Potato plants transformed with the Arabidopsis EF-Tu receptor (EFR) show restricted pathogen colonization and enhanced bacterial wilt resistance under conditions resembling natural field infections

A major constraint to tomato cultivation is bacterial wilt disease. The use of greenhouses to cultivate tomato is vital to controlling the bacterial wilt disease. Bacterial wilt can be successfully managed when farmers are well-informed with better knowledge of bacterial wilt in tomatoes. This study was conducted to assess farmers’ knowledge and experiences on the cultivation practices, prevalence, detection, spread, and control of bacterial wilt disease in tomato in greenhouses in the Volta, Eastern, Central, and Greater Accra regions of Ghana. Questionnaires were administered for fifty (50) greenhouse farmers, purposefully selected using a database of greenhouse tomato producers in southern Ghana provided by the Ministry of Food and Agriculture (MOFA). Frequency data was analyzed using descriptive statistical analysis. The majority (86%) of respondents had formal education. Most of the greenhouses in operation were in the Greater Accra Region, and none was under cultivation in the Volta region at the time of the study. Most respondents have been involved in greenhouse tomato cultivation for barely three years. The frequency of greenhouse tomatoes production varied from one region to the other. Only 28% of greenhouse farmers knew the test to detect the disease with 64% of greenhouse farmers without any knowledge about how the disease spreads. 62% of respondents used roughing and burying of the infected plants to control the disease. Out of the 54 greenhouses (domes) surveyed, 12 were infected with the bacterial wilt disease. Greenhouse farmers had little knowledge on the spread, detection, and control of the bacterial wilt disease of tomato. The findings of this study would lead to the design of targeted training programs on cultivation practices, detection, spread and management of bacterial wilt of tomato to increase yield and boost income levels of greenhouse tomato farmers in Ghana. Key words: bacterial wilt, tomatoes, spread, detection, control, greenhouse, farmers, constraints

Background: Bacterial wilt incited by Ralstonia solanacearum is the most important disease affecting ginger production in southwestern Ethiopia. Unavailability of disease-free planting materials, resistant cultivars, and effective chemical compounds are the key constraints in managing the disease. Objective: The study was initiated to determine the effect of integrated management methods on bacterial wilt disease and yield loss of ginger through combining hot water, bio-fumigation, soil-solarization and chemical pesticides. Methods: A total of seven treatment combinations comprising hot water, bio-fumigation, soil-solarization, Mancozeb, and bleaching powder were tested in a randomized complete block design in three replications. Data on disease incidence, growth, yield, and yield components were recorded from randomly selected plants. Results: The use of Mancozeb for seed socking and soil drenching combined with bio-fumigation and soil-solarization reduced the incidence of bacterial wilt by 63.3% and enhanced the rhizome yield by 66.8%. Rhizome and soil treatment using bleaching powder along with soil bio-fumigation also reduced the disease incidence by 38.9% and increased ginger yield by 61.5%. It also provided the highest (6678.7%) marginal rate of return of any treatment combination tested in the experiment. Disease incidence was highly significantly and inversely (r= -0.98**) correlated with rhizome yield. The regression slope estimated that 83.4% of ginger yield loss was associated with the bacterial wilt disease. Conclusion: A combined application of Mancozeb, bio-fumigation and soil-solarization can be used to control ginger bacterial wilt. Alternatively, bleaching powder for rhizome and soil treatment in conjunction with bio-fumigation can be employed as an integrated management system against the disease.

