Persistencia, internalización y translocación de Escherichia coli O157:H7, O157:H16 y O105ab en plantas y frutos de tomate (Solanum lycopersicum L.) / Persistence, internalization and translocation of Escherichia coli O157:H7, O157:H16 and O105ab in plants and tomato fruits (Solanum lycopersicum L.)

La presencia de bacterias patógenas, como Escherichia coli, afecta la calidad e inocuidad de las hortalizas que se consumen en fresco y se relaciona con graves problemas de salud. El objetivo de este trabajo fue determinar si 3 cepas diferentes de E. coli tienen la capacidad de penetrar y permanecer en plantas y frutos de tomate. Se siguió un diseño experimental completamente al azar, para lo cual se estableció un cultivo de tomate (variedad «Cid¼) en condiciones de invernadero y se evaluaron 3 tratamientos, T1 (E. coli O157: H7), T2 (E. coli de cultivo de tomate -#91;EcT-#93; O157: H16), T3 (E. coli de cultivo de espinaca -#91;EcH-#93; EcH O105ab) y un testigo T4, con 100 plantas cada uno y 4 formas de inoculación: en el sustrato, en el tallo, en el pecíolo y en el pedúnculo. Se realizaron muestreos en etapa vegetativa, floración, fructificación y madurez fisiológica para cuantificar en placa las UFC/g y saber si las bacterias lograban moverse y recuperarse en la raíz, el tallo, la flor y el fruto. Los grupos filogenéticos a los que correspondieron las bacterias recuperadas fueron confirmados mediante pruebas bioquímicas, serotipificación y PCR. A los 120 días la recuperación de bacterias en la planta fue del 23% (E. coli O157: H7), 28% (EcT O157: H16) y 55% (EcH O105ab) con la inoculación al sustrato, mientras que con la inoculación por punción la recuperación fue (en igual orden) del 5%, 3% y 4% a los 30 días; del 37%, 35% y 30% a los 90 días; y del 42%, 39% y 13% a los 65 días. Las cepas utilizadas mostraron la capacidad de entrar en la planta de tomate y de permanecer en ella y transportarse hasta llegar al fruto, sin producir síntomas que indiquen su presencia.

The presence of pathogenic bacteria, such as Escherichia coli affects the quality and safety of vegetables that are consumed fresh and is associated with serious health problems. The objective of this study was to determine if three different strains of E. coli can penetrate and remain in plants and tomato fruits. A completely randomized experimental design was followed for which a tomato crop ("Cid" variety) was established under greenhouse conditions and three treatments were evaluated, T1 (E. coli O157: H7), T2 (E. coli from tomato cultivation -#91;EcT-#93; O157: H16), T3 (E. coli from spinach cultivation -#91;EcH-#93; O105ab) and a T4 control, with 100 plants each and four forms of inoculation: in the substrate, steam, petiole and the peduncle. Samples were carried out in vegetative stage, flowering, fruiting and physiological maturity to quantify in petri dish CFU/g and know if the bacteria managed to move around and recover in root, stem, flower and fruit. The phylogenetic groups that corresponded to the bacteria recovered were confirmed by biochemical tests, serotyping and PCR. At 120 days the recovery of bacteria in the plant was 23% (E. coli O157: H7), 28% (EcT O157: H16) and 55% (EcH O105ab) whit inoculation to the substrate while the inoculation by puncture the recovery was (in the same order) of 5%, 3%, and 4% at 30 days; 37%, 35% and 30% at 90 days; and 42%, 39% and 13% at 65 days. The strains submit the ability to enter the tomato plant and to stay in it and transported to the fruit, without producing that indicate their presence.

