COMPARATIVE MORPHOLOGY AND TAXONOMIC STATUS OF GRACILARIOPSIS (GRACILARIALES,RHODOPHYTA)1

The vegetative organization and reproductive development of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik [including Gracilaria sjoestedtii Kylin] were investigated. Our observations on spermatangial development and post-fertilization features establish that Gracilariopsis Dawson is distinct at the generic level from Gracilaria Greville, and ice propose the resurrection of Gracilariopsis Dawson as a result. Spermatangial parent cells of Gracilariopsis are superficial, initiated in pairs or groups of three by concavo-convex longitudinal and transverse divisions. Each spermatangial parent cell cuts off a single, colorless spermatangium distally by a transverse division. The female reproductive apparatus consists of a supporting cell that bears a two-celled carpogonial branch flanked by two sterile branches, as in Gracilaria. Likewise, up to six sterile cells fuse with the carpogonium after fertilization to produce a primary fusion cell that generates the gonimoblasts; however, a secondary fusion cell is absent. Inner gonimoblast cells unite with cytologically modified cells of the inner pericarp by means of secondary pit-connections. Tubular nutritive cells are absent. The gonimoblast consists of a central sterile tissue interconnected throughout by secondary pit-connections surmounted by a fertile layer composed of carposporangia aligned in straight chains. The distribution of Gracilariopsis is extended to Western Europe.     

Molecular and morphological diversity of Zygnema and Zygnemopsis (Zygnematophyceae,Streptophyta) from Svalbard (High Arctic)

ABSTRACT

Filamentous conjugating green microalgae (Zygnematophyceae, Streptophyta) belong to the most common primary producers in polar hydro-terrestrial environments such as meltwater streamlets and shallow pools. The mats formed by these organisms are mostly composed of sterile filaments with Zygnema morphology, but the extent of their diversity remains unknown. Traditional taxonomy of this group is based on reproductive morphology, but sexual reproduction (conjugation and formation of resistant zygospores) is very rare in extreme conditions. In the present study we gave the first record of zygospore formation in Svalbard field samples, and identified conjugating filaments as Zygnemopsis lamellata and Zygnema cf. calosporum. We applied molecular phylogeny to study genetic diversity of sterile Zygnema filaments from Svalbard in the High Arctic. Based on analysis of 143 rbcL sequences, we revealed a surprisingly high molecular diversity: 12 Arctic Zygnema genotypes and one Zygnemopsis genotype were found. In addition, we characterized individual Arctic genotypes based on cell width and chloroplast morphology using light and confocal laser scanning microscopy. Our findings highlight the importance of a molecular approach when working with sterile filamentous Zygnematophyceae, as hidden diversity might be very beneficial for adaptation to harsh environmental conditions, and experimental results could be misinterpreted when hidden diversity is neglected.     

Effects of Petunia cytoplasmic male sterile (CMS) cytoplasm on the development of sterile and fertility-restored P. parodii anthers

The developmental defects causing cytoplasmic male sterility in Petunia parodii are described in isonuclear fertile, sterile, and fertility-restored plants using both light- and scanning electron microscopy. The aberrant development of the sporogenous tissue and tapetal layer caused by the cytoplasmic male sterile cytoplasm in both Petunia hybrida and P. parodii nuclear backgrounds is similar in onset and progression. The degeneration of the sporogenous tissue and tapetal layer of sterile anthers is first apparent late in meiosis and results in highly abnormal sterile sporogenous tissue by tetrad stage of fertile anthers. The stomium and endothecium do not show major developmental differences between fertile and sterile anthers, but the inner connective tissue of sterile anthers contained calcium crystals not found at high abundance in fertile anthers. Ovoid bodies containing magnesium and phosphorus were seen only in the vascular bundles of fertile anthers. Material prepared for the scanning electron microscope by freeze drying showed better retention of fragile morphological features, while critical-point drying permitted examination of nonvolatile structures, such as cell walls.     

