This study was conducted at several periods of time from 2000 to 2005 in two commercial ‘Hass’ avocado orchards in the municipalities of Tepic and Xalisco, Nayarit, México. The objective was to determine the growth cycles of ‘Hass’ avocado trees under rainfed conditions. ‘Hass’ showed two flushes of vegetative growth: winter (greatest intensity) and summer (lowest intensity). The complete floral development process, from closed pointed bud to anthesis, required 11.5 and 7.5 months for winter and summer shoots, respectively. Greatest production of roots occurred in August. “June fruit drop” maximum intensity (45 %) was observed during the first summer rains (June). Fruit growth (length), from set (March) to harvest (November), took eight months. Average annual maximum air temperatures fluctuated between 26.8 and 33.4 °C and minimum temperatures were 9.3 to 20.4 °C. Average monthly maximum soil temperatures varied from 20.1 to 24.5 °C throughout the year and the minimum ranged from 18.5 to 23.4 °C. Soil moisture level was ³85 % from the rainy season (June to October) to December; afterwards it decreased, reaching 65 % in May.

The aim of this work was to develop an edible film based on arabic gum (AG), carboximethylcellulose (CMC) and glycerol (GL) as plasticizer and assess its potential for covering fruits to preserve them in a modified atmosphere. We evaluated its mechanical properties in terms of impermeability and light transmission. In an evolutionary design phase an approximate formulation of the film was obtained. With this basis, a range of concentrations for AG (20 and 30 %), CMC (0.25, 0.50 and 0.75 %) and GL (5, 10 and 15 %) were defined to characterize the material. The combination of 30 % AG, 0.25 to 0.50 % CMC and 5 to 10 % GL was adequate for use in fruit preservation in modified atmosphere systems. By changing concentration of AG, CMC and GL O2 and CO2 permeabilities and mechanical resistance could be regulated. Transparency was more than 80 %.

This two-stage study was conducted to assess the effect of prior conditioning on the chilling injury index (CII) and enzymatic activity of b-galactosidase in zucchini fruits in cold storage (2.5 or 10 °C). In the first stage, zucchini fruits were conditioned at 15 °C for 48 h prior to storage at 2.5 °C. In the second stage, the polyamines putrescine (PUT), spermidine (SPD) and spermine (SPM) at concentrations of 0.1, 0.25, 0.5, 1.0, 1.5, 2.0 y 4.0 mM, were applied exogenously on fruits stored at 2.5 °C for 12 days. It was found that conditioning at 15 °C and storage at 10 °C reduced CII by 84 and 40 %, respectively. b-galactosidase activity increased gradually in the course of 12 d in response to all of the treatments, except for a decrease on day four at 10 °C. Polyamine application at all the concentrations decreased the CII, PUT being the most effective, followed by SPM and SPD. Infiltration of polyamines induced a reduction of b-galactosidase activity during 12 days of storage at 2.5 °C, with SPM having the greatest effect. All the polyamines at 4.0 mM caused a CII similar to that of the control.

The effect of vermicompost and manure was tested for the management of Nacobbus aberrans. Under greenhouse conditions gall index of tomato (Lycopersicon esculentum Mill.) roots (GI) was reduced significantly (P£0.05), by 27 and 40 %, respectively, when vermicompost and manure were incorporated to soil, in comparison to the control with nematode and without amendments. They also increased significantly the root volume (RV) 13.1 and 14.7 more times, dry root weight (DRW) 5.8 and 7 more times and dry shoot weight (DSW) 1.6 and 1.9 more times; furthermore root necrosis was reduced by 28.5 and 25 %, respectively. In the field, 85 days after planting, only the variables GI, root necrosis and DSW showed significant differences among treatments; generally, plants grown in soil amended with vermicompost at 12.5 t·ha-1 (500 g·plant-1) and 7.5 t·ha-1 (300 g·plant-1) reduced GI and root necrosis, and increased DSW. The GI was significantly reduced, as compared to the control, by 29 and 28 % with 7.5 and 12.5 t·ha-1 of vermicompost, respectively; similarly, they increased the DSW by 91.6 y 84.8 %.

