Evaluation of Detached Strawberry Leaves for Anthracnose Disease Severity Using Image Analysis and Visual Ratings

Abstract

<jats:p>Inoculation of detached strawberry leaves with <jats:italic>Colletotrichum</jats:italic> species may provide an accurate, rapid, nondestructive method of identifying anthracnose-resistant germplasm. The purpose of this study was to statistically compare two methods (visual and image analysis) of evaluating disease severity of strawberry germplasm screened for anthracnose resistance. Detached leaves of 77 susceptible and resistant strawberry clones were inoculated with one <jats:italic>Colletotrichum gloeosporioides</jats:italic> (Penz.) Penz. &amp; Sacc. and two <jats:italic>C. fragariae</jats:italic> A. N. Brooks isolates. Anthracnose disease symptoms on each leaf were assessed quantitatively via computer-based image analysis to determine percentage lesion area and qualitatively by two independent raters using a visual disease severity rating scale (0 = no symptoms to 5 = entire leaf dead). The two visual raters’ average disease severity ratings (n = 3413) were in substantial agreement with a weighted Cohen’s kappa coefficient (<jats:italic>k</jats:italic>) of 0.80 [95% confidence interval (CI) 0.79–0.82]. There was a strong positive correlation between percent lesion area determined by image analysis and the visual disease scores of the two raters (<jats:italic>r</jats:italic><jats:sub><jats:italic>p</jats:italic></jats:sub> <jats:italic>=</jats:italic> 0.79). Image analysis provided a precise measurement of percent lesion area of infected leaves while visual assessment provided more rapid results. Our results indicate that detached leaf inoculations can be used as a rapid preliminary screen to separate anthracnose-susceptible from -resistant germplasm in large populations within breeding programs. It also may be used for assessing the resistance/susceptibility of parental breeding lines to various <jats:italic>Colletotrichum</jats:italic> species and isolates, for mapping germplasm for resistance genes, and in pesticide development studies.</jats:p>

Determination of anthracnose (Colletotrichum gloeosporioides) resistance group in shallot (Allium cepa var. aggregatum)

“…Previous research by Monteon-Ojeda et al (2017) found that extended incubation periods were negatively associated with disease severity and low incidence. In contrast, incidence positively correlated with disease severity-a positive correlation between spot diameter and disease severity (Miller-Butler et al, 2019).…”

Strawberry (&lt;i&gt;Fragaria&lt;/i&gt; spp.): Cultivation, Production, Consumption, and Marketing in Cameroon

“…White leaf spots (Figure 5D) (Cérès Agricole, Red Gold of Africa, Mbidjoro Sustainable Living Environment, and KAFFO Farm); leaf yellowing (Figure 5E) (Cérès Agricole, Red Gold of Africa, BIO Farm of Lolodorf, and Bafoussam Farm), and whitish down on the upper and lower leaf surfaces (Figure 6F) (KAFFO Farm) were also recorded. Melinda [27], Baroncelli [28], Abd-El-Kareem [29], and Mykhailenko [30] attribute these black spot symptoms to anthracnose caused by Colletotricum acutatum or Colletotricum gloeosporioides, or Cercospora fragariae, and purple blight caused by Diplocarpon earlianum, while the common leaf spots are caused by Mycosphaerella fragariae. On the other hand, white leaf spots are thought to be the result of Ramularia grevilleana attacks [29] [30].…”

Possible Morphological and Chemical Resistance Mechanism of Shallots (Allium Cepa Var Ascalonicum) to Colletotrichum Gloeosporioides Penz

“…The estimated severity of anthracnose symptoms in leaves was as follows: severity = (infected leaf area/total leaf area) × 100% (Miller-Butler et al, 2019).…”