Michiganensis Subsp Research Articles

Morphological and molecular characterization of Clavibacter michiganensis subsp. michiganensis causing bacterial canker in tomatoes

Bacterial canker is one of the emerging diseases of tomatoes caused by Clavibacter michiganensis subsp michiganensis (Cmm) in the Northern hill region of India. The present investigation was conducted to estimate the presence and spread of Cmm in the newer areas, to isolate and identify the cause of bacterial canker through conventional, serological and molecular diagnostic tools. 25 tomato plant samples along with the infected fruits collected from different tomato growing regions of the Uttarakhand and Himachal Pradesh were analyzed, and the bacterium was isolated from the seed of the infected tomato fruits. The present study revealed overall mean Cmm incidence of 19.57% and overall disease severity of 16.11% in the Northern hill region of India. The isolated bacterial strains were characterized culturally in semi-selective media (D2ANX and SCM), morphologically (SEM) and molecularly (16S rRNA and pat-1 genes). A total of 10 samples produced yellow colored colonies on D2ANX medium and 9 samples produced grey colored colonies on the SCM medium suggesting them to be of Clavibacter michiganensis subsp michiganensis (Cmm). Amongst the 10 isolates collected three isolates were serologically identified as Cmm through the DAS – ELISA technique. However with PCR reactions we found that only 2 strains out of 10 were of Cmm and the sequence of the most virulent Cmm isolate was submitted at NCBI with the accession number MH321815. These findings suggest that Cmm is present in the tomato seed, which can serve as a potential means of spread of a quarantine pest in the relatively newer areas of Northern hill regions of India.

Carrier-Free Small Molecular Self-Assembly Based on Berberine and Curcumin Incorporated in Submicron Particles for Improving Antimicrobial Activity.

Nanocarrier-based pesticide formulations have been severely restricted in agriculture practices due to their high-cost preparation process, poor loading capacity, and toxicity issues. To overcome these issues, carrier-free small molecular self-assembled submicron particles (SMPs) with an improved photoactivated antimicrobial activity based on two natural microbicides berberine hydrochloride (BBR) and curcumin (CM) are constructed by noncovalent interactions through a simple and fast preparation process (solvent exchange method) without using any adjuvant. The results show that the optimized molar ratio of BBR to CM is 2:1 at pH 5 and 25 °C in an aqueous solution for the formation of B-C SMPs. The obtained B-C SMPs exhibit excellent physicochemical properties, such as uniform morphology (407 nm), low polydispersity index (0.283), and strong ζ-potential (+24.4 mV). The antibacterial activities of B-C SMPs against Pseudomonas syringae pv. lachrymans, Clavibater michiganensis subsp. Michiganensis, and Sclerotinia sclerotiorum are 4, 2, and 1.5 times that of B + C MIX, respectively, suggesting a synergistic antimicrobial activity based on BBR and CM incorporation in the submicron particles. The genotoxicity evaluation results show that the self-assembled B-C SMPs are harmless to plant cells. Therefore, due to rational utilization of natural resources (natural microbicides, sunlight, and oxygen), carrier-free small molecular self-assembled B-C SMPs with synergistic photoactivated antimicrobial activity developed by a simple and fast preparation process would have great potential for sustainable plant disease management.

Deleterious Effects of Storage Environmental Conditions on The Seed Quality of Two Varieties of Tomato (Solanum lycopersicum L.) Stored in Triple Laminated Aluminum Packing in Sri Lanka