Growth kinetics of Escherichia coli O157: H7 on the epicarp of fresh vegetables and fruits

ABSTRACT Despite the increasing reports on the incidence of fresh vegetables and fruits as a possible vehicle for human pathogens, there is currently limited knowledge on the growth potential of Escherichia coli O157:H7 on different plant substrates. This study analyzed the selective adhesion and growth of E. coli O157:H7 on chili habanero (Capsicum chinense L.), cucumber (Cucumis sativus), radish (Raphanus sativus), tomato (Lycopersicon esculentum), beet (Beta vulgaris subsp. vulgaris), and onion (Allium cepa L.) under laboratory conditions. The Gompertz parameters were used to determine the growth kinetics. Scanning electron microscopy was used to visualize the adhesion of E. coli O157:H7 on the epicarp of the samples. Predictive models were constructed to compare the growth of E. coli O157:H7 on the samples with different intrinsic factors and to demonstrate the low selectivity of the pathogen. No significant difference was observed in the lag-phase duration (LPD), generation time (GT), and exponential growth rate (EGR) of the pathogen adhered to the samples. The interaction between the microorganism and the substrate was less supportive to the growth of E. coli O157:H7 for onion, whereas for tomato and cucumber, the time for the microorganism to attain the maximum growth rate (M) was significantly longer than that recorded for other samples.

Influence of iron and copper on the activity of laccases in Fusarium oxysporum f. sp. lycopersici

ABSTRACT Fusarium oxysporum f. sp. lycopersici is a phytopathogenic fungus that causes vascular wilt in tomato plants. In this work we analyze the influence of metal salts such as iron and copper sulphate, as well as that of bathophenanthrolinedisulfonic acid (iron chelator) and bathocuproinedisulfonic acid (copper chelator) on the activity of laccases in the intra (IF) and extracellular fractions (EF) of the wild-type and the non-pathogenic mutant strain (rho1::hyg) of F. oxysporum. The results show that laccase activity in the IF fraction of the wild and mutant strain increased with the addition of iron chelator (53.4 and 114.32%; respectively). With copper, it is observed that there is an inhibition of the activity with the addition of CuSO4 for the EF of the wild and mutant strain (reduction of 82 and 62.6%; respectively) and for the IF of the mutant strain (54.8%). With the copper chelator a less laccase activity in the IF of the mutant strain was observed (reduction of 53.9%). The results obtained suggest a different regulation of intracellular laccases in the mutant strain compared with the wild type in presence of CuSO4 and copper chelator which may be due to the mutation in the rho gene.

Isolation, identification, and biocontrol of antagonistic bacterium against Botrytis cinerea after tomato harvest

ABSTRACT Tomato is one of the most important vegetables in the world. Decay after harvest is a major issue in the development of tomato industry. Currently, the most effective method for controlling decay after harvest is storage of tomato at low temperature combined with usage of chemical bactericide; however, long-term usage of chemical bactericide not only causes pathogen resistance but also is harmful for human health and environment. Biocontrol method for the management of disease after tomato harvest has great practical significance. In this study, antagonistic bacterium B-6-1 strain was isolated from the surface of tomato and identified as Enterobacter cowanii based on morphological characteristics and physiological and biochemical features combined with sequence analysis of 16SrDNA and ropB gene and construction of dendrogram. Effects of different concentrations of antagonistic bacterium E. cowanii suspension on antifungal activity after tomato harvest were analyzed by mycelium growth rate method. Results revealed that antifungal activity was also enhanced with increasing concentrations of antagonistic bacterium; inhibitory rates of 1 × 105 colony-forming units (cfu)/mL antagonistic bacterial solution on Fusarium verticillioides, Alternaria tenuissima, and Botrytis cinerea were 46.31%, 67.48%, and 75.67%, respectively. By using in vivo inoculation method, it was further confirmed that antagonistic bacterium could effectively inhibit the occurrence of B. cinerae after tomato harvest, biocontrol effect of 1 × 109 cfu/mL zymotic fluid reached up to 95.24%, and antagonistic bacterium E. cowanii has biocontrol potential against B. cinerea after harvest of fruits and vegetables.

