Does decreased mowing frequency enhance alkaloid production in endophytic tall fescue and perennial ryegrass?

Tall fescue, Festuca arundinacea, and perennial ryegrass, Lolium perenne. are widely infected with fungal endophytes (Neotyphodium spp.). The symbiosis between plant and fungus leads to synthesis of alkaloids that have been shown to be either toxic or act as feeding deterrents against insect pests. As cultural practices have the potential to regulate production of plant secondary metabolites, we evaluated the influence of mowing frequency on the levels of major alkaloids in tall fescue and perennial ryegrass in the greenhouse. Tall fescue and perennial ryegrass maintained in 15-cm-diam. pots were cut to 5-cm height weekly or biweekly. Samples were taken monthly and the alkaloids extracted and analyzed by reverse-phase LC-MS. In tall fescue, ergovaline, ergonovine, and ergocristine were identified, whereas only ergocristine was identified in perennial ryegrass samples. In tall fescue, we observed a trend showing higher levels in samples cut biweekly than in those cut weekly. A similar pattern was seen in some putative alkaloids that were not identified. In perennial ryegrass, ergocristine and two putative alkaloids followed a pattern similar to that of alkaloids in tall fescue. A survey of a few samples of perennial ryegrass using extractions specific to peramine and lolitrem B yielded evidence suggesting their presence as well as several other identified alkaloids. These data support the hypothesis that decreased mowing frequency enhances alkaloid production/accumulation in tall fescue and perennial ryegrass.