To measure the inbreeding intensity produced in finite populations of alogamous species that undergo random mating without selfing [as in the case of some ornamental species of the Primula genus and husk tomato (Physalis ixocarpa Brot.)], a formula for the inbreeding coefficient (IC) has been derived in probabilistic terms under the assumption that in the studied population each cycle was formed by n families of m half sibs each. Each family is formed by the seed of a set of n random individuals from the previous generation, as occurs in mass selection. Since for m = 1 this formula is not reduced to any known formula for this case, theoretical research in probabilistic terms was undertaken to explain the cause of this discrepancy and to identify or derive an exact IC for the case under study. It was found that when cycle zero is formed by mn noninbred and unrelated individuals, for cycles 0, 1, and 2 the exact ICs were F0 = 0, F1 = 0, and F2 = 1/(2mn), respectively, and for t = 3,4,5, … the exact IC was Ft = (1+Ft-2) /(2mn) + (m-1)(1+Ft-3 + 6Ft-2) /(8mn) + (n-1)Ft-2 /n. For the case where cycle zero is formed by n families of m noninbred half sibs each, the IC formula, as of cycle one produces higher IC values than those produced by the previous case.

‘Maguey bruto’ (Agave inaequidens Koch) is a wild, little studied endangered species. It is used to make the alcoholic spirit “Raicilla”. To develop a method for reproduction to increase the population, several explants, concentrations of hormone, inorganic Murashige and Skoog (1962) salts, plant sizes and root conditions were evaluated in vitro. Some variables showed statistical significance. The stem sections formed 72 shoots in 8 weeks; the concentration of 3.0 mg·liter-1 of 6-benziladenine (BA) produced an increase in length and number of shoots (6.39 mm and 2.02 respectively). The concentration of BA, kinetin (Kin) and 6-g,g-dimethylallylamino purine (2ip) produced a wide variety of responses: larger plants in a medium with MS salts at 100 % concentration produced more and larger roots in less time, and 100 % of the plants larger than 4.0 cm with more than 2 roots survived.

The otomies (the hñähñü) of the Nicolás Flores municipality, Hidalgo, have maintained their knowledge of medicinal plants over generations. Allopathic medicine is limited mostly to prevention of diseases such as poliomyelitis, measles, smallpox, and malaria. It is considered that traditional medicine is more viable for this group of people because of the socioeconomic, cultural and physiographic conditions prevalent in the region. The objectives of this work were to identify the medicinal plant species used by the hñähñü, the diseases treated with them, and their geographic affinity. For the field study, interviews were conducted with people in the municipality, and plant samples in different “ethno-ecological units” were collected. The use of 112 species was reported in treatment of disorders such as shock (“susto”), stomach pain, kidney pain, diarrhea, fever, and “mal de ojo” (“evil eye”), among others. Although most of the inhabitants know the medicinal use of some plant species, the elders are the keepers of the deepest knowledge. In hñähñü wisdom, magical-religious thought is part of their cosmovision. Like other Mexican ethnic groups, they consider the duality cold-hot in the treatment of diseases. The range of diseases the plants presumably heal is very broad, from colds to cancer. 75 % of the species used by this ethnic group are native to the American continent, principally Mexico and Central America (39 %), suggesting that the basic stock of traditional botanical knowledge is still observed.

Spaghetti squash is an alternative crop with qualities that have aroused interest among Argentinean consumers. The objective of this experiment was to study the influence of sowing date and density in Cucurbita pepo var. vegetable spaghetti. The study was conducted in the experimental unit of the Facultad de Agronomia in Azul, Argentina, in a typical argiudol soil on a total area of 5,952 m2. Each plot had an area of 88 m2 and comprised four 11 m rows, 2 m apart. The two middle rows were evaluated. There were two sowing dates (November 10th and 24th) and four sowing densities (0.25, 0.5, 0.75, and 1 m between plants, that is, 20 000, 15 000, 10 000 and 5000 pl·ha-1). Band fertilization as well as preventive chemical weed-control with Naptalan, on sowing line and Trifluralina between rows with a cultivator, took place at presowing. Data were analyzed under a model of divided plots, in which the main plot was biostimulants and the sub-plots density and sowing date. The interactions between main factors were also considered. No significant differences were detected for total crop weight among the effects of interaction between sowing density and date. With crop densities two and three, more medium (two and three caliber) fruits (1.05 and 1.44 kg) were obtained. These calibers are suitable for marketing.