Tricalcium phosphate solubilization and nitrogen fixation by newly isolated Aneurinibacillus aneurinilyticus CKMV1 from rhizosphere of Valeriana jatamansi and its growth promotional effect

Abstract Aneurinibacillus aneurinilyticus strain CKMV1 was isolated from rhizosphere of Valeriana jatamansi and possessed multiple plant growth promoting traits like production of phosphate solubilization (260 mg/L), nitrogen fixation (202.91 nmol ethylene mL-1 h-1), indole-3-acetic acid (IAA) (8.1 µg/mL), siderophores (61.60%), HCN (hydrogen cyanide) production and antifungal activity. We investigated the ability of isolate CKMV1 to solubilize insoluble P via mechanism of organic acid production. High-performance liquid chromatography (HPLC) study showed that isolate CKMV1 produced mainly gluconic (1.34%) and oxalic acids. However, genetic evidences for nitrogen fixation and phosphate solubilization by organic acid production have been reported first time for A. aneurinilyticus strain CKMV1. A unique combination of glucose dehydrogenase (gdh) gene and pyrroloquinoline quinone synthase (pqq) gene, a cofactor of gdh involved in phosphate solubilization has been elucidated. Nitrogenase (nif H) gene for nitrogen fixation was reported from A. aneurinilyticus. It was notable that isolate CKMV1 exhibited highest antifungal against Sclerotium rolfsii (93.58%) followed by Fusarium oxysporum (64.3%), Dematophora necatrix (52.71%), Rhizoctonia solani (91.58%), Alternaria sp. (71.08%) and Phytophthora sp. (71.37%). Remarkable increase was observed in seed germination (27.07%), shoot length (42.33%), root length (52.6%), shoot dry weight (62.01%) and root dry weight (45.7%) along with NPK (0.74, 0.36, 1.82%) content of tomato under net house condition. Isolate CKMV1 possessed traits related to plant growth promotion, therefore, could be a potential candidate for the development of biofertiliser or biocontrol agent and this is the first study to include the Aneurinibacillus as PGPR.

Inactivation of Listeria monocytogenes ATCC 7644 on fresh-cut tomato using nisin in combinations with organic salts

ABSTRACT The inhibition of Listeria monocytogenes ATCC 7644 on fresh-cut tomato was investigated using nisin alone, and in combinations with organic salts. Nisin at a concentration of 5000 UI/mL was introduced alone or in combination with an organic salt (sodium citrate or sodium acetate each at 3 and 5 g/100 mL each) on fresh-cut tomato previously inoculated with 108 CFU/mL of L. monocytogenes ATCC 7644. Chlorine at 200 ppm was used as a control. The inoculated samples were incubated at different temperatures (4, 10 and 25 °C) and examined at 0, 24, 48 and 72 h. The effects of the antimicrobial treatments on quality parameters of tomato (pH, soluble solids, titratable acidity and vitamin C) were also evaluated, and colour parameters were observed at the lowest storage temperature for 10 days. Both nisin and the organic salts inhibited growth of L. monocytogenes, but the combinations of two compounds were more effective. The nisin-sodium citrate (5%) combination was significantly (p ≤ 0.05) effective, while chlorine was least effective against L. monocytogenes. The quality parameters were substantially retained, especially at 4 °C, suggesting good shelf stability at a low temperature. These results substantiate the use of the cheap and eco-friendly approach to reducing this pathogen of health concern in common fresh produce.

