Dollar spot resistance among blends of creeping bentgrass cultivars

Disease is a major problem in creeping bentgrass (Agrostis stolonifera L.) on golf course putting greens. Genetic composition and uniformity of host p opulations can affect disease development. This study was conducted to dete rmine the effects of blending creeping bentgrass cultivars on dollar spot ( caused by Sclerotinia homoeocarpa F. T. Bennett) severity. 'Penn A-4', 'Cre nshaw', 'L-93', 'Mariner', and 'Penncross' were planted in monostands or as two-way or three-way blends in a completely random design with three repli cations on a sand-based putting green in the field at College Station, TX. Disease severity was determined by the number of infection centers and by t otal blighted area. Crenshaw was most susceptible, L-93 most resistant, and all other cultivars were moderately resistant to dollar spot in monostands . Cultivar susceptibility in monostands to S. homoeocarpa was representativ e of each cultivars contribution to dollar spot severity in blends. In blen ds, L-93 suppressed, whereas Crenshaw increased dollar spot. Penncross, Pen n A-4, and Mariner did not affect dollar spot severity across all blend com binations. Number of infection centers and infected area pooled across all monostands were sum ar when compared to all two- and three-way blends indic ating that dollar spot activity in blends was a compromise between resistan ce levels of individual cultivars. Two-way blends of Penn A-4, L-93, Marine r, or Penncross with Crenshaw, however, resulted in 46 to 67% fewer infecti on centers and 71 to 98% less blighted area, when compared to the Crenshaw monostand. These data indicated that blending a resistant cultivar with a s usceptible cultivar reduced dollar spot severity in the blended population.