A Potential Application of Pseudomonas psychrotolerans IALR632 for Lettuce Growth Promotion in Hydroponics

Abstract

Controlled environment agriculture hydroponic systems grow plants year-round without restriction from outside environmental conditions. In order to further improve crop yield, plant growth-promoting bacteria were tested on hydroponically grown lettuce (Lactuca sativa) plants. From our bacterial endophyte library, we found one bacterium, Pseudomonas psychrotolerans IALR632, that is promising in promoting lettuce growth in multiple hydroponic systems. When Green Oakleaf lettuce seeds were inoculated with IALR632 during germination, IALR632 significantly increased lateral root development by 164%. When germinated seedlings were inoculated with IALR632 and then transplanted to different hydroponic systems, shoot and root fresh weights of Green Oakleaf increased by 55.3% and 17.2% in a nutrient film technique (NFT) system in the greenhouse, 13.5% and 13.8% in an indoor vertical NFT system, and 15.3% and 13.6% in a deep water cultivation (DWC) system, respectively. IALR632 also significantly increased shoot fresh weights of Rex by 33.9%, Red Oakleaf by 21.0%, Red Sweet Crisp by 15.2%, and Nancy by 29.9%, as well as Red Rosie by 8.6% (no significant difference). Inoculation of IALR632-GFP and subsequent analysis by confocal microscopy demonstrated the endophytic nature and translocation from roots to shoots. The results indicate that P. psychrotolerans IALR632 has a potential application in hydroponically grown lettuce plants.

Biocontrol potential of endophytic Pseudomonas strain IALR1619 against two Pythium species in cucumber and hydroponic lettuce

“…Both 'Red Rosie' and 'Cristabel' cultivars of lettuce inoculated with IALR1619 produced better yield in the presence of Pythium species, but 'Pensacola' cultivar failed to produce A previous study conducted at this institute tested the response of six hydroponically grown lettuce cultivars to a growth promoting bacterium Ps. psychrotolerans IALR632 [32]. The Green Oakleaf cultivar gave the best growth in response to IALR632 inoculation over the control while romaine cultivar 'Red Rosie' shoot and root growth were not significant.…”

“…A previous study conducted at this institute tested the response of six hydroponically grown lettuce cultivars to a growth promoting bacterium Ps . psychrotolerans IALR632 [ 32 ]. The Green Oakleaf cultivar gave the best growth in response to IALR632 inoculation over the control while romaine cultivar ‘Red Rosie’ shoot and root growth were not significant.…”

“…Another investigation reisolated Ps . psychrotolerans strain IALR632 from lettuce leaf samples 10 d after root inoculation [ 32 ]. The above experiments show bacterial endophytes first colonize in roots and eventually translocate into other parts of the plants.…”

“…After germination, seedings were irrigated for 1 min every six hours with the Virginia Tech fertilizer solution adjusted to EC 1.0 ±0.1 mS cm -1 and pH 5.9 ±0.1. The vegetative hydroponic fertilizer solution developed at Virginia Tech (Blacksburg, VA, USA) consisted of two 100x stock solutions: Stock A (Lettuce) and Stock B (Lettuce) (see [ 32 ] for solution composition). Equal amounts of Stock A and B were used to create a final dilute solution with EC 1.0 mS cm -1 .…”