Background: Bacterial wilt incited by Ralstonia solanacearum is the most important disease affecting ginger production in southwestern Ethiopia. The unavailability of disease-free planting materials, resistant cultivars, and effective chemical compounds are the key constraints in managing the disease. Objective: The study was initiated to determine the effect of integrated management methods on bacterial wilt disease and yield loss of ginger through combining hot water, bio-fumigation, soil-solarization and chemical pesticides. Methods: A total of seven treatment combinations comprising hot water, bio-fumigation, soil-solarization, Mancozeb, and bleaching powder were tested in a randomized complete block design in three replications. Data on disease incidence, growth, yield, and yield components were recorded from randomly selected plants. Results: The use of Mancozeb for seed socking and soil drenching combined with bio-fumigation and soil-solarization reduced the incidence of bacterial wilt by 63.3% and enhanced the rhizome yield by 66.8%. Rhizome and soil treatment using bleaching powder along with soil bio-fumigation also reduced the disease incidence by 38.9% and increased ginger yield by 61.5%. It also provided the highest (6678.7%) marginal rate of return of any treatment combination tested in the experiment. Disease incidence was highly significantly and inversely (r= -0.98**) correlated with rhizome yield. The regression slope estimated that 83.4% of ginger yield loss was associated with bacterial wilt disease. Conclusion: A combined application of Mancozeb, bio-fumigation and soil-solarization can be used to control ginger bacterial wilt. Alternatively, bleaching powder for rhizome and soil treatment in conjunction with bio-fumigation can be employed as an integrated management system against the disease.

Biological control of bacterial wilt disease caused by Ralstonia solanacearum: Insights into the ecology of antagonists and their complex interaction with the pathogen and the host plant rhizosphere microbiome

Ralstonia solanacearum is a soil-borne pathogen that causes bacterial wilt and has a wide range of hosts in numerous plant species. This pathogen undergoes phenotypic conversion (PC) from a wild-type strain pathogenic form to a non-pathogenic form in broth culture, soil, plant, and water extract of the plant. Pre-inoculation of PC mutants to Solanum plants has been shown to have a protective effect against bacterial wilt disease. To select effective PC mutants as biocontrol agents against bacterial wilt disease in eggplant, control effect was investigated using five eggplant cultivars and 10 PC mutants. Control effects differed depending on PC mutants and eggplant cultivars. Two PC mutants (8224PC and 8103PC) showed highly suppressive effects in many eggplant cultivars and are anticipated to be practicable biocontrol agents. Furthermore, the antibacterial activities of PC mutants against the wild-type pathogen were tested to elucidate the relation between antibacterial activity of PC mutant and protective effect against bacterial wilt by PC mutant. Even the PC mutants that did not indicate antibacterial activity showed high suppression of bacterial wilt, suggesting that there are factors other than antibacterial activity involved in the suppression of bacterial wilt by PC mutant.

Major constraints in potato production includes bacterial wilt disease (Ralstonia solanacearum) and late blight disease (Phytophthora infestans). To support environmentally-friendly agricultural system, a microbial consortium containing Trichoderma harzianum, Bacillus subtilis and non pathogenic Pseudomonas sp. has been studied for biocontrol plant diseases in horticultural crops. For application, the microbial consortium was mixed with organic matters (10%, v/v). The objective of this research was to obtain dosage and application frequency of microbial consortia mixed with chicken manure for controlling bacterial wilt disease and their effects on airborne disease, late blight disease, in potato. The experimental design used was Randomized complete design with 10 treatments and three replications. The treatments consisted of application of the mixture in planting hole at the dosage of 25, 50 or 100 g solely or in combination with drenching the water suspension of the mixture weekly or every two weeks. The results showed that the dosage and application frequency of the microbial consortia mixed with chicken manure influenced their abilities in suppressing the bacterial wilt disease in potato. The application of the mixture at planting hole with the dosage of 50 g per plant followed by drenching the water suspension of the mixture every week suppressed the bacterial wilt disease by 75.0 - 81.9%.

