First Report of Guignardia psidii, an Ascigerous State of Phyllosticta psidiicola, Causing Fruit Rot on Guava in Venezuela

During August 2003, guava fruit (Psidium guajava L.) cv. Red Dominicana from Cojedes state in Venezuela showed circular, purple-to-brown lesions (0.5 to 1.0 cm) that spread over all surfaces and became black and shrunken on severely affected fruit. Symptomatic tissues were plated aseptically on potato dextrose agar (PDA). Colonies that were initially gray and turned black with age were consistently isolated. The fungus was characterized by dense, submerged, brown-to-black mycelium with septate hyphae. Ascocarps were perithecial, abundant, granulose, subglobose to cylindric obpyriform, solitary or aggregated, mostly unilocular with prominent long necks; ascocarp walls were stromatic, composed of several layers of cells, thick walled, and deeply pigmented on the outside. Asci were subclavate to cylindrical, stipitate, 44 to 84 × 7 to 9 μm, and eight-spored; asci walls were thick and bitunicate. Ascospores were unicellular, hyaline, guttulate, fusiform ellipsoid, widest in the mid-region with rounded ends and gelatinous plugs, and 12 to 17 × 4.5 μm. Conidiomata were pycnidial, intermixed among ascocarps, variable in shape, dark brown, solitary or aggregated, ostiolate, and with long necks up to 1 mm. Pycnidial walls were pseudoparenchymatic, multicellular, and composed of many layers of brown compressed cells. Conidiogenous cells were hyaline, subglobose to cylindrical, and smooth, and holoblastic. Conidia were hyaline, unicellular, obovate, 6 to 12 (7.5) × 5 to 8 μm, slightly truncate at the bases, rounded at apices, guttulate, and provided a gelatinous envelope and apical appendage. Appendages were hyaline, tubular, smooth, and 3.0 to 4.5 × 0.5 μm. The fungus is homothallic because single ascospores and single conidia developed ascigerous states. The ascigerous state was identified as Guignardia psidii (1) and the anamorph as Phyllosticta psidiicola (1,2). Pathogenicity tests were conducted on detached fruits inoculated with monosporic cultures. Pathogenesis and symptom development only occurred when a mixture of mycelium, ascospores, and conidia was used as inoculum. The fungus was reisolated from symptomatic fruit tissues. To our knowledge, this is the first report of Guignardia psidii, an ascigerous state of Phyllosticta psidiicola from guava fruits in Venezuela. References: (1) B. A. Ullasa and R. D. Rawal. Curr. Sci. 53:435, 1984. (2) H. A. van der Aa. Page 95 in: No. 5, Stud. Mycol., 1973.

Life without a cell membrane: regeneration of protoplasts from disintegrated cells of the marine green alga Bryopsis plumosa

When the multi-nucleate giant cells of the green alga Bryopsis plumosa (Huds.) Ag. are injured, the protoplasm is extruded from the cells and can generate spontaneously numerous new cells. The cell organelles aggregate rapidly in seawater and become covered with a gelatinous envelope within 15 minutes. A lipid cell membrane is formed inside the envelope within 9 to 12 hours and about 15% of the original cell membrane is recycled to make the membrane of new protoplasts. Cytochemical studies using Nile Red and various enzymes revealed that the primary envelope is initially composed of polysaccharides, and then transformed into a polysaccharide-lipid complex. Fluorescein diacetate staining showed that the primary envelope has some characteristics of a cell membrane including semi-permeability and selective transport of materials. The aggregation of cell organelles appears to be mediated by two kinds of materials, one present in vacuolar sap and the other on the surface of the cell organelles. About a thousand new cells were generated from a single disintegrated branch and 40% of them eventually developed into mature plants.

The Population cycle of the bivalve Abra tenuis and its mode of reproduction

The annual cycles of the Abra tennis populations in the Plym Estuary and the Fleet (Dorset) were studied from March 1980 to June 1982. In the Plym Estuary the highest numbers occurred in autumn following juvenile recruitment and the lowest numbers were recorded in mid-summer. In the Fleet such an annual cycle in numbers was not apparent since juvenile recruitment in 1980 was very high but in 1981 it was very low. The recruitment failure in 1981 may have resulted, at least in part, from the heavy summer infection of A. tenuis by digenean parasites that destroy the gonads of the host, thereby reducing the population fecundity.A. tenuis spawns in July and August: the mature egg has a diameter of 140 μm and is enclosed in a sticky gelatinous envelope. Females produce 450–1800 eggs which, when fertilized, are laid in a mass within the sediment and, following a direct development, the juveniles hatch as miniature adults after 2–3 weeks. This non-pelagic, lecithotrophic development is interpreted as being a means of ensuring the maintenance of populations within restricted estuarine habitats. Data suggest A. tenuis lives for 1 or 2 years and that the species is monotelic.