The spermatogenous body cell of the coniferPicea abies (Norway spruce) contains actin microfilaments

Summary In conifer pollen, the generative cell divides into a sterile stalk cell and a body cell, which subsequently divides to produce two sperm. InPicea abies (Norway spruce, Pinaceae) this spermatogenous body cell contains actin microfilaments. Microfilament bundles follow the spherical contour of the body cell within the cell cortex, and also traverse the cytoplasm and enmesh amyloplasts and other organelles. In addition, microfilaments are associated with the surface of the body cell nucleus. The sterile stalk cell also contains microfilament bundles in the cytoplasm, around organelles, and along the nuclear surface. Within the pollen grain, microfilament bundles traverse the vegetative-cell cytoplasm and are enriched in a webbed cage which surrounds the body cell. Microfilaments were identified with rhodamine-phalloidin and with indirect immunofluo-rescence using a monoclonal antibody to actin. The majority of evidence in literature suggests that the spermatogenous generative cell in angiosperms does not contain actin microfilaments, so the presence of microfilaments within the spermatogenous body cell inP. abies appears to be a fundamental difference in sexual reproduction between conifers and angiosperms.     

CHARACTERIZATION OF SCHIZOSERIS CONDENSATA,SCHIZOSERIDEAE TRIB. NOV. (DELESSERIACEAE,RHODOPHYTA)1

The Myriogramme group of Kylin contains two distinct clusters of genera that merit recognition at the tribal level. We previously established the tribe Myriogrammeae, and in this paper we erect the Schizoserideae based on a study of the type species of Schizoseris, S. laciniata (=S. condensata), from the southern hemisphere. The Schizoserideae is characterized by 1) marginal and diffuse intercalary meristems; 2) nuclei initially arranged in a plate in the median plane in meristematic and mature cells; 3) chloroplasts one to few, lobed or dissected; 4) microscopic veins absent; 5) procarps scattered, formed singly on either side of the blade with cover cells absent and consisting of a one- to two-celled lateral sterile group, a one- to two-celled basal sterile group, and a four-celled carpogonial branch in which the trichogyne passes beneath the lateral sterile group and emerges anterior to it; 6) auxiliary cell diploidized by a connecting cell cut off posteriolaterally from the fertilized carpogonium; 7) gonimoblast initial cut off laterally from one side of the auxiliary cell and giving rise to unilaterally branched gonimoblast filaments bearing carposporangia in branched chains; 8) gonimoblast fusion cell highly branched, candelabra-like, incorporating all but the basalmost cells of the carposporangial chains and radiating through the central cells in the floor of the cystocarp; 9) spermatangial and tetrasporangial sori formed from surface cells in both monostromatic and polystromatic portions on both sides of the blade; and 10) tetrasporangia formed primarily from cortical rather than from central cells. The Schizoserideae presently includes Schizoseris Kylin, Neuroglossum Kützing, Abroteia J. Agardh, and Polycoryne Skottsberg in Kylin and Skottsberg.     

VIRUSLIKE PARTICLES IN THE MARINE ALGA CHORDA TOMENTOSA LYNGBYE (PHAEOPHYCEAE)1

Polyhedral viruslike particles 170 nm in diameter were found in 3-day-old spores of the brown alga Chorda tomentosa Lyngbye grown in unsterilized seawater. In sterile seawater, spores of the same species were free of these particles and cell wall development around naked settled, zoospores and subsequent spore germination proceeded, normally. Spores containing the putative virus particles did not develop cell walls or show signs of germination. Severe lysis of cell organelles always accompanied, the presence of these particles.     

Notes onLaboulbenia stenolophi andLaboulbenia anoplogenii (Ascomycetes, Laboulbeniales)

Laboulbenia stenolophi is reported for the first time from Japan.Stenolophus iridicolor andS. propinquus are added as new hosts. The crowded antheridia and the protruding (bulging) cell IV are characteristic of this fungus, although thalli with an almost normal cell IV sometimes occur.Laboulbenia anoplogenii onAnoplogenius is easily distinguished from what has been calledL. anoplogenii onStenolophus, Astigis, Abacetus andChlaeminus by the following characters: 1) no crowded antheridia can be observed throughout thallus development, but many sterile long branches can be observed instead; 2) cell IV starts to undergo cell division early in thallus development; 3) cell V extends downward to the level of cell VII, rather than extending only as far as the perithecial basal cells; and 4) cell VI is usually longer and extends farther distally than cell III.Anoplogenius is the host genus ofL. anoplogenii and the records from other hosts represent misapplied names.     

