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G.S. Guzman, I.C.A Alvarez, and L.J. Farias

In the commercial production of silver king plants and other ornate plants, the substrates are treated with fungicides, which affect the vesicular–arbuscular mycorrhizal (VAM) fungi and the plant growth negatively. The restoration of de VAM fungi to the substrate, after its disinfection, might improvement the development. The effectiveness and infectiveness of Glomus fasciculatum and Glomus aggregatum on silver king (Aglaonema commutatum) plants was evaluated in this work. Seedlings of 4-week-old, growing treated with mancozeb, were removed and planted in pots filled with a disinfected mixture of sand soil, cow manure and coconut powder (1:2:2), containing the inoculum of VAM fungi (soil with spores and colonized roots). After 3 and 4 months of the inoculation, plants were removed and dry weight of roots and shoot, number and length of leaves, and mycorrhizal colonization were evaluated. A better development was showed in plants inoculated, resulting highest values in number and length of leaves in relation to control plants. Both VAM fungi improvement the number and length of leaves. The percentage root length colonized (80%) and visual density of endophyte in roots was highest in plants inoculated with Glomus aggregatum in both sampling period.

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S. Guzman, H. Alejandro, J. Farias, A. Michel, and G. Lopez

Watermelon (Citrullus vulgaris Schrad.) is a widely grown crop throughout the tropics and subtropics. In Mexico, it is an economically important crop. In vitro adventitious shoot regeneration of watermelon has been reported from shoot tip culture, leaf, hypocotyl, and cotyledons. Hence, the objective of this study was to evaluate in vitro plant regeneration from axillary buds of triploid watermelon. Axillary buds explants were prepared from shoot of commercial cultivar in field of 60 old day plants. Explants of 2 to 3 mm were incubated 2 weeks on Murashige and Skoog (MS) shoot regeneration medium containing 2.5 mg/L kinetin (KT) or indole-3-butyric acid (IBA), or gibberellic acid (GA3), followed by 3 weeks on shoot elongation medium supplemented with different combinations of the same phytohormones. The percentage of explants (83% to 90%) that produced shoots, expansion in size of explant (0.81–1 cm) and shoot length (6 mm) were highest in MS medium containing KT or IBA. In the shoot elongation step, shoot length (0.9–1 cm) and leaves number (6–7) were highest in MS medium supplemented with 2.5 mg/L of KT or GA3 and 0.2 mg/L IBA, but the better induction of roots in elongated shoot occurred on MS medium with 2.5 mg/L KT and 0.2 mg/L IBA. The results show that axillary buds from watermelon is an alternative for the micropropagation of this crop.

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A. Michel-Rosales, J. Farias, S. Guzman, G. Lopez, and G. Valdovinos

In western Mexico, banana is traditionally multiplied by vegetative reproduction in the orchard; recently, micropropagation of this species has increased considerably. Banana has been shown to give a positive response to AM fungal inoculation. However, the selection of efficient AM fungi species, currently propagated in vitro, has not been documented. The selection of the most-effective arbuscular mycorrhizal (AM) fungi for growth enhancement of banana vitroplants is the first step toward development of an AM inoculation system. This work reports the effect of nursery inoculation of Glomus aggregatum, G. clarum, G. etunicatum, G. intraradices, G. monosporum, G. mosseae, and Gigaspora margarita on the banana vitroplants growth. Pots (4 kg) containing a mixture of soil and coconut fiber (1:1) sterilized with methyl bromide were used. Treatments were arranged under a fully randomized experimental design with eight replications. The plants were harvested 120 days after inoculation and plant height, number of leaves, leaf area, fresh weight of roots, mycorrhizal colonization, and intensity of infection were measured. Glomus etunicatum, G. monosporum, G. mosseae, and G. aggregatum were shown to be the most-effective endophytes. Plant height was increased, as well as the production of banana roots in response to mycorrhizal inoculation with these fungi. On the other hand, G. intraradices and G. clarum showed low levels of colonization. The data clearly show the most efficient AM fungi for future inoculation studies in nursery banana production.

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G.S. Guzmán, O.C.E. Cuevas, L.J. Farias, and S.M. Orozco

Citrus macrophylla is an important citrus rootstock for Mexican lemon (Citrus aurantifolia S.). Citrus are highly dependent of vesicular–arbuscular mycorrhizal (VAM) fungi. Four Glomus species were screened for their symbiotic response with C. macrophylla. Seedlings were inoculated with VAM fungi in pots containing sterilized soil. After 3 and 4 months, plants were harvested. Glomus fasciculatum (following by G. intraradices) gave the greatest improvements in growth, resulting in larger plant height and higher shoot dry weight. Glomus aggregatum, G. mosseae, and control plants showed the lowest rates of growth. Plants inoculated with the first three species showed the highest percent of root length colonized. However G. aggregatum gave the highest values of visual density of endophyte in root and soil hyphae. Root colonization and soil hyphae were lowest in plants with G. mosseae.

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J.G. Lopez-Aguirre, J. Molina-Ochoa, J. Farias-Larios, S. Guzman-Gonzalez, and A. Michel-Rosales

Amelioration and/or reclamation of saline and non-saline soils is based on the application of high quantities of agrochemical products or high volumes of water, which causes an injury in soil or downward displacement of nutrients to the lower layers in soils. Research was conducted to evaluate the effect of application of citric industry waste on saline and non-saline soil. The waste has an electrical conductivity (EC) of 2.7 dS/m and pH of 3–4.2, 35% is organic material that is readily decomposed. This experiment was carried out on field conditions using applications of three different volumes, T1 = 3200, T2 = 6400, and T3 = 9600 m3·ha–1·m–1 and a control, no-waste, (T0), using just irrigation water (EC = 2.5 dS·m–1). The same treatments were added to non-saline soil. Effect of citric industry waste application in both saline and non-saline soils was similar. In all the treatments, EC was decreased with respect to T0 and soil before application (BA), the largest decrease was found in T3. pH decreased in the top soil layer much more than in the bottom layers. Ions were decreased in all soil profile. Organic matter (OM) was increased in the profile in treatment T1 with respect to treatment T0, as well as in the top soil layers in T2 and T3, but no changes were detected in the remainder of the layers in treatments T2 and T3. We can suggest that the waste studied can be used in the amelioration of saline and non-saline soils.