Indole acetic acid and ACC deaminase from endophytic bacteria improves the growth of Solarium lycopersicum

Background: Endophytic bacteria are ubiquitous in all plant species contributing in host plant's nutrient uptake and helping the host to improve its growth. Moringa peregrina which is a medicinal plant, growing in arid region of Arabia, was assessed for the presence of endophytic bacterial strains. Results: PCR amplification and sequencing of 16S rRNA of bacterial endophytes revealed the 5 endophytic bacteria, in which 2 strains were from Sphingomonas sp.; 2 strains from Bacillus sp. and 1 from Methylobacterium genus. Among the endophytic bacterial strains, a strain of Bacillus subtilis LK14 has shown significant prospects in phosphate solubilization (clearing zone of 56.71 mm after 5 d), ACC deaminase (448.3 ± 2.91 nM α-ketobutyrate mg-1 h-1) and acid phosphatase activity (8.4 ± 1.2 nM mg-1 min-1). The endophytic bacteria were also assessed for their potential to produce indole-3-acetic acid (IAA). Among isolated strains, the initial spectrophotometry analysis showed significantly higher IAA production by Bacillus subtilis LK14. The diurnal production of IAA was quantified using multiple reactions monitoring method in UPLC/MS-MS. The analysis showed that LK14 produced the highest (8.7 uM) IAA on 14th d of growth. Looking at LK14 potentials, it was applied to Solanum lycopersicum, where it significantly increased the shoot and root biomass and chlorophyll (a and b) contents as compared to control plants. Conclusion: The study concludes that using endophytic bacterial strains can be bio-prospective for plant growth promotion, which might be an ideal strategy for improving growth of crops in marginal lands.

Detecção de Salmonella em tomates (Lycopersicon esculentum MILL) pelos métodos FDA-BAM e Mini Vidas ­ Biomérieux / Detection of Salmonella in tomatoes (Lycopersicon esculentum MILL) by FDA-BAM methods and Mini Vidas - Biomerieux

Diversos surtos de Salmonella ocasionados pelo consumo de tomate contaminados com este micro -organismo têm sido relatados ultimamente, o que torna primordial a investigação sobre a presença desse patógeno nesse alimento. Métodos que permitam a avaliação rápida da presença de Salmonella em alimentos são de suma importância. O objetivo desse estudo foi comparar o método tradicional da Food and Drug Administration - Bacteriologycal Analytical Manual (FDA-BAM) com um método rápido da mini Vitek Immuno Diagnostic System Assay (Mini­Vidas-SLM)-bioMérieux, para detecção de Salmonella Brazil inoculada artificialmente na superfície de tomates. Foram analisadas 215 amostras de tomates inoculadas artificialmente com Salmonella Brazil com níveis de inóculos variando de 0,4 a 940 UFC/tomate. Os resultados obtidos mostraram que os métodos estudados apresentaram uma ótima concordância entre si, para todas as faixas de inóculo analisadas.

Eficiencia de la desingección con aceites esenciales y ultrasonido sobre Escherichia coli inoculada en frutos de tomate y el impacto sobre la actividad antioxidante / Efficacy of disinfection treatments using essential oils and ultrasound on tomato fruits inoculated with escherichia coli and impact on antioxidant activity

La creciente demanda de frutos frescos puede constituir un riesgo para la salud de los consumidores, teniendo en cuenta la gran variedad de microorganismos que estos suelen albergar. El objetivo del presente estudio fue evaluar la eficacia de varios procedimientos de desinfección sobre Escherichia coli enterotoxigénica (enterotoxigenic E. coli [ETEC]) inoculada en tomate y la conservación de las propiedades antioxidantes de los frutos desinfectados. Los frutos fueron sumergidos durante 5 o 10min en dispersiones de aceites esenciales de orégano o tomillo (5 o 10ppm), combinados o no con la aplicación de ultrasonido. La actividad antioxidante se determinó por la neutralización del radical 2,2-difenil-1-pricrilhidrazil (DPPH) y se reportó como porcentaje de inhibición (%I). Los tratamientos de desinfección más eficaces para una significativa reducción log10 UFG/g (S) de ETEC fueron con 10ppm de aceite de orégano durante 10min, con reducciones S=3,05 en tratamientos individuales y S=4,03 en mixtos. Los %I más altos se lograron con tratamientos individuales con sonicación (69,52 y 72,48) y en tratamientos combinados con aceite de tomillo 5ppm y ultrasonido durante 5 y 10min, con valores de 51,27 y 53,31%, respectivamente

