María del Socorro González-Elizondo

Chromosome reduction in Eleocharis maculosa (Cyperaceae)

Chromosome numbers in Cyperaceae lower than the typical basic number x = 5 have been described for only three species: Rhynchospora tenuis (n = 2), Fimbristylis umbellaris (n = 3) and Eleocharis subarticulata (n = 3). Eleocharis maculosa is recorded here as the fourth species of Cyperaceae that has a chromosome number lower than 2n = 10, with 2n = 8, 7 and 6. The karyotype differentiation in E. maculosa was studied using conventional staining (mitosis and meiosis), FISH with 45S and 5S rDNA and telomere probes. The results allow us to determine which chromosomes of the chromosome race with 2n = 10 fused to form the remaining reduced numbers, as well as to understand how the symploidy and translocation mechanisms were important in karyotype differentiation and the formation of chromosome races in Eleocharis.

Cytogenetical and cytotaxonomical analysis of some Brazilian species of Eleocharis (Cyperaceae)

Karyotype analysis of 21 samples of 11 species of Eleocharis (Cyperaceae) from 10 localities in Brazil, showed the presence of chromosomes without primary constrictions and parallel movement of chromatids at metaphase–anaphase transition. Only the terminal nucleolar constrictions (satellites) were visualised. The chromosome numbers varied from 2n = 6 in E. subarticulata to 2n = 54 in E. acutangula, but the chromosome basic number x = 5 was confirmed. Generally, C-CMA3+ bands appear mostly in the extremities of the chromosomes, associated to NOR, and interstitial C-CMA3 bands were found only in E. geniculata and E. acutangula. C-DAPI+ bands were not found. Fluorescence in situ hybridisation (FISH) with the 45S rDNA probe was performed in five species. The results showed from four to eight hybridisation signals, always terminal. The analysed species include representatives of the following three subgenera of Eleocharis that occur in Brazil: Limnochloa, Scirpidium and Eleocharis. Species from the subgenus Limnochloa have small and numerous chromosomes. The remaining species, belonging to subgenera Eleocharis and Scirpidium, possess fewer and larger chromosomes. In subgenus Eleocharis, karyotypes of the section Eleocharis were differentiated by symploidy, agmatoploidy and polyploidy, whereas species of the section Eleogenus were all polyploids. Polyploidy seems to be the most frequent event in the karyotype differentiation in Eleocharis, but changes in the chromosome size and repetitive DNA sites were also observed.

Flavonoid composition and antioxidant capacity of the edible flowers of Agave durangensis (Agavaceae)

The antioxidant properties and the flavonoid composition of extracts of different hydrophobicity prepared from the entire edible flowers of Agave durangensis were evaluated. Separately, total extracts of tepals and anthers–pollen were analyzed in the same manner. The high performance liquid chromatography with photodiode array detection (HPLC–DAD) analysis revealed a total of eight flavonols (five quercetin glycosides and three kaempferol glycosides), varying in number and concentration in the different extracts. The total extracts of the entire flowers showed the highest flavonoid content (1210.4 µg/g dry extract) and the most complex flavonoid profile (eight compounds). All the extracts showed important antioxidant activity, which was not evidently associated with their flavonoid content. The total extracts of tepals showed the highest antioxidant properties (total antioxidant capacity, free radical scavenging activity, and iron reducing capacity: 30.2 mg ascorbic acid equivalents, EC50 = 0.074 µg/mL, and IC50 = 43.28 µg/mL, respectively). The flowers of A. durangensis represent an important source of antioxidant flavonols.

Karyotypic diversification and its contribution to the taxonomy of Eleocharis (Cyperaceae) from Brazil

A karyotype analysis of 147 populations of 25 Brazilian species of Eleocharis (Cyperaceae) was carried out, including representatives of the three subgenera that occur in the country: Limnochloa, Scirpidium and Eleocharis. The analyses showed chromosomes without centromeres, but with terminal nucleolar constrictions (satellites) in some chromosomes. The chromosome numbers varied from 2n = 6 in E. subarticulata and E. maculosa to 2n = 60 in E. laeviglumis, but the chromosome basic number x = 5 was confirmed. Species of the subgenera Eleocharis and Scirpidium possess fewer and larger chromosomes, while those in the subgenus Limnochloa have small and more numerous chromosomes. These features indicate that the karyotypes of the subgenera Eleocharis and Scirpidium are more closely related, in agreement with morphological and phylogenetical data. The representatives of the section Eleocharis exhibited the largest differences in chromosome number and size, probably due to chromosome fission and fusion. Polyploidy was the most common event in this group. Nevertheless, most of the studied species exhibited regular meiosis with only bivalent formation, even the polyploids, such as in E. geniculata and E. sellowiana. The cytogenetic information obtained showed quite variable karyotypes with chromosomes gradually decreasing in size, and predominance of polyploidy. These results are useful in the differentiation of the subgenera.

