The objective of this study was to determine the effect of residual and non residual herbicides on weed control in a soursop (Annona muricata L.) plantation established in a square system at Los Idolos, Actopan, Ver. The randomized complete block design with four replications was used. The experimental plots had a 5 x 5 m area, each with one soursop tree in the center. Twelve treatments were evaluated (diuron + hexazinone at 1.09 + 0.14, 1.63 + 0.20, 0.87 + 0.33 and 1.31 + 0.49 kg a.i.·ha-1, diuron + paraquat at 0.20 + 0.40 and 0.30 + 0.60 kg a.i.·ha-1, oxyfluorfen + glyphosate at 0.48 + 0.71 kg a.i.·ha-1, oxyfluorfen + paraquat at 0.48 + 0.40 kg a.i.·ha-1, paraquat at 0.40 kg a.i.·ha-1, glyphosate at 0.71 kg a.i.·ha-1, glufosinate at 0.30 kg a.i.·ha-1 and a weedy check). The dominant weed species was crowfoot grass [Dactyloctenium aegyptium (L.) P. Beauv.], 10 broadleaf weed species were also present. Weed control was evaluated at 15, 30, 60 and 90 days after application (DAA), and dry weed weight was quantified at 90 DAA. It was found that diuron + paraquat at 0.30 + 0.60 kg a.i.·ha-1 was the treatment with the highest control of D. aegyptium. Broadleaf weeds were efficiently controlled with diuron + hexazinone at 1.63 + 0.20, 0.87 + 0.33 and 1.31 + 0.49 kg a.i.·ha-1. Weed biomass production was lower with residual herbicides than with non-residual herbicides.

Gladiolus rust caused by Uromyces transversalis (Thümen) G. Winter is listed as a major quarantine disease in Mexico. In Mexico, this fungus is controlled by continuous fungicide applications, which can result in fungus resistance, risk to human health and environmental pollution. The objectives of this research were to identify the most adequate method of artificial inoculation of U. transversalis on gladiolus plants under laboratory conditions and in vivo, to identify the main isothiocyanates of the extracts from plants of the Brassicacea family, and to determine their fungicidal potential together with the isothiocyanates of benzyl and phenyl to control this fungus under field and greenhouse conditions. Experiments were carried out in the regions of Yautepec and Ayala, Morelos, Mexico, and at the Center for Development of Biotic Products (CEPROBI) at the Instituto Politecnico Nacional. The main parameters evaluated in the field were disease severity, affected area, percentage infection and disease progress. In the greenhouse only percentage of infection and disease progress were studied. The results associated with artificial inoculation by the methods of spraying and steaming resulted in infection of 2 to 3 plants. The main isothiocyanates identified in the extracts applied were phenyl, benzyl, 2- phenylethyl, alyl and propyl. In the experiments carried out in Yautepec and Ayala, plants treated with the extract at the concentration of 0.1 % had a lower percentage infection than those treated at 0.2 % and 0.5%. Under greenhouse conditions, the isothiocyanates of phenyl and benzyl exerted good control of the fungus. In plants treated with extracts and isothiocyanates under greenhouse and field conditions no phytotoxicity was observed.

Greenhouse crop production, compared with field production, yields greater quality and quantity and higher prices in any period of the year. These advantages are related to the climatic conditions in which crop grows and the specific climatic conditions of each region Thus, it is important to have a system of control to maintain the values of climate variables within an optimum range for crop development. However, the design of these systems is based on mathematical models that describe a given process, but it is necessary to have a model to predict the behavior of internal greenhouse environment. The goal of this work was to fit a mathematical model for greenhouse environment under the climatic conditions of central México. Furthermore, analyses of sensitivity, calibration and validation were performed and coefficient of correlation (r) of the model was obtained. Data were obtained from Universidad Autónoma of Querétaro’s biotronic laboratory greenhouse. The model’s input variables were outside temperature and relative humidity, wind velocity and solar radiation. Results showed that estimated air temperature inside the greenhouse had a better fit to the measured air temperature (r = 0.86) and, the estimated relative humidity fit less well to the measured relative humidity (r = 0.78).

The juvenile pecan tree produces vigorous apical shoots which limits the induction and development of lateral shoots, a characteristic that delays the initiation of the productive stage and stimulates considerable development of the canopy with the consequent problem of shading between trees, especially in high-density orchards. This study was carried out to evaluate the effect of tipping on growth reduction of apical shoot growth and the generation of lateral bud break, necessary aspects for limiting the excessive development of the canopy in juvenile pecan trees. Five year-old pecan trees were selected from a high-density orchard established in Viesca, Coahuila. In the spring of 2007, three treatments were established consisting of tip pruning, leaving 5, 10 and 15 formed buds on fully active growing shoots. A control without tip pruning was included. Tip pruning to five developed buds increased the percentage of lateral shoots by 55 %, while tip pruning to 10 and 15 buds increased percentage of laterals by 53 and 50 %, respectively. Relative to the control, treatments reduced length, leaves number, leaf area and dry weight of new shoots.

