INFLUENCE OF GROWTH MEDIUM ON THE PATHOGENICITY OF SOME ISOLATES OF RHIZOCTONIA SPP. ON COTTON SEEDLINGS | ||||
| Egyptian Journal of Agricultural Research | ||||
| Article 3, Volume 81, Issue 1, March 2003, Page 33-54 PDF (5.41 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/ejar.2003.276032 | ||||
 View on SCiNiTO | ||||
| Authors | ||||
| EMAN A. OSMAN; SALWA A. F. EL-AKKAD; SEHAM E. ABD-EL-GHAFOUR | ||||
| Plant Pathology Research Institute, Agricultural Research Center, Giza, Egypt | ||||
| Abstract | ||||
| The nutritional status of seven multinucleate isolates of Rhizoctonia solanl (AG4) and one binucleate isolate of Rhizoctonia was varied by growing the isolates on four growth media with variable nutritional values (water agar, potato dextrose agar, Czapeck's-dox agar, and sorghum extract agar). Effect of growth medium on pathogenicity of the isolates, on cotton cultivars Gin 80 and Giza 89, was evaluated under laboratory and greenhouse conditions. Percentage of seed germination and radicle length were used as criteria for judging pathogenicity of the isolates under laboratory conditions. Pre-emergemce damping-off, post-emergence damping-oll, survival, and dry weight were used for judging pathogenicity under greenhouse conditions. Growth medium was a highly significant (p50.01) or a significant (p50.05) source of variation in all the laboratory or greenhouse variables used for evaluating pathogenicity of the isolates. This result confirms the importance of the mycelium nutritional status in determining its pathogenicity. Pathogenicity showed differential responses to the growth media that is, a single isolate can be highly pathogenic when it is grown on a particular medium, but may show only low pathogenicity on another medium. Significant positive and negative correlations were observed between laboratory and greenhouse variables. Two regression models, derived from stepwise multiple regression analysis, were constructed for each cultivar to predict pathogenicity of the isolates under greenhouse conditions. The results indicate that laboratory tests by using sorghum extract agar as growth medium can be used as a rapid method for evaluating differences among Rhizoctonia isolates; however, this should not replace pathogenicity tests with seedlings under greenhouse conditions. | ||||
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