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

BOENEL MICAELA; VERONICA BELLA; MARIA CECILIA MESTRE; SONIA FONTENLA

San Carlos de Bariloche

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

Plant?s roots harbors diverse population of microorganisms including fungi and bacteria. Thesemicroorganisms could play important roles in plant development and growth, as well as in theregulation of the endophytic populations. Poplar species present different behavior respectsymbiosis, with mixed mycorrhizae or only one of them. The aim of the present study was toevaluate the effect of endophytic bacterial on growth and mycorrhizal colonization of poplarscuttings produced under greenhouse conditions. Endophytic bacteria were isolated from roots ofPopulus xcanadensis ?Guardi? (PG) in commercial plantation on saline soil, and the mycorrhizalstatus of these was assessed. Bacterial isolates were identified by 16S rDNA gen fragmentsequencing, and auxin production and tolerance to NaCl were evaluated. These isolates wereinoculated on a pot trial with PG and P. nigra ?Jean Pourtet? (PJP) cuttings, with soil from potentialproduction sites. After one growing season, cuttings were harvested, growth parameters andmycorrhizal colonization were evaluated. Adults trees from the plantation were colonized byarbuscular mycorrhizae (AM, 85%) and ectomycorrhizae (80%). Two bacterial isolates wereidentified as Pseudomonas sp., belonging to the ?fluorescens groups?, and Bacillus sp.;bothisolates were tolerant to NaCl (5 and 10%, respectively). Only Pseudomonas sp. strain showedhigh auxin production (2,8mM) which increased growth of PG cuttings, but with no significancedifference. Bacillus sp. reduce shoot/root rate in PJP cutting at significant level. Noectomycorrhizal 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 highlycolonized by arbuscular mycorrhizae and ectomycorrizae, despite the saline condition of soils.Bacterial inoculation had different effects. Pseudomonas seems to improve height and biomassproduction on PG cuttings. Bacillus was able to enhance mycorrhizal colonization by naturalinoculum (residing in soil used for pot trial) in PJP but not in PG. Bacillus isolate will be a goodcandidate for production assays in stressed condition due to be used as mycorrhizal-helper andto its tolerance to NaCl. Here we highlight the potential use of poplar?s endophytic bacterial toenhance Populus production under saline conditions