The occurrence of the alkaloidsN-formyl andN-acetyl loline, peramine, lolitrem B, and ergovaline and the response of aphids to plants containing these compounds were determined in species and cultivars ofFestuca,Lolium, and other grass genera infected with fungal endophytes (Acremonium spp., andEpichloe typhina). Twenty-nine of 34 host-fungus associations produced one or more of the alkaloids, most frequently peramine or ergovaline. Three alkaloids (lolines, peramine, and ergovaline) were found in tall fescue and in perennial ryegrass infected withA. coenophialum, while peramine, lolitrem B, and ergovaline were present in perennial ryegrass and in tall fescue infected withA. lolii and inF. longifolia infected withE. typhina. WhileA. coenophialum andA. lolii produced similar patterns of alkaloids regardless of the species or cultivar of grass they infected, isolates ofE. typhina produced either no alkaloids or only one or two different alkaloids in the grasses tested. Aphid bioassays indicated thatRhopalosiphum padi andSchizaphis graminum did not survive on grasses containing loline alkaloids and thatS. graminum did not survive on peramine-containing grasses. Ergovaline-containing grasses did not affect either aphid.

Fungal endophyte-infected grasses: Alkaloid accumulation and aphid response.

Since the discovery of the effects of endophytes in the genus Acremonium on insect resistance, our understanding of these fungi has progressed greatly. However, many interactions associated with the endophytes, their hosts, and insect herbivores affect the use and expression of this resistance. This review centers on these topics, focusing on our current thinking about the use of endophyte-enhanced resistance to insects. A broader perspective is stressed in the belief that this phenomenon is only one example of many microbial-plant interactions that affect insect resistance. I begin with a review of the biology of the Acremonium endophytes, followed by a discussion of other fungal endophytes and fungal-plant interactions that result in increased insect resistance. The status of our knowledge of the effects of Acremonium endophytes on insect resistance is then presented. Finally, plant breeding, resistance management, and other influences endophytes have on agroecosystems are discussed.

Acremonium endophyte interactions with enhanced plant resistance to insects

Loline alkaloids: Currencies of mutualism.

Chapter Four - Chemistry, Biology and Chemoecology of the Pyrrolizidine Alkaloids

Epichloae endophytes of family Clavicipitaceae (comprising genera Epichloe and Neotyphodium) are fungal symbionts of Pooideae grasses. The associations formed, range from mutually beneficial to antagonistic and the nature of this relationship is dependent upon the importance of vertical (via host seeds) versus horizontal (ascospore mediated) transmission of the fungus. These endophytes can enhance their hosts’ survival through protection from abiotic and biotic stresses and can thus be utilized in an agricultural context. Animal-safe grass-endophyte associations that confer bio-protective properties for increased pasture persistence and productivity have been developed and commercialized. One of the crucial drivers underpinning the selection of epichloae strains for commercial development is endophyte derived bioactivity. The potential of next generation endophytes is determined by testing a number of attributes such as agronomic fitness, animal and food safety as well as compatibility with host plants of interest. Strategic research supports these activities by focusing on elucidating mechanisms of compatibility between host and fungal symbiont, as well as investigating other molecular drivers of symbiosis such as siderophore mediated iron-uptake, fungal signalling, fungal growth in host plants and fungal secondary metabolism. This review weaves together the different strands of multidisciplinary research aimed at ultimately exploiting epichloae endophytes for increased pasture performance.

James C. Fenster

Papers

Assay of tall fescue seed extracts, fractions, and alkaloids using the large milkweed bug