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In New Zealand, the fungal endophyte Epichloë festucae var. lolii Latch, Christensen & Samuels ( Hypocreales) is widely used to enhance productivity and survival of mature perennial ryegrass, Lolium perenne L. ( Poaceae) plants. These endophytes produce alkaloids that reduce damage by insect pests, such as Argentine stem weevil ( ASW), Listronotus bonariensis ( Kuschel) ( Coleoptera: Curculionidae). However, knowledge of the effect of these fungi on seedlings is limited. High concentrations of grass-endophyte-derived alkaloids occur in endophyte-infected seed and can be translocated into seedlings to provide early protection from insect herbivory. A glasshouse experiment was conducted in which adult ASW were given a choice between perennial ryegrass cultivar 'One50' without endophyte (Nil) or containing endophyte strains AR1, AR37, or NZCT, and cv. 'Trojan' containing strain NEA2, in three post-sowing time periods. ASW feeding damage was assessed together with plant survival and dry weight production. Plant survival and dry matter production was reduced in all treatments with mortality highest in endophyte-free and AR37 treatments, especially in the first and second time period. Strongest adult ASW deterrence occurred on seedlings infected with endophyte strains that produce peramine ( AR1, NZCT, and NEA2). Strain NZCT was virtually undamaged in the third time period whereas damage initially increased in AR1 and NEA2 up until day 50-53 post-sowing and then declined. Endophyte-free and AR37 treatments were significantly more damaged than AR1, NZCT, and NEA2. This research indicated there is a period of seedling vulnerability to adult ASW attack during germination, even for strains producing peramine. Possible explanations for these results are discussed. [ABSTRACT FROM AUTHOR]

A series of laboratory experiments was carried out with the main objective of contributing to the development of biosafety testing methods for transgenic plants or plants produced by other novel technologies. The adult stage of a New Zealand native weevil, Nicaeana cervina (Broun) (Coleoptera: Curculionidae: Entiminae), was used as a test insect as this has become well-adapted to introduced pasture species, feeding on both ryegrass [ Lolium perenne L. (Poaceae)] and white clover [ Trifolium repens L. (Fabaceae)]. Ryegrass plants used in experiments were infected with strains of the symbiotic endophytic fungi Neotyphodium lolii (Latch, M.J. Chr. & Samuels) and Epichloe festucae Leuchtm., Schardl & M.R. Siegel and included a transgenic endophyte, which was modified to eliminate production of the insect deterrent, peramine. Nicaeana cervina was exposed to these endophyte-infected plants along with endophyte-free ryegrass. Weevils were also exposed to white clover with high or low levels of cyanogens, and to white clover selections bred conventionally to contain high or low levels of crude protein. These bioassays were carried out sometimes over a series of time intervals, and weevil survival, feeding, and reproductive performance variables were measured. Nicaeana cervina survival was generally high, although feeding and oviposition were variable between experiments despite high replication in some cases. A summary of significant differences obtained across all experiments suggested that data on the proportion of weevils feeding and amounts of leaf material consumed were more often significantly different than treatment effects on survival or reproductive performance. A positive relationship between the proportion of weevils feeding and those ovipositing was found, suggesting that a 50% reduction in feeding would result in a 28% reduction in the proportion of weevils ovipositing. Power analysis using the range of values recorded for the variables measured indicated that for proportions of weevils surviving, feeding, or fecund, about 35–42 replicates would be required for a 40% difference in values. For measures of leaf consumption and numbers of eggs per female, fewer replicates were required for 95% power when these values were at the higher end of the range than when they were at the lower end of the observed range. The usefulness of the case study test insect and risk assessment protocols used for biosafety testing are discussed. [ABSTRACT FROM AUTHOR]

Parasitoid fitness is closely associated with the condition of the host insect, and the condition of the host is partly dependent on the quality and quantity of plant food available. The relationship between host diet and parasitoid fitness therefore has the potential to indirectly mediate complex multitrophic interactions. This relationship may be influenced both by the presence of mycotoxins from endophytic fungi, which share symbiotic relationships with plants and cause reductions in host-plant quality for herbivores, and by the availability of beneficial nutrient-rich plant foods such as pollen. This study used a multitrophic system involving ryegrass, a fungal endophyte, pollen, and an insect herbivore and its parasitoid to study the effect of host diet on parasitoid fitness. Previous studies showed that the larval stage of the parasitoid was negatively influenced by the presence of fungal-derived alkaloids in the diet of its host, but no assessment of effects on the adult stage of the parasitoid had been made. Similarly, the effect of pollen in the diet of the host on the fitness of the parasitoid had not previously been examined. In this study, the fitness of parasitoids reared from hosts fed endophyte-free ryegrass, endophyte-free ryegrass plus pollen, or endophyte-infected ryegrass was assessed in two laboratory experiments. Host insects exhibited significant responses to treatment, but remarkably, there were no significant treatment effects on parasitoid development times, the number of successful parasitoid emergences, tibia length, or preoviposition egg complement. The absence of a strong relationship between host diet and parasitoid fitness in this study differs markedly from studies of other parasitoid–host systems in that the adult stage of this parasitoid appears remarkably unresponsive to variation in host condition. This work contributes to a better understanding of multitrophic interactions and to the refinement of integrated pest management tactics in a temperate pastoral agroecosystem. [ABSTRACT FROM AUTHOR]