Halotolerant endophytic bacteria enhance arbuscular mycorrhizal colonization in poplar production under greenhouse condition

BOENEL M; BELLA V; MESTRE M. C.; FONTENLA S

San Carlos de Bariloche

Workshop; II International Symposium, Mycorrhizal Symbiosis in South America; 2019

IPATEC - UNCo

Plant?s roots harbors diverse population of microorganisms including fungi and bacteria. These microorganisms could play important roles in plant development and growth, as well as in the regulation of the endophytic populations. Poplar species present different behavior respect symbiosis, with mixed mycorrhizae or only one of them. The aim of the present study was to evaluate the effect of endophytic bacterial on growth and mycorrhizal colonization of poplars cuttings produced under greenhouse conditions. Endophytic bacteria were isolated from roots of Populus xcanadensis ?Guardi? (PG) in commercial plantation on saline soil, and the mycorrhizal status of these was assessed. Bacterial isolates were identified by 16S rDNA gen fragment sequencing, and auxin production and tolerance to NaCl were evaluated. These isolates were inoculated on a pot trial with PG and P. nigra ?Jean Pourtet? (PJP) cuttings, with soil from potential production sites. After one growing season, cuttings were harvested, growth parameters and mycorrhizal colonization were evaluated. Adults trees from the plantation were colonized by arbuscular mycorrhizae (AM, 85%) and ectomycorrhizae (80%). Two bacterial isolates were identified as Pseudomonas sp., belonging to the ?fluorescens groups?, and Bacillus sp.;both isolates were tolerant to NaCl (5 and 10%, respectively). Only Pseudomonas sp. strain showed high auxin production (2,8mM) which increased growth of PG cuttings, but with no significance difference. Bacillus sp. reduce shoot/root rate in PJP cutting at significant level. No ectomycorrhizal were observed on either species, but both have AM. Bacillus sp. inoculation of PJP cuttings result on significant higher arbuscular colonization (75%) than control plants (69%, p=0,04). Our results revealed that adult tree growing in the commercial plantation were highly colonized by arbuscular mycorrhizae and ectomycorrizae, despite the saline condition of soils. Bacterial inoculation had different effects. Pseudomonas seems to improve height and biomass production on PG cuttings. Bacillus was able to enhance mycorrhizal colonization by natural inoculum (residing in soil used for pot trial) in PJP but not in PG. Bacillus isolate will be a good candidate for production assays in stressed condition due to be used as mycorrhizal-helper and to its tolerance to NaCl. Here we highlight the potential use of poplar?s endophytic bacterial to enhance Populus production under saline conditions