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Mario Orozco-Santos, Javier Farías-Larios, Jaime Molina-Ochoa, and José Gerardo López-Aguirre

Development of resistance to chemical pesticides has been reported in about 150 plant pathogenic species, mostly fungi. Biocontrol of plant pathogens is an alternative to chemical pesticides. Actually, there are products formulated with beneficial microorganisms, such as mycorrhizal fungi, rhizobacteria, antagonistic fungi, and others. The objective was to evaluate the development of Fusarium oxysporum f. sp. melonis (FOM) on melon plants inoculated with commercial biological formulations based on beneficial microorganisms. Twelve treatments were evaluated: T1) VAM media nursery + FOM; T2) Hortic Plus + FOM; T3) BioPak F + FOM; T4) Glomus intraradices + FOM; T5) FOM; T6) control; T7) VAM media nursery; T8) Hortic Plus; T9) BioPak F; T10) Glomus intraradices; T11) FOM + Mancozeb wp80; and T12) FOM + BioPak F. The melon cultivar used was `Colima' (Peto Seed Co.). Seeds were planted in Styrofoam growing containers containing coconut fiber powder as substrate. One seed was planted per cell and maintained until transplanting. Plants were transplanted to pots containing sterile soils 13 days postemergence. Inoculation of treatments with Fusarium was made with a concentrated suspension at 1 × 106 conidia/mL. For inoculation with beneficial microorganisms, manufacturer specifications were followed. A completely randomized design with 12 treatments and 12 replications was used to estimate the incidence of Fusarium, number of leaves, leaf area, root biomass, and percentage of roots colonized by mycorrhizal fungi. Overall, T10 showed the best behavior in all variables. Inoculation of cantaloupe plants with Fusarium affected their performance, but those treatments including mycorrhizal fungi enhanced their performance withstanding the damage by Fusarium.

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Mario Orozco-Santos, Javier Farías-Larios, José Gerardo López-Aguirre, and Jaime Molina-Ochoa

In the Pacific Central region of Mexico, 17,000 ha are cultivated with cucurbitaceous crops. Most are affected with wilt caused by Fusarium oxysporum f. sp. melonis. The use of fungicides, such as methyl bromide, for soil disinfecting is a common practice; however, this practice has adverse effects on beneficial microorganisms, and soil is rapidly infected again. Soil solarization is a sustainable alternative, and it is feasible to be integrated in production systems. It has been used to delay the establishment of symptoms and to reduce the incidence of fusarium wilt in watermelon fields. The objective of this study was to evaluate the effect of soil solarization and methyl bromide on control of fusarium wilt on cantaloupes in western Mexico. The experiment was conducted in the Ranch Fatima located in the municipality of Colima. Severe wilt incidence and damage were previously observed in the cantaloupe cultivar Impac. Dripping irrigation system was used. Treatments established were: 1) solarization; 2) solarization + vermicompost; 3) solarization + chemical products [methyl bromide + chloropicrine (98/2%)]; 4) methyl bromide; and 5) control (without solarization or chemicals). Soil solarization was done during the 6 months before planting using clear plastic mulching (110 thick). A completely randomized design with five treatments and four replications was used. Six beds, 10 m long and 1.5 m wide, were used as experimental unit. Variables registered were: leaf area, leaf number, dry and fresh weight, propagule number, soil temperature, number of diseased plants showing wilt symptoms, and yield. Treatments 1 and 3 exhibited the highest agronomic variable values, and best control of fusarium wilt and fruit yields.

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Mario Orozco-Santos, Javier Farías-Larios, Jaime Molina-Ochoa, and José Gerardo López-Aguirre

Melon wilt (MW) is one of the main diseases affecting the cucurbitaceous crops in the Pacific Central region of Mexico. The use of resistant varieties is the most effective strategy to reduce the damage caused by MW; however, variety performance depends on the fungal race occurring in the field. The use of fungicides, such as benzimidazols and methyl bromide, is a common practice, but there are contamination concerns, and a search is on for alternatives to diminish the negative effects on the agro-ecosystem. The aim was to determine the effect of the application of soil amendments and mulching on the incidence of MW, and on melon yield. Soil amendments incorporated were: rice straw (3 t·ha-1); compost 1, prepared with chicken and bovine manure, and banana and orange wastes (5.7 t·ha-1); compost 2, prepared with bovine and horse manure, coconut wastes and grasses (8 t·ha-1), vermicompost (3 t·ha-1), and a control. All treatments were established using transparent mulching during 21 days. The number of MW propagules in amended soils were similar at 5, 10, and 20 cm deep, but the percentage of diseased plants was higher (4.5%) in the control, which could be caused by the incidence of other fungi propagules, perhaps antagonistic, that contributed in diminishing the MW when compared with the control. The fruit weights and fruit sizes were not different between treatments on small (21–30 sizes), medium (15–18 sizes), and large (9–12 sizes), but total fruit numbers were 1.15-, 1.07-, 0.99-, and 1.09-fold higher when compared with the control. The application of soil amendments affected the antagonistic fungal populations even when it did not affect the cantaloupe yield. We suggest that soil amendments will improve soil fertility and increase melon yields, and studies are currently running.