Apple pepper inter-varietal hybrid (Capsicum pubescens R y P) “Puebla x Zongolica” is high-yielding due to its volume, pericarp thickness, and fruit weight. Fruit yield is explained mainly by its size, and it is of interest to describe fruit growth dynamics. Fruit growth analysis generally has been based on destructive sampling since it is impossible to use the same fruit throughout the growing season. Competition among the different plant organs decrease fruit size and weight, negatively affecting fruit quality and yield. For these reasons, this study was conducted to assess and identify mathematical models that describe fruit growth without destructive sampling. Simple linear regression, multiple linear regression, and four non-linear models were tested. The hypothesis was that one of the six models efficiently explains fruit growth using the independent variable volume of displaced water. Chili plants were cultivated under an intensive production system in 2004 and 2005. The dependent variable was fresh fruit weight and the independent variables were fruit growth time, and average fruit length and width at shoulder, volume of displaced water and fruit volume. Significant differences were found between the means of the evaluated variables in the two sampling periods (Pd”0.0). The models that best explained fruit growth were simple linear regression (only in 2004) in function of volume of displaced water and fruit volume and the multiple linear regression model which adequately describes growth using, besides the above mentioned variables, growth time and average length and width, in both 2004 and 2005. However, the monomolecular method (in both sampling periods) estimates fresh fruit weight simply and precisely using a single non-destructive variable, either the volume of displaced water or volume, making this model the most practical for the description of fruit growth.

The objective of this investigation was to evaluate the effect of low temperatures on the anti-senescence catalase (EC. 1.11.1.6; CAT)–superoxide dismutase (EC. 1.15.1.1; SOD) enzymatic system of pitahaya (Hylocereus undatus) fruit during storage. Groups of fruits from Tehuacan, Puebla, were stored four days at room temperature (22±1 °C), and at 3, 7 and 11±1 °C for 7, 14 and 21 days, and after each cold-storage period they were kept for four days at 22±1 °C. Catalase and SOD activity was evaluated in fruit pulp from 20 treatments, including a control without storage. Four days at 22±1 ºC did not modify CAT nor SOD activity (18.75 y 3.25 U·g-1, respectively) compared with the control. Cold storage significantly diminished CAT activity, relative to the control. Inhibition of CAT activity was not dependent on cold storage temperature or time, but mean inhibition in fruits stored at 11±1 °C (13.07 U·g-1) was slightly lower than at 3 and 7±1 °C (12.39 U·g-1). After cold storage, CAT inhibition was partially or totally reverted after four days of storage at 22±1 °C. SOD activity was not significantly affected by low temperatures, and in general, after cold storage, it was activated with complementary storage at 22±1 °C. CAT activity is inhibited by cold storage, but SOD activity, which diminishes the process of senescence generated by oxidative stress, is activated in the pitahaya fruits.

The use of foreign varieties of chilaca-type chili peppers has had negative consequences: high production costs and limited acceptance primarily because of a lack of a pleasant spicy flavor. To improve these characteristics, a plant breeding program was developed with 3 commercial varieties (Colegio 64, Negro and Sandía), from which 11 materials were obtained with characteristics accepted by consumers. To determine the genetic relationship of these materials with their parents, the PCR-RAPDs technique was used. Twenty oligonucleotides were tested and five of these exhibited polymorphism among the three commercial varieties. Later, these varieties were compared with 11 genotypes using the selected oligonucleotides. The genetic relationship of the 11 materials to the three commercial varieties was determined by the Jacard index. Results showed that 86 % of the studied materials had a high degree of similarity, with genetic distances that varied from 0.825 to 1 for group one (two genotypes) and from 0.083 to 0.101 for group two (twelve genotypes).