Fresh produce often harbors a great number of microorganisms; hence, its growing demand may constitute a risk for consumers. The aim of this study was to evaluate the efficacy of several disinfection procedures against enterotoxigenic Escherichia coli (ETEC) inoculated on tomato fruits and the conservation of the antioxidant properties of these disinfected fruits. Fruits were immersed for 5 or 10min in oregano or thyme essential oil dispersions (5, 10ppm), with or without ultrasound treatment. Antioxidant activity of disinfected fruits was determined as the ability to scavenge 2,2-diphenyl-1-pricrylhydrazyl (DPPH) radicals and was reported as percentage of inhibition (%I). The most efficient disinfectant treatments showing significant differences (p≤.05) between the reductions log10 CFU/g (S) of ETEC were those using 10ppm oregano for 10min, with S=3.05 in individual treatments and S=4.03 in mixed treatments. The highest %I was obtained with individual sonication treatments (69.52 and 72.48), while in combined treatments the %I values increased with thyme oil 5ppm and ultrasound for 5min (51.27%) and 10min (53.31%)

Chemical products induce resistance to Xanthomonas perforans in tomato

The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L⁻¹), fluazinam (0.25 g.L⁻¹), pyraclostrobin (0.08 g.L⁻¹), pyraclostrobin + methiran (0.02 g.L⁻¹ + 2.2 g.L⁻¹), copper oxychloride (1.50 g.L⁻¹), mancozeb + copper oxychloride (0.88 g.L⁻¹ + 0.60 g.L⁻¹), and oxytetracycline (0.40 g.L⁻¹)) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and β-1,3-glucanase in the Santa Clara cultivar.

Plant growth promoting capability and genetic diversity of bacteria isolated from mud volcano and lime cave of Andaman and Nicobar Islands

Twenty four bacterial strains from four different regions of mud volcano and lime cave were isolated to estimate their diversity, plant growth promoting and biocontrol activities to use them as inoculant strains in the fields. An excellent antagonistic effect against four plant pathogens and plant growth promoting properties such as IAA production, HCN production, phosphate solubilization, siderophore production, starch hydrolysis and hydrolytic enzymes syntheses were identified in OM5 (Pantoea agglomerans) and EM9 (Exiguobacterium sp.) of 24 studied isolates. Seeds (Chili and tomato) inoculation with plant growth promoting strains resulted in increased percentage of seedling emergence, root length and plant weight. Results indicated that co-inoculation gave a more pronounced effects on seedling emergence, secondary root numbers, primary root length and stem length, while inoculation by alone isolate showed a lower effect. Our results suggest that the mixed inocula of OM5 and EM9 strains as biofertilizers could significantly increase the production of food crops in Andaman archipelago by means of sustainable and organic agricultural system.

Microorganisms associated to tomato seedlings growing in saline culture act as osmoprotectant

Less than 0.5% of total water in the world is available for human consumption and agriculture. The major part of the world's water is saline and salinity in soils interferes in germination of seeds and the posterior development of the plant. In order to increase the osmotolerance of tomato, seedlings were associated with Azospirillum brasilense Cd, Azospirillum brasilense Cd transformed bacteria with a plasmid harboring a trehalose biosynthesis gene-fusion or Chlorella vulgaris. Two plant culture media: Hydroponic and Murashige and Skoog were tested. In the first set of studies seedlings were associated to single free cells meanwhile in a second set single and combined free cells were studied. A positive interaction between transformed Azospirillum and Chlorella vulagris and tomato plants was observed. Seedlings showed a salt concentration tolerance, as sodium chloride, up to 200 mM. According to our results, the association of plants with A. brasilense Cd-BIF and C. vulgaris is a viable approach to increase their salt tolerance and biomass, as consequence the possible use of sea water to irrigate horticultural plants.

