Solanacearum Isolates Research Articles

Genome-wide analysis of the potato GRF gene family and their expression profiles in response to hormone and Ralstonia solanacearum infection.

Potato (Solanum tuberosum L.) is one of the most economically significant crops globally. Nevertheless, potato cultivation is becoming increasingly susceptible to a multitude of diseases, including bacterial wilt, which is caused by Ralstonia solanacearum. To identify the GRF gene family in potatoes and to examine their expression profiles in response to hormones and R. solanacearum infection. A comprehensive genome-wide analysis was conducted to identify the GRF gene family in the potato genome. A total of 13 GRF genes were identified from the latest potato genome, including five StGRFs belonging to the ɛ group and eight of the non-ɛ group. The transcriptional responses of the StGRFs to two biotic stress-related phytohormones (SA and MeJA) were defined, as well as the response to infection with R. solanacearum in a bacterial wilt-sensitive cultivar, S. tuberosum 'Qingshu 9'. Many StGRF genes exhibited high induction levels in response to R. solanacearum infection and SA treatment while displaying a marked decline in expression in the presence of MeJA. Furthermore, protein interaction network analysis revealed that the StGRF proteins interact with several candidate target proteins, indicating that GRF proteins are ubiquitous regulators in potatoes. However, the associations between two type III effectors (T3Es) RipAC/RipH2 from R. solanacearum isolates and StGRF7 were not detectable in a yeast two-hybrid assay. This study provides comprehensive information on the GRF gene family and lays a foundation for further research on the molecular mechanism of potato biotic stress adaptation.

An Evaluation of Bacterial Wilt (Ralstonia solanacearum) Resistance in a Set of Tomato Germplasm from the United States Department of Agriculture

Bacterial wilt (BW), caused by Ralstonia solanacearum, is one of the devastating diseases in tomatoes (Solanum lycopersicum L.). The use of resistant cultivars and breeding for genetic resistance is the most effective, economical, and environmentally friendly management strategy for this disease. It is necessary to screen diverse germplasm and cultivated genotypes to identify resistant resources and to develop resistant cultivars in tomatoes to combat the changing pathogen isolates. This study evaluated 40 United States Department of Agriculture (USDA) tomato accessions for their BW resistance to the R. solanacearum isolate P822 under greenhouse conditions. The tomato plants were inoculated and visually assessed to observe their symptoms, and the disease severity was scored on a scale of 0 to 4 (0 = no leaf wilted, 1 = 25% of leaves wilted, 2 = 50% leaves wilted, 3 = 75% of leaves wilted, and 4 = 100% leaves wilted). Five accessions (PI 645370, PI 647306, PI 600993, PI 355110, and PI 270210) were observed as BW resistance, with PI 645370 showing the greatest resistance. The broad-sense heritability for BW resistance was estimated as 59.9% and 42.8% based on a 0–4 scale of disease incidence and the disease severity index, respectively. Two distinct clusters (sub-populations) were detected among 39 of the 40 accessions. The five identified BW-resistant accessions were distributed in both clusters, suggesting a likely difference in the genetic base among the five resistance accessions. The resistant accessions will contribute significantly to the tomato breeding program to develop new cultivars with BW resistance.

Molecular identification of the causal agent of bacterial wilt in tomato plants in southwestern Paraná

Bacterial wilt, caused by phytopathogenic species of the genus Ralstonia, is one of the main diseases affecting the tomato crop. The Ralstonia solanacearum species complex occurs as a result of variants being widely diverse in terms of adaptation to different climatic conditions, host variations, and aggressiveness, which complicate disease control recommendations. In this study, we employed molecular methods to analyze 26 R. solanacearum isolates collected from tomato plants cultivated in the southwest region of Paraná, Brazil. Isolates were obtained from plants exhibiting wilt symptoms in a protected cultivation system and in an open field. The specific primers 759/760 confirmed the isolates as part of the Ralstonia solanacearum complex, and Nmult primers were used to identify the phylotype. Variability analysis using BOX-PCR with the BOX-A1R primer on 19 isolates revealed molecular diversity. All 26 isolates were confirmed as Ralstonia solanacearum, belonging to phylotype II. Comparison of genomic DNA band patterns amplified by BOX-PCR indicated molecular variability, forming eight groups at a similarity level of 0.63. These results confirm the prevalence of R. solanacearum phylotype II in southwestern Paraná. This information aids decision-making in disease management and contributes to breeding efforts aiming at the development of resistant cultivars.