Tomato is one of the most commonly growing vegetable crops among the farmers in Sri Lanka. Standard laboratory germination of tomato seeds fulfills the regulatory requirements of seed marketing. However, poor field performance is an overwhelming problem to farmers. Present study was focused on the longevity of two varieties of tomato seeds as affected by their quality characters (percentage germination, moisture, field emergence and vigour index, seed protein and carbohydrate contents) including seed health (exposure of Clavibacter michiganensis subsp. Michiganensis (CMMV), Spotted wilt virus (TSWV) and Leaf curly top virus (LCTV)) under four different storage environmental conditions during a one-year long storage study. Seeds were packed in triple-laminated aluminum packets (TLA) and stored in low temperature storage conditions (17±1 °C and 65% RH) and in ambient conditions in Gannoruwa, Kundasale, and MahaIlluppallama that represent the three agro-ecologically zones; Mid Country Wet Zone (MCWZ), Mid Country Intermediate Zone (MCIZ) and Low Country Dry Zone (LCDZ) respectively. Seed quality parameters displayed varied responses depending on the variety. Physiological changes that occur in seeds due to temperature, RH, changes in proteins and carbohydrate content, CMMV and TSWV during storage were manifested as reduction in seed germination, field emergence and vigour index. However, none of the seedling carried LCTV and therefore its effect on seed quality parameters could not be assessed. The seeds could be stored for ca. 29 months at low and constant temperatures and RH conditions without compromising local seed germination standards compared to ambient storage in the three environments. CMMV and TSWV detected in all seed samples indicated potential threats to tomato farmers in Sri Lanka.

Identification and Biochemical Characterization of some Strains of Clavibacter michiganensis subsp. Michiganensis, in Romania

Clavibacter michiganensis subsp. michiganensis is responsible for the ʻbacterial canker of tomato’. The study aimed to identify and characterize biochemically some strains of the bacteria. Five strains were used for biochemical identification and characterization and two reference strains were used as positive controls. The biochemical characterization was performed with Biolog Microbial Identification System. All the strains used many carbon sources and were positive for growth in the presence of: 1%NaCl, Nalidixic Acid, Aztreonam, Potassium Tellurite and pH 6, but negative for growth and sensitivite to: Troleandomycin, Lincomycin, Vancomycin, Fusidic Acid, Eimfamycin SV, Guanidine HCl, D-Serine, Minocycline and Niaproof 4. The differences between the Biolog system database and the studied strains did not change their classification at the level of genus and species, but modifed or did not allow the classification at the subspecies level. Furthermore, the analyzed strains had metabolic diversity.

Testing the effect of new biopesticides on soilborne pathogens of vegetable diseases using DNA markers

In protected ground, vegetables are exposed to various pests and pathogens of viral, bacterial or fungal diseases. Growing vegetables indoors requires the elimination of all chemical treatments and control over pathogens and pests. In this regard, the application of sensitive methods based on molecular markers in the diagnostics of pathogens is highly relevant. In this work, polymerase chain reaction was used to identify the most common diseases of tomato (Xanthomonas euvesicatoria), cucumber (Ascochyta cucumis) and potato (Clavibacter michiganensis subsp. Sepedonicus) plants. It was established that early diagnosis of vegetable diseases using polymerase chain reaction allows rapid detection of trace amounts of pathogenic microorganisms thus facilitating selection of effective fungicidal preparations. The creation of biological protection for vegetable crops is relevant considering their nutritional importance. New biological methods for protecting vegetables in greenhouses were tested. Thus, the fungicidal effect of the authors’ patented preparation developed for pre-sowing treatment of vegetable seeds in protected ground on the pathogens of tomato black bacterial spot (Xanthomonas euvesicatoria) and cucumber stem hypertrophy (Ascochyta cucumis) was confirmed. Another preparation patented as a means of pre-sowing treatment of pea seeds demonstrated fungicidal action against the development of Phytophthora infectants on potato plants. It was observed that these preparations are effective at concentrations of 10-4 % for soaking seeds and double treatment of plants during the flowering period.

Superior antibacterial activity against seed-borne plant bacterial disease agents and enhanced physical properties of novel green synthesized nanostructured ZnO using Thymbra spicata plant extract

