Douhan, Greg W. , de al Cerda, Karla , Huyrn, Karyn , Greer, Chris , Wong, Frank .
Contrasting genetic structure between Magnaporthe grisea populations associated with the golf turf grasses Lolium perenne and Pennisetum clandestinum in California.
Gray Leaf Spot (GLS) disease of perennial ryegrass ( Lolium perenne) and kikuyugrass (Pennisetum clandestinum) in golf courses in California was first noted in 2001 and 2003, respectively, and within five years has become well established. The causal agent of the disease is the fungus Magnaporthe grisea, which is known to consist primarily of clonal lineages that are highly host specific. Therefore, our objective was to investigate host specificity and population dynamics among isolates associated primarily from perennial ryegrass and kikuyugrass since the disease emerged at similar times and both grasses can be found on a single golf course. We also obtained isolates from additional hosts (Tall fescue, St Augustinegrass, Weeping lovegrass, and Rice) for comparative purposes. A total of 38 polymorphic AFLP makers were scored from 450 isolates which clustered by host with high bootstrap support (71 to 100%). Genetic structure between Kikuyugrass and perennial ryegrass isolates differed significantly. Isolates from kikuyugrass were genotypically diverse (n = 34), possessed both mating-types, and tests for random mating could not be rejected whereas isolates from perennial ryegrass were less genotypically diverse (n = 10) and only consisted of a single mating-type. Low genotypic diversity was also found among the other host specific isolates which also only consisted of a single mating-type. This is the first study to document evidence for the potential of sexual reproduction to occur in M. grisea isolates not associated with rice (Oryzae sativa). Moreover, given the significant host specificity and contrasting genetic structures between turfgrass associated isolates, the recent emergence of GLS on various grass hosts in CA suggests that potential cultural practices or environmental changes have become conducive for the disease and that the primary inoculum may have already been present in the state.
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1 - University of California, Plant Pathology and Microbiology, Riverside, CA, 92521, USA
2 - UC Cooperative Extension, Colusa, CA, 95932, USA
Presentation Type: Poster:Posters for Topics
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM