Microbe-Plant Growing Media Interactions Modulate the Effectiveness of Bacterial Amendments on Lettuce Performance Inside a Plant Factory with Artificial Lighting

Abstract

There is a need for plant growing media that can support a beneficial microbial root environment to ensure that optimal plant growth properties can be achieved. We investigated the effect of five rhizosphere bacterial community inocula (BCI S1–5) that were collected at three open field organic farms and two soilless farms on the performance of lettuce (Lactuca sativa L.). The lettuce plants were grown in ten different plant growing media (M1–10) composed of 60% v/v peat (black peat or white peat), 20% v/v other organics (coir pith or wood fiber), 10% v/v composted materials (composted bark or green waste compost) and 10% v/v inorganic materials (perlite or sand), and one commercial plant growing medium inside a plant factory with artificial lighting. Fractional factorial design of experiments analysis revealed that the bacterial community inoculum, plant growing medium composition, and their interaction determine plant performance. The impact of bacterial amendments on the plant phenotype relied on the bacterial source. For example, S3 treatment significantly increased lettuce shoot fresh weight (+57%), lettuce head area (+29%), root fresh weight (+53%), and NO3-content (+53%), while S1 treatment significantly increased lettuce shoot dry weight (+15%), total phenolic content (+65%), and decreased NO3-content (−67%). However, the effectiveness of S3 and S1 treatment depended on plant growing medium composition. Principal component analysis revealed that shoot fresh weight, lettuce head area, root fresh weight, and shoot dry weight were the dominant parameters contributing to the variation in the interactions. The dominant treatments were S3-M8, S1-M7, S2-M4, the commercial plant growing medium, S1-M2, and S3-M10. Proper selection of plant growing medium composition is critical for the efficacy of bacterial amendments and achieving optimal plant performance inside a plant factory with artificial lighting.

Root-Associated Bacterial Community Shifts in Hydroponic Lettuce Cultured with Urine-Derived Fertilizer

“…Root-associated bacterial samples were collected after harvest following the procedure described by Barillot et al [ 46 ] and Van Gerrewey et al [ 40 ] with slight modifications. In brief, for each treatment, three plant root systems (1 plant root system per treatment replicate) were pooled together, and 3 g of roots were sampled.…”

“…The soil and soilless culture experiments also identified the plant host as an important driver shaping the root-associated microbial community [ 35 , 36 , 37 ]. In addition, the type of growing medium used in soilless culture can affect the microbial community structure [ 39 , 40 ].…”

Agro-industrial-residues as potting media: physicochemical and biological characters and their influence on plant growth

“…A significant interaction exists between microbial community and PM with respect to plant growth. Same bacterial community performed differently in different PM with respect to plant growth [ 83 ]. Total phenolic content (TPC) of lettuce was not significantly different in plants grown either in bark compost or green waste compost.…”

“…Total phenolic content (TPC) of lettuce was not significantly different in plants grown either in bark compost or green waste compost. However, inoculating both the PM with the same microbial community raised the TPC of lettuce grown in composted bark PM while the TPC levels observed in the green waste compost growing media were unchanged [ 83 ]. In a similar study, Vandecasteele et al [ 84 ] reported that biocontrol fungi showed better colonisation in defibrated miscanthus, reed straw, and flax shives in comparison to peat.…”

Effect of Applying Struvite and Organic N as Recovered Fertilizers on the Rhizosphere Dynamics and Cultivation of Lupine (Lupinus angustifolius)

“…The combination of organic fertilizers in growing media is not always easy, as the delivery of nutrients depends on microbial breakdown and interaction. Similarly, in order to assure optimal plant performance, the effect of incorporating recovered fertilizers such as struvite in the growing media needs to be analyzed taking into account its influence in the bacterial community (Van Gerrewey et al, 2020).…”