Thin cell suspension layer as a new methodology for somatic embryogenesis in Agave tequilana Weber cultivar azul

Commercial micropropagation of plants is enhanced with the use of liquid media cultures; however the presence of hyperhydricity is commonly observed in cultures of the succulent plant Agave tequilana Weber cultivar azul, this phenomenon persists even with the use of temporary immersion systems (TIS). Thin cell suspension layer technology is proposed to solve this problem. This technology fuses the advantages of a liquid culture made through cellular dissociation, and the use of solid medium for somatic embryogenesis expression of the species. The technology was evaluated by means of two experiments in order to know the influence of gelling agent phytagel®, and of sucrose concentrations through interaction with three cellular suspension densities. It was clear that concentrations of phytagel at 6, 8, 10 or 12 g l-1 are not significant for embryoid expression of A. tequilana. On the other hand, sucrose at 30 and 60 g l-1 have statistically superior values than concentration of 120 g l-1. A larger cellular density (161 × 103 cells ml-1) gave a statistical difference in number of embryoids. The advantages of thin cell suspension layer were remarkable: it encouraged complete expression of embryoids without transfer to extra media cultures, and a higher number of generated embryoid was obtained. Absence of hyperhydricity was observed in all regenerants. © 2008 Elsevier B.V. All rights reserved

Cellular and molecular changes associated with somatic embryogenesis induction in Agave tequilana

In spite of the importance of somatic embryogenesis for basic research in plant embryology as well as for crop improvement and plant propagation, it is still unclear which mechanisms and cell signals are involved in acquiring embryogenic competence by a somatic cell. The aim of this work was to study cellular and molecular changes involved in the induction stage in calli of Agave tequilana Weber cultivar azul in order to gain more information on the initial stages of somatic embryogenesis in this species. Cytochemical and immunocytochemical techniques were used to identify differences between embryogenic and non-embryogenic cells from several genotypes. Presence of granular structures was detected after somatic embryogenesis induction in embryogenic cells; composition of these structures as well as changes in protein and polysaccharide distribution was studied using Coomassie brilliant blue and Periodic Acid-Schiff stains. Distribution of arabinogalactan proteins (AGPs) and pectins was investigated in embryogenic and non-embryogenic cells by immunolabelling using anti-AGP monoclonal antibodies (JIM4, JIM8 and JIM13) as well as an anti-methyl-esterified pectin-antibody (JIM7), in order to evaluate major modifications in cell wall composition in the initial stages of somatic embryogenesis. Our observations pointed out that induction of somatic embryogenesis produced accumulation of proteins and polysaccharides in embryogenic cells. Presence of JIM8, JIM13 and JIM7 epitopes were detected exclusively in embryogenic cells, which supports the idea that specific changes in cell wall are involved in the acquisition of embryogenic competence of A. tequilana. © 2012 Springer-Verlag

Effect of plant growth regulators on plant regeneration of Dioscorea remotiflora (Kunth) through nodal explants

Dioscorea remotiflora (Kunth) is an important wild plant that produces tuberous roots used as a source of food in the Western part of Mexico. Lack of planting material and inefficiency of traditional methods of propagation are the main constraints for implementing large-scale cultivation. In contrast, tissue culture techniques allow increasing multiplication and rapid production of plant material. In this regard, leaves or nodal segments were incubated on MS, B5 and WPM culture media with different PGRs in order to obtain an efficient micropropagation protocol. Leaves explants were unable to inducing shoots or callus. However, nodal segments produced axillary shoots and/or callus in all culture media. MS containing 2. 33 ?M KIN was the most suitable to inducing shoots; an average of 6. 6 shoots per segment for 100 % explants was obtained, which displayed also the greater number of nodes (5. 0) and leaves (7. 9) per segment. A decrease on shoot proliferation was observed combining BA or KIN with 2,4-D or NAA. However, small brownish callus were induced on 100 % of segments using 2. 33 ?M KIN with 5. 37 ?M 2,4-D or 9. 30 ?M KIN plus 2. 69 ?M NAA. In contrast, by adding 2. 69 ?M NAA, 66. 4 % of the nodal segments formed shoots and produced also yellowish friable callus on the base of the shoots. Shoots were easily rooted with 8. 28 ?M IBA (96. 9 %), displaying the greatest root and shoot biomass, but maximum number of tuberous roots, and root or tuberous root biomass was produced increasing IBA (20. 7 ?M). � 2012 Springer Science+Business Media B.V

