Various technologies, such as light-emitting diodes (LEDs) and beneficial plant micro-organisms, have been applied to enhance plant growth and development. We aimed to develop appropriate technology by incorporating the benefits of LED light, plant growth promoting rhizobacteria (PGPR), and arbuscular mycorrhiza fungi (AMF) into sweet girl cherry tomato (Solanum lycopersicum L.) seedling production. Our results demonstrated that incorporating red (R) and blue (B) LED lights, PGPR, and AMF positively affected tomato seedling growth. The optimal lighting conditions for tomato seedling growth were LEDs at 200 $\mathsf{\mu }$mol/m²/s with a ratio of R60:B40 and 20 h/d exposure. The optimum LED-illuminated tomato seedlings significantly upregulated photosynthesis-related genes, including psbA, psbB, fdx, atpB, and rbcL. Plants inoculated with PGPR Bradyrhizobium sp. SUTN9-2, Bacillus velezensis SD10 and B. megaterium A20 had a high health index after inoculation. Furthermore, the optimized LED-illuminated tomato seedlings inoculated with SD10 had the highest health index. In addition, the optimum LED-illuminated tomato seedlings inoculated with SD10 and AMF had the highest biomass. Our experiment demonstrated that tomato seedlings produced under optimized LED lights inoculated with SD10 and AMF increased yield by about 16% under field conditions. Therefore, these results provided the optimum conditions for a high-quality tomato seedling production system.

Mung bean (Vigna radiata L.), a vital legume in Asia with significant nutritional benefits, is highly susceptible to Cercospora leaf spot (CLS) caused by Cercospora canescens, leading to significant yield losses. As an alternative to chemical fungicides, bio-priming with rhizobacteria can enhance plant resistance. This study explores the potential of Bradyrhizobium sp. strain DOA9 to augment resistance in mung bean against CLS via root priming. The results reveal that short (3 days) and double (17 and 3 days) priming with DOA9 before fungal infection considerably reduces lesion size on infected leaves by activating defense-related genes, including Pti1, Pti6, EDS1, NDR1, PR-1, PR-2, Prx, and CHS, or by suppressing the inhibition of PR-5 and enhancing peroxidase (POD) activity in leaves. Interestingly, the Type 3 secretion system (T3SS) of DOA9 may play a role in establishing resistance in V. radiata CN72. These findings suggest that DOA9 primes V. radiata CN72′s defense mechanisms, offering an effective bio-priming strategy to alleviate CLS. Hence, our insights propose the potential use of DOA9 as a bio-priming agent to manage CLS in V. radiata CN72, providing a sustainable alternative to chemical fungicide applications.

The symbiotic interaction between leguminous and Bradyrhizobium sp. SUTN9-2 mainly relies on the nodulation process through Nod factors (NFs), while the type IV secretion system (T4SS) acts as an alternative pathway in this symbiosis. Two copies of T4SS (T4SS₁ and T4SS₂) are located on the chromosome of SUTN9-2. ΔT4SS₁ reduces both nodule number and nitrogenase activity in all SUTN9-2 nodulating legumes. The functions of three selected genes (copG₁, traG₁, and virD2₁) within the region of T4SS₁ were examined. We generated deleted mutants and tested them in Vigna radiata cv. SUT4. ΔtraG₁ and ΔvirD2₁ exhibited lower invasion efficiency at the early stages of root infection but could be recently restored. In contrast, ΔcopG₁ completely hindered nodule organogenesis and nitrogenase activity in all tested legumes. ΔcopG₁ showed low expression of the nodulation gene and ttsI but exhibited high expression levels of the T4SS genes, traG₁ and trbE₁. The secreted proteins from ΔT4SS₁ were down-regulated compared to the wild-type. Although ΔcopG₁ secreted several proteins after flavonoid induction, T3SS (nopP and nopX) and the C₄-dicarboxylate transporter (dct) were not detected. These results confirm the crucial role of the copG₁ gene as a novel key regulator in the symbiotic relationship between SUTN9-2 and legumes.

The symbiotic interaction between leguminous and Bradyrhizobium sp. SUTN9-2 mainly relies on the nodulation process through Nod factors (NFs), while the type IV secretion system (T4SS) acts as an alternative pathway in this symbiosis. Two copies of T4SS (T4SS1 and T4SS2) are located on the chromosome of SUTN9-2. ΔT4SS1 reduces both nodule number and nitrogenase activity in all SUTN9-2 nodulating legumes. The functions of three selected genes (copG1, traG1, and virD21) within the region of the T4SS1 were examined. We generated deleted mutants and tested in Vigna radiata cv. SUT4. ΔtraG1 and ΔvirD21 exhibited lower invasion efficiency at the early stages of root infection but could be lately restored. In contrast, ΔcopG1 completely hindered nodule organogenesis and nitrogenase activity in all tested legumes. ΔcopG1 showed low expression of nodulation gene and ttsI, but exhibited high expression levels of T4SS genes, traG1 and trbE1. The secreted proteins from ΔT4SS1 were down-regulated compared to the wild type. Although ΔcopG1 secreted several proteins after flavonoid induction, T3SS (nopP and nopX) and C4-dicarboxylate transporter (dct) were not detected. These results confirm the crucial role of the copG1 gene as a novel key regulator in the symbiotic relationship between SUTN9-2 and legumes.