Effect of pencycuron on the osmotic stability of protoplasts of Rhizoctonia solani

Pencycuron shows a specific inhibitory activity on the mycelial growth of Rhizoctonia solani. Even in the same anastomosis groups (AGs), e.g. AG4, there are both isolates sensitive and less sensitive (inherently resistant) to pencycuron. The regeneration of colonies from protoplasts of R-C (pencycuron-sensitive isolate in AG4) significantly decreased by the osmotic shock in the presence of pencycuron, while such effect was cancelled by washing off the chemical prior to the osmotic shock. However, in Rh-131 (a less sensitive isolate in AG4), the application of the chemical appeared to stimulate the regeneration from protoplasts. Further the measurement of optical density of protoplasts suspensions was performed to elucidate the effect of pencycuron on the osmotic stability of protoplasts in a short period. The optical density of suspensions of R-C protoplasts rapidly declined in a short period of incubation by the osmotic shock in the presence of pencycuron, but the effect on Rh-131 protoplasts was not statistically significant regardless of the presence or the absence of the chemical. These results suggest that the cell membrane of the pencycuron-sensitive isolate (R-C) is specifically affected by pencycuron

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