AOBPreview originally published online on January 30, 2006
Annals of Botany 2006 97(4):571-577; doi:10.1093/aob/mcl004
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Effects of Neotyphodium Fungi on Lolium multiflorum Seed Germination in Relation to Water Availability

1 Cátedra de Ecología, 2 Cátedra de Fisiología Vegetal and 3 Cátedra de Cerealicultura, Facultad de Agronomía, Universidad de Buenos Aires/IFEVA-CONICET, Av. San Martín 4453-C1417DSE, Ciudad de Buenos Aires, Argentina
* For correspondence. E-mail: gundel{at}agro.uba.ar
Received: 30 August 2005 Returned for revision: 25 October 2005 Accepted: 2 December 2005 Published electronically: 30 January 2006
Background and Aims Temperate endophyte-infected (Neotyphodium sp.) grasses have been shown to exhibit an ecological advantage over endophyte-uninfected grasses under abiotic stressful conditions. It is predicted that endophyte-infected plant populations will display higher rates of germination and proportion of germinated seeds under limiting water conditions.
Methods The hydrotime regression model was used to describe the effect of Neotyphodium endophyte on seed germination of Lolium multiflorum at different water potentials. Additionally, seed mortality after water stress exposure was estimated in endophyte-infected and -uninfected seeds.
Key Results Endophyte infection inhibited seed germination at all water potentials. The hydrotime model described satisfactorily the germination responses, and revealed that endophyte-free seeds exhibited higher rates of and final percentage germination, probably due to a lower base water potential compared with endophyte-infected seeds. However, Neotyphodium endophyte conferred a higher rate of survival in those seeds that remained ungerminated when exposed to highly water stress conditions.
Conclusions Changes produced by Neotyphodium endophyte in L. multiflorum seeds might affect fitness in particular ecological scenarios. For example, the presence of the endophyte may curtail seed germination when water is limiting, reducing the risk of seedling death. Conversely, endophyte-free seeds would display an enhanced germination, ensuring a more rapid seedling establishment if later water conditions do not restrict plant growth.
Key words: Endophyte, germination, hydrotime model, Lolium multiflorum, Neotyphodium sp., seed, water stress
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