نوع مقاله : مقاله پژوهشی
نویسندگان
1 بخش تحقیقات گیاه پزشکی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان گلستان، سازمان تحقیقات،آموزش و ترویج کشاورزی، گرگان، ایران
2 کارشناس گیاهپزشکی، گروه گیاهپزشکی، دانشکده تولید گیاهی، دانشگاه علوم کشاورزی و منابع طبیعی گرگان، گرگان، ایران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Sarri & Prescott (1975) scale (A) is one of the most popular scales for measuring foliar diseases of small-grain cereals, which is expressed as 0-9. Double digit scale (AB) is made from incorporating A and disease severity on top leaves (B). Scales A and AB are of ordinal rating scales and their recorded data (descrete variables) are not analysable by parametric statistical methods. If they transformed suitably to disease severity index (or percent of disease index = PDI), a continous variable which cab be analyzed by parametric methods. In this study, severity of wheat tan spot (caused by Drechslera tritici-repentis) was measured as these four variables, in a randomized block design with 10 treatments (cultivars) and 3 replicates. Results of ANOVA revealed significatly difference (P<0.05) between treatments, pnly based on B and PDI, whereas the difference was nonsignificant based on A and AB. Study of these variables relations via correlation coefficient and linear regression revealed a strong relationships between A with AB, and B with PDI. It is concluded that after the evaluation of disease severity based on scale A or AB, and before statistical analyses, data should be transformed to PDI, then ANOVA or analysis of regression can be performed.
کلیدواژهها [English]