Polyploid and hybrid evolution in roses east of the Rocky Mountains

This study investigates the impact of hybridization and polyploidy in the evolution of eastern North American roses. We explore these processes in the Rosa carolina complex (section Cinnamomeae), which consists of five diploid and three tetraploid species. To clarify the status and origins of polyploids, a haplotype network (statistical parsimony) of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) nuclear gene was estimated for polyploids of the complex and for diploids of section Cinnamomeae in North America. A genealogical approach helped to decipher the evolutionary history of polyploids from noise created by hybridization, incomplete lineage sorting, and allelic segregation. At the diploid level, species west of the Rocky Mountains are distinct from eastern species. In the east, two groups of diploids were found: one consists of R. blanda and R. woodsii and the other of R. foliolosa, R. nitida, and R. palustris. Only eastern diploids are involved in the origins of the polyploids. Rosa arkansana is derived from the blanda-woodsii group, R. virginiana originated from the foliolosa-nitida-palustris group, and R. carolina is derived from a hybrid between the two diploid groups. The distinct origins of these polyploid taxa support the hypothesis that the three polyploids are separate species.     

Embryo development and ageing in birds and mammals

The rate of ageing is a genetically influenced feature of an individual's life history that responds to selection on lifespan. Various costs presumably constrain the evolution of prolonged life, but these have not been well characterized and their general nature is unclear. The analyses presented here demonstrate a correlation among birds and mammals between rates of embryonic growth and ageing-related mortality, which are quantified by the exponents of fitted power functions. This relationship suggests that rapid early development leads to accelerated ageing, presumably by influencing some aspect of the quality of the adult individual. Although the mechanisms linking embryo growth rate and ageing are not known, a simple model of life-history optimization shows that the benefits of longer life can be balanced by connected costs of extended development.     

Embryo sac development in Arabidopsis thaliana

Summary Aspects of megasporogenesis in Arabidopsis thaliana have been investigated using a variety of histochemical techniques to visualize general cell organization, DNA and callose in whole ovules and sections by bright field, fluorescence, differential interference contrast and scanning electron microscopy. The microtubular cytoskeleton has been studied using immunofluorescence localization of tubulin in sections and whole cells. The observations deviate from reports of preceding studies in that the megasporocyte was found to undergo both meiotic divisions followed by simultaneous cytokinesis (i.e. without an intermediate dyad stage) to give a multiplanar tetrad of megaspores. This represents a variation of monosporic development not previously described. Polarized distribution of organelles prior to meiosis ensures that the functional megaspore receives the largest share. Aberrant wall formation is common between degenerating megaspores. Localized callose deposition in the tetrad separates these cells from the active megaspore. Their pattern of degeneration and displacement is extremely flexible within the embryo sac space. The microtubular cytoskeleton is extensive and largely cytoplasmic, as distinct from cortical, throughout megasporogenesis. In the megasporocyte, megaspores and one-nucleate embryo sac, randomly oriented microtubules throughout the cells may serve to maintain cytoplasmic integrity and position organelles. Numerous microtubules (MTs) associate closely with the nucleus and some radiate from it, perhaps functioning in nuclear positioning. During meiosis MTs are restricted to the spindle configurations and later to the phragmoplasts which form between daughter nuclei. The lack of interphase cortical arrays suggests that the role of internal influences on cell shape is small.     

Meiosis in garden roses

Summary Meiosis in 96 varieties of garden roses was studied. While the euploid numbers were most frequent, in exceptional cases, aneuploid numbers were recorded. Intervarietal variation in chromosome pairing is reflected in the varying degrees of expression of univalents, heteromorphic bivalents, bivalents with double secondary constrictions and multivalents. Supernumerary fragments in addition to the euploid chromosome complement were recorded in three varieties. Three varieties of floribundas and one of hybrid polyanthas were chromosome numerical mosaics.A part of Ph. D. thesis submitted by the senior author to the Post Graduate School, Indian Agricultural Research Institute, New Delhi, India.     

Dispersal and size fractionation of embryogenic callus increases the frequency of embryo maturation and conversion in hybrid tea roses

Plant regeneration from embryogenic cells of two Rosa hybrida cultivars, Kardinal and Classy, was increased by dispersing embryogenic callus in liquid medium for 3 h followed by size-fractionation to isolate proembryogenic masses that were smaller than 530 m. Dispersed callus of three cultivars, Kardinal, Classy, and Tineke, produced 61–135 cotyledonary-stage embryos/100 mg fresh weight (FW) as compared to intact callus that had not been dispersed, which produced only zero to three cotyledonary-stage embryos/100 mg FW. Over 500 cotyledonary-stage embryos/100 mg FW callus developed from proembryogenic masses of Kardinal, Classy, and Tineke following 2 months of culture on solidified Murashige and Skoogs basal salts medium supplemented with 0.25% activated charcoal. Cotyledonary-stage embryos of Classy that developed from both dispersed callus and fractionated cells of various sizes showed a significantly higher conversion frequency to plants (28%) than cotyledonary-stage embryos isolated from intact callus (9%). The highest conversion frequencies for Kardinal (50–58%) occurred from cotyledonary-stage embryos that developed from dispersed callus and from the fraction of cells smaller than 850 m.Abbreviations BAP 6-Benzyladenine - FeEDDHA Ferric ethylenediamine di(o-hydroxyphenylacetate) - FW Fresh weight - PEMs Proembryogenic masses - PGRs Plant growth regulatorsCommunicated by S.A. Merkle     

