em viveiros clonais de eucalipto, no período de abril a setembro de 2005, resultou no descarte de cerca de 553.991 minicepas, 6.837.691 propágulos na fase de enraizamento e 11.266.819 mudas, nos Estados da Bahia, do Espírito Santo, do Maranhão, de Minas Gerais e do Pará, totalizando um prejuízo estimado em, no mínimo, seis milhões de reais (US$ 2,7 milhões). Em minijardim clonal, a doença caracteriza-se por necrose foliar, escurecimento anelar ou completo do lenho, murcha e morte de minicepas. Os sintomas na parte aérea são similares à morte gradual de minicepas submetidas a podas drásticas ou com sistema radicular malformado. Na fase de enraizamento, miniestacas infectadas podem apresentar arroxeamento das nervuras do limbo foliar e podridão. No campo, a doença caracteriza-se por bronzeamento e necrose foliar, desfolha basal, ascendente escurecimento interno do lenho e morte da planta, geralmente a partir do quarto mês após o transplantio. Os sintomas geralmente se agravam em árvores com enovelamento de raízes e afogamento de coleto. A etiologia da doença foi confirmada por meio de testes de exsudação, microscopia de varredura, isolamento da bactéria, análises de PCR/RFLP, reação de hipersensibilidade (HR) em mudas de fumo, testes de patogenicidade em plântulas de eucalipto e tomate e re-isolamento da bactéria. Como o sistema de produção de mudas clonais de eucalipto é altamente favorável à multiplicação bacteriana e na falta de conhecimento sobre a resistência genética e de outras estratégias de controle da doença, é essencial evitar a introdução da bactéria em viveiros.

Allelopathic Suppression of Pseudomonas solanacearum Infection of Tomato ( Lycopersicon esculentum ) in a Tomato-Chinese Chive ( Allium tuberosum ) Intercropping System

Tomato plants were grown alone or intercropped with Chinese chive plants, with or without the inoculation of Pseudomonas solanacearum. Chinese chive plants had no detrimental effects on the growth of tomato plants but significantly delayed and suppressed the occurrence of bacterial wilt of tomato. P. solanacearum population decreased faster in the soil grown with tomato alone than that in the soil grown with both tomato and Chinese chive. However, P. solanacearum population in bare soil was higher than that grown with Chinese chive. Root exudates of Chinese chive collected with a continuously trapping system were inhibitory to multiplication of P. solanacearum.

Occurrence of Bacterial Wilt and Soft Rot of Seed Cabbage Plants (Brassica oleracea var. capitata L.) in Yugoslavia

AbstractSoft rot and wilt symptoms were noticed on 2‐year‐old seed cabbage plants grown in field crops. Soft rot Erwinia was isolated from the diseased tissues. Pathogenicity tests showed that the bacterium effectively colonised different vegetable species and sunflower, indicating a wide host range.Pathogenicity, morphological, biochemical and physiological characteristics showed that the investigated strains are of Erwinia carotovora subsp. carotovora (Jones) Bergey et al.