Publication Date: 2011.
Author affiliation: Gundel, Pedro E. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura (IFEVA)-CONICET; Argentina.
Author affiliation: Garibaldi, Lucas A. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. INIBIOMA-CONICET. Laboratorio Ecotono; Argentina.
Author affiliation: Martínez Ghersa, María A. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura (IFEVA)-CONICET; Argentina.
Author affiliation: Ghersa, Claudio M. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas vinculadas a la Agricultura (IFEVA)-CONICET; Argentina.
Author affiliation: Garibaldi, Lucas A. Universidad de Buenos Aires (UBA). Facultad de Agronomía; Argentina.
Frequency and distribution of symbiosis in nature depend both on the direct symbiont effect on the host fitness and on its efficiency to spread within host populations (transmission). For vertically transmitted Neotyphodium fungi, the attention has been centered on the endophyte effect on host grass plants but little is known about the controls of transmission. Environmental and genetic factors have been suggested as important controls of transmission efficiency. We studied the effect of these two factors on the transmission efficiency of the Neotyphodium endophyte in Lolium multiflorum plants. Plant genotype of a host population naturally endophyte-infected (95%) was manipulated by conducting controlled crosses with genetically distant plant populations. The resulting progeny was subjected to two types of factors, resource shortage and oxidative stress induced by an herbicide. Irrespective of plant genotype, high resource level increased seed yield per plant by 26-fold, spike-to-seed transmission by 12%, and plant-to-seed transmission by 10% (not significant). Although herbicide effects could be mediated indirectly by changes in plant density or directly by oxidative stress, neither plant fitness nor transmission efficiency was affected. An interesting pattern between transmission efficiency and seed yield per plant was revealed when plants (from both experiments) were plotted together. Low yielding plants, that is plants that grew under low resource level at high plant density, showed high transmission failures whereas high yielding plants, that is plants growing at low density with and without herbicide treatment, showed high transmission rates. Transmission failures may be a consequence of the endophyte cost for host plants growing under restrictive conditions, suggesting that lower transmission efficiency may partially explain previous evidence showing lower endophyte infection frequency for grasses under stressful conditions. Host plants could be penalizing the endophyte through a competition-like mechanism, instead of depressing their own fitness.
Repository: RID-UNRN (UNRN). Universidad Nacional de Río Negro