Embryo development after vitrification of immature and in vitro-matured equine oocytes

Effects of meiotic stage and cumulus status on development of equine oocytes after vitrification was evaluated. Immature oocytes with corona radiata (IMM); in vitro-matured oocytes with corona radiata (MAT CR+); and in vitro-matured oocytes denuded of cumulus (MAT CR-) were vitrified using the Cryotech® method. Warming medium was equilibrated either in 5% CO₂ or Air. IMM oocytes underwent in vitro maturation after warming. Recovery, survival, and maturation rates, and cleavage and blastocyst rates after ICSI, were evaluated. Recovery was higher for oocytes warmed in CO₂- than Air-equilibrated medium (86 ± 3 vs. 76.9 ± 4%, respectively). Maturation for all vitrified-warmed oocyte treatments (37 ± 6.5 to 45.9 ± 5.8%) was not different from control (50 ± 4.1%), except for MAT CR- CO₂ (20.3 ± 4.6%). Cleavage for MAT CR- CO₂ and Air groups was similar to control (67.7 ± 12.1, 71.4 ± 8.1, and 78 ± 5.3%, respectively). One blastocyst was produced (MAT CR + CO₂), representing the first equine blastocyst reported after vitrification of an in vitro-matured oocyte.     

In vitro flower induction in roses

Summary Vegetatively propagated plantlets of six rose cultivars were induced to flower in vitro on media containing full-strength Murashige and Skoog (MS) inorganic salts, Gamborg's B5 organic elements with 400 mg l⁻¹ myo-inositol, and different phytohormone combinations of 6-benzyladenine (BA) with α-naphthaleneacetic acid (NAA); thidiazuron (TDZ) with NAA; and zeatin (ZT) with NAA. The most efficient flower bud induction (49.1% and 44.1%) was obtained on media supplemented with 0.5 mg l⁻¹ (2.27 μM) TDZ and 0.1 mg l⁻¹ (0.54 μM) NAA or 0.5 mg l⁻¹ (2.28 μM) ZT and 0.1 mg l⁻¹ (0.54 μM) NAA for cultivar Orange Parade. Scanning electron microscopy (SEM) showed that in vitro flower bud induction occurred mostly between 15 and 30 d in induction medium through the normal flower development processes. With TDZ and ZT as the best choice for flower induction in all six cultivars tested, different rose cultivars varied in their responses to phytohormone treatments. Our study also revealed that the total time from original culture and subculture time before flower induction were two very important factors for in vitro flower induction. Plantlets 156–561 d from original culture and subcultured for 45 d were the best for flower induction. These authors contributed equally to this work.     

Embryo origin and development in Crocus sativus L. (Iridaceae)

Abstract

Fruit and seed set were obtained in the triploid Crocus sativus (saffron) either by hand crossing with pollen of the diploid C. cartwrightianus or by free pollination. The morphology of the capsules and seeds was similar in both Crocus species. The embryo is comparatively small, whereas the endosperm is formed of numerous layers of cells with hemicellulose-thickened walls and a cytoplasm containing few lipid and protein reserves. Seed germination gave rise to a white prophyll from which a green leaf emerged. At the base of this leaf, a small corm without tunics developed, which, after leaf desiccation, became dormant. These corms sown separately in pots were again capable of growth and emitted a single long green leaf. Vegetative development of new corms was similar in the diploid and hybrid saffron plants. In sites of past saffron cultivation the beds were found to contain degenerated corms and corms at different development stages. The absence of fruit and seed set in emasculated and self- and out-pollinated plants suggests that saffron does not form apomictic embryos.     

Inheritance of B chromosomes in garden roses

Transmission of B chromosomes in tetraploid (2n=28) garden roses was studied. A total of 1 304 seeds were used in the experiment which were obtained from various crossings and selfings made between two 1B and four 0B parents. B chromosomes were inherited in only 51 plants out of a progeny of 143. In the progeny 1B was more common in occurrence than 2Bs. About 17% of the plants were aneuploids. In general, the b chromosomes adversely affected survival, vigour and pollen fertility of the progeny plants.This work is a part of a Ph.D. thesis of the University of London (1980).     

