Gene Action of Dollar Spot Resistance in Creeping Bentgrass

The dollar spot disease, incited by Sclerotinia homoeocarpa F.T. Bennet, is one of the most important diseases of creeping bentgrass (Agrostis stolonifera L.) on golf courses. An understanding of the inheritance of dollar spot resistance could enhance genetic improvement efforts in creeping bentgrass. The objectives of this study were to evaluate the response of two creeping bentgrass crosses to two different isolates of S. homoeocarpa, determine gene action and identify number of loci involved in resistance to individual fungal isolates. Parental clones, pseudo F₂, pseudo F₃, BC₁ and BC₂ progenies from two crosses were established in a field trial in a randomized complete block split‐plot design in the fall of 2002. Progeny of each generation (subplots) were inoculated with each of two isolates of S. homoeocarpa (main plots) applied at a rate of 0.25 g/m² of prepared inoculum and evaluated for dollar spot disease. Minimum loci calculations averaged 1.0–2.6. Midparent heterosis calculations were not significant. Backcross population means were closest to the recurrent parent. Generation mean analysis supports a simple additive‐dominance model for both crosses and both isolates, although there was also some evidence of epistatic gene action depending on the cross and the isolate. These results confirm previous research that dollar spot disease is quantitatively inherited and indicate that there may be a few genes interacting in a mainly additive fashion to confer dollar spot disease resistance in creeping bentgrass.