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S. Perez-Gonzalez

The garambullo is a native cactus that grows wild in the semiarid region of central and northeastern Mexico. It is highly appreciated by local people for the quality of its fruits and as a pigment source for the food industry. However, there is no information available about its real production potential. The main objective of this work is to collect field data about tree density, phenology, and yield components of natural stands. Six plots (2000 m2 each) were randomly selected where garambullo grows wild in southwestern Querétaro and the following data was collected: number and distance among trees, age distribution, blossom and harvest season, fruit weight and number/tree, fruit/areole, areoles/fruiting arm, arms/branch and branches per tree. Tree density and yield varied greatly among plots and trees, from less than 20 to 237 trees/ha, and from less than 100 to 10,000 fruits/tree. Average fruit weight was 0.97 g and mean yield/tree was 2.79 kg. Possibilities for increasing yield efficiency will be discussed.

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S. Pérez-González

Previous work has concluded that 7C is the optimum temperature for promoting peach and apricot seed germination. However, these results were based only on genotypes from septentrional regions. The objective of this study is to describe the behavior of a wider range of genotypes and species from temperate-subtropical regions, as a background to detect potential germplasm sources for adaptation to this environment. Seed samples from five species of Prunus were evaluated during stratification at several temperature regimes: Ambient fluctuating from 8 to 16C, 7C, 10C, and 14 ± 1.5C, from 1993 to 1995. Seed germination was monitored twice a week. Great differences were registered among species and genotypes for both speed and percent germination within each temperature treatment. With local species and genotypes germinating equally well and faster at warm temperatures than previously reported. These results will provide an important screening tool when selecting for adaptation to local climates, and also as a way to determine annual “winter quality,” in terms of chilling accumulation in the southern distribution range of temperate fruit crops in the north hemisphere.

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S. Pérez-González

The variability of species under local ecosystems, particularly in response to temperatures during endodormancy, permits adaptation of temperate fruit trees to subtropical climates. Information about the behavior of endodormant fruit trees and seeds is based on a narrow genetic base from higher latitudes. This work was conducted to generate information about responses of endodormant seeds from several subtropical peach (Prunus persica L.) genotypes, as a basis for breeding and selection in these regions. Samples of peach seeds were collected from genotypes originating at a range of altitudes in tropical-subtropical regions to evaluate their responses to different temperatures and lengths of stratification periods. When seeds were stratified at 7 °C, some genotypes with very low-chilling requirement registered a high percent germination in <40 days, and all accessions studied reached 95% germination before day 80. When seeds were stratified at warmer temperatures (10 and 14 °C), germination started earlier and was high at 10 °C for most accessions. Although seeds of some late-blooming accessions germinated earlier at 10 or 14 °C than at 7 °C, percent germination was lower and time-response curves were flatter. This contrasts with previous reports on genotypes with high-chilling requirement, where no germination was registered at 14 °C. These observations provide a background for screening seedlings for adaptation to local conditions, and suggest that endodormancy models should be based on information generated from local genotypes when applied in subtropical regions.

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S. Pérez-González

A highly significant correlation was observed between time of bloom of individual peach trees [Prunus persica (L.) Batsch.] and number of days required for resulting selfed seed to reach 80% germination on both local (r = 0.71) and introduced (r = 0.87) genotypes that exhibited a wide range in time of blossom. When genotypes with low chilling requirement (LCR) were pollinated with high chilling requirement (HCR) pollen sources, germination was delayed up to 16 days with respect to seeds that originated from selfing, while LCR pollen sources on late-blossoming genotypes accelerated germination 20 to 24 days.

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C. Mondragón-Jacobo and S. Perez-González

Cactus pear production has been an outstanding activity during the last two decades in central Mexico. It has been devoted mainly to fresh consumption for the national market and for exporting to the USA to a lesser extent. Official statistics report ≈200,000 ton of fresh fruit entering the market every year from June to September. Such a volume is supported on a limited stock of varieties that were originally selected by growers. They were first cultivated in backyards and now as commercial orchards under rainfed conditions. With the exception of `Reyna', there are no formal descriptions of such varieties. This information will be valuable to growers and could provide a background to define breeding goals and strategies. Data was collected in 1992–94 from 12 of the most important cactus pear varieties in central Mexico. The following traits related with fruit quality we registered: fruit weight and color, peel thickness, seed number, and weight and soluble solids. Average fruit size ranged from only 679 in `Charola' to more than 200 g in `Cristalina' with 2.8 and 5.6 g of seeds/fruit, respectively. Commercially, white fleshed fruit is highly appreciated, but there is a wide range from yellow and orange to deep red. Edible portion ranges from 46% in `Cardona' to 64% in `Centenario', while percent soluble solids showed less variability (13.2–15–9), which seems to be strongly influenced by light and temperature at harvest.