Geosiphon

Geosiphon (lat. Geosiphon pyriformis) is not a phytopathogenic organism or a plant disease. It is a unique example of endocytobiosis, in which a fungus from the Glomeromycota division absorbs cyanobacteria of the Nostoc genus. In an agronomic context, this organism is of interest primarily as an object of soil biology rather than a threat to crop production.

This organism is a unicellular or sparsely branched fungus that forms special structures, called siphons, to capture cyanobacteria. Within these structures, photosynthetic bacteria live and reproduce, supplying the fungus with carbohydrates, while the fungus provides them with protection and minerals from the soil.

Geosiphon does not affect agricultural crops; therefore, there are no symptoms of "infection." It inhabits specific soil conditions, preferring open areas with disturbed ground cover where cyanobacteria are available for colonization. Its presence in the soil does not have any negative impact on the development of agricultural plants.

In agroecosystems, Geosiphon is extremely rare. Its development is closely linked to soil moisture and surface light intensity. Unlike true plant diseases, it does not require the use of fungicides or other control agents, as it does not enter into parasitic relationships with cultivated plants.

The agricultural significance of this organism is limited to fundamental science. Researchers study it as a model for the evolutionary transition to complex symbiotic relationships, similar to those that support the nutrition of higher plants through arbuscular mycorrhiza. Preventive measures are not needed as it is not a pest or pathogen.