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J. Farias-Larios, M. Orozco, S. Guzman, and A. Gutiirrez

Sweetpotato whitefly (Bemisia tabaci Gennadius) is one of the serious pests on cucurbits and causes injury by sucking sap and by the transmission of virus. In Western Mexico, melon and other vegetable crops have been subjected to losses as a results of whitefly feeding and whitefly-transmitted virus infection. Traditional control is based in the Metamidophos and Endosulfan applications (more than 10 times). Recently, Imidacloprid has been reported as new alternative to whitefly control. Thus, this study was conducted to determine the effect of Imidacloprid under different applications methods on sweetpotato whitefly populations and cantaloupe yield. Ten treatments were evaluated: 1) seed + basal stem, 2) seed + soil at 8 cm, 3) seed + soil (near to seed), 4) seed + soil (seedlings emergence), 5) seed only, 6) basal stem, 7) soil (plant emerged), 8) foliage, 9) Metamidophos and Endosulfan (regional application), and 10) control, without application. These were arranged in a randomized complete-block design with four replications. Each replication had four beds 7.5 m long. Number of whitefly adults was determined weekly on 24 plants selected at random for each treatment (two leaves/plant). At 22, 39, 57, and 73 days after showing, the whitefly nymphs/cm2 were also counted. Imidacloprid applied to foliage five times showed the best whitefly control during the entire crop season, reducing injury and increasing melon yield at 1346.7 cartons/ha, while Metamidophos and Endosulfan showed an intermediate effect (1073.6 cartons/ha).

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J. Farias-Larios, S. Guzman-Gonzalez, and A. Michel-Rosales

The productivity of marginal soils frequently found in the arid tropics might be improved by using VAM fungi as “biofertilizer” and as a tool of sustainable agricultural systems. Study of mycorrhizas of fruit trees was performed in 1987 in western Mexico. More progress has been made in resources, taxonomy, anatomy and morphology, physiology, ecology, effects, and application of mycorrhizas in fruit trees and ornamental plants production. Currently, five genera has been identified and inoculated plants showed significant difference in respect to plants not inoculated with mycorrhizal fungi. Citrus trees were highly dependent on mycorrhizae for normal growth and development, while the banana plants showed lower levels of root colonization by different strains of VAM fungi. The added endomycorrhizal inoculum significantly increased root fungal colonization in fruit trees and reduce the time in nursery. The current status and research trends in the study of fruit tree mycorrhizas in western Mexico are introduced, and the application prospects in sustainable agriculture also are discussed.

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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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J. Farias-Larios, M. Orozco, S. Guzman, and J. Perez

This work was conducted for evaluate the influence of clear and black polyethylene mulches, used alone or combined with floating rowcover (FRC) and plastic perforated microtunnels, on insect populations, growth and yield of muskmelon. Treatments evaluated were 1) clear plastic + FRC, 2) polyethylene perforated microtunnel, 3) clear plastic + polyethylene not perforated microtunnel, 4) black plastic + FRC, 5) clear plastic, 6) black polyethylene, 7) clear plastic + oil, and 8) bare soil. Aphids and sweetpotato whitefly adults and nymphs were completely excluded by floating rowcovers while the plots covered. The export and national quality fruit yield was major in the mulched beds in relation to control. Clear polyethylene mulch + FRC increased number of fruit and export marketable fruit of cantaloupe (45.2% and 44.8%) with respect to black plastic + FRC, respectively. It is proposed that, under tropical conditions and under high insect stress, mulches combined with floating rowcovers should be selected for their effects on insects in addition to their effects on melon yield. Polyethylene microtunnels were found not economical for cantaloupe production in western Mexico.

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M. Arias-Gonzalez, J. Farias, S. Guzman, and A. Michel

Our purpose was to evaluate the vegetative growth and flowering of African violet (Saintpauila ionantha) grown in seven soils subtrates under greenhouse conditions. The following were tested: river lime, pine ushers, black clay, oak soil, peatmoss, Canadian peatmoss, and a compost soil. Pots were in a fully randomized experimental design with seven treatments, and four replications was used. A monthly 10N–20P–10K fertilization was applied to potted plants. The study lasted for 135 days, taking data every 15 days on leaf perimeter, length and elasticity of the petiole, plant height, and leaf color. Best vegetative growth was observed with oak and canadian peat moss due to their high capacity to hold water and their very good aeration. Least vegetative growth was observed with black clay, where plants failed to flower. Other substrates did not show differences in plant growth.

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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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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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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.

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Liliana S. Muñoz-Ramírez, Laura P. Peña-Yam, Susana A. Avilés-Viñas, Adriana Canto-Flick, Adolfo A. Guzmán-Antonio, and Nancy Santana-Buzzy

The Yucatan Peninsula is recognized as the center of genetic diversity of Habanero peppers (Capsicum chinense Jacq.), which can be distinguished from those cultivated in other regions of the world by their aroma, taste, and—most of all—by their pungency. We evaluated three commercial varieties of chili peppers reported as being the hottest in the world: ‘Bhut Jolokia’, ‘Trinidad Moruga Scorpion’, and ‘Carolina Reaper’. The aim of our study was to determine the behavior of the pungency when cultivated under the edaphoclimatic conditions of Yucatan. Our results show that the three varieties registered greater contents in comparison with those reported in other regions of the world. ‘Carolina Reaper’—considered to be the hottest variety in the world, with a pungency of 2,200,000 Scoville heat units (SHU)—when cultivated in Yucatan, had a pungency of 3,006,330 SHU, which was greater than all the other varieties analyzed.