Races and Biovar Characterization of Ralstonia solanacearum Causing Bacterial Wilt Disease of Potato

Ralstonia solanacearum, the causative agent of brown rot/bacterial wilt, is a major cause of severe potato illnesses in many impoverished nations located in tropical and subtropical regions of the world. When it occurs, the disease is to blame for significant losses to the potato industry. The illness has the potential to completely destroy a crop and stop using a piece of land for potato cultivation for a number of years. A survey was carried out to investigate the extent of Ralstonia solanacearum-caused bacterial wilt of potato crops in important potato-growing talukas in the Banaskantha district of Gujarat, India, including Deesa, Dantiwada, Palanpur, and Amirgadh. The frequency of bacterial wilt disease in potatoes is rather low in this region. Four talukas were utilised to identify ten isolates (RsSt1 to RsSt10) of R. solanacearum, which were then used to determine the biovar and race. Gram-negative rod-shaped cells were present in the isolates of R. solanacearum. On TZC agar medium, these isolates developed colonies that were creamy or dull white in colour with a hint of pink or red in the centre. The oxidation of disaccharides (sucrose, lactose, maltose) and sugar alcohols (manitol, sorbitol, and dulcitol) by R. solanacearum isolates was used to determine the biovar characteristics. This revealed that, of the ten isolates, eight were classified as bv2, and the two remaining isolates (RsSt5 and RsSt7) belonged to bv2T. The pathogenicity test conducted on tobacco, tomato, and brinjal allowed for the race identification of R. solanacearum isolates, which were classified as race 3 due to their limited host range and ability to exclusively elicit wilt symptoms in potatoes and tomatoes. As a result, Races 3 and bv2 and bv2T were represented among the R. solanacearum isolates that caused bacterial wilt of potatoes in the Banaskantha district.

Bacterial wilt of tobacco in Bangladesh: a pilot study for assessment of the status, detection of seed-borne nature and genetic variation of its pathogen, Ralstonia solanacearum

Bacterial wilt of tobacco caused by Ralstonia solanacearum poses a significant threat to tobacco cultivation in Bangladesh. In this study, fourteen tobacco growing areas of Bangladesh were surveyed to assess the status of bacterial wilt disease in tobacco. The result revealed that the higher level of bacterial wilt incidence and severity was recorded in Bandarban followed by Naikhonchari, Lama, Rangpur, and Lalmonirhat and the lower level was in Chakaria, Kushtia, Meherpur, Chuadanga, and Jhenaidah. However, a moderate level of incidence and severity was recorded in Manikgonj, Khagrachori, and Tangail. After estimating the bacterial population in the soil of respective regions it was observed that the highest bacterial population was counted at 22.4 x 107 CFU/g soil in Chakaria and the lowest was counted at 4.3 x 107 CFU/g soil in Tangail. Among the seed samples, sample no BWT Seed 21 had the highest level of infection (93%), sample no BWT Seed 37 had a medium level (39.46%), and sample no BWT Seed 57 had the lowest level of infection (5.14%) with R. solanacearum as detected by plating tobacco seed samples by TTC agar medium. Biovar and races of R. solanacearum were identified through the sugar oxidation test and pathogenicity test and it was found that R. solanacearum isolates from all the fourteen growing areas were grouped into race 1 and biovar 1, biovar 2, biovar 3. Genetic diversity of R. solanacearum analysis was done by using REP and ERIC primers where both primers showed three clusters (I, II, and III) at 60% similarity. The results are very crucial for the development of sustainable management of bacterial wilt of tobacco and for future population analyses of R. solanacearum. Asian Australas. J. Biosci. Biotechnol. 2023, 8(3), 56-69

