Histopathological changes of Ceroplastes japonicus infected by Lecanicillium lecanii

The infection process and pathological changes of Japanese wax scale, Ceroplastes japonicus Green, by the hyphomycete Lecanicillium lecanii (Zimmermann) Gams & Zare were investigated by light, scanning and transmission electron microscopy. The results showed that L. lecanii generally infected the wax scale by penetrating the integument. The anal area, the body margin, around the base of mouthparts and legs, over the stigmatic furrow and the area around the vulva were susceptible places, while the wax test had an inhibitory effect on L. lecanii. Within 24 h after inoculation, conidia became attached to the cuticle, and within 48 h, hyphae adhered to the integument of the scale and their tips differentiated into specialized infection pegs. Penetration of the cuticle occurred within 72 h of inoculation; the fungus caused the insect cuticle to rupture and hyphae entered the insect body through these openings. Within 72 h after inoculation, L. lecanii entered the hemocoele of the scale and formed blastospores. After 96 h, blastospores were dispersed throughout the hemolymph and completely disrupted the hemocytes, resulting in damage of the cell nucleus and agglutination of chromatin. Concomitant to colonization of the hemolymph, the internal organs and tissues, e.g., tracheae, malpighian tubules and muscle fibers, were also infected. As the infection progressed, the wax test and body changed color from white and red, respectively, to yellowish. After 144 h, the internal tissue structure was totally compromised and the insects died. After this time, new conidiophores bearing conidia were produced on the surface of the cadavers.     

Gonidiogenesis in Padixonia bispora Subram. (Hyphomycetes)

(Hyphomycetes). Padixonia bispora produces two kinds of conidium arranged as acropetal tandem pairs. The pair consists of a distal enteroblastic conidium connected via a narrow neck to a proximal broad-based holoblastic conidium. The proximal blastospore is derived from a branched conidiphore axis and initially forms as a distal conidiogenous cell from which arises the distal blastospore. The wall between the two conidia is formed from the narrow neck occluded by a layered plug. Conidial maturation is concurrent with conidiogenesis. Secession of the proximal spore is by a rounding-off mechanism with circumscissile rupture of the outer layer of the continuous wall between the conidiogenous cell and the conidium and concurrent schizolysis of the duplex septum. The distal blastospore is released by mechanical transverse tearing of the plug through an undulate abscission zone. The abscission zone has two major concentric rings of thickening. The outer ring is derived from the outer layer of proximal spore cell wall.     

Infection of Barley by <Emphasis Type="Italic">Ramularia</Emphasis> <Emphasis Type="Italic">collo-cygni</Emphasis>: Scanning Electron Microscopic Investigations

Ramularia collo-cygni causes leaf spots on barley (Hordeum vulgare), a disease of growing economical importance. Scanning electron microscopy was used to study the life cycle of the fungus on barley during the vegetation period and in winter. The infectious stage started with conidium germination on the surface and the penetration into the leaf via the stomatal pore where the hyphae grew within the cells that became necrotic. The conidiophores emerged through the stomatal pore. On older leaves, however, they frequently emerged apart from it and the results suggested a pushing apart of adjacent cell walls of the epidermal cells. An assessment of the amount of conidium formation of one heavily infested barley plant resulted in 4.05 × 10⁶ conidia per plant. For the first time, conidiophores, conidium production and germination of conidia were also observed in winter on barley and on maize leaves.     

Ultrastructural studies on zygomycotan fungi in the Zoopagaceae and Cochlonemataceae

The morphology of fungi in the Zoopagaceae and Cochlonemataceae (Zoopagales, Zoopagomycotina, Zygomycota) is reviewed, and some new ultrastructural information is added on conidia and zygospores, as well as haustoria in the former family and vegetative thalli in the latter. The cell wall of the conidia of Acaulopage dichotoma, Ac. tetraceros, Stylopage cephalote, Zoophagus insidians, and Zph. tentaclum (Zoopagaceae), and of Cochlonema odontosperma and Endocochlus gigas (Cochlonemataceae), is known to be composed of outer electron-dense and inner less dense layers in ultrathin sections, and no additional cell walls were found on the conidial cell wall. Although two nuclei were found in the zygosporangium before maturation to the zygospore in Acaulopage rhaphidospora (Zoopagaceae), more than one nucleus had never been observed previously in a zygospore in either of these families in ultrathin sections.     

Mildew of oleaster (Elaeagnus oxycarpa Schlecht.) registered in large industrial cities (Pavlodar,Aksu, Ekibastuz) of the Pavlodar region

Purpose: Vegetation plays a very important role in industrial regions in terms of not only air purification, but also oxygen enrichment, air humidity, and city aesthetics. The paper presents the authors’ study of oleaster mildew during 2012–2013 in the cities of Pavlodar, Ekibastuz, and Aksu. Method: The species composition of mildew, patterns of its growth and reproduction, seasonal dynamics, and the level of trees infection according to a six-score scale were determined. Result: Three cultivars of mildew from three genera were registered. The species composition of mildew of oleaster is studied for the first time in large industrial cities of the Pavlodar region. The comparative analysis of the systematic structure of phytopathogenic fungi was followed by the study of the micro flora of green planting in megalopolises. The seasonal dynamics of growth, development, and reproduction was determined. The impact of pests on host-plants was studied. Conclusion: Timely diagnosis and localization of disease outbreak increases the likelihood of successful treatment and saving of plants.     

Effects of long-term storage at different temperatures on conidia of Botrytis cinerea Pers.: Fr.