An easy and eco-friendly approach using Thymbra spicata var. spicata L. (TS) plant extract was developed for the formation of nanostructured ZnO. TS aqueous leaf extract was used for the green synthesis of nanostructured ZnO via the Successive ionic layer adsorption and reaction (SILAR) method. Electron microscope images exhibit the morphological adjustments of the samples with respect to change in TS concentration in the growth solution. The nanostructured ZnO grown by SILAR was observed to be polycrystalline with hexagonal crystal structure. The optical energy bandgap value of the samples varies from 3.21 to 3.09 eV as the content of TS increases from 2.5 to 5.0%. Also, the effect of TS additive to ZnO on electrical properties was investigated. It was determined by Van der Pauw measurements that TS contribution to ZnO significantly increased electrical resistance. In addition, impedance analyzes of the produced films were carried out in the frequency range of 20Hz −1 MHz. Nyquist plots showed the single semicircle for all samples, and the values of capacitance and resistance were calculated. Its antibacterial activities was investigated against economically important Gram-positive (Clavibacter michiganensis subsp. Michiganensis) and negative (Pseudomonas syringae pv. Phaseolicola, Pseudomonas cichorii and Pectobacterium carotovorum subsp. Carotovorum) seed-borne plant bacterial disease agents by using paper disc diffusion assay for the first time. In vitro laboratory screenings of green synthesized nanostructured ZnO have given encouraging results, indicating their potential use in the management of seed-borne bacterial diseases.

Induction of Bacterial Canker Resistance in Tomato Plants Using Plant Growth Promoting Rhizobacteria

Background: By inducing the production of inhibitory allelochemicals and mechanisms of systemic resistance plant growth promoting bacteria (PGPB) help plants to cope with stresses. Materials and Methods: In this study cell suspensions of Bacillus subtilis, Pseudomonas fluorescens or Azotobacter chroococcum were used to test the efficacy of these PGPB in inducing resistance in tomato (Lycopersicon esculentum Mill) against Clavibacter michiganensis subsp michiganensis, a bacteria known to cause canker disease. To test this hypothesis, seedlings of Chaika variety, characterized by short growing, early-ripening, high productivity and resistance against fusarium and the C. michiganensis strain ІZ-38 isolated in Kyiv were employed. Results and Conclusion: The use of cell suspensions of the PGPB B. subtilis, A. chroococcum or P. fluorescens induced an increment in the resistance of tomato plants against the causative agent of bacterial canker (C. michiganensis subsp. michiganensis) by 42–50%. PGPB in fact promoted in C. michiganensis infected tomato plants: i) the accumulation of chlorophyll a and b and carotenoids; ii) the thickening of the upper and lower epidermis of leaves; iii) the deposition of biopolymers with protective properties in epidermal cells; iv) the activity of the peroxidase enzyme and v) the net productivity of photosynthesis.

Multiple Introductions of Tomato Pathogen Clavibacter michiganensis subsp. michiganensis into Iran as Revealed by a Global-Scale Phylogeographic Analysis.

Tomato bacterial canker caused by Clavibacter michiganensis subsp. michiganensis is one of the most important seed-borne tomato diseases around the globe. The disease was initially reported in 1993 in Iran, and it became a rising threat for the multibillion dollar tomato industry of the country during the last decade. In this study, using phylogeographic analyses, we determined genetic diversity and geographic distribution of C. michiganensis subsp. michiganensis in Iran. Our field surveys showed that the pathogen is expanding into the southern and eastern areas of the country. Furthermore, multilocus sequence analysis and typing (MLSA/MLST) using the sequences of five housekeeping genes (atpD, gyrB, ppk, recA, and rpoB) revealed that 37 C. michiganensis subsp. michiganensis strains isolated in Iran had high genetic diversity and placed in 15 sequence types (STs), while all the available 184 worldwide C. michiganensis subsp. michiganensis sequences were placed in 43 STs. MLSA divided the worldwide C. michiganensis subsp. michiganensis strains into two phylogroups (I and II). Among the 37 strains isolated in Iran, 30 strains clustered in phylogroup I, while 7 strains clustered in phylogroup II. Phylogeographic data inferred from the allelic profile of the five housekeeping genes suggested multiple introductions of C. michiganensis subsp. michiganensis inoculum into Iran, while the geographic origin of the Iranian C. michiganensis subsp. michiganensis strains remains undetermined. Further analyses using higher numbers of strains are warranted to decipher the evolutionary history of C. michiganensis subsp. michiganensis in Iran. Additionally, stricter seed/transplant inspections are recommended to reduce the risk of pathogen expansion to areas with no history of the disease.IMPORTANCEClavibacter michiganensis subsp. michiganensis, the causal agent of tomato bacterial canker disease, is one of the economically important pathogens of solanaceous crops (e.g., eggplant, pepper, and tomato) around the world. The disease occurs in many countries, with a particular importance in regions characterized by high precipitation and humid environmental conditions. As a seed-borne pathogen, C. michiganensis subsp. michiganensis is included in the A2 (high risk) list of quarantine pathogens by the European and Mediterranean Plant Protection Organization (EPPO). Bacterial canker disease was reported for the first time in 1993 in Iran, while the geographic distribution, genetic diversity, and phylogenetic position of the causal agent remain undetermined. In this study, using the multilocus sequence analysis and typing (MLSA/MLST) approach, we provided a phylogeographic scheme for the C. michiganensis subsp. michiganensis strains isolated in Iran. Furthermore, global-scale phylogenetic analyses led to determination of phylogenetic position of Iranian C. michiganensis subsp. michiganensis strains among worldwide population of the pathogen. Based on diversity parameters and population structure, we suggest relatively higher genetic diversity of the bacterial canker pathogen in Iran than has so far been observed in the other areas of the world. Results obtained in this study provide a novel insight into the genetic diversity and population structure of the bacterial canker pathogen on a global scale.