Isolation and characterization of Ralstonia solanacearum causing wilt disease in tomato

Bacterial wilt, caused by Ralstonia solanacearum, is the most serious and common disease that affects tomatoes globally. Tomato bacterial wilt is among the worst and most prevalent diseases in Ethiopia. It causes substantial tomato production losses in various parts of the country. The purpose of this study was to isolate and characterize Ralstonia solanacearum causing wilt disease in tomato. Ralstonia solanacearum isolates were isolated from wilted tomato stem samples using Casamino Acid Peptone Glucose Agar (CPG) plates and incubated at 28 ± 2 °C for 48 h. Bacterial colonies showing big, irregular smooth, and cream-white, were considered presumptive Ralstonia solanacearum isolates. Morphological, biochemical, and pathological characterization were used for identification of the bacterium. Biovar identification was determined based on the utilization of carbohydrates. A total of 76 Ralstonia solanacearum isolates were screened and identified as Ralstonia solanacearum. Out of all the isolates, 28.9% of the isolates were isolated from Mecha, followed by Fogera (27.6%), Dera (23.7%), and Bahir Dar Zuria (19.7%) districts. The pathogenicity test results also revealed that all Ralstonia solanacearum isolates tested caused wilt symptoms in tomato plants and had varying levels of virulence on tomato plants, ranging from highly virulent (G1B1, G2M2, G3H1, and G4F3 isolates) to moderately virulent (G1B1, G2M1, G2M3, G3H2, G4F1, and G4F2 isolates). Besides, 48 Ralstonia solanacearum isolates were identified as Biovar II, and 28 Ralstonia solanacearum isolates were identified as biovar III. The overall findings of this study could provide valuable information for integrated tomato bacterial wilt disease management. The molecular characterization should be carried out on Ralstonia solanacearum in different host ranges.

Physio-biochemical, molecular characterization, and phage susceptibility of Ralstonia pseudosolanacearum associated with tomato (Solanum lycopersicum) and eggplant (Solanum melongena)

Abstract. Nurdika AAH, Arwiyanto T, Sulandari S. 2022. Physio-biochemical, molecular characterization, and phage susceptibility of Ralstonia pseudosolanacearum associated with tomato (Solanum lycopersicum) and eggplant (Solanum melongena). Biodiversitas 23: 5149-5158. Ralstonia solanacearum is a plant pathogen that causes bacterial wilt diseases in various plant species. The high diversity of these bacteria strains is the basis for their grouping into the R. solanacearum species complex (RSSC). RSSC associated with tomato and eggplant in Indonesia are commonly known as R. solanacearum. It is necessary to characterize R. solanacearum which infects tomatoes and eggplant according to the latest classification. The high diversity of strains also affects their susceptibility to bacteriophages as host-specific biocontrol agents. This research was conducted by characterizing R. solanacearum isolates from different locations based on their physio-biochemical properties, biovar, virulence, phylotype, sequevar, and susceptibility to 12 bacteriophage isolates. The phylotype identification was carried out using multiplex polymerase chain reaction with several specific primers for R. solanacearum. Amplification and sequencing based on the egl gene region were carried out to determine the sequevar of R. solanacearum isolates. As a result, isolates RS18, RS19, RS23, and RS24 had morphological, physio-biochemical, and biovar characteristics according to Ralstonia pseudosolanacearum phylotype I, biovar 3. The two most virulent isolates, RS19 and RS24 were identified as sequevar 14. RS19 and RS24 isolates were susceptible to 7 of the 12 bacteriophage isolates used in this study. Variations of bacteriophage isolates resulted in different plaque morphology which could be attributed to R. pseudosolanacearum susceptibility and bacteriophage virulence.