As for many ornamental crops in Mexico, forest soil and peat moss are commonly used as substrates for cyclamen production. It is important to find substitutes for both to protect forests and to avoid imports of peat moss. Cyclamen seedlings emerge 30 days after sowing (das) and usually the percentage of emergence is low. To improve the percentage and time to emergence, this study was carried out to test coconut coir dust (CCD) as a substrate. Cyclamen seedlings were produced and the following factors were evaluated: seed soaking (with and without), substrates (peat moss, washed CCD, unwashed CCD and CCD+ peat moss) and genotype (six series) in a factorial treatment combination in a randomized complete blocks design with three replications. Soaking seeds 24 hours before sowing did not affect percentage of emergence but did shorten time to seedling emergence by 1.5 and 2.3 days on average in substrates composed of washed and not washed CCD, respectively, and shortens the time to seedling emergence for Giant Lugano, Pannevis® and Halios® by 3.7, 1.0 and 1.1 days, respectively. Those seedlings that reached establishment emerged before 37 days. The shortest period of time for seedling emergence and the highest percentage of seedling establishment were obtained with substrates having water retention capacity of 75 and 82 %. The physical and chemical characteristics of CCD allows its use in formulating substrates for cyclamen seedlings since it has characteristics similar o superior to peat moss or commercial substrates that contain it. Differences were found among the studied genotypes in terms of seedling emergence and establishment, growth rate and biomass production.

A diallel cross among three jamaica genotypes (Hibiscus sabdariffa L.) was carried out to estimate combining ability and heterosis. The evaluation was conducted during the fall growing season 2004 in Xalisco, Nayarit; 13 traits were evaluated. The analyses for general combining ability (GCA) and specific combining ability (SCA) showed that both additive and non-additive effects were important. The most important additive effects were days to flowering, plant height, number of branches per plant, calyx diameter, calyx length, fresh fruit weight, fresh calyx weight, total anthocyanin content, total soluble solids and acidity. The most important non additive effects were number of fruits per plant, number of fruits on main branch and dry calyx weight. For GCA effects, the parent Reina expressed the largest values for calyx length, number of fruits per plant, number of fruits on main branch, fresh fruit weight, fresh calyx weight and dry calyx weight, whereas the cultivar China exhibited the best effects for calyx diameter, fresh fruit weight, fresh calyx weight, dry calyx weight and total anthocyanin content. Finally, the parent Huajicori had important effect on days to flowering, plant height, number of branches per plant and total soluble solids. The crosses Huajicori x Reina and Huajicori x China showed strong effects of SCA for plant height, number of fruits per plant, number of fruits on main branch, fresh fruit weight, fresh calyx weight and dry calyx weight. High percentages of heterosis relative to the best progenitor were exhibited by the cross Huajicori x Reina for number of branches per plant (27 %), number of fruits per plant (96 %), number of fruits on main branch (46 %), fresh fruit weight (15 %), fresh calyx weight (14 %) and dry calyx weight (36 %).

Mexico has the largest genetic diversity of chia (Salvia hispanica L.). Recently, chia seed derivates have attracted commercial attention. However, too little is known about its breeding system to define a genetic improvement strategy and to preserve its germplasm. In this study, the percentage of natural outcrossing of S. hispanica was determined in Chapingo, Mexico. Flower color was used as the genetic marker, considering purple flowers dominant over white and blue flowers. Two cross-pollination plots were established in 1999. In the first plot, seeds of purple-flowered plants and white-flowered plants of a cultivated genotype from Jalisco were sown alternately in each row; in the other, the same cultivar were sown alternately with seeds of purple-flowered cultivated plants and blue-flowered wild plants collected in Sinaloa. Determination of natural outcrossing rate was based on the percentage of purple-flowered plants in both the F1 progeny of white-flowered cultivated plants and of blue-flowered wild plants. Outcrossing was more frequent in the cultivated genotype (22.17 %) than in the wild genotype (1.51 %), which might indicate that the breeding system was modified under cultivation. Since there was no reproductive isolation, the cultivated and wild genotypes should be considered subspecies or races of S. hispanica. The resulting hybrids were vigorous, like the cultivated parent, and had dehiscent fruits, like the wild parent.

