Patterns of meiotic chromosome pairing were compared between three sunflower plants: cultivated sunflower (Helianthus annuus L. var. macrocarpus, public line HA 89), wild sunflower (Helianthus annuus L. ssp. texanus Heiser, collected in Saltillo, Coah.), and the F 1 hybrid. The study was carried out through analysis of meiocytes in diakinesis and metaphase I, based on the meiotic configuration frequency. Pollen viability was evaluated by means of a staining method. Chromosome pairing was normal in the three materials, with absence of univalents and multivalents, and only chain and ring bivalents were observed, therefore the parental genomes are highly compatible in meiosis. The hybrid showed a chromosome pairing index of 0.82, close to the midparent value (0.80), and the differences between the hybrid and each parental taxon (cultivated 0.87, and wild 0.75) were highly significant. Besides, this index was variable within populations. This indicates that the chiasma number is under multigenic control and is affected by the environment. Thus, a population formed with both progenitors could be used to analyze the quantitative trait loci (QTLs) for meiotic chromosome pairing. The pollen viability in the hybrid (92.58%) was similar to that found in the parental taxa (wild 95.57%, and cultivated 95.33%). The pollen viability of the F 1 was high, it showed fertility, and the parental genomes were highly compatible in meiosis, confirming that there is no barrier for the sexual reproduction, and that gene flow and transference of desirables characters from wild to cultivated H. annuus are easily attainable.
Recent molecular studies on the Burseraceae phylogeny point out that the Bursera -Commiphora complex is monophyletic. Both genera develop a brightly colored paseudaril, and it is possible to presume which tissue is a homologous character. This work analyzes the development of this tissue in 14 species of Bursera, with the aim to determine the existence of a single type of ontogenetic origin. The overall development of the pseudaril in Bursera is described from a histological point of view and it is compared with the development of this tissue in Commiphora, as reported in the literature. Results indicate that the exocarp and endocarp sensu stricto derive from the external and internal epidermis, respectively, whereas the pseudaril differentiates from mesocarp in both genera. The primary difference in fruit development between the 2 sections of Bursera consists in the pseudaril differentiation, which initiates in earlier developmental stages in species of section Bullockia compared to those of section Bursera. To conclude, ontogeny and function of the pseudaril of Bursera agree with that described for Commiphora; thus, it is strongly suggested that the aforesaid tissue is homologous in both genera.
En este trabajo se estudiaron los cromosomas de Turbinicarpus valdezianus en diacinesis y metafase I, de plantas nativas de la región aledaña a Saltillo, Coahuila (México). Se encontró un número cromosómico 2n = 2x = 22, lo cual es consistente con el número básico x = 11 previamente conocido para otros miembros de la familia Cactaceae. El apareamiento normal bivalente observado en todas las células analizadas indica que la especie estudiada es diploide con una segregación cromosómica regular. El análisis de frecuencias de configuraciones meióticas apoya la hipótesis de que uno o más pares de cromosomas podrían ser no metacéntricos.
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