Survival of Botrytis cinerea conidia was studied after storage without pretreatments at different temperatures (-80 degrees C, -20 degrees C, 4 degrees C and 21 degrees C). Germination tests performed during 3 years showed that viability at 21 degrees C was completely lost after 1 month. Conidia stored for 30 months at -80 degrees C, -20 degrees C and 4 degrees C were able to germinate, respectively, at 79%, 8% and 0.2%. Changes in adenylate level, energy charge and respiration (O(2) consumption) made on each set of conidia were correlated to the germination rate. The 30-month-old stored conidia showed differences in pathogenicity tests on apples. While the pathogenic aggressiveness of conidia stored at -80 degrees C was almost the same as for fresh conidia, it decreased with increasing temperature of storage. An ultrastructural study made on conidia stored for 30 months at -80 degrees C has shown the emergence of a new wall layer in a retraction zone of the cytoplasm by comparison to fresh conidia. However, the integrity of the cytoplasmic content was maintained. The effects of low temperature storage, maintenance of cell integrity and pathogenicity of conidia of B. cinerea are discussed.     

Effects of insect cuticular fatty acids on in vitro growth and pathogenicity of the entomopathogenic fungus Conidiobolus coronatus

Eighteen fatty acids identified in the cuticle of three insect species representing differing susceptibilities to C. coronatus infection, were tested for effects on the in vitro growth and pathogenicity of the parasitic fungus. At all applied concentrations (0.1-0.0001% w/v) growth was inhibited by C_16:0, C_16:1, C_18:0, C_18:1, C_18:2, C_18:3, C_20:0 and C_20:1. At high concentrations spore germination was inhibited by C_7:0, C_8:0, C_9:0, C_10:0, C_12:0, C_18:2 and C_18:3 and hyphal growth was merely retarded by C_5:0, C_6:0, C_6:2, C_14:0, C_16:0, C_16:1, C_18:0, C_18:1, C_20:0 and C_20:1. The presence of C_15:0 at the 0.1% concentration stimulated growth of C. coronatus. Sporulation was inhibited by all concentrations of C_16:0 and C_18-20 fatty acids. Low concentrations of C_5:0, C_6:0, C_6:2 and C_7:0 enhanced sporulation. Fatty acids C_5-12 as well as C_18:3, C_20:0 and C_20:1 decreased the ability of fungal colonies to infect G. mellonella while C_16:1 elevated it thus suggesting that C_16:1 may stimulate production of enzymes involved in the host invasion. Toxicity of metabolites released into incubation medium decreased with varying degrees in the presence of C_6:0, C_6:2, C_7:0, C_9:0, C_12:0, C_16:1, C_18:2, C_18:3, C_20:0 and C_20:1; other fatty acids had no effect. Further work is needed to analyse the effects of exogenous fatty acids on the C. coronatus enzymes implicated in fungal pathogenicity as well as on the production of insecticidal metabolites.     

Effects of Culture Age, Washing and Storage Conditions on Desiccation Tolerance of Colletotrichum truncatum Conidia

Colletotrichum truncatum conidia produced from a one week-old culture in a liquid semi-defined medium with a C:N ratio of 5:1 were more tolerant of desiccation than those harvested from two or three week-old cultures. Conidia washed with 20% (w/v) sucrose germinated better than unwashed conidia or those washed in 10% (w/v) sucrose, 10 and 20% (w/v) glucose or fructose, 0.1% (w/v) soluble starch, 0.9% (w/v) NaCl or deionized water. Washing with sucrose (20% w/v) also resulted in significantly longer germ tubes than those produced by unwashed conidia or conidia washed with deionized water or NaCl (0.9% w/v). Conidia washed twice in sucrose showed greater desiccation tolerance during storage at 15% relative humidity (RH) and 15°C than at 30% RH and 15 or 25°C or at 15% RH and 25, 5 or -10°C.     

Successful induction and recognition of conidiation,conidial germination and chlamydospore formation in pure culture of Morchella

Morels, fungi from the genus Morchella, are popular edible mushrooms. However, little knowledge of their asexual reproduction and inaccessible pure mitospores hamper illumination of their life cycle. Herein, we successfully induced conidiation, conidial germination and chlamydospore formation in pure culture of Morchella sextelata. Conidiation proceeded via four morphologically distinct stages: development of the conidiophore stalk, stalk branching, phialide differentiation, and conidium production. Terminal and intercalary chlamydospores were formed on conidial hyphae. The development of conidiophores occurred earlier, with more conidia produced, in cross-mating cultures than in single-spore cultures. Mature conidia were spherical and 2.5–8 μm in diameter, with a vast majority (nearly 99%) 2.5–5 μm in diameter. Each conidium contained one to three nuclei (80.2% conidia contained one nucleus, 19.1% contained two nuclei, and 0.7% contained three nuclei). The conidial nucleus diameter was 1–2 μm. The nuclear mitosis in detached conidia that was observed may benefit their colony initiation. Additionally, morel conidia formed conidial anastomosis tubes. Conidia (mitospores) likely not only function as spermatia, but also as reproductive propagules in Morchella. Further research is imperative to elucidate the relationship between the conidia and chlamydospores, and their unique function in the morel life cycle.     

β-Galactofuranoside glycoconjugates on conidia and conidiophores of Aspergillus niger

Galactose in the furanoic conformation appears to be limited to bacteria and lower eukaryotes. Galactofuranoic (Galf)-containing glycoconjugates that occur in organisms pathogenic or allergenic to man are frequently antigenic and immunodominant. We have used an immunochemical approach, employing a monoclonal antibody that recognises Galf epitopes, to investigate the presence of Galf-containing glycoconjugates within conidia and conidiophores of Aspergillus niger. ELISA and immunofluorescence microscopy indicated that specific and saturable binding sites were found on both. Inhibition studies confirmed that this binding was to Galf-containing glycoconjugates. Interestingly, the conidiophore heads were particularly rich in these glycoconjugates. Western blotting identified a Galf glycoprotein of 150-200 kDa from disrupted conidia.