ARTICULO POR INVITACIÓN

ARTÍCULO POR INVITACIÓN

Transgenic broccoli plants were obtained by transformation with Agrobacterium tumefaciens carrying endochitinase, gus and nptII genes. The effects of the type and age of explant, Agrobacterium strain, and silver nitrate on transformation efficiency were exam-ined. Cotyledonary-petioles from 5-day-old seedlings were successfully transformed with octopine strain LBA4404 or nopaline strain GV3101. No transformed shoots were obtained from 15-day-old cotyledonary-petioles or from hypocotyls at any developmental stage. Higher transformation rates were obtained with GV3101 (11-16%), compared to LBA4404 (1-6%). Improvement in transforma-tion rates was also observed when explants were exposed to silver nitrate during the first 7 days of selection, but only when the LBA4404 strain was used. Use of silver nitrate on explants inoculated with GV3101 did not increase shoot differentiation. Selection for kanamycin resistance allowed differentiation of many escapes, but transgenic shoots were also recovered. Transgenic status of green regenerated plants was confirmed by NptII and PCR assays which showed a high correlation with root formation on selective medium. The efficient protocol developed for broccoli transformation is suggested for use with other Brassica oleracea varieties.

In order to estimate genetic parameters and heritability of physiological quality traits in tomato seeds, a complete diallel was gener-ated including ten experimental lines. Two experiments were conducted: germination at 25ºC with 24 hours of light in a germination chamber and emergence in a greenhouse seedbed. The variance components were obtained considering an inbreeding coefficient of 7/8 for all lines. In both experiments, the genetic effects were mainly dominant, except for initial germination and seed mortality, where they were additive and dominant. Narrow sense heritability values were low. There were significant maternal effects for total germination and for seed mortality. In addition, reciprocal effects were significant for all germination variables and for speed of emer-gence, except for abnormal seedlings. The best lines in terms of general combining ability were CPJL-1-2-1 and CPJL-24-5-4; in ma-ternal effects the best were CPJL-1-2-1, CPJL-3-2-1, CPJL-7-8-4, and CPJL-25-8-4, and in emergence the best were CPJL-2-2-1 X CPJL-21-1-4 AND CPJL-2-2-1 X CPJL-22-4-4. In terms of their reciprocal effects in germination, the best hybrids were CPJL-25-8-4 X CPJL-10-1-4 and CPJL-22-4-4 X CPJL-7-8-4, and in emergence the best were CPJL-24-5-4 X CPJL-10-1-4 AND CPJL-10-1-4 X CPJL-2-2-1.

Chrysolbalanus icaco is considered a species that has morphological differences. Analyses of the content of secondary metabolites in its fruit could be a useful tool for classification. Flavonols and flavones can serve chemical taxonomy to determine relationships of hybrids and to identify and register new cultivars. As a preliminary study, a series of phytochemical analyses were done using paper chromatography and UV/VIS spectrophotometry to obtain Rf and spectral values to identify flavonols and flavones of C. icaco fruit and contribute to further phytochemical studies. The preliminary results indicated the presence of quercitine 3-arabinoside and api-genin 7-O-glucoside.

Chrysolbalanus icaco is considered a species that has morphological differences. Analyses of the content of secondary metabolites in its fruit could be a useful tool for classification. Flavonols and flavones can serve chemical taxonomy to determine relationships of hybrids and to identify and register new cultivars. As a preliminary study, a series of phytochemical analyses were done using paper chromatography and UV/VIS spectrophotometry to obtain Rf and spectral values to identify flavonols and flavones of C. icaco fruit and contribute to further phytochemical studies. The preliminary results indicated the presence of quercitine 3-arabinoside and api-genin 7-O-glucoside.

One-dimensional profiles of agricultural product prices, domestic price indexes for consumers and producers, and exchange rates of Mexican pesos per US dollar can be characterized by the statistical fractal dimension D, estimated through the slopes of the log-log geostatistical variograms, assuming that the relationships between the average variances and time increments are described by a power law. This assumption corresponds to the concept of self-affinity. D values between 1 and 1.5 indicate predictability, while D values from >1.5 to 2 indicate chaotic behavior and unpredictability. Monthly price series of white garlic, ‘bola’ onion, medium-size cabbage, yellow peach and ‘Flor de Mayo’ beans show finite variance, while the other variables showed infinite a priori variance. The white garlic price series is described by D=1.460.179, with a behavior similar to the Brownian motion fractal function.

A combined selection of maternal half sib was applied to a local pipiana squash population under the maize-squash association sys-tem. Genetic variances for plant, fruit and seed characters were estimated. The results indicate that genetic variance exists for the different characters under study. The total genetic variance was determined mainly by additive effects of the genes. The heritability changed with the cycles of evaluation and selection; in 1997 it fluctuated between 24 and 83 %, and in 1998 between 6 and 90 %. Characters of fruit such as color, thickness and flavor of flesh were improved by selection: color turned from an unpleasant green to a pleasant yellow; the seed enlarged 0.02 cm in width; thickness of flesh gained 0.14 cm, and flavor went from insipid and sour to sweet.

Huitlacoche is a fungus that infects maize plants. It is very appreciated as a human food in central Mexico, where six industries commercialize the canned fungus. Total industrialized production depends on spontaneous fungus recolection from cultivated maize fields used to obtain grain. The objectives of this study were to evaluate and select Ustilago maydis teliospores with a high virulence on corn, and to evaluate and select half sib families with a susceptibility and resistance to huitlacoche. In 1997, 100 isolations were evaluated in an experimental hybrid and 12 were selected, which showed an average 190 g of fungus per infected plant and 135.24 g per inoculated plant (8.11 t(ha1; 60 000 plant(ha1); a severity index of 36.82, and 70.64 % of incidence. In 1998, 300 half sib families were inoculated with a mixture of the 12 isolations selected in the previous cycle. Then, 16 susceptible families were se-lected, and they showed an average 154.97 g of fungus per infected plant, 112.88 g per inoculated plant (6.67 t(ha1), 76.67 % of in-cidence and 34.82 of severity index. In addition, 14 resistant families to huitlacoche were selected (0 % incidence).