Embryology ofMalaxis saprophyta,with comments on the systematic position ofMalaxis (Orchidaceae)

InMalaxis saprophyta, anther wall development corresponds to the Monocotyledonous type. The uninucleate tapetum is of secretory type and the endothecium develops U- and V-shaped thickenings on the inner tangential and radial walls. Cytokinesis is simultaneous; tetrahedral, isobilateral and T-shaped tetrads are formed which are compactly aggregated in pollinia. At anthesis the microspore tetrads are 2-celled. The ovule is anatropous, bitegmic and both integuments are dermal in origin. A single hypodermal cell develops directly into a megaspore mother cell. Embryo sac development is predominantly monosporic and less often bisporic. Irrespective of the type of development, the mature embryo sac is 6-nucleate. Although double fertilization occurs, the primary endosperm nucleus degenerates. Embryogeny is of the Onagrad type. The mature embryo lacks differentiation into cotyledon, plumule and radicle. The reticulate seed coat is formed entirely by the outer layer of outer integument. There are three sterile and three fertile valves in the ovary. Although initially parenchymatous, the entire three sterile valves in the ovary and the upper half of the three fertile valves become sclerified after fertilization. The embryological characters support the disputed systematic position ofMalaxis within subtribeMalaxidinae ofEpidendreae.     

The persistence and lignin-like appearance of the primary cell wall of microsporocytes in male-sterile (CMS) sweet pepper,Capsicum annuum L

Using differential staining of cell walls the anatomy of microsporogenesis was investigated on cross-sections of anthers of fertile plants of the sweet pepperCapsicum annuum L. cv. Severka, as well as of its sterile analogues. The lignin-like staining as observed in the microsporocyte primary walls of fertile plants disappears with their getting independent in the course of meiosis. On the contrary, in sterile plants the stain increases in intensity, the thick-walled microsporocytes usually form a continuous block up to the period of tetradogenesis, and so far as microspores originate, they are not dissociated outwards. Moreover, in sterile anthers the external tapetum is usually not differentiated.     

ARTIFICIAL INTERSPECIFIC HYBRIDIZATION IN RUELLIA (ACANTHACEAE)

Observations were made on the morphology, seed fertility, pollen viability and meiotic configurations of 22 different interspecific hybrids of 12 North American taxa representative of 3 sections of Ruellia. The hybrids were classified as (1) fully vigorous and fertile; (2) vigorous but with reduced fertility; (3) reduced vigor and fertility; (4) weak and sterile. Hybrids showed meiotic irregularities in microsporogenesis: univalents, chains, precocious separation of bivalents, nondisjunction, and micronuclei were commonly observed. Interspecific pollinations within sect. Dipteracanthus resulted in fertile or partially sterile F₁ hybrids. Intersectional crosses produced partially or completely sterile hybrids or failed. Assuming that crossability is correlated with degree of evolutionary relationship, the parental species are interpreted in genecological terms to be grouped in polytypic ecospecies. Hybridization experiments doubtless would be of value in clarifying relationships in tropical and subtropical species of Ruellia.     

Ultraviolet mutagenesis and genetic analysis of resistance to methylglyoxal-bis (guanylhydrazone) in tobacco

