Digital image analysis to measure lesion area of cucumber anthracnose by Colletotrichum orbiculare

Abstract

A method was developed using scanned computer images and software programs to measure the lesion area on leaves with cucumber anthracnose caused by Colletotrichum orbiculare. After cucumber plants were inoculated with various concentrations of conidia, lesions on diseased leaves were scanned, manipulated with Adobe Photoshop 6.0, and measured using the blob analysis feature in Matrox Inspector 2.2. The method requires relatively low-cost equipment including a scanner, a personal computer, and two programs: Adobe Photoshop 6.0 and Matrox Inspector 2.2. Because stored images are used, the lesion area can be measured as time permits. Processing the images requires about 3 min per sample. The image assessment accurately detected anthracnose lesions on cucumber leaves and could be applied to other foliar necrotic or spot diseases.

Visual and Electronic Evaluations of Detached Strawberry Leaves Inoculated withColletotrichumSpecies

“…Kwack et al (2005) compared visual to image assessment of cucumber leaf anthracnose lesions and found the visual assessment had significantly higher scores than the image analysis on almost all tests. The over estimation of disease severity by visual assessment at the lower disease incidence was confirmed by Sherwood et al (1983) with the greatest overestimation occurring in leaves with the least infected areas.…”

“…Image analysis may decrease the possibility of making such mistakes. Kwack et al (2005) used scanned images of cucumber leaves and digitally manipulated the photographs for disease assessment. They determined that the photographic manipulation required about 3 min per cucumber leaf sample and surmised their method would work well for a small number of samples.…”

“…Digital imaging and analytical software was used by Wang et al (2008) to determine percent disease and percent phytotoxicity on strawberry leaves in a miniaturized antifungal bioassay. Kwack et al (2005) used digital image analysis to assess the severity of cucumber anthracnose caused by Colletotrichum orbiculare. However, the time it took to photograph inoculated tissues, utilize software to identify necrotic tissue (lesions), and determine the ratio of lesion to healthy tissue was considerable.…”

HrpNEa-induced deterrent effect on phloem feeding of the green peach aphid Myzus persicae requires AtGSL5 and AtMYB44 genes in Arabidopsis thaliana

“…Leaf photos were resolved by Adobe Photoshop to determine relative levels of callose in leaves. The size of a leaf and the size of callose-deposited areas were determined using the Magic Wand and Edit Tools of Adobe Photoshop as described (Kwack et al 2005;Sun et al 2010). The relative level of callose in a leaf was qualified as the ratio of violet callosedeposited area vs. leaf size.…”

A novel algorithm for semi-automatic segmentation of plant leaf disease symptoms using digital image processing

“…Thresholding, also referred to as binarization, consists of defining one or more threshold value(s) that define the range of pixel values that are associated with the objects of interest, such that only these remain after the thresholding procedure. There are many challenges in determining thresholds, which explains why this value is often defined manually (Bock et al 2008;Cui et al 2010;Kwack et al 2005;Contreras-Medina et al 2012). The negative impact of the automated thresholding using a relatively rigid thresholding system, such as the one available in Assess (Lamari 2002), was highlighted (Bock et al 2009).…”