-The objectives of this work were to evaluate the frequency of polyembryony, and to identify zygotic and nucellar seedlings of Citrus volkameriana using RAPD. Twenty-five polyembryonic and eight monoembryonic seeds were cultivated in vitro for six months. DNA from seedlings was extracted and used in combination with five RAPD primers to identify zygotic or nucellar origin of the seedlings. Environmental conditions of the year affected significantly (P≤0.05) the morphological characteristics of fruits and the number of embryos per seed. Polyembryonic seeds ranged from 30.9%, 44.8% to 54.4% over three years. Morphological characteristic was not correlated with polyembryony. In vitro culture enable all embryos of each seed to grow, favoring the percentage of seedlings identified as zygotic. In polyembryonic and monoembryonic seeds, 25.9% and 87.5% of the seedlings, respectively, were sexually originated. In polyembryonic seeds, not all zygotic seedlings were produced by small embryos located at the micropyle.Index terms: Citrus volkameriana, rootstock, embryo culture, molecular markers, polymorphism. Termos para indexação: Citrus volkameriana, porta-enxerto, cultura de embriões, marcadores moleculares, polimorfismo. Poliembrionia e identificação de seedlings zigóticos e nucelares de limão volkameriano com RAPD

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Phenotypic variation in different populations of Opuntia cantabrigiensis, O. leucotricha, O. rastrera, O. robusta and O. streptacantha was evaluated by examining 28 anatomical and morphologic variables through discriminant analysis. These populations are separated from each other by di stances ranging between 32 and 1 JO km. Altitude and annual average temperature showed no variation in the study area. Discriminant analysis separated populations of O. cantabrigiensis, which is the species having the lowest density (13 individuals ha-1), whilst sorne populations of other Opuntia species, whose densities were as high as 1,852 individuals ha•1, overlapped. No different ploidy levels were found among populations, although we recorded levels of ploidy between species that ranged from diploid (O. rastrera) to octoploid (O. streptacantha). Therefore, phenotypic differences between populations appear to be related to the density of individuals rather than to environmental variables, given the Jack of environmental gradients or change in level ploidy.

Para conocer el cruzamiento intraespecífico y su posible implicación en la domesticación del Cempoalxochitl (Tagetes erecta L.), se realizó manualmente la autopolinización y la polinización cruzada intrapoblacional (PaP) en T. erecta cultivada y su pariente silvestre. La autopolinización en el silvestre produjo poca semilla (17 %), mientras que en el cultivado fue mayor (74 %); con la polinización PaP, hubo alta producción de semillas en ambas poblaciones (91 a 95 %). En el silvestre, las semillas de polinización PaP germinaron poco (0-4 %), pero las de autopolinización germinaron más (19-31 %); en el cultivado, la germinación fue mayor (93- 96 % de autopolinización y 100 % de PaP) que en el silvestre. Plantas silvestres obtenidas por cruzamiento PaP presentaron morfología floral normal, pero las obtenidas por autopolinización presentaron morfología floral cercana a la del cultivado, con incrementos hasta del 100 % respecto del fenotipo normal; en plantas cultivadas hubo mayor expresión floral, resultando mejor en plantas de polinización PaP que de autopolinización. Plantas silvestres derivadas de polinización PaP formaron pocas semillas (6 %), pero las de autopolinización formaron más (24 %); en las cultivadas, las plantas originadas de polinización PaP formaron 32 % de semillas, lo cual fue menor que en aquellas de autopolinización (62 %). Las respuestas que mostró la progenie silvestre obtenida por autopolinización, con tendencia parecida a las respuestas del cultivado, permiten plantear que la autopolinización en la población silvestre, produjo progenies con modificaciones seleccionadas durante el proceso de domesticación de T. erecta.

A mutant causing partial desynapsis (dissociation of paired chromosomes), and consequently a high frequency of univalents at metaphase 1, was found in Rhoeo spathacea among the selfed progeny of a wild-collected ring-forming complex interchange heterozygote. All the plants were diploid, 2n = 2x = 12. The mutant formed univalents in all microsporocytes (range 2–12; average 7.56/cell), and 23.69% of the pollen mother cells contained the maximum of 12 univalents at metaphase I. There was no significant difference in pollen fertility between the mutant and parental plants. The desynaptic mutant produced microspores with chromosome numbers of n = 6–14 in the same anther. Unreduced pollen was formed at telophase II by second division restitution and comprised 52.74% of the pollen grains. By selfing, diplandrogynous tetraploid progeny (2n = 4x = 24) of 12 seedlings were obtained. The results demonstrate that both male and female gametes are unreduced.Key words: Rhoeo, desynapsis, univalent, second division restitution, tetraploid.