Bacterial wilt incited by Ralstonia solanacearum is the most important disease threatening ginger production in southwestern Ethiopia. A field experiment was conducted to determine the effect of integrated management methods on bacterial wilt disease and yield of ginger. Thus, a total of seven treatment combinations comprising hot-water, bio-fumigation, soil-solarization, Mancozeb, and bleaching powder were tested in a randomized complete block design with three replications. Data on disease incidence, yield, and yield components of ginger were collected from a random sample of plants. Then, analysis of variance (ANOVA) was performed using R-studio 9.9 statistical software, and the means were compared by the least significant test. The results from ANOVA revealed that the incidence of bacterial wilt, rhizome yield, and its components were highly significantly (P < 0.001) affected by management methods. An integrated application of rhizome seed treatment (0.1 L−1) and soil drenching (0.3%) using Mancozeb, lemongrass for soil bio-fumigation at a rate of 10 t ha−1, along with solarization significantly reduced the incidence of bacterial wilt, the disease progress over time and produced the highest rhizome yield per hectare. Seed soaking and soil drenching in Mancozeb along with bio-fumigation was effective in reducing the disease, but a comparative yield advantage was gained through the application of bleaching powder as a seed treatment at 10% solution and soil amendment at a rate of 25 kg ha−1, along with bio-fumigation. Thus, a combined application of Mancozeb, bio-fumigation using lemongrass, and solarization with polyethylene plastic sheet can be applied to control ginger bacterial wilt disease. Alternatively, bleaching powder, bio-fumigation with lemongrass and solarization can also be used as an integrated management system against the disease.

Bacterial wilt caused by Ralstonia solanacearum is an important disease in ginger which can cause yield losses of more than 90%. One way to control the disease is by biological control using the microorganism, Bacillus. Bacillus spp. is recognized to have the ability to control pests and diverse phytopathogens through the induction of systemic resistance in plants. This study aimed to obtain Bacillus spp. that can prevent the bacterial wilt disease in ginger caused by Ralstonia solanacearum. This study was carried out at the Microbiology Laboratory and Greenhouse, Faculty of Agriculture, Universitas Andalas, from July to October 2022. The experiment introduced 5 Bacillus (Bacillus cereus Se07, Bacillus cereus P14, Bacillus sp. SJI, Bacillus sp. HI, and Bacillus subtilis) and control, inoculated with Ralstonia solanacearum at one month old. The parameters of ginger that will be observed were incubation period, disease incidence, and disease severity. The results show that the treatment of B. cereus P14 is the best ability to suppress the severity of bacterial wilt disease by 37.03% with an effectiveness of 47.38%.

Objective: Bacterial wilt disease caused by Ralstonia solanacearum is a major constrain to production of potatoes (Solanum tuberosum). Control of bacterial wilt is very difficult as there are no effective curative chemicals. This study was aimed at investigating the potential roles of essential oil plants in control of the disease. Methodology and Result: The plants used included: Lippie javanica (Sage brush), Ocimum suave (Cambodia) and Tarchonanthus camphorates (Camphor brush).Experiments were conducted with potatoes grown in greenhouse condition. Freshly harvested leaves, stems and flowers from L. javanica, O. suave and T. camphorates were chopped into small portions that were soaked in water for one hour then applied in the inoculated experimental plots. Each plot was planted with disease-free potato tubers and disease development observed and recorded for a period of two months. Plots treated with T. camphorates had significantly low bacterial wilt incidence (P&lt; 0.05) having been reduced by more than 90%.Treatment with the other two plants, O. suave and L. javanica reduced the disease by 38% and 21% respectively and were not significantly different from untreated plots. Conclusion and Application of Results: This finding shows that use of essential oils isa potential approach to bacterial wilt disease management. It can be concluded that essential oils plants possess antibacterial activity that is effective in control of R. solanacearum. Application of these essential oils can volatilize with increase of temperature. The application can be done by burying chopped essential oil plant parts in the soil during the time of land preparation just before planting. Further studies on the mode of action of these essential oils particularly those of T. comphrates in the control of R. solanacearum are suggested.Keywords: Essential oil plants; Potatoes; Ralstonia solanacearum; Wilt incidence

Ralstonia solanacearum is a soil-borne gram-negative bacterium that causes bacterial wilt disease in more than 250 plant species belonging to botanical families. Over the last decades, R. solanacearum infestation has increasingly been observed in temperate climate regions. Three R. solanacearum isolates have been obtained from wilt infected brinjal (eggplant) plant from Mizoram, North East India. Different morphological and biochemical testes confirmed the typical characteristic features of bacterial wilt pathogen. Amplification of 280bp DNA fragment in PCR with (759,760) egl gene primer, further confirmed the existence of Ralstonia solanacearum pathogen in North East India.

