Population and identification of mycorrhizal fungi in St. Augustinegrass in Florida and their effect on soilborne pathogens

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of more than 90% of all land plants. Mycorrhizae are documented in many crops as positive associations with roots of plants that help reduce disease severity soilborne pathogens and increase nutrient and water uptake while lowering plant stress and ultimately management costs. However, there is no information concerning the effects of AMF colonization in St. Augustinegrass.; In Florida, St. Augustinegrass sod production contributes hundreds of millions of dollars to the economy annually while supplying a product to homeowners and commercial entities with great aesthetic value. The use of AMF in St. Augustinegrass sod production has many potential benefits to the sod industry and the environment including lowered management costs, pesticide use and pollution. In these studies, a survey of St. Augustinegrass sod farms in north central Florida revealed a moderate level of AMF colonization as well as a diverse population of AMF species. Direct and indirect pathogen challenges with the ubiquitous AMF, Glomus intraradices, in St. Augustinegrass plants suggested a limited role for AMF in lowering disease severity in two of the more devastating diseases of St. Augustinegrass in Florida, brown patch and take-all root rot.; While no positive correlation was observed between AMF colonized St. Augustinegrass plants and the soilborne pathogens Rhizoctonia solani or Gaeumannomyces graminis var. graminis , effective assays for mycorrhizal St. Augustinegrass evaluations were developed and foundation information concerning the association between St. Augustinegrass and AMF provided valuable data, which may help in the development of future AMF evaluations in St. Augustinegrass field trials and with other AMF species. These results were the first to suggest an association between AMF and St. Augustinegrass, and to evaluate their potential effects on disease severity.