Summary We have isolated cell lines of Nicotiana tabacum resistant to methylglyoxal-bis(guanylhydrazone) (MGBG), a potent inhibitor of S-adenosylmethionine decarboxylase. We obtained 31 resistant lines from ultraviolet light mutagenized cultures, representing at least 13 independent events. No resistant lines were obtained from non-mutagenized control cultures. The increase in mutation rate due to the ultraviolet light treatment was 22 to 62 fold increased over an estimate of the maximum possible spontaneous rate. In reconstruction experiments we reselected resistant cell lines from varying dilutions into a background of a constant concentration of wild type cells; at the minimum ratio of resistant cells to wild type cells, 1:125,000, we recovered resistant colonies at an estimated plating efficiency of 12.5%. A number of resistant lines have been regenerated into plants. All of the ones that flowered are male sterile, sometimes associated with morphological transformations. Some are female sterile as well. Meiotic genetic analysis of one resistant line, Mgr12, suggests that the MGBG resistance is segregating as a nuclear dominant trait. The male sterility and abnormal floral development of Mgr12 cosegregate with the MGBG resistance, suggesting the two phenotypes are coincident.     

Radiation effects on Drosophila suzukii (Diptera: Drosophilidae) reproductive behaviour

Female remating is a widespread behaviour, reported in several insect species. This behaviour can affect the efficiency of sterile insect technique (SIT); however, little is known about the postcopulatory behaviour of some pest species considered as candidates to be controlled by this technique, such as Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae). In this study, we investigated the effects of male and female sterilization on mating and remating behaviour of D. suzukii. First, we tested the occurrence of multiple mating in different combinations between sterile and fertile males and females. Then, we tested the effects of male and female sterility on female propensity to mate and remate. We found an overall low remating rate by D. suzukii females. Male sterility did not influence mating and remating likelihood; however, copula duration of sterile males was shorter compared to fertile males. On the other hand, sterile females were less likely to mate. Our findings encourage further research regarding the use of SIT to control D. suzukii.     

Study of male sterility in Taiwania cryptomerioides Hayata (Taxodiaceae)

Summary. A study of male sterility over a period of three consecutive years on a conifer species endemic to Taiwan, Taiwania cryptomerioides Hayata (Taxodiaceae), was done for this article. With the aids of fluorescence and electron microscopic observations, the ontogenic processes in the fertile and sterile microsporangia are compared, using samples collected from Chitou Experimental Forest and Yeou-Shoei-Keng Clonal Orchard of the National Taiwan University, Nantou, Taiwan. The development of male strobili occurred from August to the end of March. Microsporogenesis starts with the formation of the archesporium and ends with the maturation of 2-celled pollen grains within the dehiscing microsporangium. Before meiosis, there was no significant difference in ultrastructure between the fertile and sterile microsporangia. Asynchronous pollen development with various tetrad forms may occur in the same microsporangium of either fertile or sterile strobili. However, a callose wall was observable in the fertile dyad and tetrad, but not in the sterile one. After dissolution of the callose wall, the fertile microspores were released into the locule, while some sterile microspores still retained as tetrads or dyads with intertwining of exine walls in the proximal faces. As a result, there was no well developed lamellated endexine and no granulate ectexine or intine in the sterile microspores. Eventually, the intracellular structures in sterile microspores were dramatically collapsed before anthesis. The present study shows that the abortion in pollen development is possibly attributed to the absence of the callose wall. The importance of this structure to the male sterility of T. cryptomerioides is discussed. Correspondence and reprints: Department of Life Science, National Taiwan University, 106 Taipei, Taiwan.     

Molecular phylogeny and developmental studies of Apoglossum and Paraglossum (Delesseriaceae,Rhodophyta) with a description of Apoglosseae trib. nov.