Objective: Bacterial wilt disease caused by Ralstonia solanacearum is a major constrain to production of potatoes (Solanum tuberosum). Control of bacterial wilt is very difficult as there are no effective curative chemicals. This study was aimed at investigating the potential roles of essential oil plants in control of the disease. Methodology and Result: The plants used included: Lippie javanica (Sage brush), Ocimum suave (Cambodia) and Tarchonanthus camphorates (Camphor brush).Experiments were conducted with potatoes grown in greenhouse condition. Freshly harvested leaves, stems and flowers from L. javanica, O. suave and T. camphorates were chopped into small portions that were soaked in water for one hour then applied in the inoculated experimental plots. Each plot was planted with disease-free potato tubers and disease development observed and recorded for a period of two months. Plots treated with T. camphorates had significantly low bacterial wilt incidence (P&lt; 0.05) having been reduced by more than 90%.Treatment with the other two plants, O. suave and L. javanica reduced the disease by 38% and 21% respectively and were not significantly different from untreated plots. Conclusion and Application of Results: This finding shows that use of essential oils isa potential approach to bacterial wilt disease management. It can be concluded that essential oils plants possess antibacterial activity that is effective in control of R. solanacearum. Application of these essential oils can volatilize with increase of temperature. The application can be done by burying chopped essential oil plant parts in the soil during the time of land preparation just before planting. Further studies on the mode of action of these essential oils particularly those of T. comphrates in the control of R. solanacearum are suggested.Keywords: Essential oil plants; Potatoes; Ralstonia solanacearum; Wilt incidence

Potency of antagonist bacteria in inhibiting the bacterial wilt disease progress gingerBacterial wilt disease caused by Pseudomonas solanacearum is an important disease in ginger plant (Zingiber oicinale Rose.) in Indonesia. The objective of this research was to study the effectiveness of biological agents in inhibiting the progess of bacterial wilt on ginger. The research was conducted at the geenhouse of Research Institute for Spice and Medicinal Crops in 1997-1998 then was followed with a ield experiment at Sukamulya Experimental Garden in 1998/1999. At the greenhouse experiment seven kinds of antagonists bacteria were formulated either individually or combination. Pseudomonas fluorescens (PF), P. cepacia (PC) and Bacillus sp. (BC), mixtue of PF + PC, mixtue of PC + BC, mixture of PF + BC, and mixtue of PF + PC + BC were tested in the geenhouse on ginger plant cultivars putih besar grown in the pot containing soil formerly used for growing P. solanacearum infected tomato. I he results of this experiment indicated that the combination of PF+PC+BC significantly suppressed the progress of bacterial wilt disease compaed to control and other tested combination. In the ield experiment carried out at the bacterial wilt disease endemic area the combinations of PF+PC+BC, Trichoderma harzianum (Bit-1) and combination of PF+PC+BC+BII-I were tested with two levels of application, i.e. two applications with two months interval and 4 application with one month interval. The results showed that the application of antagonists bacteria inhibited Ihe bacterial wilt disease progress and signiicantly increased ginger rhizome yield. The yield of the rhizome from the plants teated with different intervals were not different. However, the application of the antagonist bacteria were not able to eradicate ginger infection by Pseudomonas solanacearum thoroughly.