Efficient in vitro propagation of Agave parrasana Berger

An efficient method for the in vitro propagation of Agave parrasana Berger, an important ornamental plant species native to the state of Coahuila, Mexico, was developed. Proliferation of good quality shoots was achieved on agar-solidified basal MS medium supplemented with L2 vitamins and 13.3 μM benzyladenine. Rooting was successful in the basal medium with no growth regulators; however, a light intensity of 100 μmol m-2 c-1 was found to promote better rooting that 25 μmol m-2 s-1

Somatic embryogenesis in Agave tequilana Weber cultivar azul

Somatic embryogenesis was achieved from leaves of Agave tequilana Weber cultivar azul utilizing MS medium supplemented with L2 vitamins and the addition of cytokinins: 6-benzylaminopurine (BA), 1-phenyl-3(1,2,3-thiadiazol-5-yl)urea (TDZ), 6-(?-?-dimethylamino)purine (2ip) and 6-furfurylaminopurine (KIN), combined with the auxin 2,4-dichlorophenoxyacetic acid (2,4-D). Differences among the six genotypes studied with regard to their embryogenic response in culture were found. Embryos produced by genotype S3 under a hormone regime of high cytokinin (44.4 to 66.6 ?M BA) compared to auxin (4.5 ?M 2,4-D) contained chlorophyll, whereas those produced when auxin was high compared to cytokinin (9.0 and 13.6 ?M 2,4-D and 1.3 and 4.0 ?M BA, respectively) were whitish and morphologically similar to their zygotic counterparts. Somatic embryos matured and germinated after transferring the embryogenic calli to maturation and germination medium without growth regulators and enriched with organic nitrogen. Microscopic observations demonstrated a unicellular origin for production of indirect somatic embryos. � 2007 The Society for In Vitro Biology

Effect of liquid seaweed extracts on growth of tomato seedlings (Solanum lycopersicum L.)

Seaweed extracts are used as nutrient supplements, biostimulants, or biofertilizers in agriculture and horticulture to increase plant growth and yield. In this study, we examined the effect of liquid seaweed extracts (LSEs) made from Ulva lactuca, Caulerpa sertularioides, Padina gymnospora, and Sargassum liebmannii as biostimulants on the germination and growth of tomato (Solanum lycopersicum) under laboratory and greenhouse conditions using foliar and soil drench applications of LSEs. We assessed LSEs at different concentrations (0.2, 0.4, and 1.0 %) on germination parameters (percentage, index, mean time, energy, and seedling vigor index) and growth parameters (plumule length, radical length, shoot length, root length, fresh weight, and dry weight) of tomato seedlings. Our results indicate that seeds treated with LSEs of U. lactuca and P. gymnospora at lower concentrations (0.2 %) showed enhanced germination (better response in germination rate associated with lower mean germination time, high germination index and germination energy, and consequently greater seedling vigor and greater plumule and radicle length). Application as a soil drench was found to be more effective in influencing the height of the plant (up to 79 cm) than the foliar spray application (75 cm). Plants receiving LSEs of U. lactuca and P. gymnospora showed increased shoot length, root length, and weight. Furthermore, U. lactuca and P. gymnospora were found to be more successful and better candidates for developing effective biostimulants to improve the growth of tomato plants. This study provides important information on the identification and utilization of Mexican seaweed resources for agriculture and is the first study to report on the uses of these seaweeds as a source of liquid extracts as biostimulants in agriculture. © 2013 Springer Science+Business Media Dordrecht

Seed dormancy in Mexican teosinte

Seed dormancy in wild Zea species may affect f tness and relate to ecological adaptation. The primary objective of this study was to characterize the variation in seed germination of the wild species of the genus Zea that currently grow in México and to relate this variation to their ecological zones of adaptation. In addition, we compared methods to break dormancy and measured the germination responses of seeds to environment factors that are related to seasonal changes. Teosinte populations representing all the taxonomic and racial groups known in México were collected during the period 2003 to 2008 in twelve states of México. Seed dormancy was classif ed according to the rate of its loss (depth of dormancy). Results indicated that more than 90% of populations studied had some degree of seed dormancy. Nondormant populations are distributed predominantly in semicold areas, while deep and very deep seed dormancy was found in populations distributed in hot and very hot environments in well def ned geographic regions of the Balsas River Basin and in San Felipe Usila, Oaxaca. Mechanical seed scarif cation was the best method to break dormancy. © Crop Science Society of America