Antimicrobial activities of bio-synthesized silver nanoparticles on strains of clavibacter michiganensis subsp. michiganensis

Silver nanoparticles (Ag-NPs) have been known to possess unique antimicrobial properties which help in medicine and water treatment, but their potentials in agriculture have not been fully utilized. This study was conducted to determine the inhibitory activity of bio-synthesized Silver nanoparticles on strains of Clavibacter michiganensis subsp. Michiganensis, causative agents of canker disease of tomato plant. The Ag-NPs were synthesized using Cladosporium cladosporioides, leaf extracts of Azadirachta indica and Vernonia amygdalina. The synthesized silver nanoparticles were characterized using UV-visible absorption spectroscopy. The antibacterial activities of bio-synthesized Ag-NPs on strains of C. michiganensis subsp. michiganensis were evaluated using agar well diffusion method. UV-visible spectroscopic analysis revealed rapid reduction of silver ions by C. cladosporioides, A. indica and V. amygdalina extracts where surface Plasmon absorption maxima were observed at 400nm – 450nm from the UV-visible spectra. The in-vitro antibacterial activities revealed that Ag-NPs synthesized using V. amygdalina and A. indica extracts inhibited the growth of C. michiganensis subsp. michiganensis strains with zones of inhibition ranging from 15.70 mm - 24.70mm and 21.00mm – 30.00mm, respectively, while those synthesized using C. cladosporioides showed zones of inhibition ranging from 0.00mm – 12.00mm. Growth curves of C. michiganensis subsp. michiganensis strains in the presence of biosynthesized Ag-NPs showed inhibition of growths after 4 – 10 hours of exposure. The results of this study indicated that the bio-synthesized silver nanoparticles could be effective in controlling bacterial canker disease of tomato plant caused by strains of C. michiganensis subsp. michiganensis thereby reducing the toxic effects of chemical bactericides on important agricultural products.Keywords: Silver nanoparticles; inhibitory activity; canker, tomato; zones of inhibition

Mycorrhiza-Induced Alleviation of Plant Disease Caused by Clavibacter michiganensis Subsp. Michiganensis and Role of Ethylene in Mycorrhiza-Induced Resistance in Tomato