In vitro Studies on Antimicrobial Activities of Lactic Acid Bacteria Isolated from Fresh Vegetables for Biocontrol of Tomato Pathogens.

Aims: This study was focused on using Lactic Acid Bacteria (LAB) isolated from fresh vegetables which has been molecularly identified for in vitro control of some tomato pathogens. Study Design: The inhibitory potentials of supernatant obtained from previously characterized LAB isolates or vegetable origin were investigated against some tomato phytopathogens using agar-well method with the view to develop biological agents for some tomato disease causing organisms. Place and Duration of Study: Biotechnology Centre of Federal University of Agriculture, Abeokuta, Ogun State, Nigeria, between January 2011 and February 2012. Methodology: The antimicrobial activities of LAB against some tomato phytopathogenic bacteria which include (Xanthomonas campestries, Erwinia caratovora, and Pseudomonas syringae) were obtained by using the agar well diffusion method. Results: The result indicates that cell free culture of LAB from fresh vegetables origin (Weissella paramesenteroides, Lactobacillus pentosus, Weissella cibaria, Pediococcus pentosaceus, Weissella kimchi and Lactobacillus plantarum) can inhibits these bacteria by creating clear zones of inhibition around the wells containing cell free supernatants of the above mentioned strains of lactic acid bacteria. Pediococcus pentosaceus showed the highest zone of inhibition against Xanthomonas campestries at 15 mm radius, Weissella kimchi was the least effective against Pseudomonas syringae at 3.67 mm and Erwinia caratovora at 3.50 mm radius. Conclusion: Tomato disease causing organisms can be most likely biologically controlled by using extracts from LAB. This finding will reduce the potential hazard from the use of chemical herbicides on plant.

Occurrence of Candida orthopsilosis in Brazilian tomato fruits (Lycopersicum esculentum Mill)

We aimed to isolate and identify yeasts found in the tomato fruit in order to obtain isolates with biotechnological potential, such as in control of fungal diseases that damage postharvest fruits. We identified Candida orthopsilosis strains LT18 and LT24. This is the first report of this yeast on Lycopersicum esculentum fruits in Brazil.

use of aqua ammonia for the control of soil borne diseases in tomato

The efficacy of aqua ammonia [NH[4]OH, 28% N] for the control of nematodes and Fusarium and Verticillium wilts on tomato was studied in three greenhouse experiments grown in infected soil plots in Lebanon. Aqua ammonia [NH[4]OH] was applied as diluted liquid in furrows and by a drip irrigation system at the rates of 50 [normal N fertilization rate], 75 and 100 mL m[-2] [double N fertilization rate]. Levels of control of aqua ammonia, applied as a single application before planting, were comparable to those of Agrocelhone [soil fumigant, mixture of Dichloropropene 55.4% + Chloropicrin 33.7%] achieved at a rate of 100 ml NH[4]OH m[-2]. Root galling in the control treatment was much higher than the other treatments. The yield and number of hairy roots of the control treatment were very restricted when compared to the NH[4]OH and Agrocelhone treatments.

Análise bromatológica de polpa de tomate industrial / Food analysis of tomato pulp industry

Os produtos industrializados derivados de tomate são tradicionalmente comercializados no Brasil, tendo atingido cerca de 362 mil toneladas em 1995. Ligado ao conceito de conveniência, os molhos prontos vêm se destacando no mercado nacional com 20% desta participação e constantes lançamentos de novas formulações, podendo ser encontrados nas diversas embalagens como metálicas (66%), vidro (6%) e cartonada (28%). Os molhos existentes no mercado brasileiro são do tipo “peneirado” ou “tradicional” (com pedaços de cebola e de tomate). Em geral os molhos prontos contém cebola, tomate, óleo comestível e ervas finas, sendo que algumas formulações incluem ainda pedaços de carne. O presente estudo teve como objetivo verificar a padronização com relação à rotulagem e avaliar a qualidade físico-química e microscópica das polpas de tomate disponíveis no mercado consumidor de Campos dos Goytacazes – RJ. Após a realização das pesquisas e observação dos resultados, conclui-se que apenas a marca “H” apresentou resultados diferentes em relação às outras marcas analisadas, foram eles: maior percentual de massa do que o indicado nas embalagens; alto teor de sólidos solúveis totais, conseqüentemente, alteração da densidade; alto percentual de acidez; baixo percentual de umidade e alto teor de sólidos totais.

