Picture: Conidiobolus thromboides Drechsler ARSEF 41 (FSU 715) 1, 2. Pyriform primary conidia with prominent basal papilla; bar = 40 ?m. 3. Primary conidia, germinating conidia, and developing secondary conidia (*); bar = 40 ?m. 4, 5. Secondary conidia developing from primary conidia; bar = 20 ?m. 6. Nuclei (arrows) with clear nucleoplasm and darker central nucleolus in hyphal cell; bar = 10 ?m 7. Resting spores (probable azygospores) with doubled thickened wall and, when mature, prominent central oil droplets, bar = 20 ?m. Credit: Richard Humber.

Conidiobolus thromboides Drechsler 1953, strain FSU 715

Conidiobolus thromboides occurs commonly in soil and plant detritus but that is also known as a pathogen of aphids and other insects. This species grows well on a wide range of solid and liquid media (MEA, PDA, Sabouraud dextrose, etc.), and sporulates easy under laboratory conditions by developing forcibly discharged conidia and/or putatively sexual resting spores (zygospores). Conidia are discharged towards the strongest source of light, and can form dense "clouds" of deposited spores on the inner sides of petri plates. Conidia germinate to form either germ tubes that may lead to vegetative growth, or they can form a short conidiophore from which a secondary conidium is forcibly discharged. If any individual conidium continues to land on a substrate unsuitable for the development of a germ tube but still retains enough internal reserves, it may make and discharge still another forcibly discharged (tertiary) conidium. If the conidia of this fungus land on the cuticle of insects - mostly (but not exclusively) of aphids - the germ tube may penetrate the insect's cuticle, cause lethal infections and then sporulate from the surface of the host within a few days. Conidiobolus thromboides has a significant potential for control of some pests of economically important crops such as cereals and orchard trees. Conidiobolus thromboides has also been isolated from basidiomycete fruitbodies, such as those of black trumpet, Craterellus cornucopioides.

Comparison of genomes of C. thromboides and C. coronatus, which was previously sequenced at JGI, suggested that these species do not belong in the same genus but represent species from related but distinct phylogenetic clades despite their morphological similarities and long-accepted placement in a single genus.