Nuclear acridine orange fluorescence in Rhizoctonia isolates from rice.

Ethical disclosures The genus Rhizoctonia DC (1805) has long been studied as an important soilborne pathogen that causes a wide variety of symptoms because it is a non-specialized pathogen3. Rhizoctonia sensu lato is characterized by the lack of conidiogenous cells and this taxon is composed of two groups based on the number of nuclei per cell: the multinucleate group that belongs to Rhizoctonia s. str. and the binucleate group that belongs to Ceratorhiza5. Currently, other authors consider the group a Ceratobasidium--Rhizoctonia complex7 and divide it into two groups: BNR (binucleate Rhizoctonialike) and MNR (multinucleate Rhizoctonia-like)9. Many methods are used to observe the number of nuclei in fungal cells, e.g. safranine O, aniline blue, HCl-Giemsa. Some of these methods apply a staining solution involving laborious, time-consuming procedures that require no equipment (Fig. 1). Other methods use fluorophores, which are rapid and precise1,2,4,6,8,10. Since a reliable and rapid method was needed to explore the MNR and BNR groups associated with rice crops in Argentina, we applied an accurate technique to observe the number of nuclei in the strain cells belonging to the Ceratobasidium--Rhizoctonia complex.