Plant growth promoting bacteria and drought stress in Eucalyptus grandis seedlings

CHAIN JM; TUBERT E; CASTAGNO LN; PIECKENSTAIN FL; ESTRELLA MJ; GRACIANO C; GUDESBLAT GE; AMODEO G; BAROLI I

Bariloche

Conferencia; Adapting forest ecosystems and wood products to biotic and abiotic stress; 2019

Eucalyptus grandis is a commercially important timber tree in Argentina. Outplanting of greenhouse-grown seedlings to the field is a critical step, since the availability of water and nutrients in the rhizosphere determines seedling survival and hence the plantation performance. Plant-growth promoting bacteria (PGPB) are used in many crops to improve nutrition and abiotic stress tolerance, however their use in trees is limited, in part due to difficulties in the application and viability of the inoculum. In this work we evaluated the potential improvement of tolerance to soil water deficit stress of E. grandis seedlings by inoculating with two strains of Pseudomonas genus, one of them selected for its phosphate solubilization capacity and the other by its growth promoting ability. The PGPBs were applied utilizing a commercial superabsorbent acrylic-cellulosic polymer gel at transplantation. Using green fluorescent protein (GFP) tagged strains we were able to verify the survival of the bacteria in the seedling rhizosphere, two weeks after inoculation. We monitored growth, gas exchange and water management in seedlings exposed to two different severities of drought stress, attained by growing the plants in an environmentally controlled chamber or in a greenhouse. In chamber assays, both strains significantly enhanced formation of new leaves after the sudden defoliation caused by the intense drought stress. In the greenhouse, under long-term milder water deficit conditions, inoculated plants adjusted physiological traits to improve drought tolerance. We are currently assessing the fate and localization of the GFP-tagged bacteria at time intervals after inoculation to elucidate the mechanisms behind plant-PGPB interaction.