An assay for the quantification of pathogenicity and virulence of two strains of Podosphaera xanthii (Erysiphaceae) on different hosts from digital images. SYDOWIA 74: 277-285.
http://www.sydowia.at/syd74/T19-Gregorio-Cipriano-3002.pdf
DOI: https://doi.org/10.12905/0380.sydowia74-2022-0277
Abstract
The predominant species of powdery mildew in the Cucurbitaceae is Podosphaera xanthii. However, there is little information on the epidemiology of this disease in Mexico despite its importance. As a first assay, we explore the applicability of a quantitative technique to estimate differences in the severity of disease caused by P. xanthii on leaves of Cucurbitaceae. We obtained two samples from different hosts: cultivated (Cucurbita pepo) and wild (C. radicans) cucurbits. Conidia were inoculated onto the leaves of growing plants of seven cucurbit species. We used the ImageJ program to quantify the infected area for each leaf as the sum of several polygons. The severity of the infection was calculated as the percentage of the infected foliar area. The two inocula of P. xanthii were pathogenic in five of seven inoculated cucurbits. Our analyses of variance to compare the variation of the percentage values among susceptible hosts revealed different levels of severity. This result indicates that this is a promising method to quantitatively compare differences in disease severity of different strains or hosts of powdery mildews.
