Histology of Healthy and Diseased Orchardgrass Leaves Subjected to Digestion in Rumen Fluid¹

Abstract

Few studies have been conducted on the effects of stem rust caused by Puccinia graminis Pers. f. sp. dactylidis Guyot et Massinot on forage quality in orchardgrass ( Dactylis glomerata L.). Orchardgrass grown in the field was infected with the pathogen or kept free of the pathogen by spraying twice a week with a fungicide to study the effect of the pathogen on digestibility. Cross sections (12μ) of healthy and diseased leaves were examined under a microscope after 2 to 48 hours of digestion in rumen fluid. After 48 hours, 6 to 7 mm sections from healthy leaves were completely digested except for lignified structures, whereas sections from diseased leaves showed no apparent digestion of tissues under uredia and only partial digestion of adjacent tissues. Stem rust of orchardgrass not only reduces forage yield but also reduces forage quality.