Influence of temperature on alkaloid levels and fall armyworm performance in endophytic tall fescue and perennial ryegrass

• Published in: Entomologia experimentalis et applicata Vol. 115; no. 3; pp. 417 - 426
• Main Authors: Salminen, S.O, Richmond, D.S, Grewal, S.K, Grewal, P.S
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.06.2005; Blackwell
• Subjects: Acremonium lolii; alkaloids; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; chemical constituents of plants; Clavicipitacea; endophytes; endophytic fungi; Festuca arundinacea; Fundamental and applied biological sciences. Psychology; fungal alkaoids; insect growth; Lepidoptera; Lolium perenne; mortality; Neotyphodium coenophialum; Neotyphodium lolii; Noctuidae; pest resistance; plant alkaloids; Plants and fungi; Poaceae; Spodoptera frugiperda; temperature; temporal variation; Monocotyledones; Temperature; Insecta; Environmental factor; Poaceae; Neotyphodium coenophialum; Fungi; Alkaloid; Neotyphodium lolii; Gramineae; endophytic fungi; Angiospermae; Lolium perenne; Clavicipitacea; Festuca arundinacea; Thallophyta; Symbiosis; Defensive secretion; alkaloids; Spodoptera frugiperda; Concentration; Arthropoda; Lepidoptera; Endophyte; Pest resistance; Spermatophyta; Noctuidae; Fodder crop; Invertebrata
• ISSN: 0013-8703; 1570-7458; 1570-8703
• DOI: 10.1111/j.1570-7458.2005.00303.x

The symbiotic relationships between Neotyphodium endophytes (Clavicipitacea) and certain cool-season (C3) grasses result in the synthesis of several alkaloids that defend the plant against herbivory. Over a 3 month period we evaluated the effects of temperature on the expression of these alkaloids in tall fescue, Festuca arundinacea Schreb, and perennial ryegrass, Lolium perenne L. (Poaceae). Response surface regression analysis indicated that month, temperature, and their interaction had an impact on the alkaloid levels in both grasses. We aimed to identify the alkaloids most closely associated with enhanced resistance to the fall armyworm, Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and clarify the role of temperature in governing the expression of these alkaloids. The dry weights and survival of fall armyworms feeding on endophyte-infected tall fescue or perennial ryegrass were significantly lower than for those feeding on uninfected grass, whereas endophyte infection had no significant influence on survival. For tall fescue, a four-alkaloid model consisting of a plant alkaloid, perloline, and the fungal alkaloids ergonovine chanoclavine, and ergocryptine, explained 47% of the variation in fall armyworm dry weight, whereas a three-alkaloid model consisting of the plant alkaloid perloline methyl ether and the fungal alkaloids ergonovine and ergocryptine explained 70% of the variation in fall armyworm dry weight on perennial ryegrass. Although temperature had a significant influence on overall alkaloid expression in both grasses, the influence of temperature on individual alkaloids varied over time. The levels of those alkaloids most closely linked to armyworm performance increased linearly or curvilinearly with increasing temperature during the last 2 months of the study. We conclude that the growth temperature of grasses can influence the performance of fall armyworm, and that this effect may be mediated through a set of plant- and endophyte-related alkaloids.