Results (8):

Potentiality in controlling nematode infection on tomato roots by indigenous arbuscular mycorrhizal fungi

HORTICULTURE | Mondino, E. A.; Thougnon Islas, A. J.; Covacevich, F.

Tags: mycorrhizal biocontrol, Meloidogyne incognita, inoculation

PDF 720.2 KB (21 downloads)

Our objective was to evaluate the suppression of root infection by the nematode Meloidogyne incognita in tomato roots previously colonized by arbuscular mycorrhizal fungi (HMA) native of Buenos Aires Province. Tomato plants were inoculated at sowing with a consortiumcontaining HMA= HMA0, HMA50 and HMA100 corresponding to 0, 50% and 100% of substrate with HMA (8 replications). At 40 days, inoculated plants showed HMA colonization higher than 60%. Plants were transplanted and each treatment was inoculated or not with M. incognita (4 replications of each nematode inoculation treatment). At harvest (115 days of growth) plants inoculated with HMA without nematodes showed mycorrhizal colonization higher than 90%. Although plants inoculated with nematodes showed decreases of mycorrhizal colonization, the obtained levels were higher than colonization prior to transplant. Inoculation with HMA decreased both soil abundance of nematode larvae (j2) and number of root galls. Although aerial growth of tomato was not affected by inoculation (HMA or nematodes), HMA0 plants (independently of nematode inoculation) showed higher root growth, that can be considered a strategy of the plant in order to compensate the lower volume of root exploration in the absence of HMA hyphae. Our results showed reduction of nematode density (j2, galls and egg masses) after inoculation of tomato with HMA. It may be concluded that the adequate establishment of mycorrhizal colonization prior to infection with nematodes exerts an apparent control of the infection of the M. incognita nematode in tomato roots. It could be a strategic tool for the biological control of pathogens of horticultural crops.

Application of plant growth promoting rhizobacteria as biological control of Sclerotium rolfsii in tomato.

HORTICULTURE | Regeiro D. B, Molina C, Riva D. S, Llamazares Vegh J. F, Ribaudo C. M

Tags: defensin, snakin, Solanum lycopersycum, PGPRs, Sclerotium rolfsii

PDF 916.8 KB (91 downloads)

Tomato crop is one of the most important vegetables because of its high demand. During the crop cycle it can be attacked by different pathogens, so the use of Plant Growth Promoting Rhizobacteria (PGPR) is an option for the protection of plants against pathogens. PGPR can be set endophytically inside the plant and trigger various defense mechanisms. One such mechanism is the synthesis of antimicrobial peptides. The aim of this research was to evaluate the protection of Solanum lycopersicum var. Río Grande previously inoculated with PGPR against infection with the necrotrophic pathogen, Sclerotium rolfsii. The percentage of mortality and peptides: defensin and snaking expression were evaluated. Combined experiments with Pseudomonas pseudoalcaligenes and Azospirillum brasilense inoculation and subsequent confrontation with S. rolfsii were performed. In plants treated with P. pseudoalcaligenes, mortality percentage was 40% lower than in control plants. Plants treated with A. brasilense were 20% lower. The expression of defensin and snakin messengers was higher in both cases for plants inoculated with PGPR. Based on these results, the use of PGPR is proposed as a biological alternative against S. rolfsii and could be evaluated for other soil pathogens.  

Applications of mushrooms residual substrate in horticultural production

HORTICULTURE | Postemsky, P. D.; López-Castro, R. I.

