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  • Author or Editor: Javier Farías-Larios x
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The contribution of arbuscular endomycorrhizal fungus (AMF) on hormonal levels increase in chili plants, at different steps is currently unknown. In this experiment was evaluated the effect of Glomus sp. Zac-19, G. etunicatum and G. intraradices, inoculation mirasol and ancho cultivars, under greenhouse conditions. Plants were growing in pots containing 1 kg of substrate (3 sand: 1 soil ratio). The effect was measured on fresh fruit production and indolacetic acid, giberellin GA3 and 6-aminopurine concentration. Also plant parameters measured were: plant height, foliar area, stem diameter, root length, aerial fresh weight, total fresh weight, fruit weight and mycorrhizal colonization. All treatments were imposed using 16 replications in a full random design. Results shown that mycorrhizal colonization average of the three fungus was 44% in mirasol cultivar y 42% in ancho cultivar. Mycorrhizal colonization had an effect on growth and development in both cultivars, expressed in a greater height, leaf number, foliar area, total fresh weigh and fruit mass. Was registered an increase of 80% in the yield in inoculated plants respecting to control. Indolacetic acid and gibberellins concentration in shoots, were bigger in plants colonized by arbuscular mycorrhizal fungus (AMF) than in control. The 6-aminopurine levels in roots of colonized plants by AMF shown higher values. These results suggest that AM fungi modify the hormonal concentration and some growth factors in chili plants.

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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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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.

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Scyphophorus acupunctatus is the main pest of Agave tequilana. Its adults are vectors of Erwinia carotovora, which causes plant destruction. The susceptibility of S. acupunctatus larvae to various strains of entomopathogenic nematodes has been demonstrated previously (Molina et al., 2004). In the current paper, the use of seven different concentrations: 0, 10, 20, 50, 100, 200, and 500, of infected juveniles per larva in petri dishes containing a filter paper against Steinernema carpocapsae strains All, Ca, and Fl, and also against native insolated N1, N2, N4, belonging to the genera Steinernema sp. The studies were conducted under laboratory conditions to determine the susceptibility of S. acupunctatus larvae to entomopathogenic nematodes. One hundred percent mortality of S. acupunctatus larvae was achieved by S. carpocapsae strains All, Ca, and Fl with exposure to 100 infected juveniles. In the case of native isolates, N2 registered 95% mortality, and for N4 and N1, mortality registered was 75%. An analysis of variance was conducted in order to determine whether strain or isolate had the highest virulence against S. acupunctatus larvae. Means for S. acupunctatus larvae by entomopathogenic nematodes presented significant differences (F = 57.01; df = 55, 223; P < 0.0001), resulting in two levels. At the first level, S. carpocapsae All, Fl, and Ca are statistically the same as isolate N4. At the second level, the isolates N4 and N1 are statistically the same. The results indicate the high susceptibility of S. acupunctatus larvae. The infectivity of native isolates as well as S. carpocapsae strains All, Fl, and Ca are associated with the symbiotic bacterium Xenorharbdus sp., suggesting they have potential for use against S. acupunctatus larvae.

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