|DELGADO, N - UNIVERSITY OF WISCONSIN
|CASLER, M - UNIVERSITY OF WISCONSIN
|GRAU, C - UNIVERSITY OF WISCONSIN
|Jung, Hans Joachim
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2002
Publication Date: 11/1/2002
Citation: DELGADO, N.J., CASLER, M.D., GRAU, C.R., JUNG, H.G. REACTIONS OF SMOOTH BROMEGRASS CLONES WITH DIVERGENT LIGNIN OR ETHERIFIED FERULIC ACID CONCENTRATION TO THREE FUNGAL PATHOGENS. CROP SCIENCE. 2002. V. 42. P. 1824-1831.
Interpretive Summary: Perennial forage grasses are the primary feed resource for livestock grazing systems, and these grasses help protect the environment by preventing soil erosion and removing excess nutrients from the soil. However, diseases caused by certain fungi can seriously reduce forage yield and long term survival of perennial grasses. We found that selection for lower levels of lignin, a plant component that limits digestibility of forages by livestock, resulted in increased infection severity by the fungus that causes crown rust disease in smooth bromegrass. A literature review suggests that other perennial forage grass species may exhibit a similar negative response for disease resistance to rust causing fungi when plants are selected for improved forage quality. If this negative association is proven to be genetically controlled, forage grass breeders will have difficulty selecting for rust disease resistance or improved forage quality without negatively impacting the other trait.
Technical Abstract: Selection for improved digestibility of smooth bromegrass has been associated with a reduction in lignin concentration and an increase in esterified ferulic acid concentration, which may reduce the resistance of smooth bromegrass to fungal diseases. The objective of this study was to determine the relationship of lignin and etherified ferulic acid (EthFA) concentration with disease reaction in smooth bromegrass. Host clones, divergently selected for lignin and etherified ferulic acid concentration, were challenged by three pathogenic fungi, one biotroph (Puccinia coronata Corda) and two necrotrophs [Drechslera bromi (Died) Shoem and Bipolaris sorokiniana (Sacc.) Shoem]. Significant positive and negative associations were found between lignin or EthFA and host reaction to D. bromi or B. sorokiniana. The frequencies of these associations suggested that they arose by chance associations between genes rather than tight linkages or pleiotropic (causal) effects. Host reactions to P. coronata were consistently and negatively associated with lignin, less so with EthFA. These associations, together with results from other species, suggest that lignin and perhaps EthFA may be important components of rust resistance mechanisms in the Poaceae. If these mechanisms are real, they will cause considerable difficulty for breeders attempting to simultaneously improve both rust resistance and forage nutritional value.