Resumen

PETIGROSSO, L.R. et al. Respuesta a la frecuencia de defoliación de plantas de festuca alta de una población naturalizada infectada con endófito silvestre y un cultivar comercial libre. RIA. Rev. investig. agropecu. [online]. 2020, vol.46, n.2, pp.195-202. ISSN 1669-2314.

The objective of the present work was to evaluate the effect of two defoliation frequencies on the vegetative and reproductive growth of tall fescue plants originated from seed harvested in a naturalized population infected with Epichloë coenophiala (FNE+) and from a commercial endophyte-free cultivar (FCE-, cv Continental Taita). In addition, the effect of the defoliation frequencies applied on the vertical transmission of the endophyte to the seeds produced by FNE+ plants was analyzed. On 2 May 2016 seeds were sown in micropastures at a density of 200 plants m-2. The experimental factors were: type of tall fescue micropasture (FNE+ and FCE-) and frequency of defoliation (AF: high and BF: low, defoliated every 450±100°Cd and every 850±100°Cd, respectively, during the period between 20 October 2016 and 16 August 2017). Eight cuts were carried out in AF and 4 cuts in BF. A completely randomized experimental design with a factorial arrangement and five replicates was used. Under AF, FNE+ plants presented higher accumulation of total biomass than FCE- (168.19±8.84 and 149.12±3.74 g DM m-2 respectively, p=0.009), while the opposite occurred under BF (FNE+: 104.13±7.07 and FCE-: 120.13±5.79 g DM m-2, p=0.009). Independently of micropasture type, the number of tillers per plant was higher under AF than under BF (2346±302 and 1940±250 tillers m-2 respectively, p<0.0001). The number of panicles per plant was higher in FNE+ than in FCE- (2.85±0.20 and 1.55±0.34, respectively, p=0.002) and was not affected by the frequency of defoliation (p=0.065). The FNE+ plants tended to show a greater reproductive effort than FCE-, although the difference was only significant under BF. Seed production was higher in FNE+ than in FCE- plants (316.44±35.03 and 183.53±18.19 seeds/plant, respectively, p=0.0033) and it was not affected by the defoliation frequency (p=0.2581), although the highest frequency of defoliation tended to decrease the seed production of FNE+ plants. All the analyzed seeds produced by FNE+ plants were positive to the endophyte diagnosis, so endophyte transmission was not affected by the frequency of defoliation. In conclusion, despite the fact that the defoliation frequency affected differentially total plant biomass of both types of micropastures, FNE+ plants always showed a better reproductive performance than FCE- plants. The last finding together with the fact that the transmission of the endophyte to the seeds was perfect and not affected by the defoliation frequency, would help to explain the progress of the percentages of infected plants commonly observed in the field.

Palabras clave : Festuca arundinacea; Epichloë coenophiala; biomass production; number of tillers per plant; reproductive effort; endophyte vertical transmission..

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