In this research 22 collections and five crosses of Mexico’s peppers were studied, with the purpose of determining their genetic di-versity, for this it was used starch gel electrophoresis. Monomorphics (only one allele) and polimorphics with one or several predo-minant alleles were obtained. The variation of alleles number for locus were 1.4 a 1.8. The variation of the polimorphic loci (PLP) was low (47%), intermediate (57.6%) or high (66%). Moreover, the heterozygosis was low (43%), to high (62%). The genetics distance matrix was used for finding the relationships between 22 collections and five crosses with base in 13 loci. Moreover, with the resul-ting matrix we constructed the tree diagram for separating in four groups according to similarities.

In order of contribute to the generation of a tomato vegetative propagation method, the growth and yield of plants cv Daniela using as treatments cuttings of different source (lateral or terminal buds), size (10 and 15 cm), with or without pruning in the basal leaf be-fore rooting and without or with partial pruning of largest leaf (removing 1/2 or 1/3 of the leaf) were evaluated. The experiment was carried out in Cuautlalpan, Estado de México, México under glasshouse conditions and in a soilless system, using a completly ran-dom design, arranged in subdivided plots, corresponding the source factor to plots, the size of cuttings to subplots and the combina-tion of type of pruning in the basal leaf and partial pruning in the largest leaf to subsubplots. The experimental unit after trasplant consisted of five cuttings with three replications. The plants were trimmed (pruning of terminal bud) to leave just one truss per plant and were growing at a density of 25 plantsm-2. The evaluated traits were: plant height and stem diameter 45 days after trasplant, fruit yield, fruit number and mean fruit weight. There were significant differences of the studied factors for plant height and stem dia-meter, bud only pruning of the basal leaf negatively affected the fruit yield (0.8 kgm-2 more fruit yield was obtained when the basal leaf was not removed).

In the southeastern part of Mexico State and adjacent area of Morelos State, Mexico, the tomato cultivar Río Grande, is heavily af-fected by basal stem and root rot diseases; however, little is known about their etiology. Therefore, the present work had as main ob-jective to investigate which of the soilborne fungi cause these diseases; their incidence was also determinated. Among the isolated soilborne fungi, Fusarium oxysporum, F. solani, F. roseum, Phytophthora capsici, Rhizoctonia solani and Sclerotinia sclerotiorum showed pathogenicity. The disease incidence of these fungi was higher in 1993 (2.0-16.3%) than in 1992 (3.1-7.2%).

This work was made with the objective to have information about the concentration of N-NO3 in the celular extract of petioles and stem of husk tomato in four phenological phases, for determining the relationship between this nutrimental index and yield. Six dif-ferent concentrations were evaluated using the Steiner’s nutritive solution at a hydroponic open system. The results showed a sig-nificant (P≤ 0.05) correlation between crop yield and the concentrations of the N-NO3 in the celular extract of petioles and stem, wich permited to know the nutrimental status of the plant at certain phenological phase and its relationship with yield.

The Iguala Valley, Guerrero, Mexico, is the principal producer and exporter of okra in Mexico. It is thus important to study manage-ment practices and their relationship to production. The objective of this study was to determine the effect of number of plants per hill and distance between hills on the quality of fresh fruit and dry seed weight in okra. The cv. Clemson Spineless was sown on Novem-ber 26, 1987 in rows 80 cm apart, with 30, 35, and 40 cm between hills and 1, 2, 3, and 4 plants per hill. This resulted in populations of between 2.8 and 14.8 plants m-2. With respect to quality, 56% of the fruits were of first quality, 32% of second quality and 12% of third. Increasing the number of plants per hill and reducing the distance between hills increased principally the production of first qua-lity fruit and seed. The highest fruit an seed production was obtained with 4 plants per hill and 30 cm between hills. Harvesting fresh fruits prolonged the crop’s growth cycle.

Internodal segments of pot cultivar Mini Pinky were exposed to ionozing radiation. Six doses of X- and gamma rays in the range of 5-30 Gy were applied. For the regeneration of adventitious shoots, 2 to 3 mm stem segments were cultured on MS medium with 0.02 mgliter-1 BA, 1.75 mgliter-1 IAA and macroelements reduced to one half. Adventitious shoots were growing up directly from epider-mal tissue of explants and sporadically with an intermediate callus phase. Number of adventitious shoots developed from one irradi-ated explant ranged from 0 to 5. Most of internodal segments regenerated only one adventitious shoot. Dose 30 Gy of X-rays com-pletely reduced the regeneration ability of internodal segments.

