IANNONE Leopoldo Javier
congresos y reuniones científicas
Diversity of Epichloë endophytes of the forage grass Bromus auleticus, alkaloid gene profiles with managing perspectives.
MC CARGO, P.D.; CHARLTON N.; ROSSI, M.S; NOVAS, M.V.; YOUNG C; ROSSI, M.S; IANNONE L.J.
Congreso; 5TH International Symposium of Forage Breeding; 2015
Epichloë species are fungal systemic symbionts of cool-season grasses (Poaceae subfamily Pooideae) conferring advantages to their hosts. Most of these symbionts can produce alkaloids that provide protection from herbivory, which can be insect deterrents (e.g. lolines and peramine) or toxic to livestock (e.g. the indole-diterpene lolitrem-B and the ergot alkaloid ergovaline). In South America only asexual vertically transmitted Epichloë species have been found. Bromus auleticus is a native forage grass from Argentina, Uruguay and southern Brazil and Epichloë pampeana and E. tembladerae have been described as mutualistic endophytes associated to this host species. We studied the genetic diversity of 51 Epichloë isolates from B. auleticus of different regions in Argentina using the calmodulin gene (calM) for phylogeny, and mating type and alkaloid gene profiles. These analyses provided assessment of the potential alkaloid production of the endophyte, which is considered agronomically important for selection and future development of the grass cultivars. Seven interspecific hybrid endophyte lineages were inferred through calM phylogenies. Lineages 1 and 2 represented the previously known E. pampeana and E. tembladerae, lineage 3 was closely related to E. pampeana and lineages 4 to 7 were clustered in clades with four well-supported sub-clades. Six genotypes corresponding to variation of presence and absence of the alkaloid and mating type genes associated with the calM phylogenies were revealed across the seven identified lineages. The six genotypes reduced to four different predicted chemotypes. All lineages are predicted to produce peramine, but only E. pampeana and lineage 3 would likely synthesize lolines (N-formylloline predicted). Lineages 4 to 7 are predicted to synthesize the ergot alkaloid intermediate compound chanoclavine-I that is non-toxic to cattle. The genotypes with indole-diterpene biosynthesis genes showed greater genetic variation. Lineages 4 to 7 would likely produce paxiline and terpendole-I. Two different indole-diterpene chemotypes were predicted within E. tembladerae, some isolates would likely be terpendole-C producers while others would produce paspaline. According to the predicted alkaloid chemotypes, B. auleticus endophytes have the potential to produce alkaloids with anti-insect activity but are likely safe for livestock, so they could be an adequate resource for the improvement of this and other forage grasses.