VARIATION IN SENSITIVITY TO FUNGICIDES AMONG ISOLATES OF Rhizoctonia spp. INVOLVED IN DAMPING- ," OFF OF COTTON SEEDLINGS | ||||
| Journal of Plant Production | ||||
| Article 8, Volume 27, Issue 2, February 2002, Page 991-1006 PDF (4.89 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jpp.2002.253320 | ||||
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| Authors | ||||
| Eman Osman,; Mona M. A. Abou Taleb; Salwa A. F. EI-Akkad | ||||
| Plant Path. Res. Inst., Agric. Res. Center, Giza, Egypt. | ||||
| Abstract | ||||
| Five isolates of multinucleate Rhizoctonia so/ani and one isolate of binucleate Rhizoctonia sp. were evaluated in vitro for sensitivity to certain fungicides i.e., Rizolex T, Monceren T, Maxim, Premis, Beret MLX, and Tachigaren. All the R. so/ani isolates were tolerant to Tachigaren, while the binucleate isolate of Rhizoctonia sp. was sensitive; In the contrary, all the isolates were highly sensitive to Rizolex T. The efficiencies of the same funqicides-in reducing damping-off of cotton cultivar Giza 89 were evaluated under greenhouse conditions in soil infested with each individual isolate at two inoculum densities. Analysis of variance showed highly significant . effects of both fungicides and isolate, while the fungicide x isolate interaction was a nonsignificant source of variation. in percentage of seedling mortality, regardless of the inoculum density. Due to the nonsignificant interaction between fungicide and isolate, a least significant difference was used to compare between the general means of fungicides. These comparisons showed that Rizolex T and Beret MLX were the most effective fungicides in controlling damping-off at the lower inoculum density, while Rizolex T and Premis were the most effective ones atthe higher inoculum density. Tachigaren was effective in controlling the disease only at the higher inoculum density; however, it was the least efficient fungicide. There was no correlation between the in vitro efficiencies of the fungicides and their in vivo efficiencies when fungicidal efficiency was evaluated based on the effects of each fungicide on individual isolates. On the other hand, a highly significant correlation between in vitro and in vivo efficiencies of the fungicides was observed only when fungicidal efficiency was expressed as the mean efficiency of each fungicide over all the tested isolates. Regression analysis showed that in vitro mean of fungicidal efficiency accounted for 88 and 86% of the explained (model) variation in mean of fungicidal efficiency under greenhouse conditions when the inoculum densities were 0.1 g and O.Sg/Kg soil, respectively, | ||||
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