The use of ammonia and urea as nitrogen sources in the production of seedlings for transplant is very limited due to lack of information and the potential risk of toxicity caused by these two forms of nitrogen. Therefore, the objective of this study was to evaluate the effect of four proportions of nitrate/ammonium/urea (100/0/0, 85/15/0, 85/0/15 and 85/7.5/7.5) and two concentrations of potassium (7 and 9 mol·m-3) in the nutrient solution on growth and mineral composition of tomato seedlings produced in greenhouse. A completely randomized design with a complete 4x2 factorial arrangement of treatments with four replications was used. The growth data were taken 46 days after sowing and mineral concentrations were determined in leaves, stem and roots. The 85/0/15 proportion and 7 mol K+ m-3 produced the largest stem diameter, while 85/7.5/7.5 with 9 mol K+ m-3 yielded the largest root volume. The 85/0/15 proportion increased the stem/root ratio and fresh weight of seedlings 16.3% and 14.6%, respectively, relative to 100/0/0. The interaction nitrate/ ammonium/urea-K had a highly significant effect on the concentrations of nitrogen in leaves, stem and roots; of phosphorus in leaves and roots; of calcium and magnesium in roots. Replacing 15% of the total nitrate nitrogen in the nutrient solution with a similar percentage of nitrogen or urea or a mixture 7.5 % N-ammonia-7.5 % N-urea increased some quality parameters of tomato seedlings.

Fertigated cantaloupe grown on plastic mulch is subjected to intense use of water and fertilizer for the aim of obtaining high fruit yields and quality. The objective of this study was to evaluate the effect of nutritional management on fruit yield, fruit quality and leaf nutrient content in leaves and petiole cellular extract (PCE) of cantaloupe grown with fertigation and plastic mulch. Two experiments were carried out, one in 2006 and one in 2007; both experiments were started in March. Evaluated soil-applied treatments were seven fertilizer combinations consisting in five dosages of nitrogen (N) (0, 60, 120, 180 and 240 kg·ha-1), two of phosphorus (P) (0 and 100 kg·ha-1), and two of potassium (K) (0 and 200 kg·ha-1); a treatment of 180-100-200 was used as the control. Furthermore, three treatments of leaf applications of inorganic and organic fertilizer and plant growth promoters were also evaluated. N-NO3 and K+ content in PCE, N and K content in leaves plus fruit yield, fruit quality and sugar content were determined. The results indicated that N was the main factor affecting fruit quality, fruit yield, PCE N-NO3 content, and total N concentration in leaves. A significant relationship (r>0.70, P<0.05) between fruit yield and nutritional condition was found. Maximum N-NO3 values were between 230 and 418 mg•L-1 while total foliar N was 2.41 %. We concluded that it is feasible to reduce N fertilizer up to rates of 120 kg•ha-1 while P2O5, K2O, and foliar fertilizer applications can be suppressed without affecting fruit yield, fruit quality, PCE and leaf nutritional status in cantaloupe

Producing high-quality and high-yielding tomatoes (Lycopersicon esculentum Mill.) in Mexico is expensive, largely due to the high cost of seed. To contribute to solving this problem, an experiment was carried out under greenhouse and hydroponics conditions to assess the potential of saladette tomato hybrids of indeterminate growth and long shelf-life for the development of varieties with lowcost seed. Nine saladette hybrids and their 72 direct crosses were evaluated according to Griffing’s design I. The 81 entries were assessed in a randomized complete block design with four replications. Results showed significance (P≤0.01) of the mean squares for general (GCA) and specific combining ability (SCA) effects for all measured variables except for shelf life (SL) and plant height, but significance (P≤0.05) was not found for maternal and reciprocal effects in any case. However, six crosses that involved at least one of the top five hybrids for fruit yield equaled the SL of their parents (P≤0.05) and showed heterotic effects with respect to the best and mean parent that ranged from 9 to 11 and 7 to 17 kg of fruit per experimental unit of eight plants, respectively (P≤0.01 or P≤0.05). This information suggests that these crosses should be cheap and economically successful for the producer. The fruit yield heterotic effects were related to those for total fruit number and number of fruits per cluster which were also significant (P≤0.01 or P≤0.05). In addition, one hybrid, which showed the largest effect of GCA and mean for fruit yield, can be used in a breeding program designed to exploit the additive gene action.

The tomato (Solanum lycopersicum L.) is one of the most widely consumed vegetables. However, phytopathogical problems have underlined the need to look for alternatives for its cultivation, such as grafting, using rootstock resistant to environmental factors and diseases. For this technique, compatibility between the graft and the rootstock must be taken into account, especially of the water conduction system. The variability in xylem and water conduction indexes in local race rootstock onto which three different commercial cultivars were grafted was studied and compared with non-grafted plants. The anatomy of the xylem of the grafted cultivars and the local race rootstocks exhibited differences with respect to the non-grafted plants. Area, perimeter, and axis length of the largest and smallest axes of stem xylem vessels were statistically superior in grafted plants, but not for ‘Charleston’/’Criollo de Honduras’, ‘Sun 7705’/’Criollo de Honduras’, and vice versa, with respect to ‘Charleston’ and ‘Sun 7705’ without grafts. ‘Reserva F1’, in both combinations (‘Reserva F1’/Criollo de Honduras’; ‘Criollo de Honduras’/‘Reserva F1’) and without grafts, showed no changes in anatomy. The same characteristics in ‘Charleston’ had the maximum values with respect to the other cultivars. In general, the values of the xylem vessel anatomy characteristics were increased, of both the cultivars and rootstocks in the scion/rootstock relationship.