The protective role of arbuscular mycorrhizal fungi (AMF) against the phytopathogen Clavibacter michiganensis subsp. michiganensis (Cmm) was examined in tomato plants. Seven different AMF isolates were used to determine which ones were able to induce effectively resistance against Cmm. Stems of seven-week tomato plants were infected with Cmm, then a disease severity index (DSI) was determined during the next three weeks. In addition to different responses to mycorrhizal inoculation, three levels of responses to the bacterial disease were recognized in treatments. Plants inoculated with Rhizophagus irregularis (Ri) showed both the highest colonization and the highest induced resistance to Cmm while the effect of Funneliformis mosseae, Gigaspora margarita and Claroideoglomus claroideum on mycorrhizal colonization and on the induced resistance were intermediate and high, respectively. Subsequently, Ri was chosen to inoculate ethylene-insensitive tomato mutant line Never ripe (Nr) and its background (Pearson) to investigate the possible role of ethylene (ET) in the mycorrhiza-induced resistance (MIR). The results showed that Ri could induce systemic resistance against Cmm in the Pearson background, whereas ET-insensitivity in Nr plants impaired MIR. These results suggest that ET is required for Ri-induced resistance against Cmm. To our knowledge, this is the first study to examine the effect of different AMF isolates on the response of tomato plants to Cmm and involvement of ET in MIR against Cmm.

Screening of Tomato Cultivars through Qualitative and Quantitative Evaluation for Bacterial Canker (Clavibacter michiganensis subsp michiganensis) in Open and Protected Conditions

Screening of Tomato Cultivars through Qualitative and Quantitative Evaluation for Bacterial Canker (Clavibacter michiganensis subsp michiganensis) in Open and Protected Conditions

Efecto de los ácidos fenólicos en plantas de tomate (Lycopersicon esculentum Mill.) inoculadas con Clavibacter michiganensis

Con el objetivo de evaluar el efecto de aplicaciones exógenas de ácidos fenólicos en el cultivo de tomate, se establecieron cuatro tratamientos: 1) un testigo absoluto; 2) plantas inoculadas con Clavibacter michiganensis subesp. Michiganensis (Cmm); 3) plantas inoculadas con Clavibacter michiganensis subesp. michiganensis y con aplicación de ácidos fenólicos; y 4) plantas solo con aplicación de ácidos fenólicos. Las aplicaciones se realizaron con intervalos de una semana hasta acumular un total de 10 aplicaciones durante el ciclo de cultivo. Los resultados indican que la aplicación de ácidos fenólicos no promovió efectos en las variables agronómicas del cultivo, sin embargo, si se observó una disminución significativa en severidad de Cmm. Además, se demostró que la aplicación de ácidos fenólicos modifica la densidad e índice estomático y en combinación con estrés biótico induce un menor tamaño de estomas. En las variables histológicas se encontró que con la aplicación de ácidos fenólicos el parénquima empalizada disminuyó su longitud, también indujo un menor número y área de vasos de xilema en hoja y raíz respectivamente y una mayor longitud de córtex en la raíz. Los resultados demostraron que la aplicación de ácidos fenólicos puede ser una alternativa viable para el control de Cmm.
 

Prevalence of (Clavibacter michiganensis subsp. Michiganensis) Causal Organism of Bacterial Canker in Weed Species in Tomato Fields of North West Pakistan

Prevalence of (Clavibacter michiganensis subsp. Michiganensis) Causal Organism of Bacterial Canker in Weed Species in Tomato Fields of North West Pakistan

English

English

Keefektifan Perlakuan Fisik dan Minyak Atsiri untuk Mengeliminasi Bakteri Clavibacter michiganensis subsp. michiganensis pada Benih Tomat

Clavibacter michiganensis subsp. michiganensis is the causal agent of bacterial canker disease of tomato. The bacteria is seed borne and may cause yield loss up to 70%. Seed treatment is an alternative method for controlling bacterial canker. The objective of the research was to study the effectiveness of physical and essential oil treatment for elimination of C. michiganensis subsp. michiganensis from tomato seed. Research was conducted in 4 separate experiments, i.e. (1) screening essential oils to control C. michiganensis subsp. Michiganensis ; (2) to determine the treatment window of physical and essential oil treatment; (3) to determine the physical and essential oil treatment on tomato seed infested by C. michiganensis subsp. Michiganensis ; and (4) to determine the effectiveness of treatment combination of physical and essential oil . The results showed that betel oil at concentration of 8% had the greatest inhibitory level (approximately 27.33 mm). Hot water treatment (53 °C) for 25 minutes reduced 90.94% of C. michiganensis subsp. michiganensis population; whereas dry heat treatment (60 °C, 24 hours) and betel oil treatment at 0.25% concentration reduced C. michiganensis subsp. michiganensis population (85.13 and 99.82% respectively). The combination of betel oil (0.5%), hot water (55 °C), and dry heat treatments (60 °C) was the most effective control method, because it reduced 99.99% of C. michiganensis subsp. michiganensis population and maintained the germination level of seed up to 100%. This combination might be recommended for seed treatment to eliminate C. michiganensis subsp. michiganensis .

