Using R based image analysis to quantify rust on perennial ryegrass

Abstract

Crown and stem rust caused by Puccinia coronata f. sp. lolii and Puccinia graminis subsp. graminicola are major diseases of perennial ryegrass (Lolium perenne L.) when grown for turfgrass, forage, and seed. Plant breeders and pathologists often quantify rust severity in the field using the modified Cobb scale, but this method is subjective, labor intensive, and dependent on the skill and experience of the scorer. Our objective was to develop a novel, open-source system that couples both ImageJ and R to quantify rust severity on simple RGB images.