Degree of Hybridization in Seed Stands of Pinus engelmannii Carr. In the Sierra Madre Occidental, Durango, Mexico

Hybridization is an important evolutionary force, because interspecific gene transfer can introduce more new genetic material than is directly generated by mutations. Pinus engelmannii Carr. is one of the nine most common pine species in the pine-oak forest ecoregion in the state of Durango, Mexico. This species is widely harvested for lumber and is also used in reforestation programmes. Interspecific hybrids between P.engelmannii and Pinus arizonica Engelm. have been detected by morphological analysis. The presence of hybrids in P. engelmannii seed stands may affect seed quality and reforestation success. Therefore, the goals of this research were to identify introgressive hybridization between P. engelmannii and other pine species in eight seed stands of this species in Durango, Mexico, and to examine how hybrid proportion is related to mean genetic dissimilarity between trees in these stands, using Amplified Fragment Length Polymorphism (AFLP) markers and morphological traits. Differences in the average current annual increment of putative hybrids and pure trees were also tested for statistical significance. Morphological and genetic analyses of 280 adult trees were carried out. Putative hybrids were found in all the seed stands studied. The hybrids did not differ from the pure trees in vigour or robustness. All stands with putative P. engelmannii hybrids detected by both AFLPs and morphological traits showed the highest average values of the Tanimoto distance, which indicates: i) more heterogeneous genetic material, ii) higher genetic variation and therefore iii) the higher evolutionary potential of these stands, and iv) that the morphological differentiation (hybrid/not hybrid) is strongly associated with the Tanimoto distance per stand. We conclude that natural pairwise hybrids are very common in the studied stands. Both morphological and molecular approaches are necessary to confirm the genetic identity of forest reproductive material.

Evaluation of foliar phenols of 25 Mexican varieties of common bean (Phaseolus vulgaris L.) as antioxidants and varietal markers

The antioxidant properties and the foliar phenol composition of 25 Mexican varieties of Phaseolus vulgaris L. (common bean) were evaluated. Phaseolus coccineus was analysed with comparative aims. The high performance liquid chromatography with photodiode array detection analysis revealed 27 phenolics in the leaves of P. vulgaris (13 quercetin-3-O-glycosides, 8 kaempferol-3-O-glycosides, 2 myricetin glycosides and 4 phenolic acids) and 5 in P. coccineus (2 kaempferol-3-O-glycoside, 2 apigenin-7-O-glycoside and 1 luteolin-7-O-glycoside). All extracts showed high levels of phenols and flavonoids (0.964–5.601 mg g− 1 dry tissue, and 0.287–1.418 mg g− 1 dry tissue, respectively) and relevant antioxidant properties, suggesting that the leaves of the varieties of P. vulgaris are a significant source of natural antioxidants. The foliar phenol profiles were species-specific and, besides, the qualitative variation allowed discriminating among varieties of P. vulgaris. These profiles can represent an important varietal authenticity proof.

Genome differentiation, natural hybridisation and taxonomic relationships among Eleocharis viridans, E. niederleinii and E. ramboana (Cyperaceae)

Abstract. The role of natural hybridisation and genome changes in the differentiation and speciation of Eleocharis (Cyperaceae) was addressed through the study of the following three closely related species of the polyphyletic series Tenuissimae: Eleocharis viridans Kük. ex Osten, E. ramboana R.Trevis & Boldrini and E. niederleinii Boech., which often reproduce asexually. Molecular and cytogenetic data were used to understand the genomic and karyotypic relationships in the group. Genomes were compared using internal transcribed spacer–cleaved amplified polymorphic sequence (ITS-CAPS) marker and confirmed with random amplified polymorphic DNA, which allowed identification of different genetic groups, with clear evidence of natural hybrids. Karyotype analysis showed numerical variation from 2n = 20–42, with occurrence of chromosome heteromorphisms and polymorphisms, including variability in 35S rDNA site numbers. Meiotic studies demonstrated irregular pairing in some samples, which is associated with hybridisation and asexual reproduction. Genomic in situ hybridisation (GISH) reactions were conducted using two well defined genetic groups as probes, with 2n = 20 and normal meiosis. Probes were tested against each one of the genetic groups and showed positive, partial and negative GISH results, which supported the molecular analysis data. The results indicated that the three studied species are undergoing an intense process of genomic and karyotypic re-arrangement, which results in overlapping of morphological and genomic characteristics. The present study has exemplified the value of an integrative taxonomic approach to solve conflicts in species delimitation in groups undergoing hybridisation.

Effects of density and structure on production in the communal forests of the Mexican Sierra Madre Occidental

The Sierra Madre Occidental in the Mexican State of Durango, is home to about 5 million ha of species-rich forest ecosystems. Local communities depend on these forests for their livelihood. The preservation of the species richness and productivity of this unique resource requires improved understanding of the effects of forest structure and density on production. The community structure was analysed for three species groups (all species; 12 species of Pinus; and 16 species of Quercus). Based on data gathered in 580 remeasured observational field plots, the main results of this study were as follows: (1) two distinct clusters were identified in each species group, (a) the dominant species with a smaller range of growth rates, and (b) the remaining species which have a smaller maximum size and a greater variation of growth rates. (2) Density (expressed as basal area per hectare) and the percentage contribution to the total basal area of all pine species have a significant effect on forest production (expressed as volume increment per hectare per year). (3) Potential production is surprisingly high (in excess of 20 m3 ha−1 y−1 for some stands) in these forests, but the high potential cannot be realised in many areas because of reduced basal areas caused by overharvesting. (4) The available evidence does not confirm the findings of a recent study that suggests a continuous increase in production with increasing richness. Our observations show that production attains a potential maximum at intermediate levels of richness (between 7 and 9 species per 0.25 ha) and declines with further increases in species richness. This study represents a comprehensive analysis of the effects of density and structure on the community forests of the Sierra Madre Occidental based on a large set of permanent field plots where all trees have been mapped.