A conserved type III effector RipB is recognized in tobacco and contributes to Ralstonia solanacearum virulence in susceptible host plants

Ralstonia solanacearum, the causal agent of bacterial wilt, causes devastating diseases in a wide range of plants including potato, tomato, pepper and tobacco. The pathogen delivers approximately 70 type III effectors (T3Es) into plant cells during infection. In this study, we confirmed that a T3E RipB is recognized in tobacco. We further demonstrated that RipB is conserved among R. solanacearum isolates and five different ripB alleles are all recognized in tobacco. The ripB from GMI1000 was transformed into susceptible host Arabidopsis, and a defect in root development was observed in ripB-transgenic plants. Pathogen inoculation assays showed that ripB expression promoted plant susceptibility to R. solanacearum infection, indicating that RipB contributes to pathogen virulence in Arabidopsis. Expression of ripB in roq1 mutant partially suppressed reactive oxygen species production, confirming that RipB interferes with plant basal defense. Interestingly, ripB expression promoted cytokinin-related gene expression in Arabidopsis, suggesting a role of cytokinin signaling pathway in plant-R. solanacearum interactions. Finally, RipB harbors potential 14-3-3 binding motifs, but the associations between RipB and 14-3-3 proteins were undetectable in yeast two-hybrid assay. Together, our results demonstrate that multiple ripB alleles are recognized in Nicotiana, and RipB suppresses basal defense in susceptible host to promote R. solanacearum infection.

Rep-PCR Analyses Reveal Genetic Variation of Ralstonia solanacearum Causing Wilt of Solanaceaous Vegetables in Bangladesh.

Ralstonia solanacearum, a soil-borne and seed-borne plant pathogenic bacterium, causes bacterial wilt to several important crop plants causing substantial economic losses. To provide population information on this pathogen for developing effective control strategies, Rep-PCR was used to analyze the genetic variation of 18 representative isolates of R. solanacearum collected in Bangladesh. Phenotypic analyses revealed that all eighteen isolates belong to biotype 3 with wide diversity in aggressiveness on eggplant, tomato, and chili. Rep-PCR studies utilizing the REP, ERIC, and BOXIR primers showed a wide variation at the genetic level among the R. solanacearum isolates used in this study. Dendrogram constructed using REP, ERIC, and BOXIR primers based on banding patterns implied that R. solanacearum isolates were genetically diversified and distributed in four clusters at 83%, 80%, and 63% similarity index, respectively. The genetic relationship assayed by rep-PCR highlighted a wide range of genetic variation but no relation among geographical origin, aggressiveness, and phylogenetic groups of R. solanacearum isolates. These results conceded that other molecular markers related to virulence gene(s) might reveal the complex relationship among geographical origin, aggressiveness, and phylogenetic groups.

QTL Mapping for Resistance to Bacterial Wilt Caused by Two Isolates of Ralstonia solanacearum in Chili Pepper (Capsicum annuum L.).

Bacterial wilt caused by the β-proteobacterium Ralstonia solanacearum is one of the most destructive soil-borne pathogens in peppers (Capsicum annuum L.) worldwide. Cultivated pepper fields in Korea face a continuous spread of this pathogen due to global warming. The most efficient and sustainable strategy for controlling bacterial wilt is to develop resistant pepper varieties. Resistance, which is quantitatively inherited, occurs differentially depending on R. solanacearum isolates. Therefore, in this study, we aimed to identify resistance quantitative trait loci (QTLs) in two F2 populations derived from self-pollination of a highly resistant pepper cultivar ‘Konesian hot’ using a moderately pathogenic ‘HS’ isolate and a highly pathogenic ‘HWA’ isolate of R. solanacearum for inoculation, via genotyping-by-sequencing analysis. QTL analysis revealed five QTLs, Bwr6w-7.2, Bwr6w-8.1, Bwr6w-9.1, Bwr6w-9.2, and Bwr6w-10.1, conferring resistance to the ‘HS’ isolate with R2 values of 13.05, 12.67, 15.07, 10.46, and 9.69%, respectively, and three QTLs, Bwr6w-5.1, Bwr6w-6.1, and Bwr6w-7.1, resistant to the ‘HWA’ isolate with phenotypic variances of 19.67, 16.50, and 12.56%, respectively. Additionally, six high-resolution melting (HRM) markers closely linked to the QTLs were developed. In all the markers, the mean disease index of the paternal genotype was significantly lower than that of the maternal genotype. The QTLs and HRM markers are expected to be useful for the development of pepper varieties with high resistance to bacterial wilt.

