Research of Disease Severity Index for Comparisons of Treatments

• Main Authors: Ju-Wei Tsai, 蔡儒維
• Other Authors: 蔣國司
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/11747728014351034589

碩士 === 國立中興大學 === 農藝學系所 === 105 === The disease severity index (DSI) is a single index number for summarizing disease severity data so that it can represent the gross intensity of the disease in a plot or region. The DSI be used to indicate the disease resistance of a cultivar, the effectiveness of fungicides and the relationship between the disease severity and the yield by agricultural researchers. The purpose of this study is to explore the application of DSI in a comparison of the treatment (e.g., varieties, fungicides, etc.). First, to compare treatments, the estimated values of field sampling are obtained by simulation methods. Subsequently, transformed into the category scale to calculate DSI. The calculated DSI were compared with the weighted average of the midpoint from the corresponding interval. From the result of the study, the use of DSI is superior to the midpoint. In the assessment methods, nearest percent estimate (NPE) and 10% category scale have the better results. Moreover, the performance of amended 10% category scale with additional grades at low severity is good in the category scale with unequal intervals. Furthermore, as for comparing the differences between the two treatments, three analytical methods (meta analysis, Mann-Whitney U test, and t-test) were used. In these analytical methods, the fixed effect model of the meta analysis is the best.Also,the results of the analysis method were affected by the plots or samples.Meta analysis is inferior for smaller sample sizes. Besides, Mann-Whitney U test is not suitable for testing when the numbers of plots was small.The results of this study could be helpful for appropriate analytical methods when using DSI.