Rapid Tentative Identification of Rhizoctonia spp. Associated with Diseased Turfgrasses

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Abstract
Fluorescence microscopy using the DNA-binding probe 4'',6''-diamidino-2-phenylindole (DAPI) was used successfully to determine number of nuclei per hyphal cell of Rhizoctonia spp. that cause patch diseases of turfgrasses. The procedure included growth of the hyphae from diseased tissue [Poa pratensis, Festuca arundinacea] onto agar-coated microscope slides followed by rapid fixation with 3% formaldehyde. Samples were rinsed with distilled water and flooded with a 1-ppm solution of DAPI, then destained by flooding the sample with distilled water. Most of the water was then removed, a drop of glycerin was applied followed by a coverslip, and the sample was viewed using ultraviolet excitation with epiillumination and Neofluar objectives. Nuclei within isolates of R. solani, R. cerealis, R. zeae, and R. oryzae were clearly differentiated by the method. This method combines speed and reliability as a diagnosic tool.