Investigation of virulence diversity in Ralstonia solanacearum isolates by a random amplified polymorphic DNA collected from Egyptian potato fields

In this study, a total of ten bacterial isolates obtained from the wilted potato plants in Egypt, identified as Ralstonia solanacearum race 3 (biovar II) were used to study the differentiation among the isolates by RAPD marker analysis. In pathogenicity experiments, all isolates demonstrated typical wilt disease symptoms on potato plants. However, the level of virulence was significantly different as the isolates GK1, GT2, and AM8 were highly virulent one isolate “ES6” was moderate virulent and one isolate “SA9” was virulent.Molecular characterization of virulent, moderate virulent, and low virulent isolates along with five avirulent isolates (originated from the same regions) was performed by RAPD marker analysis using six random ten-mer primers. The results of RAPD marker analysis showed significant variation (9-12) in the number of fragments having molecular weight from 219 to 1120 bp. The results presented here demonstrated that no correlation was observed between the RAPD profile and the geographicaly originated strains.

Distribution and Incidence of Tomato Bacterial Wilt Caused by Ralstonia solanacearum in the Central Region of Togo

Tomato (Solanum lycopersicum L.) is one of the most important vegetables in Togo. Unfortunately, tomato is susceptible to many diseases, among which bacterial wilt caused by Ralstonia solanacearum causes major yield losses. In this study, incidence of bacterial wilt and its distribution was evaluated in the central region of Togo, the major tomato-producing area in the country. Overall, 16 localities were surveyed in four prefectures. In each locality, three fields were visited, the incidence of the disease was recorded, and diseased samples were collected for laboratory investigation. The results showed that bacterial wilt occurred in all of the fields visited, indicating a field incidence of 100%, whereas the plant incidence ranged from 10.00 ± 00 to 43.33 ± 3.33%, with an average of 20.94 ± 1.77%. The antibody-based ImmunoStrip test was positive for R. solanacearum in 100% of the visited fields. From 144 samples collected from fields, 45 R. solanacearum isolates were isolated on modified selective medium from South Africa. These survey results show that tomato bacterial wilt is a real threat to tomato production in the central region of Togo.

Genomic and Biological Characterization of Ralstonia solanacearum Inovirus Brazil 1, an Inovirus that Alters the Pathogenicity of the Phytopathogen Ralstonia pseudosolanacearum.

Filamentous bacteriophages contain a single-stranded DNA genome and have a peculiar lifestyle, since they do not cause host cell lysis, but establish a persistent association with the host, often causing behavioral changes, with effects on bacterial ecology. Over the years, a gradual reduction in the incidence of bacterial wilt has been observed in some fields from Brazil. This event, which has been associated with the loss of pathogenicity of Rasltonia spp. isolates due to infection by filamentous viruses of the inovirus group, is widely reported for Ralstonia spp. Asian isolates infected by inoviruses. In an attempt to elucidate which factors are associated with the phenomenon reported in Brazil, we investigated one isolate of R. solanacearum (UB-2014), with unusual characteristics for R. solanacearum, obtained from eggplant with mild wilt symptoms. To verify if the presence of filamentous bacteriophage was related to this phenotype, we performed viral purification and nucleic acid extraction. The phage genome was sequenced, and phylogenetic analyses demonstrated that the virus belongs to the family Inoviridae and was named as Ralstonia solanacerarum inovirus Brazil 1 (RSIBR1). RSIBR1 was transmitted to R. pseudosolanacearum GMI1000, and the virus-infected GMI1000 (GMI1000 VI) isolate showed alterations in phenotypic characteristics, as well as loss of pathogenicity, similarly to that observed in R. solanacearum isolate UB-2014. The presence of virus-infected UB-2014 and GMI1000 VI plants without symptoms, after 3months, confirms that the infected isolates can colonize the plant without causing disease, which demonstrates that the phage infection changed the behavior of these pathogens.

