|STEKETEE, CLINTON - University Of Georgia|
|MARTINEZ-ESPINOZA, ALFREDO - University Of Georgia|
|HENRY, GERALD - University Of Georgia|
|RAYMER, PAUL - University Of Georgia|
Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2015
Publication Date: 2/8/2016
Citation: Steketee, C.J., Martinez-Espinoza, A.D., Harris-Shultz, K.R., Henry, G.M., Raymer, P.L. 2016. Effects of genotype and isolate on expression of dollar spot in seashore paspalum. HortScience. 51(1):67-73.
Interpretive Summary: Seashore paspalum is a salt-tolerant warm-season turfgrass on golf courses and athletic fields. Cultivars of seashore paspalum are often infected with the disease dollar spot caused by the fungus Sclerotinia homoecarpa. Frequent applications of fungicide have led to isolates with fungicide resistance. Thus, an alternative strategy to dollar spot control is the use of seashore paspalum cultivars with genetic resistance. Five cultivars of seashore paspalum were artificially inoculated with five isolates of dollar spot during a two year study. The cultivars SeaIsle 1 and SeaIsle 2000 had the least amount of disease symptoms and the dollar spot isolate P1 was the most virulent. This information provides golf course superintendents cultivar choices when renovating their golf courses if dollar spot is a problem. Furthermore the identification of a highly virulent strain of dollar spot allows plant breeders to screen more seashore paspalum lines for enhanced resistance to dollar spot.
Technical Abstract: Seashore paspalum (Paspalum vaginatum Swartz) is a warm-season turfgrass species primarily utilized on golf courses and athletic fields and is often impacted by dollar spot disease. Dollar spot, caused by Sclerotinia homoeocarpa F.T. Bennett, is a major fungal disease and the most common turfgrass pathogen in North America. More money is spent chemically managing dollar spot than any other turfgrass pathogen. Current management of this disease relies heavily on fungicide applications and has led to an increase in the occurrence of fungicide resistance. An alternate management strategy is host plant resistance, but a better understanding of the interactions between pathogen isolates and the host species is needed to effectively incorporate this resistance into elite seashore paspalum genotypes. The goal of this study was to gather host plant/isolate response data that could be used to develop an effective and efficient screening protocol for resistance to this important disease. Five genotypes of seashore paspalum varying in dollar spot resistance were artificially inoculated with five isolates of S. homoeocarpa in repeated field studies during 2012 and 2013. Isolates used were from three warm-season and one cool-season turfgrass species. Inoculated plots were evaluated visually and using digital image analysis (DIA) for disease development over time and for the number and size of the infection centers at two rating dates each year. Statistical differences among the seashore paspalum genotypes and inoculation/isolate treatments were detected for the area under the disease progress curve (AUDPC) values, number of infection centers, and infection center size. No statistically significant interaction between seashore paspalum genotype and dollar spot isolate effects was observed, indicating that host plant resistance genes are likely not isolate specific. Utilizing this information, breeders should be able to use one highly virulent dollar spot isolate to screen for host plant resistance in seashore paspalum.