The presence of Epichloë sp. in Bromus auleticus (Trin.) seeds enhances micropropagation and growth of micropropagated plantlets from these seeds

Abstract

Bromus auleticus (Trin.) is a grass native to the southern cone with important agronomical potential as fodder. Different breeding programs have been initiated with this grass, but plant tissue culture techniques could not be used because B. auleticus is recalcitrant. The aim of the present study was to develop a micropropagation protocol in the genus Bromus and to investigate if the association between B. auleticus and Epichloe endophytes affected in vitro culture and growth of micropropagated plantlets. In different micropropagation stages, better results were obtained with endophyte-infected (E+) seeds compared to endophyte-free (E−) seeds. The E+ seeds presented higher percentages of in vitro germination (82 ± 5 vs. 57 ± 6%), callus induction (72 ± 6 vs. 37 ± 6%), and plant regeneration from callus (89 ± 5 vs. 13 ± 5%). We also compared the biomass of shoot complexes and regenerated plantlets. After 4 weeks of culture, shoot complexes obtained from E+ seeds reached greater weight than the ones regenerated from E− seeds (173 ± 24 vs. 74 ± 9 mg). More than the 80% of the regenerated shoot complexes were rooted ex vitro and acclimated, regardless of their origin (E+ or E−). Finally, after 4 weeks of acclimatization, the plantlets regenerated from E+ seeds reached a greater weight than the ones from E− seeds, (461 ± 64 vs. 172 ± 25 mg). These results indicate that the use of endophyte-infected (E+) seeds enhances significantly B. auleticus micropropagation and promotes growth of the regenerated plantlets.