Selection for stem rust resistance in tall fescue and its correlated response with seed yield

Genetic resistance to stem rust (caused by Puccinia graminis Pers.:Pers. subsp. graminicola Z. Urban) could reduce the need for fungicides to control the disease in tall fescue [Lolium arundinaceum (Schreb.) Darbysh. (=Festuca arundinacea subsp. arundinacea)] grown for seed. Two populations from 14 resistant forage-type plants (F) and 20 turf-types (T) were developed using polycross (PX) and open pollination (OP) progenies. A two-stage controlled environment inoculation was used for screening and selection for two cycles. Direct selection response was determined after two artificial inoculations in a controlled environment. Indirect selection response for seed yield was measured, using the same plants as the direct selection study, in the field using natural inoculation for 4 yr. Plants with resistant reaction, based on pustule type, increased from 5 to 54% in the F population and from 6 to 50% in the T after two cycles of PX selection and from 5 to 63%, and from 6 to 50% in the F and T populations, respectively, after one cycle of OP followed by one cycle of PX selection. In each selection scheme, the largest increase came from the first PX cycle. Seed yield of tall fescue with improved stem rust resistance was higher than for susceptible populations or cultivars with heavy stem rust presence (1998), but yields were similar with no rust pressure (1999). These results indicate that seed yields in tall fescue can be maintained using genetic resistance to stem rust sufficient to slow or eliminate disease epidemic development.