Capsules were collected in the region of Valsequillo, Puebla in 1992 and stored under ordinary room conditions till sowing. Seeds from ten capsules, each from a different plant, were sown June 6, 1995 separately. The seedlings were replanted to plastic bags filled with volcanic sandy soil. The objective of this study was to determine the annual increase in bulb mass. The fresh mass was registered annually during the plant dormancy. In the first year the size of bulbs varied from 28 to 415 mg, in the second year from 254 to 5,001 mg, the third year from 400 to 10,800 mg. The increments were: the second year from 2.1 to 151 mg, the third year from 1.06 to 52.2 mg. Some bulbs remained dormant, which resulted in a reduction of their mass. The rest period lasted four months, approximately. The bulbs entered into flowering the fourth year from sowing the seeds.

Root growth and emergence were studied from October 1996 to April 1997, during the late seasonal plant growth and bulb dormancy period. The objective was to test if the emission of roots was a continuous process and to define types of roots produced by bulbs. Bulbs, with their leaves and roots, were extracted from the soil and placed between sheets of wet newspaper in plastic bags. These were held at room temperature varying from 20-24/18°C (day/night). The sheets of paper were changed monthly. Small bulbs, below 10 g were used. The measurements included the size and the number of roots and leaves. Periodically the dying roots were re-moved. The foliated bulbs or which lost their leaves, ubicated in beds, produced new contractile roots since the second half of the flowering and continued to grow. Both, roots emergence and the longitudinal growth were maintained for a few weeks after the bulbs lost their leaves. The bulbs started to cease the emission of new roots approximately at the end of January. The root forming meris-tems were in dormancy for 4 to 6 weeks. The bulbs reinitiated emitting new roots at the end of February or at the beginning of March. This, was followed by the emission of new shoots. The bulbs produced contractile roots, from the second half of the flowering period; at the start of a new season of growth produced only the feeder roots. Both root types may be present during the flowering period.

This work was done with mamey sapote fruits (Pouteria sapota) during two productive cycles (february, 96-may, 97 and february, 97-may, 98). The objective was to evaluate some changes ocurring during development and postharvest of the mamey sapote fruit. Vari-ables measured were: respiration, weigth loss, flesh color (color index, CI), firmness, total solubles solids (tss), acidity (malic acid), hu-midity and sugars. The evaluations were at harvest and after 7 days on environmental storage conditions. The fruit harvested after 400 days after flowering (DAF) had the next caracteristics: flesh color was yellow-red to red (CI =6-16), firmness was 55-65 N, tss was 10-12 %, acidity was 0.15-0.20 %, humidity was 67-72 % and total sugars were 3-4.5 %. After 7 days, the parameters were: respiration showed a climateric rise (3-5 days after harvest) with 121.5 mlkg-1h-1 of CO2 (232°C, 50% R.H) and the weigth loss was 10-14.6 %. The flesh color was red (I C=12-21.5), firmness was 3-12 N, tss was 25-34 %, acidity was 0.10.14-0.20 %, humidity was 63-67 %, and total sugars were 20-22 % (nonreducing sugars represented more than 70 %).

The effect of low temperature on maturation of sapote mamey fruits (Pouteria sapota (Jacq.) H.E. Moore and Stearn) was determi-ned. The fruits were stored at 20°C, 12°C, 5°C and 5°C + 2°C different times with 20°C mgliter1 por 24 h of ethylene. The variables evaluated were: ethylene production, respiration rate, weigth loss, total sugars and enzimatic activity of poliphenoloxidase and cata-lase. In the first three treatments a climateric pattern was observed, fruits stored at 20°C, 12°C and 5°C being this abnormal in ex-posed fruits at 5°C where a lower accumulation of total sugars was obtained, attributed to chilling injury. Symptons of chilling dam-age were observed as stains and hard tissue in the pulp of fruits stored at 5°C + 2°C. Differences in losses of weight were found among treatments. The activity of catalase was inhibited during the storage at low temperature, incresing it later during maturation. Polyphenoloxidase incresed in more proportion in treatments where fruits were exposed at 5°C + 2°C, confirming that this enzyme is related with dimness of pulp of sapote mamey fruits at these temperatures.

