Comparison of assessment methods for rice sheath blight disease
1990
Sharma, N.R. | Teng, P.S. | Olivarce, F.M. (Bangladesh Rice Research Inst., Gazipur (Bangladesh))
Five methods for assessing the intensity of rice sheath blight disease cause by Rhizoctonia solani Kuhn were compared for their ability to characterize disease progress curves of three rice cultivars, IR72, IR64, and IR26957-86-2, respectively, highly susceptible, susceptible, and moderately resistant to the disease. The methods were % HRLH (Percent Highest Relative Lesion Height), % DS (Percent Disease Severity) % DI (Percent Disease Incidence), SES Scale (Standard Evaluation System scale of 0-9), and % RAI (Percent Real Area Infected). Both % HRLH and % DS met the criteria of simplicity, reproductibility and ease-of-use. Although % RAI is the most reliable because it represents actual infected tissue, the cost of labor and equipment to apply this method makes it impractical for the large number of samples in epidemiological studies. DI does not appear to be a suitable method for sheath blight assessment because all tillers in a hill become infected very soon after a primary source of infection was established. While the SES is not suitable for epidemiological or yield loss studies, it nevertheless has value in screening for host plant resistance.
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