Melanization and encapsulation in Aedes aegypti and Aedes togoi in response to parasitization by a filarioid nematode (Breinlia booliati)

In Aedes aegypti (Singapore strain), a refractory host, there was a marked progressive decline of developing larvae of Breinlia booliati during the incubation period. However, in Aedes togoi, a susceptible host, the filarial larvae developed normally and the number of larvae remained constant throughout the incubation period. Encapsulation and melanization of B. booliati larvae in Ae. aegypti and Ae. togoi were studied. Ae. togoi occasionally mounted a defence reaction to the infection. In Ae. aegypti, various stages of filarial larvae were frequently affected by the defence mechanisms of the host, and a relatively large number of melanized larvae were recovered in dissections throughout the incubation period. The process of melanization is described and the relationship between melanization and haemocytes of mosquitoes is discussed. Haemocytes of the mosquito host appeared to be involved in the encapsulation of filarial larvae, as evidenced by adherence of cells to the cuticle of the larvae and the formation of a translucent, gelatinous envelope which contained intact cells, necrotic cells, spaces and numerous whitish granules. The possible involvement of a humoral reaction in bringing about the degeneration and retardation of the filarial larvae is discussed.

Detecting Endogenous Growth Regulators on the Sarcotesta, Sclerotesta, Endosperm, and Embryo by Paper Chromatography on Fresh and Old Seeds of Two Papaya Varieties

Sarcotesta, sclerotesta, endosperm and embryo of fresh and old (0 and 3 years, respectively) seeds of the P.R. 6-65 and P.R. 8-65 papaya varieties were separately analyzed by paper chromatography to determine the presence of natural growth inhibitor that might be responsible for the reduction in germination of papaya seeds during storage. The results showed that in the innermost seed parts (embryo and endosperm) endogenous growth promoters were found while the outermost structures (sarcotesta and sclerotesta) contained inhibitors. Therefore, it is possible that the natural growth inhibitors of this seed might be minimized by removing the sarcotesta (the gelatinous envelope) of the seed, which contains the most endogenous growth inhibitors, plus a careful washing to eliminate the soluble inhibitors of the sclerotesta during the extraction of seeds from the fruits.

On the first changes in the ova of the mammifera, in consequence of impregnation; and of the mode of origin of the chorion

The author having, in a former paper, described the structure of the unimpregnated ovum of mammiferous animals, now proceeds to investigate the changes which the ovum undergoes in consequence of impregnation. In the rabbit, the first perceptible difference is the addition of a thick gelatinous matter surrounding the parts of which the ovum was composed in its original state, and apparently derived from the ovaries. In the progress of development the vitellary membrane gives way, as happens in the ova of the newt, and of many of the oviparous animals. The gelatinous envelope acquired in the ovary, and which is more especially circumscribed and defined after impregnation, constitutes the only covering of the vascular blastoderma, after the giving way of the vitellary membrane, and afterwards forms the chorion, which in rodent animals, at a further stage of development, presents itself under the form of a thin and transparent membrane, very similar to the vitellary membrane of a bird’s egg, and situated immediately outside the non-vascular and reflected layer of the umbilical or erythroid vesicle. The author draws similar conclusions with regard to the developement of the human ovum. The second part of the paper relates to the changes taking place in the vitellus, the inferences concerning which are deduced chiefly from observations of the developement of the ova of batrachian reptiles. The author concludes that the disappearance of the germinal vesicle is prior to impregnation. In the newt, the vesicle, at first imbedded in the substance of the yelk, gradually approaches the surface, until its situation is immediately underneath the vitellary membrane: its coat, having now become very soft, gives way, allowing the contained fluid to be effused on the surrounding surface of the yelk; and the small depression in which the vesicle was lodged now forms the cicatricula. The effused fluid gives a degree of consistence to the matter composing the surface of the yelk, and thus promotes the formation of the blastoderma. In the frog, the surface of the yelk becomes every day more and more broken up, and the resulting crystalline forms described by Prevost and Dumas become smaller and smaller, until the surface of the black blastoderma appears under a magnifying glass like shagreen. The blastoderma, consisting of an aggregation of clear globules, different from those of the rest of the yelk, is now fully formed, and has extended itself so as to close in the white spot. The change which takes place in the yelk of the bird’s egg appears to be limited to the neighbourhood of the cicatricula.