Huitlacoche (Ustilago maydis ( D.C.) Corda) has been an important food in the diet of the inhabitants of the Central-Southern region of Mexico since pre-Columbian times. Recently, its acceptance has increased all around the world. Although it is a highly perishable mushroom, there are no postharvest studies. For these reasons the objective of this work was to identify changes in physical and physiological postharvest parameters of huitlacoche on the corn ear and of cut huitlacoche galls stored at room temperature, 10 °C, and 3 °C for 11 d. The measured variables were changes in appearance, color, weight loss, respiration, production of ethylene and amino acids. The average respiration rate of huitlacoche on the ear at room temperature, 10 and 3 °C was 320.8, 120.8 and 71.5 mLCO2·kg-1·h-1, respectively, and 372.8, 346.7 and 164.1 mLCO2·kg-1·h-1 in cut galls, respectively. Weight loss was above 80, 60 and 22 % at room temperature, 10 and 3 °C at 7 days, respectively. Huitlacoche contains 18 amino acids, of these, essential amino acids accounted for 37.8 % of the total. Lysine was 27.2 % of the essential amino acids. After the storage period, there was no major change in amino acid content. The huitlacoche kept its appearance, color and weight better when it was stored at 3 ºC on the ear. Ethylene production by huitlacoche was not detected.

The objective of the present study was to determine the most suitable culture medium for in vitro propagation of Oncidium stramineum Lindl. Murashige and Skoog (MS) medium was used for germination, and for growth MS (T1) and MS (T2) medium supplemented with organic extracts, coconut milk, peptone and active charcoal, and MS (T3) supplemented with organic extracts, coconut milk, peptone and polyvinyl pyrrolidone were tested. Germination was 47.69 %. During growth seven phenological stages were observed: imbibition in four days, green seeds in eight days, germination in thirteen days, initial protocorm in sixteen days, late protocorm in nineteen days, leaf development in twenty-eight days, production of true roots in thirty-four days, and seedling development. Number of buds, leaf length, leaf width, number of roots, and seedling height were affected by the treatments, but not root length. The Tukey analysis showed significant differences among treatments in number of buds, leaf length, number of roots and seedling height. The evaluated variables showed that culture medium (T3) supplemented with organic extracts, coconut water, peptone and polyvinyl pyrrolidone increased leaf width, leaf length and seedling height. With MS (T3) all the variables evaluated correlated significantly. The best growth of Oncidium stramineum Lindl. seedlings was observed in MS culture medium supplemented with 100 mL·litter-1 coconut milk, 40 g·litter-1 organic extracts from tomato, apple and banana, 2.0 g·litter-1 peptone and 200 mg·litter-1 polyvinyl pyrrolidone .

Arbuscular mycorrhizal fungi (AMF) play an important role in metal tolerance of their host plant, but their effects on metallophyte plants are not well known. The objectives of this research were to determine the level of mycotrophy in Viola calaminaria (Gingins.) Lej., a plant endemic to metal-enriched soils, and to investigate the effect of AMF on Zn accumulation. Two experiments were conducted. The first experiment (3 months long) was carried out in pots containing inoculated and non-inoculated plants grown in river sand as substrate under non Zn -polluted conditions. The second used plants from the first experiment; these were grown for 15 days under hydroponic conditions with different levels of Zn+2 (50, 200, 300 and 400 mg×liter-1). The AMF were Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe isolates BEG-132 and BEG-25 originating from soils polluted or non-polluted by metals, respectively. Experiment 1 indicated that V. calaminaria was colonized by both fungi but did not benefit from being colonized. Dry mass, root volume and P - Zn contents in inoculated plants were not different from that in non inoculated plants. Experiment 2 showed that total Zn content per plant increased when colonized by AMF and that accumulation was higher in plants colonized by the fungus from unpolluted soil (BEG-25). Fungal root colonization was not affected by Zn content. It remains to be determined whether AMF adapted to soils with high metal contents confer a growth and survival advantage on metallophyte plants in the field.