Our morphological and molecular studies indicate that species from the southern hemisphere previously placed in Delesseria belong in Paraglossum and that Paraglossum and Apoglossum comprise a separate tribe, the Apoglosseae, S.-W. Lin, Fredericq & Hommersand, trib. nov., within the family Delesseriaceae. From a vegetative perspective the Apoglosseae is readily recognized because some or all fourth-order cell rows are formed on the inner sides of third-order cell rows. All fourth-order cell rows grow adaxially in Apoglossum, whereas both adaxial and abaxial cell rows are present in Paraglossum. Periaxial cells do not divide in Apoglossum, whereas they divide transversely in Paraglossum in the same way as in Delesseria. Major branches are formed mainly from the margins of midribs in the Apoglosseae. The procarp consists of a straight carpogonial branch and two sterile cells, with the second formed on the same side as the first. The carpogonium cuts off two connecting cells in tandem from its apical end, the terminal cell being nonfunctional and the subterminal cell typically fusing with the auxiliary cell. Gonimoblast filaments radiate in all directions from the gonimoblast initials and produce carposporangia terminally in branched chains, with pit connections between the inner gonimoblast cells broadening and enlarging. The auxiliary cell, supporting cell, and sterile cells unite into a fusion cell, which remains small in Apoglossum but incorporates the branched inner gonimoblast filaments and cells in the floor of the cystocarp in Paraglossum. Elongated inner cortical cells seen in mature cystocarps in the Delesserieae are absent in the Apoglosseae. Phylogenetic studies based on rbcL (RuBisCO large subunit gene) sequence analyses strongly support the recognition of the Apoglosseae within the subfamily Delesserioideae of the Delesseriaceae, in agreement with our previous observations based primarily on analyses of large subunit ribosomal DNA (LSU).     

Potential for controlling codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) in Argentina using the sterile insect technique and egg parasitoids

Codling moth is the main pest affecting apples and pears worldwide. Most pest control strategies used against this insect have relied on the use of broad‐spectrum insecticides which have led to non‐desirable effects like pesticide resistance, residues in the environment, human health concerns and the reduction of access to international markets. Therefore, alternative pest control strategies that would result in sustainable fruit production systems while taking care of the environment are strongly promoted. The use of the sterile insect technique has proven to be a valuable pest control tactic within area‐wide integrated pest management strategies, and its synergistic effect for Lepidoptera pests when combined with other biological control tactics such as parasitoids has been documented. The purposes of this research were to evaluate the response of an Argentinean codling moth strain to a sub‐sterilizing radiation dose of 100 Gy and to assess the acceptability and suitability of sterile codling moth eggs by the egg parasitoids, Trichogramma cacoeciae (Marchal) and Trichogramma nerudai (Pintureau and Gerding). Irradiated female moths survived better than irradiated male moths and non‐irradiated male and female moths. Also, the fecundity of irradiated female moths was reduced by more than 30% as compared to non‐irradiated ones whereas their fertility was close to zero. The F₁ generation was male biased with a lower fertility (inherited sterility) than the parental generation. Trichogramma cacoeciae and T. nerudai parasitized both fertile and sterile eggs. However, there was a significant reduction in acceptability for sterile eggs. Trichogramma nerudai parasitized more eggs than T. cacoeciae, but egg acceptability for this species was proportionally lower than for T. cacoeciae especially on eggs oviposited by irradiated females. Development to adult of both parasitoids species was not substantially affected by the origin of the eggs and the wasps had acceptable levels of adult emergence, survival and fecundity. These results provided useful information on the potential for controlling the codling moth using egg parasitoids and the sterile insect technique in Argentina.     

Amphithallia,a genus with four-celled carpogonial branches and connecting filaments in the Corallinales (Rhodophyta)

The South African marine alga Amphithallia crassiuscula, previously subsumed in the widely reported Synarthrophyton patena, is here re-described as a distinct species and genus. Thalli grow as obligate epiphytes on Gelidium capense in the upper sublittoral zone (while S. patena grows on Ballia callitricha). Gametophytes are monoecious with four-celled carpogonial branches and sterile cells are borne on supporting cells (dioecious or hermaphroditic with two or three-celled carpogonial branches and sterile cells borne on hypogynous cells in Synarthrophyton). Postfertilization stages involve a connecting filament linking the carpogonium to several putative auxiliary cells, demonstrating a non-procarpic condition with apparent absence of a fusion cell. Gonimoblast filaments develop at the level of basal cells of carpogonial branches. Spermatangial mother cells remain either unbranched (cutting off spermatangia only) or develop dendroid (branched) filaments with terminal spermatangia (as in Synarthrophyton). Multiporate conceptacles develop straight pore canals lined by non-differentiated cells (conical canals with differentiated pore cells along the base in Synarthrophyton). The here described pre- and post-fertilization characters are new for the order Corallinales motivating the establishment of the new genus Amphithallia.     