Molecular battles between plant and pathogenic bacteria in the phyllosphere

The phyllosphere, i.e., the aerial parts of the plant, provides one of the most important niches for microbial colonization. This niche supports the survival and, often, proliferation of microbes such as fungi and bacteria with diverse lifestyles including epiphytes, saprophytes, and pathogens. Although most microbes may complete the life cycle on the leaf surface, pathogens must enter the leaf and multiply aggressively in the leaf interior. Natural surface openings, such as stomata, are important entry sites for bacteria. Stomata are known for their vital role in water transpiration and gas exchange between the plant and the environment that is essential for plant growth. Recent studies have shown that stomata can also play an active role in limiting bacterial invasion of both human and plant pathogenic bacteria as part of the plant innate immune system. As counter-defense, plant pathogens such as Pseudomonas syringae pv tomato (Pst) DC3000 use the virulence factor coronatine to suppress stomate-based defense. A novel and crucial early battleground in host-pathogen interaction in the phyllosphere has been discovered with broad implications in the study of bacterial pathogenesis, host immunity, and molecular ecology of bacterial diseases.

Biological control of Rhizoctonia solani in tomatoes with Trichoderma harzianum mutants

Biocontrol of Rhizoctonia solani in tomatoes cultivated under greenhouse and field conditions was analyzed using the Trichoderma harzianum mutants Th650-NG7, Th11A80.1, Th12A40.1, Th12C40.1 and Th12A10.1 and ThF2-1, respectively. Their innocuousness on tomato cultivars 92.95 and Gondola (greenhouse assays), and on cultivar Fortaleza (field assays) was established. Alginate pellets (1.7 g pellets/L soil) containing c.a1 x 10(5) colony forming units (cfu)/g pellet were applied to a soil previously inoculated with R. solani at transplant (greenhouse) or to a naturally infected soil (field). Controls considered parental wild strains, a chemical fungicide and no additions. Th11A 80.1, Th12A10.1 and Th650-NG7 prevented the 100% mortality of tomato plants cv. 92.95 caused by R. solani, and the 40% mortality in tomato plants cv. Gondola (greenhouse assays). Mortality reduction was reflected in canker level lessening and in plant parameters increases (development, fresh and dry weights). A different degree of susceptibility of tomato plants was observed, being Gondola cv. more resistant than 92.95 cv. to infection in a soil previously inoculated with R. solani. Tomato plants of cv. Fortaleza did not show mortality in naturally infected soils (field assays), where the mutant ThF2-1 reduced significantly the canker level caused by R. solani.

Optimization of worm-bed leachate for culturing of tomato (Lycopersicon esculentum Mill) inoculated with Glomus fasciculatum and Pseudomonas fluorescens

A response surface technique was used to analyze the effect of Glomus fasciculatum, Pseudomonas fluorescens and worm-bed leachate (WBL) on growth, yield and characteristics of tomato (Lycopersicon esculentum Mill). The treatments combined inoculation with or without P. fluorescensor G. fasciculatum and the application of WBL at 20% (v/v) each day or every three days. Plant height, number of leaves and yield of tomato fruits was not affected by the factors studied. However, plants with foliar application of WBL each day developed wider stems than those with an application every three days. The pH of the fruits was lower when WBL was applied every three days compared to a daily application. The soluble solids content of the fruits was higher when WBL was applied daily compared to those sprayed every three days. Plant development was not affected by addition of P. fluorescens, G. fasciculatum or WBL, but WBL changed fruit characteristics.