First report of Pandora neoaphidis resting spore formation in vivo in aphid hosts.

The entomopathogenic fungus Pandora neoaphidis is a recognized pathogen of aphids, causes natural epizootics in aphid populations, and interacts and competes with aphid predators and parasitoids. Survival of entomophthoralean fungi in periods of unsuitable weather conditions or lack of appropriate host insects is accomplished mainly by thick-walled resting spores (zygospores or azygospores). However, resting spores are not known for some entomophthoralean species such as P. neoaphidis. Several hypotheses of P. neoaphidis winter survival can be found in the literature but so far these hypotheses do not include the presence of resting spores. Resting spores were found in an aphid population where P. neoaphidis was the only entomophthoralean fungus observed during surveys conducted in organic horticultural crops in greenhouses and open fields in Buenos Aires province, Argentina. This study sought to use molecular methods to confirm that these resting spores were, in fact, those of P. neoaphidis while further documenting and characterizing these resting spores that were produced in vivo in aphid hosts. The double-walled resting spores were characterized using light and transmission electron microscopy. The Argentinean resting spores clustered together with P. neoaphidis isolates with bootstrap values above 98 % in the small subunit ribosomal RNA (SSU rRNA) sequence analysis and with bootstrap values above 99 % the Internal Transcribed Spacer (ITS) II region sequence analysis. This study is the first gene-based confirmation from either infected hosts or cultures that P. neoaphidis is able to produce resting spores.

The hyphal tip structure of Basidiobolus sp.: a zygomycete fungus of uncertain phylogeny.

To date, among the zygomycete fungi that have been examined, a Spitzenkörper has not been reported. In this paper, the cytoplasmic order of hyphal tip cells of Basidiobolus sp., a zygomycete genus of uncertain phylogeny, has been examined using light microscopy and transmission electron microscopy methods. With phase-contrast light optics, a phase-dark body was observed at the tips of growing hyphae of Basidiobolus sp. The hyphal apex also showed high affinity for FM4-64 labelling resulting in an intense fluorescence signal. The phase-dark inclusion exhibited independent motility within the hyphal apex and its presence and position were correlated to the rate and direction of hyphal growth. The hyphal apex of Basidiobolus sp. did not contain γ-tubulin. Ultrastructural observations revealed a dense cluster of vesicles at the hyphal apex. These results suggest that the growing hypha of Basidiobolus sp. contains a Spitzenkörper, a character generally attributed to members of the ascomycete and basidiomycete fungi and not to zygomycete fungi.

Factors affecting transmission of fungal pathogens of aphids.

Fungal pathogens are the most important pathogens of aphids (Homoptera: Aphididae), and epizootics, particularly those caused by Entomophthorales (Zygomycota), are frequently observed and often rapidly reduce aphid populations. Fungi in the Hypocreales (Ascomycota) are less commonly found infecting aphids but can be important. The transmission of aphid fungal pathogens is affected by many factors, including: host biology and structure, pathogen characteristics, host-plant characteristics, and environmental factors. This paper is an overview of selected factors affecting transmission of aphid pathogens.

Thamnocephalis quadrupedata (Mucorales) as a mycoparasite of the entomophthoraceous fungus Basidiobolus ranarum.

A mycoparasite identified as Thamnocephalis quadrupedata (Mucorales) was observed on cultures of the frog dung fungus, Basidiobolus ranarum. The parasitic fungus, T. quadrupedata possessed infection hyphae with appressoria and penetrating hyphae to attack their host prey and adhere firmly to the surface. The invasion was often by slender infection hyphae or infecting pegs which grew from the appressoria and penetrated the chitin-protein cuticle by both mechanical pressure and exocellular enzymes. The host fungus, B. ranarum, possessing primary conidia, capilliconidia, hyphal bodies, vegetative mycelia and zygospores, were infected by means of direct penetration and intrahyphal growth, resulting in host cell death. T. quadrupedata may also grow as a saprophyte on damp filter paper in a Petri dish, manifesting facultative necrosis.