Tags: Agaricus sp , biotransformation, Ganoderma lucidum, humification, lignocelullose, Pleurotus sp , solid-state fermentation

PDF 515.5 KB (27 downloads)

The cultivation of edible and medicinal mushrooms generates large volumes of substrate degraded by fungi (SDF). Mushroom cultivation implies a solid-state fermentation (SSF) with production of fungal metabolites and the consequent biodegradation of lignocellulosic materials. SSF accelerates organic matter mineralization; therefore, at the end of the cultivation cycle, SDH has greater stability than the original substrate. SDF properties depend largely on whether prior to inoculation of the mushroom species, the starting substrate is composted or just decontaminated. In the first case, the cultivated mushroom species are more substrate-sensitive. In the latter, the mushroom species used are more substrate-adaptable, and are the most widely adopted by small and medium-sized producers as well. After mushroom cultivation, SDF is removed from the production site. Henceforth, depending on its further use, certain storage conditions should be observed, and physical and/or chemical conditioning is usually needed. In horticulture, particle size reduction and dilution of excess salts, by mixing with other materials or leaching, are especially required. The aim of this review is to highlight SDF’s potential as a valuable resource. Particularly, the physical and chemical properties of SDF reported in the literature are summarized, and its different uses evaluated in horticultural systems are described. Among these are: substrate for seedlings, soil amendment and biofertilizer.

Response of butterhead lettuce seedlings to the inoculation with a formulation composed of three strains of Azospirillum brasilense

HORTICULTURE | Garbi, M.; Carletti, S.; Sillon, C.; Vita, F.

Tags: biofertilizer, Lactuca sativa L, PGPR

PDF 373.1 KB (103 downloads)

Vegetables inoculation with Azospirillum sp. enhances seedling growth and crop productivity. In lettuce (Lactuca sativa L.), inoculation with Az39, Pl64 and Pl3 strains of A. brasilense improved seedlings growth. The aim of this work is to evaluate morphological modifications of seedlings when these strains are combined in a formulation. Three trials were carried out using butterhead lettuce cv. Lores (Vilmorin®), performing the inoculation at sowing with a formulation which consisted of 1 x 107 of a mixture of the strains Az39, Pl64 y Pl3 of A. brasilense, using not inoculated plants as control. It was dispensed 1ml of product per cell (1 x 107 UFC per seed). A completely randomized design with 20 replications was used. When plants showed 4 leaves, it was registered shoots, roots and plant fresh and dry weight, root absorption area and lineal length of root, submitting data to analysis of variance. Inoculated plants performed different depending on crop season. Root absorption area increased significantly in one of the three trials, exceeding the control by 27 %. Leaf, root and plant fresh weight were significantly higher in two trials, reaching values 11 %, 20 % and 12 % higher than control plants, respectively. No significant differences were observed on root length or dry weight.

Influence of aqueous extracts of Johnson grass rhizomes on mycorrhizal colonization and plant growth of Mentha x piperita L.

AROMATICS | Arango, C.; Ruscitti, M.; Ronco, M. y Beltrano, J.

Tags: Phylum Glomeromycota, allelopathy, mycorrhiza, succinate deshydrogenase, photosynthesis

PDF 458 KB (18 downloads)

The aim of this work was to evaluate the effects of aqueous extracts of rhizomes of Sorghum halepense on mycorrhizal colonization, succinate dehydrogenase activity, total dry weight, relative conductivity cell membrane and net photosynthesis in Mentha x piperita plants. Rooted cuttings non inoculated or inoculated with Glomus intraradices or Glomus mosseae grown during 60 days into an inert tyndallized substrate, irrigated with Hoagland solution and four concentrations of aqueous extracts of Johnson grass rhizomes: 0 %, 5 %, 10 % and 15 %. The experiment was carried out in a greenhouse, in 3 x 4 factorial arrangement, in completely randomized design. The higher mycorrhizal colonization occur in treatments without Johnson grass, 87 % and 92 % by G. mosseae y G. intraradices respectively, and decreasing significantly with the higher doses of extract. The fungus structures viability decreasing significantly with the higher doses of extract, and the mycorrhizal dependency increased by 35 % with the highest dose of extract. The higher concentrations of extract reduced the total biomass and photosynthesis, and increase the relative conductivity the membranes of leaves and roots. The inoculated plants showed a better performance than non-inoculated. Aqueous extracts of Johnson grass decreased plant growth while inoculation with mycorrhizal fungi reduces adverse effects.