Monoclonal outbreak of Ralstonia solanacearum catheter-related bloodstream infection associated with contaminated package of normal saline solution in a tertiary care hospital

Background/aim Ralstonia solanacearum is a very rare cause of infection in humans. There is no described nosocomial outbreak due to R. solanacearum so far. We determined R. solanacearum as the source of catheter-related bloodstream infection (CRBSI) outbreak.Materials and methods This outbreak analysis was carried out in a 1000-bed tertiary care university hospital in Turkey. The outbreak analysis included hematology, oncology, nephrology, gastroenterology wards, emergency department, and intensive care units. The first case with R. solanacearum CRBSI was detected on May 20, 2019 and R. solanacearum was isolated in catheter blood cultures in 34 patients until October 3, 2019Results Standard outbreak analysis procedures were applied. Culture samples were taken from the fluids administered via catheters. The cultures did not yield any bacteria. As a result of the investigation in storage area, it was found that there were leaks, air bubbles, and water drops inside the packaging of saline solutions. R. solanacearum was yielded in the cultures obtained from the surface of saline bags and the inner sides of plastic packings. To validate our hypothesis, a clonal analysis was performed using arbitrarily primed-PCR method and Sanger sequencing of the 16S rRNA gene for identification among isolates. All R. solanacearum isolates were monoclonal and identical.ConclusionThis is the first outbreak of R. solanacearum CRBSI described in a hospital setting. The source of the outbreak was a contamination in the surface of saline bags and the inner sides of plastic packings. Efficacy of an active surveillance system, accurate and rapid conduction of microbiological identification are essential for outbreak management.

Characterization and diversity of Indian isolates of Ralstonia solanacearum inciting bacterial wilt of tomato

Tomato (Solanum lycopersicum L.) a native of South America is a source of vitamins, minerals and antioxidant lycopene, and considered as protective food. In India, the crop is grown under the area of about 0.458 M ha with production of 7.277 M mt and productivity of 15.9 mt/ha. Biotic factors play a role in low productivity of the crops in India. Among various diseases, bacterial wilt disease incited by Ralstonia solanacearum (Smith) Yabuuchi et al. (1996) is a devastating bacterium causing damage to the crop ranging from 2 to 95% depending on the seasons and cultivars. In India, majority of the isolates of R. solanacearum infecting tomato crop belonged to biovar 3, race 1 and phylotype I. However, less than 10% isolates of the bacteria belonged to biovar 4 particularly in the states of Jharkhand and Himachal Pradesh. The genetic diversity of R. solanacearum has been studied by using methods such as random amplified polymorphic DNA (RAPD), PCR—RFLP (PCR—Restriction Length Fragment Polymorphism) of hrp gene, Repetitive element palindromic-polymerase chain reaction (Rep-PCR) and multilocus sequence typing (MLST). The genetic diversity was recorded in Indian R. solanacearum isolates irrespective of their occurrence in different agro-climatic conditions.

In-Vitro Antagonistic Effect of Bacillus thuringiensis on Ralstonia solanacearum, the Causal Agent of Bacterial Wilt Disease of Tomato (Lycopersicon esculentum Mill).