Effect of irrigation intervals and soil types on yield and yield components of tomato plants artificially inoculated with Clavibacter Michiganensis subsp. Michiganensis

To determine the effect of irrigation interval and soil type on the severity of bacterial canker of tomato, a field experiment was carried out at Agricultural Research Institute (ARI) Tarnab in March to June 2013 and 2014. Five treatments: T1 = irrigation with 8 days interval, T2 = irrigation with 9 days interval, T3 = irrigation with 10 days interval, T4 = irrigation with 11 days interval and T5 = irrigation with 12 days interval were investigated for their effect on bacterial canker of tomato. In the same experiment, another factor i.e. soil types (S1 = Sandy Loam, S2 = Loam and S3 = Silt loam) were also investigated. Trials were replicated four times in a completely randomized design with split plot arrangement. Data were recorded for; survival percentage, number of flowers plant -1 , number of fruits plant -1 , fruiting percentage, disease severity and yield plant -1 . Results revealed that keeping irrigation interval at 12 days, the disease rating score reduced to its minimum (0.83), however the yield (1.88 kg.plant -1 ) was affected due to drought. For soil types less (1.67 and 1.77) disease severity was scored for sandy loam and silt loam soil respectively, whereas for the loam soil higher (2.10) disease ratings were observed. Highest (2.29kg) yield per plant was recorded for silt loam, followed by loam soil with 2.17kg.plant -1 . While 10 days irrigation interval was found to be the best with 2.48kg yield per plant. It was therefore, concluded, that ten days interval in irrigation was found to be optimum for obtaining the maximum yield, while silt loam soil is best due to its optimum water-holding capacities for tomato crop to tolerate the bacterial canker disease.

Systemic effect of microbial preparations on causative microorganisms of bacterial diseases of tomato plants

Biologicals Phytohelp, Phytocide and Ekstrasol, based on the bacteria Bacillus subtilis, showed different antibacterial activity to phytopathogens, due to the peculiarities of used strains, cells titer and concentration of biologically active products of microorganisms. Biologicals Phytohelp and Phytocide showed high antibacterial activity against the agents of bacterial cancer C. michiganensis subsp. michiganensis and bacterial black spotting X. vesicatoria, and the no growth zone diameter ranged from 73 to 80 mm. Under these conditions no growth zone diameter of the studied strains C. michiganensis subsp. michiganensis and X. vesicatoria for microbiological preparation Ekstrasol did not exceed 40 mm. Among these preparations more active against bacterial speck of tomatoes P. syringae pv. tomato was microbial preparation Ekstrasol no growth zone diameter of which was 23±3.0 mm. Biological Azotofit, based on cells of nitrogen-fixing bacteria Azotobacter chroococcum, showed high antibacterial activity against the agent of bacterial cancer C. michiganensis subsp. michiganensis, no growth zone diameter was 78±2.0 mm. This preparation was middle-active against the agent of bacterial black spotting X. vesicatoria and showed no activity against the agent of bacterial speck of tomato P. syringae pv. tomato. It was revealed that the most active against the agents of bacterial black spotting and bacterial cancer are biologicals Phytocide and Phytohelp, based on the bacteria Bacillus subtilis that are recommended by us for use in the manufacture.