Neem (Azadirachta indica A. Juss.) was evaluated as a potential component on the integrated management of papaya (MIP) on its ability to delay incidence and reduce severity of papaya ringspot virus (PRV). Three integrated management based treatments were included: aqueous extracts of neem seeds 5% (MIP+Nim 5%), 2.5% (MIP+Nim 2.5%), and no neem (MIP Sin Nim). No significant differences among treatments were found on PRV incidence and severity (square root of the area under the curve of disease pro-gress), and estimated yield. MIP+Nim 2.5% also was compared with two commercial papaya groves: one grove used all manage-ment elements of MIP (TEST-MIP C), the other used traditional regional management practices (TEST-REG). 170 days after trans-plant MIP+Nim 2.5%, TEST-MIP and TEST-REG reached PRV incidences of 22, 40% and 100%, respectively, and severity at the same period was 7, 22, and 57%, respectively.

One of the most important traits of some Annonaceae species is their potential as rootstock. This subject has not been sufficiently studied. Most of the anonas have a good adaptation to adverse soil conditions, this characteristic allows an increased adaptation range. Highly significant differences were found in the percentage of live grafts 140 days after grafting on the following rootstocks: soursop (A. muricata) ‘Sin Fibra’ (control) and “cimarrón” soursop (A. montana). The “anono de corcho” (A. glabra ) was inferior to them. The rest of the rootstocks showed lower percentage of grafting success, being A. squamosa a was the worst rootstock. The presence of tannins was a main sympton of incompatibility in addition to absence of functionality in the secondary xilem formed at the union, in spite of the healing of parenchima was normal. The self anatomical compatibility was shown when A. montana was used as the rootstock. A cherimola, A. reticulata and A. glabra were not good as rootstocks and they are not recommended. A. squamosa were not compatible with A. muricata ‘Sin Fibra’.

Asexual propagation of macadamia (Macadamia integrifolia Maiden and Betche, and Macadamia tetraphylla Jonh.) by grafting and stem cuttings was carried out. The research was performed in 1998. For both types of propagation the plants were placed under mist. In relation to the grafting, there were significant differences among genotypes. The L-46 selection had 65% of grafting success. The grafting was on 9 month old seedlings. Stem cuttings from the selection of M. tetraphylla, A527, and the hybrid of M. integrifolia x M. tetraphylla, ‘Beaumont’, achieved an adequated rooting of 80 and 89%, respectively. In general, M. integrifolia trees had less rooting capacity.

With the purpose of finding a methodology for clonally propagate avocado (Persea americana Mill.) rootstocks this investigation was carried out. It was studied the effect of the type of graft, indolbutiric acid (IBA) concentrations, and sap obstruction on etiolated shoots of an avocado rootstock of the Mexican race rooted by air layering in pots. The rooting capacity of etiolated shoots was in-fluenced by the type of graft. Tip-grafted plants with 10,000 mgliter’ of IBA without sap obstruction of etiolated shoots achieved the highest rooting quality. Veener grafted etiolated plants treated with 5,000 mgliter’ of IBA without sap obstruction had lower number and length of roots.

The purpose of this study was to examine the influence of thidiazuron (TDZ) (0, 150, 300 and 450 mg•liter-1) and citroline (0, 2, 4 y 6 %) sprays in breaking dormancy of grape buds (Vitis vinifera L.) ‘Perlette’ and ‘Flame Seedless’, after different chilling treatments (200, 400, 600 and 800 CU) and comparing with 400 CU + 2.5 % H2CN2. In ‘Perlette’ the maxime budbreak (85 %) was obtained with 200 CU and this treatment was bether than 400 UF + 2.5 % H2CN2, with a minimun budbreak (7.5 %). In ‘Flame Seedless’, there were no differences in budbreak among CU nor CU + TDZ treatment. In both, ‘Perlette and ‘Flame Seedless’, citroline treatments had a negative effect on budbreak, as well as H2CN2. In ‘Perlette’ an negative interaction was found between CU x TDZ, decreasing the budbreak when 300 mg•liter-1 TDZ was applied on cuttings with 200 CU and low increase in cuttings with 600 CU. In ‘Flame Seedless’ didn’t have interaction. Our results indicate that, under our conditions, the chilling requirements of this cultivars is  200 CU, TDZ, CIT, and H2CN2 sprays didn’t help to improve budbreak, maybe to high temperature in the greenhouse and the active physiological conditions of the buds.

