[Infectivity and effectiveness of different strains of Frankia spp. on Atriplex cordobensis plants]

Frankia is an actinomycete that fixes atmospheric nitrogen in actinorhizal symbiosis (in non-legume plants). Atriplex cordobensis is an important Chaco Arido forage species due to the high nitrogen content. The aim of this paper was to isolate plant endophytes to be utilized as an inoculum in adapted species. A. cordobensis seedlings of 30 days were inoculated with isolated strains of Atriplex cordobensis, Colletia hystrix, Trevoa trinervis, Talguenea quinquenervia and 4-6 strains of Retanilla ephedra, courtesy of the University of Chile. A complete randomized design with 9 replications was performed. The infective ability of the strains was established through the re-isolation of the endophytes in QMOD artificial medium. The infectivity was evaluated by means of: plant aerial part length, leaf number, number and length of internodes, dry weight and total nitrogen content. The symbiotic effectivity, inoculation response and fixed nitrogen quantity were calculated. All strains treated on A. cordobensis presented Frankia typical morphological characteristics. A. cordobensis and C. hystrix showed the best nitrogen fixing effectivity, T. quinquenervia had a good aerial development but its fixing nitrogen ability was low, as a plant growth promoting rhizobacteria (PGPR). All strains were infective and A. cordobensis and C. hystrix apported the highest nitrogen amount to the plants.