An Improved Grading System for Measuring Plant Diseases.

IF 3.1 2区农林科学 Q2 PLANT SCIENCES

Phytopathology Pub Date : 2025-08-01 DOI:10.1094/Phyto-35-655

J G Horsfall, R W Barratt

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Abstract

Heretofore, in recording severity of plant diseases by grading, the grades have been assigned equal values in percentage. According to the Weber-Fechner law, the human eye distinguishes according to the logarithm of the light intensity. Hence, the grades should be based on equal ability to distinguish, not on equal disease. Below 50 percent, the eye sees the amount of diseased tissue. Above 50 percent, it sees the amount of disease-free tissue. A new scoring system is based on 50 percent as a midpoint. The grades differ by a factor of two in either direction as follows: 1 = 0, 2 = 0 to 3, 3 = 3 to 6, to 12, 5 = 12 to 25, 6 = 25 to 50, 7 = 50 to 75, 8 = 75 to 87, 9 = 87 to 94, 10 = 94 to 97, 11 = 97 to 100, 12 = 100. Several plants (20 or more) at random are graded. Mean grade = grade readings + number of readings. A calibration curve is set up with grade numbers on the X-axis and percentage disease on a special semi-log. Y-axis with one and one-half phases from either end up to 50 percent. The grid has the aspect of arithmetic-probability paper. This scheme has been very useful in fungicide research, varietal resistance, etc. It should be useful in plant disease surveying.

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一种改进的植物病害分级测量系统。

迄今为止，在用等级法记录植物病害的严重程度时，等级以百分比的形式被赋予了相同的值。根据韦伯-费希纳定律，人眼根据光强的对数进行区分。因此，分数应该基于同等的区分能力，而不是同等的疾病。在50%以下，眼睛可以看到病变组织的数量。超过50%，它可以看到无病组织的数量。新的评分系统以50%为中点。在任何一个方向上，等级相差两倍：1 = 0,2 = 0至3,3 = 3至6,12,5 = 12至25,6 = 25至50,7 = 50至75,8 = 75至87,9 = 87至94,10 = 94至97,11 = 97至100,12 = 100。一些植物（20个或更多）随机被分级。平均成绩=年级阅读数+阅读数。标定曲线在x轴上标上等级数，在特殊的半对数上标上疾病百分率。y轴从任意一端到50%的一个半相位。网格具有算术-概率纸的特性。该方案在杀菌剂研究、品种抗性研究等方面具有重要意义。它在植物病害调查中应该是有用的。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Phytopathology 生物-植物科学

CiteScore

5.90

自引率

9.40%

发文量

505

审稿时长

4-8 weeks

期刊介绍： Phytopathology publishes articles on fundamental research that advances understanding of the nature of plant diseases, the agents that cause them, their spread, the losses they cause, and measures that can be used to control them. Phytopathology considers manuscripts covering all aspects of plant diseases including bacteriology, host-parasite biochemistry and cell biology, biological control, disease control and pest management, description of new pathogen species description of new pathogen species, ecology and population biology, epidemiology, disease etiology, host genetics and resistance, mycology, nematology, plant stress and abiotic disorders, postharvest pathology and mycotoxins, and virology. Papers dealing mainly with taxonomy, such as descriptions of new plant pathogen taxa are acceptable if they include plant disease research results such as pathogenicity, host range, etc. Taxonomic papers that focus on classification, identification, and nomenclature below the subspecies level may also be submitted to Phytopathology.