Morphology and reproduction of Bostrychia pinnata (Rhodomelaceae, Ceramiales) in laboratory culture

In unialgal culture, isolates of vegetative plants of Bostrychia pinnata often developed tetrasporangial stichidia and released viable tetraspores. Most tetra‐sporelings developed normal branching before reproduction, however, some sporelings developed procarps, and later, spermatangia on juvenille unbranched stages (< 1 mm). Most normally branched gametophytes (> 2 mm) were initially female before becoming bisexual when older and larger (> 5 mm). Unisexual male gametophytes were not seen in culture. Carposporophytes developed slowly (40–70 days) and were sometimes abortive or produced reduced numbers of carpo‐sporangia (10–15 in cultures compared with 40–50 in field material). Carpospores germinated more slowly than tetraspores and the tetrasporophytes required up to 6 months to reach reproductive maturity. The Polysi‐phonia‐type life‐history was completed in 9–12 months in the laboratory. Peripherohaptera were absent in cultured plants. The isolates from Florida, Guatemala and Peru did not reproduce sexually, but regularly underwent lower branch abscission as a means of vegetative reproduction. After several years in culture, most individual isolates became self‐incompatible. In the female, 1 or 2 procarps formed on each axial segment and most were 4‐celled with a few having 3 cells. A single branched sterile group of 3–7 cells was also present. After fertilization, the diploid nucleus in the carpogonium divided twice, isolating the capping element and trichogyne and establishing the connecting element adjacent to the auxiliary cell. In mature normal cystocarps the sterile group persisted and secreted mucilage into the central cavity. The mature pericarp was four layers thick (one layer of axial filaments and three cortical cell layers). Pseudocystocarps were common, produced no carpo‐sporangia, contained elongate sterile cells, and were enclosed with a partially developed pericarp. Carpogonia in which 4 nuclei were usually seen may indicate developmental failure resulting in pseudocystocarps.     

CONCEPTACLE STRUCTURE OF THE PARASITIC CORALLINE RED ALGA CHOREONEMA THURETII (CORALLINALES) AND ITS TAXONOMIC IMPLICATIONS1

The major diagnostic features for erecting the red algal subfamily Choreonematoideae (Corallinales) were a combination of 1) absence of both cell fusions and secondary pit connections, 2) conceptacle roof and wall comprised of a single cell layer, and 3) presence of tetrasporangial pore plugs within a uniporate conceptacle in the monotypic taxon Choreonema thuretii (Bornet) Schmitz. Because this alga is a parasite, the absence of secondary cell connections is most likely an adaptation to a reduced thallus. This study shows that all conceptacles are not composed of a file of cells but rather a single layer of epithallial cells that are underlain by a thick layer of calcified acellular material; both epithallial cells and the calcified layer are produced by peripheral sterile cells. Although the outermost tetrasporangial pore canal is uniporate, there is a calcified acellular multiporate plate recessed just below the rim. The plate is produced by interspersed sterile cells and is continuous with the calcified layer supporting the conceptacle. These unique structures are likely due to parasitism rather than to the ancestral state. Based on these results and a reexamination of published micrographs depicting lenticular cells in Austrolithon intumescens Harvey et Woelkerling, we propose that both subfamily Choreonematoideae and Austrolithoideae are closely allied with subfamily Melobesioideae. This distant relationship to its host (Corallinoideae) plus a combination of unique conceptacle and unusual type of parasitism indicates that C. thuretii is an alloparasite and that it is likely the most ancient red algal parasite studied to date.     

Analysis of the Drosophila female sterile mutation fs(1) 1304 by pole cell transplantation experiments

The Drosophila melanogaster mutant fs(1)1304 is an ovary autonomous female sterile mutant that causes abnormal morphology of the egg. Vitellogenesis proceeds at an abnormally slow rate in homozygous females. We have used pole cell transplantation to construct germ line mosaics in order to determine whether the 1304 defect depends upon the genotype of the germ line cells (oocyte or nurse cells) or the somatic line (follicle cells). We have found that the germ line is the primary target tissue where the mutant gene is expressed.