Luqman Qurata Aini, Anton Meilus Putra, Nabilla Alya Anastasya, Sholikah Widyanitta Rachmawati, Bayu Aji Pamungkas, Eriyanto Yusnawan
AbstractFarmers in Indonesia typically cultivate hydroponic crops in less advanced basic greenhouses without any microclimatic regulation; hence, crops growth is often impaired with varying environmental stress along with biotic stressors, such as pests and diseases. Hence, plant growth-promoting bacteria (PGPB) inoculants that can perform under fluctuating greenhouse conditions, such as thermotolerant rhizobacteria, are desirable to promote crop growth. This study aims to evaluate the performance of thermotolerant P. koreensis UB-62 inoculation on lettuce growth, pest and/or disease damage, and metabolomic profiles under basic greenhouse hydroponic conditions. The metabolic responses of lettuce crops to the inoculation were also analyzed using the metabolomic approach. The experiment was conducted in the farmer's basic greenhouse “Lily Harvest” at Batu City, Indonesia, using the Nutrient Film Technique (NFT) hydroponic system. The experiment consisted of three treatments, i.e., an untreated control, PGPR inoculation, and P. koreensis UB-62 inoculation, which were established in a completely randomized design and replicated six times. Inoculation of P. koreensis UB-62 enhanced vegetative growth of lettuce in NFT hydroponic systems with higher plant length, leaf area, and biomass at 21–35 DAP. Moreover, it also enhanced leaf chlorophyll content but not carotenoid content. Inoculation with P. koreensis UB-62 also reduced thrips damage to lettuce crops. However, it did not affect total phenolic compound, phenylalanine ammonia-lyase (PAL), polyphenol oxydase (PPO), and peroxidase (PO). Inoculation with P. koreensis UB-62 enhanced concentrations of sugar metabolites, including d-galactitol, d-mannitol, d-xylitol, and α-d-galactopyranoside, in lettuce crops compared to uninoculated control. Furthermore, the concentration of fatty acid metabolites, such as 9, 12, 15-octadecatrienoic acid and stearic acid, was enhanced in lettuce crops inoculated with P. koreensis UB-62. The pathway analysis results provide strong evidence that the glutathione and sulfur metabolism pathways play a crucial role in enhancing homeostasis in lettuce crops inoculated with P. koreensis UB-62. © 2026 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Department of Plant Pests and Diseases, Faculty of Agriculture, Universitas Brawijaya, Jl. Veteran, Malang, 65145, Indonesia; Department of Plant Protection, Faculty of Agriculture, Universitas Sriwijaya, Jl. Raya Palembang-Prabumulih Km. 32, Ogan Ilir, South Sumatra, 30662, Indonesia; Research Center for Food Crops, Research Organization for Agriculture and Food, National Research and Innovation Agency (BRIN), West Java, 16911, Indonesia
