Inheritance of Dollar Spot Resistance in Creeping Bentgrass

Abstract

The dollar spot disease incited by Sclerotinia homoeocarpa F.T. Bennet. is a common and destructive disease of both cool‐ and warm‐season grasses throughout the world. Genetic resistance to dollar spot is an important control strategy; however, the genetic mechanism of dollar spot resistance in turfgrasses is unknown. The first objective of this study was to determine broad‐sense heritability and predicted gain from selection of dollar spot resistance in creeping bentgrass (Agrostis stolonifera L.). This was completed through dollar spot disease evaluation of 265 randomly selected creeping bentgrass clones arranged in a randomized complete block design with six and five clonally propagated replicates in each of two locations evaluated over 2 yr. Five isolates of S. homoeocarpa were used to inoculate the field studies and applied at a rate of 1.75 g m−2 of prepared inoculum. The second objective was to evaluate inheritance characteristics of dollar spot disease resistance. Major gene calculations, heterosis, maternal effects, chi square analysis of segregation ratios, and number of effective factors were determined through the evaluation of dollar spot disease resistance of progeny from controlled crosses between fixed resistant and susceptible bentgrass clones. These progenies along with parental clones were established in field trials and inoculated with dollar spot. The continuous population distribution of phenotypes for clones and progeny indicated that dollar spot resistance may be quantitatively inherited. Broad‐sense heritability estimates (0.56 on a single plant basis and 0.90 on an 11‐plant clonal mean basis) indicated replication increased selection efficiency and that improvement in dollar spot resistance in creeping bentgrass should be possible. A minimum of two to five effective factors depending on the cross may be associated with dollar spot resistance.