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Marcelino Bazán Tene, Javier Farías Larios, José Gerardo López Aguirre, Francisco Radillo Juárez, and Jorge Rogelio Flores Sánchez

Production of horticultural crops is important throughout the world, with high consumption mainly in Europe and the United States of America. Cucumber is consumed both fresh and processed. This vegetable generates important profits for producing countries such as Mexico, which, in 2003, produced 435,897 tons of fresh fruit with a value of 1.190 million Mexican pesos (around USD $109 million). The objective of this work was to evaluate the effect of the floating cover on the yield of fresh cucumbers. Four treatments and five repetitions were imposed in a randomized distribution: covered 20 days (C20) post-emergence, covered until beginning of flowering (CF), covered until beginning of harvest (CIC), and without cover (SC). Data at the first and fourth harvest were analyzed. Results showed that, in the first harvest, treatment C20 days was highest in fruit yield (3.11 ton/ha); Treatment CIC had 2.47 ton/ha, and SC produced 1.66 ton/ha. Data obtained in the fourth harvest, treatment C20, had the highest yield, with 24.12 ton/ha, and treatment CF had a yield of 21.11 ton/ha, but there was not significant difference (Tukey's P < 0.05).

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Alejandra Guadalupe Zamora-Solís, Marcelino Bazan-Tene, Javier Farias-Larios, Jose Gerardo López-Aguirre, and Jaime Molina-Ochoa

Distribution of salinity and sodicity through the world is around 80 thousand million km2. To this quantity, we must add 10 million ha of irrigated lands that are abandoned each year due to such adverse effects on irrigation as salinity and/or alkalinity. Easily available substrates, such as glucose, increase the microbial activity to imprpove soils; for example, pH decreases because of a high production of some metabolites, such as carboxylic acids and hydro phenolics group. We carried out a study to evaluate the effect of glucose application on tomato plant (Lycopersicum esculentum Mill.) growth in saline soil. The experiment was done under greenhouse conditions. Soil samples were taken from 0–20-cm depth at the “El Chococo” ranch (lat. 18°47'N; long. 103°55'W). Treatments imposed were: 2% (T1), 4% (T2), and 6% (T3) glucose and a control without glucose (T0). Soil with treatments was incubated at ambient temperature for 40 days. Tomato seeds were germinated for 30 days and later transplanted to plastic bags that contained treatments. After transplant, tomato plants were grown for 40 days and then evaluated for plant height, dry and fresh weight, aerial and radicular biomass, and foliar area. Treatments were distributed under randomized design, and Tukey's (0.05) separation means were done. When the glucose percentage was increased, the soil pH decreased 8.50, 8.0, 7.70, and 7.60 in T0, T1, T2, and T3, respectively, but electrical conductivity increased. The highest values of parameters evaluated in plants were measured in treatment T3, and all the plants died in treatment (0).

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Orlando Javier Torres-Meza, Marcelino Bazan-Tene, Javier Farias-Larios, Jose Gerardo Lopez-Aguirre, and Jaime Molina-Ochoa

Low organic matter in soil is a large problem in crop production around the world because it affects physical, chemical, microbiological, and morphological properties. On the other hand, regions with agro-industry generally generate waste that can cause some level of contamination. Therefore, it is necessary to find some use for this kind of waste. This study was done to evaluate the effect of lemon industrial waste on tomato (Lycopersicum esculentum Mill.), growth in a saline soil. The experiment was conducted under greenhouse conditions. Soil samples were taken from 0- to 20-cm depths at the El Chococo ranch, located at 18°47'N and 103°55'W. Four treatments were imposed: 0 (0), 600 (1), 1200 (2), and 1800 (3) m3/ha. Soil in treatments was incubated at ambient temperature for 40 days. Tomato seeds were germinated for 30 days and later transplanted to plastic bags containing treatments. After transplant, tomato plants were grown during 40 days, after which was measured: high plant, dry and fresh weight, aerial, and radicular biomass and foliar area. Treatments were distributed under randomized design, and Tukey's (0.05) separation means was performed. Organic matter, pH, and CE in soil before treatment application was 1.01%, 8.5, and 7.6 dS/m respectively (in 1:5 soil: water ratio). After application, OM increased until 3.7% in treatment 3. pH and CE decreased to 5.5 in treatment 2, and 1.57 dS/m in treatment 0. All data measured in plants had the highest values in treatment 1, and all plants died in treatment 0. We believe that is necessary to do this experiment in the field to obtain additional data.

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Guillermo Rodríguez, Sergio Aguilar-Espinosa, Eugenio Perez-Molphe Balch, María del Rocío Flores-Bello, Javier Farias-Larios, and José Gerardo López-Aguirre

The present work is the first report in vitro on root induction of Agave salmiana Otto, using Agrobacterium rhizogenes. Several concentrations of bacteria and acetosyringone were used, and different inoculation sites were tested, such as leaves, shaft, and root. Incubation time in darkness was 6 days. The transformed adventitious roots appeared 25 days after inoculation. The best treatment was when the shaft was inoculated with: 1 × 108 bacteria/mL and 100 μm acetosyringone; in this treatment, induction of transformed roots was 57.5% in the inoculated sites. The activity and presence of the foreign genes in the transformed roots of A. salmianawere verified as follows: 1) histochemical staining for GUS activity was determined in 80% of the tested root; and 2) molecular analysis via PCR was made to verify the presence of nptII gene and rol B gene (both were present in 60% of the tested root). This is the first report of the arbuscular mycorrhizal colonization on wild roots and transformed roots of Agavewith Glomus intraradicesSchenck and Smith. The result of the monoxenic culture was as follows: mother spore germinated 5 days; the colonization of the transformed roots was 70%. Then we proceeded to the recovery of daughter spores, in which we obtained an average 300 daughter spores per petri dish, 6 months after inoculation.