Tomato (Lycopersicon esculentum, Mill) is a rich source of vitamins, minerals and lycopene, which has many health benefits. However, its production is hampered by bacterial wilt caused by Ralstonia solanacearum resulting in significant yield losses. Use of chemicals in the control of plant pathogens has detrimental effects on humans and the environment in terms of leaving residues in soil which later find their way into underground waters. Therefore, it is desirable to find an alternative to chemical control of this bacterial pathogen. This study investigates the potential of native Bacillus thuringiensis (Bt) for biological control of Ralstonia solanacearum (Rs) under laboratory conditions. B. thuringiensis was isolated from cultivated soil, non- cultivated soil, stagnant water, sawdust, horse dung, grain dust, dead leaves and poultry manure. R. solanacearum was isolated from stem exudates of bacterial wilt infected plants and its pathogenicity assay was carried out using 2-week-old seedlings of Beske tomato variety. The Bt and R. solanacearum isolates were then characterized phenotypically. Bt isolates were further identified using endospore and parasporal staining techniques. All the Bt isolates were tested for in-vitro antagonistic activity on R. solanacearum using agar well diffusion method. Isolates Bt2, Bt16, Bt17, Bt32 and Bt34 were confirmed as Bacillus thuringiensis while isolate Rs was confirmed as R. solanacearum. Beske showed wilting symptoms from the fourth day of inoculation and eventual death of seedlings. The zone of inhibition exhibited ranged from 0.0 mm to 20.0 mm.
 Keywords: Bacillus thuringiensis, In-vitro, Bacterial wilt, Ralstonia solanacearum, Tomato

Transposable elements contribute to the genome plasticity of Ralstonia solanacearum species complex.

The extensive genetic diversity of Ralstonia solanacearum , a serious soil-borne phytopathogen, has led to the concept that R. solanacearum encompasses a species complex [ R. solanacearum species complex (RSSC)]. Insertion sequences (ISs) are suggested to play an important role in the genome evolution of this pathogen. Here, we identified and analysed transposable elements (TEs), ISs and transposons, in 106 RSSC genomes and 15 Ralstonia spp. We mapped 10 259 IS elements in the complete genome of 62 representative RSSC strains and closely related Ralstonia spp. A unique set of 20 IS families was widespread across the strains, IS5 and IS3 being the most abundant. Our results showed six novel transposon sequences belonging to the Tn3 family carrying passenger genes encoding antibiotic resistance and avirulence proteins. In addition, internal rearrangement events associated with ISs were demonstrated in Ralstonia pseudosolanacearum strains. We also mapped IS elements interrupting avirulence genes, which provided evidence that ISs plays an important role in virulence evolution of RSSC. Additionally, the activity of ISs was demonstrated by transcriptome analysis and DNA hybridization in R. solanacearum isolates. Altogether, we have provided collective data of TEs in RSSC genomes, opening a new path for understanding their evolutionary impact on the genome evolution and diversity of this important plant pathogen.

Effect of Field Treatment with Selected Soil Amendments on Bacterial Wilt Incidences in Tomatoes, Capsicum and Potatoes

Aims: The aim of this study was to establish the effect of field treatment with selected soil amendments on bacterial wilt incidences in Tomatoes, Capsicum and Potatoes. 
 Study Design: The study was laid out as randomized complete block design (RCBD) in split plot arrangement for two seasons in the field.
 Place and Duration of Study: The experiment was conducted at the experimental plots at KARLO- NARL, Kabete Nairobi County between July, 2017- September, 2017 and between November, 2017- January, 2018.
 Methodology: The three choice crops of interest (potatoes, tomatoes and capsicum) were inoculated with prepared pure bacterial isolates; 18 (2T-Kiambu-Low Land), 71(2A-Nyeri-Low Land), 67 (2A-Nyeri-High Land), 83 (2T-Kirinyaga-Highland) and MX (18/71/67/83). A plot measuring 66 m by 28.5 m was marked, cleared, ploughed, harrowed and demarcated into 150 plots each measuring 2.4 m x 3.75 m. Spacing of the host crops of interest: potato - (Tigoni variety), tomato (Caj variety) and capsicum (Califonia Wonder) was carried out at 75 cm between the rows and 30 cm within the rows. The treatments were ChalimTM, Super-hydro-grow polymer + Metham sodium, Metham sodium, Metham sodium & Orange peel, Super-hydro-grow polymer, Brassica tissues, ChalimTM + Super-hydro-grow polymer, Brassica tissue + Orange peel, Metham sodium + Super-hydro-grow polymer and Control (no amendments).
 Results: Significant differences (P≤0.05) were revealed in the bacterial wilt incidences in tomatoes, capsicum and potatoes between control and all the soil amendments used in season 1 and 2 in the five R. solanacearum isolate from Kenyan highlands and lowlands. The Brassica tissue + Super-hydro-grow polymer was superior in reducing bacterial wilt incidences in tomatoes, capsicum and potatoes in the field in all the R. solanacearum isolates from Kenyan highlands and lowlands both in season 1 and 2.
 Conclusion: The findings showed that organic and inorganic soil amendments could serve as a viable control of bacterial wilt in solanaceous crops caused by R. solanacearum in the field. We recommend the use of Brassica tissue + Super-hydro-grow polymer soil amendment in the control of bacterial wilt incidences in the field on solanaceous crops.