Morphological traits of cultivated, wild and weedy forms in climbing common bean [Características morfológicas de formas cultivadas, silvestres e intermedias de frijol común de hábito trepador]

A morphologic characterization of domesticated, wild and weedy forms of climbing common bean (Phaseolus vulgaris L., Fabaceae) was carried out. Fifteen genotypes were evaluated under a randomized complete block design with three replications. In order to know the relationships between included forms, 18 quantitative variables were registered. Data were analyzed by analysis of variance, cluster analysis based on euclidian distance and principal components. Twelve of 18 traits showed differences (P ≤ 0.05) between domesticated and wild forms, 10 between domesticated and weedy types, and five between weedy and wild beans. Domesticated forms were higher in length and width of pod, seed length, width and thickness and seed weight, compared to wild forms; the weight of 100 grains varied from 5.04 to 42.93 g. The length of stem and number of nodes were not different among forms. The number of pods per plant and seeds per pod recognized as yield components, did not show reductions in the domesticated form; these traits are associated with high yield potential in cultivated forms. Within each bean form the materials presented little morphological variation. The domesticated, wild and weedy forms of common bean of climber growth habit, constitute three groups with different morphological traits. The weedy form comprises an intermediate group, morphologically closer to wild beans

Chromosome identification in the genus Lilium using comparative genomic in situ hybridization (cGISH)

Single chromosome identification is of primal importance in the study of evolutive process in complex genomes, such as polyploidization and hybridization events, among others. Traditionally, chromosome identification is made by arranging the chromosomes by the length of the short (p) and the long (q) arms, identifying the centromeres and secondary constrictions. Furthermore, accurate chromosome identification can be performed trough chromosome differentiation techniques such as C-, N-, and Q-banding. In the last years, through the development of fluorescent in situ hybridization techniques (FISH), even more accurate single chromosome identification has been accomplished, by the hybridization of highly conserved repetitive sequences, such as rDNAs. However, particular probes must be developed through laborious isolation and cloning molecular techniques. The comparative genomic in situ hybridization (cGISH) is a straightforward technique that allows the identification of single chromosomes by the generation of signals of conserved DNA regions along the chromosomes of different species. In this study we labeled total genomic DNA of Triticum aestivum and Arabidopsis thaliana and hybridized it to chromosomes of different cultivars of the genus Lilium. Different stringencies were applied to determine the optimum removal of cross hybridization, the 80% stringency showed to be the best, giving a clear signal and removing most of the cross hybridization. Triticum aestivum total genomic DNA exhibited six landmarks on three homologous chromosomes in the three different cultivars while Arabidopsis thaliana total genomic DNA exhibited six landmarks on three homologous chromosomes of Lilium, one of these signals being in a different chromosome of those of the T. aestivum signals. Together with the DAPI bands the total genomic DNAs landmarks allowed the identification of six out of 12 single homologous chromosomes

Morphological traits of cultivated, wild and weedy forms in climbing common bean [Características morfológicas de formas cultivadas, silvestres e intermedias de frijol común de hábito trepador]

A morphologic characterization of domesticated, wild and weedy forms of climbing common bean (Phaseolus vulgaris L., Fabaceae) was carried out. Fifteen genotypes were evaluated under a randomized complete block design with three replications. In order to know the relationships between included forms, 18 quantitative variables were registered. Data were analyzed by analysis of variance, cluster analysis based on euclidian distance and principal components. Twelve of 18 traits showed differences (P ? 0.05) between domesticated and wild forms, 10 between domesticated and weedy types, and five between weedy and wild beans. Domesticated forms were higher in length and width of pod, seed length, width and thickness and seed weight, compared to wild forms; the weight of 100 grains varied from 5.04 to 42.93 g. The length of stem and number of nodes were not different among forms. The number of pods per plant and seeds per pod recognized as yield components, did not show reductions in the domesticated form; these traits are associated with high yield potential in cultivated forms. Within each bean form the materials presented little morphological variation. The domesticated, wild and weedy forms of common bean of climber growth habit, constitute three groups with different morphological traits. The weedy form comprises an intermediate group, morphologically closer to wild beans