Graminicolous downy mildew pathogens illustrated

Authors: Shishkoff, Nina; CASTROAGUDIN, VANINA - US Department Of Agriculture (USDA); Smallwood, Emily; Crouch, Jo Anne

Submitted to: American Phytopathological Society Potomac Division Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/23/2022
Publication Date: 8/4/2022
Citation: Shishkoff, N., Castroagudin, V.L., Smallwood, E.L., Crouch, J. 2022. Graminicolous downy mildew pathogens illustrated. American Phytopathological Society Potomac Division Meeting. Vol. 112, No. 8.
DOI: https://doi.org/10.1094/PHYTO-112-8-S2.16

Interpretive Summary: Downy mildews are destructive pathogens of important crops such as maize, millets, sorghum, and sugarcane. In countries where these organisms are not yet found, they are often designated as high-risk foreign pathogens and subject to oversight and quarantine by regulatory officials. Because rapid identification is important when GDMs are found on grain crops, it is important to describe them in a manner that allows easy comparison. This includes using photographs and illustrations that clearly depict them, as illustrated in the poster.

Technical Abstract: Graminicolous downy mildews (GDMs) are members of eight morphologically and phylogenetically distinct genera in the Peronosporaceae causing severe losses in crops such as maize, millets, sorghum, and sugarcane in many parts of the world. In countries where the most destructive GDMs are not endemic, these organisms are often designated as high-risk foreign pathogens and subject to oversight and quarantine by regulatory officials. Thus, there is a need to reliably and accurately identify the causal organisms. Thirty-nine species of GDMs are accepted in a recent monograph (Crouch, et al., in press). Because rapid identification is important when GDMs are found on grain crops, it is important to illustrate them in a manner that allows easy comparison. Line drawings of microscopic features were prepared from published reference materials and new images of Sclerospora farlowii. Objects and scale bars from original sources were opened in Photoshop CS6, the contour of objects traced, then the illustrations were standardized to a uniform style, with a gray mottling representing cytoplasm and solid grays representing solid walls. Thick black lines represent significant cellular boundries, such as the ones between cytoplasm and wall. Thin lines were used to represent delimitations of vesicles or zoospores, and dashed lines were used to delineate vacuoles. As much as possible, drawings were placed at the same scale to facilitate comparisons of the structures.