Control of Ralstonia solanacearum on Selected Solaneceous Crops in Greenhouse by Selected Soil Amendments

Aims: The aim of this study was to establish the effect of selected soil amendments on Ralstonia solanacearum isolates in greenhouse on selected solaneceous crops.
 Study Design: The study was laid out as randomized complete block design (RCBD) in split pot arrangement for two seasons in the greenhouse.
 Place and Duration of Study: The experiment was carried out in Kenyattta University situated in Kiambu County about 20 km from Nairobi city along Nairobi-Thika road between July, 2017- September, 2017 and between November, 2017- January, 2018.
 Methodology: The three host crops of interest (potatoes, tomatoes and capsicum) were inoculated with prepared pure bacterial isolates; 18 (2T-Kiambu-Low Land), 71(2A-Nyeri-Low Land), 67 (2A-Nyeri-High Land), 83 (2T-Kirinyaga-Highland) and MX (18/71/67/83). Potatoes, tomatoes and capsicum were planted in pots each with a radius of 0.07 m (area 0.015 m2).The experiment had a total of 450 pots having a total area of 6.93 m2. The treatments were ChalimTM, Super-hydro-grow polymer + Metham sodium, Metham sodium, Metham sodium & Orange peel, Super-hydro-grow polymer, Brassica tissues, ChalimTM + Super-hydro-grow polymer, Brassica tissue + Orange peel, Metham sodium + Super-hydro-grow polymer and Control (no amendments).
 Results: There were significant differences (P≤0.05) in the bacterial wilt incidences in selected solaneceous crops between control and all the soil amendments used in season 1 and 2. Brassica tissue + Super-hydro-grow polymer was superior in reducing bacterial wilt incidences in selected solaneceous crops in all the R. solanacearum isolates from Kenyan highlands and lowlands both in season 1 and 2.
 Conclusion: Organic and inorganic soil amendments could serve as a viable control of bacterial wilt in solaneceous crops caused by R. solanacearum in the greenhouse.

Genetic control of tomato resistance to Ralstonia solanacearum

Ralstonia solanacearum is one of the causal agent of bacterial wilt in Brazil. This is the main bacteriosis in tomato plants, which can cause losses of up to 100% in their production. The use of resistant cultivars is the main form of control. Thus, the study of genetic control of resistance provides essential information for the conduct of breeding programs. The objective of this work was to study the genetic control of tomato plant ‘Yoshimatsu’ resistance to R. solanacearum. The experiments were conducted in greehouse with the Yoshimatsu and IPA-7 parents; F1, F2, RC11, RC21 generations; and F2:3 progenies. All plants were inoculated using a R. solanacearum isolate from the collection of the Phitobacteriology Laboratory of the Federal Rural University of Pernambuco. The severity of bacterial wilt were assessed through a descriptive scale of scores at 10 and 20 days after inoculation. The resistance to R. solanacearum in the ‘Yoshimatsu’ cultivar is associated with recessive alleles, in which the genetic control of resistance is determined by two independent genes of greater effect with only additive effects, plus polygenes associated with additive and dominance effects.