Chemical rest bud break promotors were sprayed in 1996 and 1997 on Japanese plum to accelerate bud break at the end of the rest period. Chemicals were sprayed on ‘Shiro’ on January 29, 1996, and on ‘Santa Rosa’ on February 5,1997. Better results were found in the first year using citroline 2 % + thidiazuron 250 mgliter-1 and citroline 2 % + thidiazuron 500 mgliter-1. In the second year citroli-ne 3 % + thidiazuron 500 mg liter-1 was used. These treatments accelerated bud break by 19 and 15 days, respectively, compared with the control and promoted an early and highly uniform bud break. Sugars and proline were also sampled at 6, 21, 45, 94, and 241 hours after spraying in ‘Santa Rosa’. Total sugars decreased as bud break begun. The behavior of proline was similar in all treatments. The results suggest that thidiazuron + citroline can be used successfully as a chemical rest break.

Se llevó a cabo un trabajo para evaluar la eficacia biológica del thidiazurón (TDZ) como promotor de la brotación a principios de otoño en durazno ‘Diamante’ y ciruelo japonés ‘Corazón Rojo’ en condiciones de clima subtropical. Con la aspersión de 250 y 500 mglitro-1 de TDZ se obtuvo alrededor del 90 % de yemas florales brotadas 35 días después de la aplicación de tratamientos en du-razno: la concentración mayor superó significativamente al testigo comercial (cianamida de hidrógeno 5 mllitro-1 + citrolina 2 %). En ciruelo los resultados fueron similares, la aplicación de TDZ 250 mglitro-1 en árboles previamente defoliados en ambas especies promovió una floración de más del 85 % hacia mediados de octubre, lo cual significa un adelanto de ésta de alrededor de 40 días respecto al testigo sin aplicación, pero defoliado.

The efficiency of gibberellic acid did not change with the use of HCl as acidic agent to obtain low pH or NaOH to increase it. The gib-berellic acid at pH 3, 5 or 7 applied 30 days before harvesting, delayed the coloration and the texture loss of orange (Citrus cinensis) fruits cv. Valencia Tardía and the advance of the senescence of the flaved without having changes in the quality of the juice, in re-gard to total soluble solids, citric acid and juice content.

A methodology to evaluate the photosynthetic capacity in sugarcane plants by the 14C-photosynthates production is proposed. 14CO2 was produced within an acrilic chamber in which the leaf was introduced. The sugarcane plants were growing under natural condi-tions (habitat) and were exposed to a 14CO2-flux during 10 and 30 minutes, respectively. Photosynthates extract was obtained using a liquid scintillation method. The quenching was eliminated. Higher concentration of 14C-photosynthates was found in the ethanolic fraction (free sugars, aminoacids and organic acids), and then in the alkaline fraction (proteins). When sugarcane plants were ex-posed for 30 minutes to 14CO2 atmosphere a high content of nitrogen compounds was detected. It confirms that there are optimal re-lations between the C/N metabolism in the sugarcane when in situ biological fixation of 14CO2 was taking place. The highest value of 14C-fixed in the organic fractions (98.6%) allows a great confiability in the explanation of the results.

This work defined the geographic and ecological distribution of the Ephedra on the San Luis Potosi high plateau. The specimens de-posited in the herbaria were used in order to obtain a preliminary understanding of the distribution of the five species found on the San Luis Potosi high plateau and after that, botanical explorations were made in the field. Five species of Ephedra: E. antisyphilitica, E. aspera, E. compacta, E. pedunculata and E. trifurca were found in the area from 22° 02' to 24° 13' NL and from 90°50' to 101°45' WL. The altitudinal distribution of Ephedra is from 1047 to 2850 m. The genus occurs in the desert matorral zone.