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Chemical Composition of Intermediate Wheatgrass Affected by Foliar Diseases and Stem Smut. J. F. Karn, Research animal scientist, USDA-ARS, Northern Great Plains Research Center, P.O. Box 459, Mandan, ND 58554; J. M. Krupinsky, research plant pathologist, USDA-ARS, Northern Great Plains Research Center, P.O. Box 459, Mandan, ND 58554. Phytopathology 73:1152-1155. Accepted for publication 14 March 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-1152.

Intermediate wheatgrass (Agropyron intermedium) plants affected with leaf spot diseases had lower in vitro digestible organic matter (IVDOM) and higher neutral detergent fiber (NDF) than healthy plants in both field and glasshouse studies. Nitrogen in whole-plant samples was not affected by foliar diseases in either study. However, nitrogen was lower in leaves selected from plants with a high level of disease compared to leaves from the same plants with a low level of disease. Plants selected for resistance to Cochliobolus sativus were lower in NDF and higher in nitrogen than susceptible plants regardless of the inoculation treatment. However, IVDOM, averaged across treatments, did not differ between resistant and susceptible groups. The effect of C. sativus on the nutritional quality of intermediate wheatgrass varied among the six genetic strains examined in the glasshouse; for example, the effect of C. sativus averaged over resistant and susceptible groups resulted in a 7.6% decrease in IVDOM of inoculated cultivar SD10-14, but only a 3.5% decrease for inoculated cultivar Slate. Forage quality changes between susceptible and resistant groups of plants were not consistent among strains. Field-grown intermediate wheatgrass plants naturally infected with stem smut had lower IVDOM and higher NDF, acid detergent fiber, and lignin than smut-free plants.

Additional keywords: Bipolaris sorokiniana, Drechslera sorokiniana, forage quality, Helminthosporium sativum, Ustilago spegazzinii.