Óleo essencial de Lippia sidoides nativas de Minas Gerais: composição, estruturas secretoras e atividade antibacteriana

Given the diverse biological activities presented by essential oils, and the antibacterial potential of the essential oil of Lippia sidoides Cham, the objective of this work was to characterise the essential oil of this species, collected in the southern part of the state of Minas Gerais, Brazil, as well as to identify its secretory structures and evaluate its antimicrobial activity on the phytobacteria, Clavibacter michiganensis subsp. Michiganensis, Xanthomonas vesicatoria and Pseudomonas syringae pv. tomato. Plants were collected in the town of Itumirim, and the essential oils of the leaves extracted by hydrodistillation using a modified Clevenger apparatus. The essential oil presented carvacrol (26.44%) and 1.8-cineole (22.63%) as major constituents. On the leaf surface of L. sidoides both glandular and non-glandular trichomes were found. Among the glandular trichomes are peltate trichomes and type I capitate trichomes. The presence of lipidic and terpenic substances within the head cells of both the peltate and capitate trichomes was found. The essential oil of L. sidoides was able to inhibit the growth of all the microorganisms studied, showing the following MIC: 7.81 µg mL-1 for C. michiganensis, 3.9 µg mL-1 for P. syringae and 15.62 µg mL-1 for X. vesicatoria. Carvacrol, the major constituent, showed MIC values equal to 3.9 µg mL-1 for all three bacteria studied. Both exhibited the ability to inhibit the growth of gram-positive and gram-negative bacteria.

Genetic Structure of Clavibacter michiganensis subsp. michiganensis Populations in Michigan Commercial Tomato Fields.

Clavibacter michiganensis subsp. michiganensis, causal agent of bacterial canker of tomato, is distinguished into four fingerprint types (A, B, C, and D) using BOX-polymerase chain reaction (PCR). To characterize the variation within the C. michiganensis subsp. michiganensis population in Michigan, 718 strains of C. michiganensis subsp. michiganensis were isolated from infected foliage and fruit collected from 14 and 9 Michigan commercial tomato fields in 1997 and 1998, respectively. The frequency of PCR types detected with BOX-PCR in all strains, and Bayesian cluster analysis, pairwise differentiation index comparisons, and genetic diversity estimates of 96 strains genotyped for six virulence-related genes revealed that C. michiganensis subsp. michiganensis populations in Michigan tomato fields are geographically structured. A multilocus haplotype cladogram was also consistent with geographic stratification in C. michiganensis subsp. Michiganensis populations. Some regions had strains predominantly of only one PCR type or belonging mostly to one genetic cluster, while other regions presented more diversity of occurrence of PCR types and genetic clusters. Results derived from this study provide information about the genetic structure of C. michiganensis subsp. michiganensis populations in Michigan and genetic diversity of C. michiganensis subsp. michiganensis inocula, which is key in developing disease management strategies.

Antibacterial activity of moroccan plants extracts against Clavibacter michiganensis subsp . michiganensis, the causal agent of tomatoes' bacterial canker

In search for alternative ways of tomatoes’ bacterial canker control, we screened here forty medicinal and aromatic plants (MAP) sampled from 15 families, currently used in southern Moroccan traditional medicine, for their activity against Clavibacter michiganensis subsp . michiganensis the causal agent of this disease. The antibacterial efficacy of powders of these plants was determined in vitro using the agar plate’s methods. Results obtained show that all the forty plants tested inhibited the bacterial growth of this pathogen with inhibition zone diameter ranging from 5 to 50 mm. Determination of the minimal inhibitory concentrations (MIC) and the minimal bactericidal concentrations (MBC) of the most effective plants indicates that there plants gender Rubus, Anvillea and Pistacia have the lower MIC which is equal to 3,125 mg ml -1 . The other plants ( Lavandula coronopifolia, Lavandula stoechas, Rosa canina, Cistus monspliensis and Cistus crispus ) had a MIC equal to 6.25 mg ml -1 . The MBC for different plants tested are between 6.25 mg ml -1 , case of Rubus ulmifolius and 25 mg ml -1 . The germination percentage of seeds treated with the most efficient three plants extracts was significantly higher than the untreated. Seeds treated with the extract of L. coronopifolia gave the higher germination rate (98%). The rate germination is 84 to 88% respectively for Cistus monspeliensis and Rubus ulmifolius . In other hand population size of the bacterium in the seeds’ surface was significantly reduced compared to the controls for the three treatments, when tomato seeds were artificially inoculated with the pathogen before being treated with the plants extracts (aqueous extracts).