A protoplast to plant system in roses

High yields of protoplasts were isolated from embryogenic suspension cultures of Rosa persica x xanthina and Rosa wichuraiana using an enzyme mixture comprising 20 g l^-1 cellulase Onozuka R10, 1 g l^-1 Pectolyase Y-23 and 10 g l^-1 hemicellulase. Agarose-immobilized protoplasts gave the most consistent growth at a plating density of 5×10⁴ protoplasts ml^-1 on the basic medium of Kao & Michayluk (KM8p) containing 2 mg l^-1 naphthaleneacetic acid and 1 mg l^-1 benzylaminopurine. At 25°C in the dark, 0.004% of R. persica x xanthina protoplasts developed into colonies. Using similar culture conditions, but with a plating density of 9×10⁴ protoplasts ml^-1, 0.017% of R. wichuraiana protoplasts developed into colonies. On transfer of R. persica x xanthina colonies to Schenk & Hildebrandt's medium containing 3 mg l^-1 2,4-dichlorophenoxyacetic acid, globular and later stage embryos were formed. Approximately 30% of these embryos developed into plantlets on transfer to basal Schenk & Hildebrandt's medium. Further development of the plantlets took place on cellulose plugs (Sorbarods) soaked in Murashige & Skoog's medium containing 0.05 mg l^-1 naphthaleneacetic acid, 0.05 mg l^-1 indole-3-butyric acid and 0.1 mg l^-1 benzylaminopurine. Rose breeding is now open to the full range of in vitro genetic manipulation techniques involving protoplast technology.     

Untangling the hybrid origin of the Chinese tea roses: evidence from DNA sequences of single-copy nuclear and chloroplast genes

The tea-scented China roses largely correspond to the three recognized double-petaled Rosa odorata (Andrews) Sweet (Rosoideae, Rosaceae) varieties, which are the ancestors of modern hybrid tea roses and had a definite and permanent influence on the evolution of modern garden roses. Here the hypothesis of a hybrid origin of the tea-scented China roses between R. odorata var. gigantea and R. chinensis was tested. Two single-copy nuclear genes of the cytosolic glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and the chloroplast-expressed glutamine synthetase (ncpGS) together with two plastid loci (trnL-F and psbA-trnH) were sequenced for representative accessions of four R. odorata varieties, R. chinensis, and 28 other Rosa species. Phylogenetic relationships were estimated from two nuclear loci using maximum parsimony and Bayesian analyses, and a haplotype network was constructed on the combined plastid data using NETWORK. For GAPDH and ncpGS loci, the clonal sequences of the three double-petaled varieties were clustered into two clades, one clade with R. odorata var. gigantea, and the other with partial sequences of R. chinensis, which suggested that the tea-scented China roses were hybrids between R. odorata var. gigantea and R. chinensis. Two plastid loci suggested that R. odorata var. gigantea could be the maternal parent and R. chinensis the paternal parent.     

An analysis of seed development in Pisum sativum. VII. Embryo development and precocious germination in vitro

Three different culture media have been examined for their ability to support growth in culture of embryos of two pea lines near-isogenic except for the r-locus. Embryos showed a greater increase in fresh weight on a medium containing 10% sucrose and a high level of a mixture of amino acids than on either one containing an equivalent amount of glutamine as the sole nitrogen source or one containing both inorganic nitrogen and a low level of glutamine. Small embryos (up to 10 mg fresh weight) showed the greatest relative increase in fresh weight. Decreasing the osmotic pressure of an agar medium by lowering the sucrose content to 2% and reducing the concentration of amino acids induced precocious germination. Shoot growth was more sensitive than root growth to increasing sucrose concentrations and optimum development was obtained when embryos were cultured in liquid culture at a high osmotic pressure followed by growth on an agar medium at low osmotic pressure. Alternatively, precocious germination could be induced by removing the cotyledons. Embryos of all sizes and of both genotypes of pea responded in a similar manner.     

Impact of habitat on pollen germination in roses

Morphological and physiological quality of the pollen was studied in fourRosa species growing in habitats with different calcium carbonate content. In soils rich in calcium the pollen showes in all cases better physiological quality which is an assumption for good fertility. It may be also one of the reasons for species diversity and population abundance of roses in native habitats on calcareous soils.     

Wax composition of the Kazanlik and Damask roses

The Kazanlik and Damask roses ditter qualitatively and quantitatively in the composition of the flower waxes. These chemotaxonomic data suggest that these two oil-bearing roses are different from each other.     

Embryo development and survival in beef cattle administered ergotamine tartrate to simulate fescue toxicosis

Two experiments were performed to determine whether administration of ergotamine tartrate altered embryo development (Exp. 1) and uterine competency to establish pregnancy (Exp. 2) in beef cattle. Animals were fed daily either 0 (CON) or 40 mug/kg body weight of ergotamine tartrate (ERGOT). Following a 30-d period on respective diets, animals in Exp. 1 were artificial inseminated at estrus (d = 0) and single embryo recoveries performed on day 7; whereas, animals in Exp. 2 received two frozen-thawed embryos on day 7. As an indicator of ergotamine effects, prolactin was decreased throughout both experiments in ERGOT compared to CON animals (p<0.05). Furthermore, rectal temperature (RT) tended to increase during both experiments in ERGOT compared to CON (p= 0.06). In Exp. 1, embryo recovery (p=0.08) and the percentage of transferable embryos (p=0.09) tended to be greater for CON than for ERGOT. Percentage of embryos that developed to compacted morula or greater was increased for CON compared to ERGOT heifers (p<0.05). In Exp. 2, pregnancy rates of transferred embryos did not differ between treatment groups. Thus, administration of ERGOT to simulate fescue toxicosis altered developmental potential of embryos, but does not appear to affect uterine competency to establish pregnancy.