Survival of Clavibacter michiganensis subsp. michiganensis, causal agent of tomato bacterial canker, on trellising materials

HORTICULTURE | Maeso, D.; Arboleya, J. y Walasek, W.

Tags: Plastic ties, giant reed cane

PDF 495.7 KB (50 downloads)

Bacterial canker (Clavibacter michiganensis subsp. michiganensis, Cmm) is one of the most important tomato diseases in Uruguay. Crop rotation with non susceptible hosts is recommended to decrease soil inoculum level. Its efficacy depends on pathogen survival in the field, on trellising materials or on its re-introduction. Cmm survival in pieces of polypropylene ties and of giant reed cane (Arundo donax L) artificially inoculated was studied in laboratory conditions. They were inoculated by immersion in a 2 x 108 ufc·mL-1 Cmm solution in saline buffer for two hours. The presence of Cmm was analyzed 0, 1, 7, 14, 30, 60, 90, 180, 240 and 365 days post inoculation by plating on each date ten plates of nutrient agar dextrose media containing five pieces each. Concentration of bacteria developed on each plate was estimated by the OD 590 nm after resuspension in 7 mL saline buffer. Data were analized on a randomized block design with ten replications (plates). Cmm survival in cane was less than seven days and lower to 100 %, while that of the ties exceeded one year and was 100 % until 240 days. OD 590 nm decreased with days post inoculation. It was confirmed a longer pathogen survival on ties.

Synergistic effect of the combination of soil solarization and Pseudomonas fluorescens P190 inoculation on greenhouse tomate yield

HORTICULTURE | Reybet, G.E.; Bustamante, A.P.; Reybet, C.M.; Bramardi, S. y Escande, A.R.

Tags: Bacterization, Lycopersicon esculentum, soil heating

PDF 540 KB (21 downloads)

The effects of soil solarization and the growth promoter rhizobacteria, Pseudomonas fluorescens P190 on tomato (Lycopersicon esculentum), grown under greenhouse conditions, were evaluated in 2006 and 2007. A trial was performed according to a factorial arrangement, using “solarization” and “pseudomonas” as factors and “presence” and “absence” as levels for each factor. Eight variables were recorded in order to evaluate treatments effect: weight and diameter of each fruit -disregarding those showing either damage or less than commercial size- as well as root, stem and leaf fresh and dry weight. Main component analysis was used to characterize experimental units as regards the presence or absence of the studied factors. ANOVA analysis and LSD means comparison test results showed that, both solarization and seed inoculation by themselves, increased crop yield by 15 % when considered separately. When combined, a synergistic effect was apparent, and crop yield was increased by 55 % as related to the control treatment.

Timing of copper sprays to control citrus canker on leaves of lemon in Famaillá, Tucumán

FRUTICULTURE | Velazquez, P.D.

Tags: Citrus limon, Xanthomonas axonopodis, copper

PDF 296.2 KB (104 downloads)

Due to the recent occurrence of citrus canker in the NW region of Argentina there is a lack of information locally generated about the optimum timing of copper sprays for its chemical replica The disease is endemic in the NE of Argentina and successful programs of sprays were generated in that region. The objective of this work was to determine the timing of copper sprays to control canker on leaves of Limoneira 8A lemon in Famaillá, Tucumán. Sprays of copper oxychloride 50 % WP Cupravit® (50 % Cu) were applied at high pressure and high volume until run-off on three leaf-flushes: January 2004, February 2004 and November 2004, and to 0, 14, 21 and 28 days after initiation of shoot development. The incidence of canker (%) on the shoots and leaves was determined 30 days after the last spray application.replica watches uk The best results were obtained when leaf-flushes were sprayed at initiation of shoot development (3.6 cm in length) and until 14 days old (10.6 cm in length).replica watches The spray applied in this period achieved the lowest levels of incidence. These results were very similar to those obtained in the NE indicating that the programs developed in that region can be applied to control citrus canker on lemon in Famaillá, Tucumán.