HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Berg, C. C. Articles by Sherwood, R. T. Search for Related Content PubMed Articles by Berg, C. C. Articles by Sherwood, R. T. Agricola Articles by Berg, C. C. Articles by Sherwood, R. T.

Stability of Resistance to Leaf Disease in Orchardgrass and Smooth Bromegrass Germplasms

USDA-ARS, Pasture Systems and Watershed Management Research Unit, U.S. Regional Pasture Research Lab., University Park, PA 16802

^* Corresponding author.

Genetic resistance is the only practical method to control foliar diseases on forage grasses. Once developed, resistance must be transmitted, without selection, through several generations of seed increase. This study was conducted to determine whether disease resistance would be maintained when disease resistant germplasms were advanced two generations without conscious selection for disease resistance. Orchardgrass (Dactylis glomerata L.) germplasm PL-OGDR1 resistant to purple leaf spot (caused by Stagonospora arenaria Sacc.), and smooth bromegrass (Bromus inennis Leysser) germplasm PL-BDR1 resistant to brown leaf spot [caused by Pyrenophora bromi (Died.) Drechs.] were used to initiate this study. Plants of the germplasm releases, two populations produced by unselected advance, and three cultivars of each species were rated for disease reaction in two greenhouse inoculation tests. Mean spot size and disease coverage scores were low for all generations of resistant germplasms, and there were no differences among generations. The frequency distribution of disease scores within generations remained relatively constant for generations. Cnltivars were much more susceptible, with disease scores that averaged twofold to threefold higher than resistant germplasms. Results indicated that in the absence of selection pressure, disease resistant populations developed by five cycles of recurrent phenotypic selection for resistance to orchardgrass purple leaf spot or bromegrass brown leaf spot can be advanced for two successive unselected generations without a shift in resistance.

Received for publication August 30, 1993.