Ralstonia solanacearum and Meloidogyne incognita are two soilborne pathogens that cause serious damage and great losses in the production of tomato. For this purpose, a bacterial isolate, Bacillus thuringiensis CR-371, and an actinomyces isolate, Streptomyces avermectinius NBRC14893, were examined for their ability to protect tomato from root-knot nematode and bacterial wilt diseases under glasshouse conditions. Treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 followed by challenge inoculation with R. solanacearum and M. incognita significantly decreased disease severity of bacterial wilt alone, root-knot nematode alone, or mixed infection by both pathogens compared to the control. Furthermore, pretreatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 significantly reduced bacterial proliferation of R. solanacearum both in pathogen alone inoculated plants and in plants co-inoculated with R. solanacearum and M. incognita. In conclusion, our results suggest that the treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 simultaneously suppresses bacterial wilt and root-knot nematode diseases. Therefore, B. thuringiensis CR-371 and S. avermectinius NBRC14893 could provide new options for integrated pest management strategies against plant diseases, especially against bacterial-nematode disease complexes that cause synergistic yield losses.

Previous studies have described the development of control methods against bacterial wilt diseases caused by Ralstonia solanacearum. This review focused on recent advances in control measures, such as biological, physical, chemical, cultural, and integral measures, as well as biocontrol efficacy and suppression mechanisms. Biological control agents (BCAs) have been dominated by bacteria (90%) and fungi (10%). Avirulent strains of R. solanacearum, Pseudomonas spp., Bacillus spp., and Streptomyces spp. are well-known BCAs. New or uncommon BCAs have also been identified such as Acinetobacter sp., Burkholderia sp., and Paenibacillus sp. Inoculation methods for BCAs affect biocontrol efficacy, such as pouring or drenching soil, dipping of roots, and seed coatings. The amendment of different organic matter, such as plant residue, animal waste, and simple organic compounds, have frequently been reported to suppress bacterial wilt diseases. The combined application of BCAs and their substrates was shown to more effectively suppress bacterial wilt in the tomato. Suppression mechanisms are typically attributed to the antibacterial metabolites produced by BCAs or those present in natural products; however, the number of studies related to host resistance to the pathogen is increasing. Enhanced/modified soil microbial communities are also indirectly involved in disease suppression. New promising types of control measures include biological soil disinfection using substrates that release volatile compounds. This review described recent advances in different control measures. We focused on the importance of integrated pest management (IPM) for bacterial wilt diseases.

Ralstonia solanacearum causes bacterial wilt disease, leading to severe crop losses. Xylem sap from R. solanacearum-infected tomato is enriched in the disaccharide trehalose. Water-stressed plants also accumulate trehalose, which increases drought tolerance via abscisic acid (ABA) signaling. Because R. solanacearum-infected plants suffer reduced water flow, we hypothesized that bacterial wilt physiologically mimics drought stress, which trehalose could mitigate. We found that R. solanacearum-infected plants differentially expressed drought-associated genes, including those involved in ABA and trehalose metabolism, and had more ABA in xylem sap. Consistent with this, treating tomato roots with ABA reduced both stomatal conductance and stem colonization by R. solanacearum. Treating roots with trehalose increased xylem sap ABA and reduced plant water use by lowering stomatal conductance and temporarily improving water use efficiency. Trehalose treatment also upregulated expression of salicylic acid (SA)-dependent tomato defense genes; increased xylem sap levels of SA and other antimicrobial compounds; and increased bacterial wilt resistance of SA-insensitive NahG tomato plants. Additionally, trehalose treatment increased xylem concentrations of jasmonic acid and related oxylipins. Finally, trehalose-treated plants were substantially more resistant to bacterial wilt disease. Together, these data show that exogenous trehalose reduced both water stress and bacterial wilt disease and triggered systemic disease resistance, possibly through a Damage Associated Molecular Pattern (DAMP) response pathway. This suite of responses revealed unexpected linkages between plant responses to biotic and abiotic stress and suggested that R. solanacearum-infected plants increase trehalose to improve water use efficiency and increase wilt disease resistance. The pathogen may degrade trehalose to counter these efforts. Together, these results suggest that treating tomatoes with exogenous trehalose could be a practical strategy for bacterial wilt management.