Soil salinity is a major abiotic stress affecting plant growth and yield, due to both osmotic and ionic stresses. JUBGBRUNNEN1 (JUB1) is a NAC family transcription factor that has been shown to be involved in responses to abiotic stresses, such as water deficit, osmotic, salinity, heat and oxidative stress. In Arabidopsis thaliana (Arabidopsis), JUB1 has been shown to improve plant stress tolerance by regulating H2O2 levels. In the horticultural crop, Solanum lycopersicum cv. Moneymaker (tomato), overexpression of AtJUB1 has been shown to partially alleviate water deficit stress at the vegetative stage. In this study, we investigated the effect of Arabidopsis JUB1 overexpression in salinity tolerance in tomato. In hydroponically grown tomato seedlings, AtJUB1 overexpression results in higher prolines levels and improves the maintenance of water content in the plant under salinity stress. The transgenic tomato plants are more tolerant to salinity stress compared to control lines based on plant biomass. However, at the reproductive stage, we found that overexpression of AtJUB1 only provided marginal improvements in yield-related parameters, in the conditions used for the current work. The combination of improved water deficit and salinity stress tolerance conferred by AtJUB1 overexpression may be beneficial when tomato plants are grown in the field under marginal environments.

Pre-exposing (priming) plants to mild, non-lethal elevated temperature improves their tolerance to a later higher-temperature stress (triggering stimulus), which is of great ecological importance. ‘Thermomemory’ is maintaining this tolerance for an extended period of time. NAM/ATAF1/2/CUC2 (NAC) proteins are plant-specific transcription factors (TFs) that modulate responses to abiotic stresses, including heat stress (HS). Here, we investigated the potential role of NACs for thermomemory. We determined the expression of 104 Arabidopsis NAC genes after priming and triggering heat stimuli, and foundATAF1expression is strongly induced right after priming and declines below control levels thereafter during thermorecovery. Knockout mutants ofATAF1show better thermomemory than wild type, revealing a negative regulatory role. Differential expression analyses of RNA-seq data fromATAF1overexpressor,ataf1mutant and wild-type plants after heat priming revealed five genes that might be priming-associated direct targets of ATAF1:AT2G31260(ATG9),AT2G41640(GT61),AT3G44990(XTH31),AT4G27720andAT3G23540. Based on co-expression analyses applied to the aforementioned RNA-seq profiles, we identifiedANAC055to be transcriptionally co-regulated withATAF1. Likeataf1,anac055mutants show improved thermomemory, revealing a potential co-control of both NAC TFs over thermomemory. Our data reveals a core importance of two NAC transcription factors, ATAF1 and ANAC055, for thermomemory.

Shrimp waste is rich in organic compounds and essential plant nutrients, e.g., calcium (Ca), and converting these wastes to organic fertilizer is important for environmental preservation and to achieve sustainable agricultural management. In the current study, Ca-rich biochar was prepared from shrimp wastes (SWB) by pyrolysis at 300 °C. We hypothesized that the Ca-rich biochar will help in solving the problem of plant growth in saline soil by reducing sodium (Na) uptake and mitigating oxidative stress. The current study aimed to investigate the effect of SWB on the quality of saline sandy soil and the mechanism of salt resistance in pearl millet (Pennisetum glaucum L.). Pearl millet plants were planted in saline sandy soil (10 dS m⁻¹) in wooden boxes (1.3 × 0.8 m size and 0.4 m height), and 5 doses (0, 1.0, 1.5, 2.0, and 2.5% (w/w)) of SWB were added. SWB application increased the soil quality and nutrient uptake by pearl millet plants. The highest rate of SWB increased the soil microbial biomass carbon and the activity of dehydrogenase enzyme by 43 and 47% compared to the control soil. SWB application reduced the uptake of sodium (Na⁺) and chloride (Cl⁻) and increased the K/Na ratio in the leaf tissues. SWB addition significantly increased the activity of antioxidant enzymes, e.g., ascorbate peroxidase (APX), polyphenol oxidase (PPO), and pyrogallol peroxidases (PPX). The application of 2.5% SWB to the saline soil increased the soluble carbohydrates and proline in plant leaves by 75 and 60%, respectively, and reduced the malondialdehyde (MDA) by 32% compared to the control. SWB enhanced the antioxidant defense and mitigated oxidative stress by improving the synthesis of osmoprotectants, e.g., soluble carbohydrates and proline. Sandy saline soils in arid and semiarid areas suffer greatly from low organic matter contents, which reduces the soil quality and increases the risk of salt during plant growth. The high organic matter and calcium content (30%) in the shrimp waste-derived biochar improved the quality of the saline sandy soil, reduced the uptake of toxic salts, and increased the quality of the forage material. The addition of recycled shrimp waste to saline low-fertility soils improves soil productivity and is safe for soil health.

The most important disease of tomato is Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (FOL). To control this disease, this study examined the combined use of bacterial bioagents and peppermint oil (PO). Seven bacterial isolates were collected from tomato plant rhizospheres and tested in vitro against FOL. The highest growth inhibition against FOL was shown by isolate No.3. This isolate was identified using 16S rRNA sequencing gene as Bacillus amyloliquefaciens (BA). Peppermint oil tested at different concentrations (1, 2, and 3%) against FOL mycelial growth in vitro showed the highest inhibition at 3%. The effects of BA, PO, and BA + PO in vitro on the seed germination and seedling vigor index of the tomato cv. ‘Tala F1’ was also tested. All “BA, PO, and BA + PO” treatments increased the percentage of germinated seeds and seedlings’ main shoots and root length compared to control treated seeds. The BA, PO, and BA + PO treatments were further tested under greenhouse and field conditions with pre-treated seedlings in FOL-contaminated soil. Under greenhouse conditions, each treatment decreased disease severity compared to untreated seedlings. Under field conditions, pre-treatment of tomato seedlings with BA and PO treatments reduced disease severity greater than BA + PO in combination and the mock-treated plants (66.6% for BA, 66.6% for PO and 55.3% for BA + PO, respectively). These findings support the use of BA or PO as bio-control agents against F. oxysporum in tomato. The interplay between peppermint oil, B. amyloliquefaciens, F. oxysporum, and the host plant requires further study to identify the causative mechanism for this increased disease resistance.

The scarcity of high-quality water resources may lead to the use of lower quality water for plant production. Quinoa (Chenopodium quinoa) plants have great potential for human nutrition, but poor water quality, such as metal contamination in wastewater, affects the seed quality. This study aims to investigate the effects of shrimp-waste-derived biochar (SWB) on the uptake of toxic metals from wastewater by quinoa plants. Additionally, the study investigates how quinoa plants’ antioxidant defenses respond to wastewater and SWB treatments. Shrimp-waste-derived biochar (SWB) was prepared by pyrolysis at 350 °C for 3 h and added to the soil at the levels of 0, 1, and 2% (based on soil weight), which are namely C, SWB₁, and SWB₂, respectively. SWB was applied to quinoa plants cultivated in pots filled with sandy soil and irrigated with fresh or wastewater for a continuous 90 days. The wastewater was contaminated with manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb). Quinoa seeds that were irrigated with wastewater had Cd and Pb concentrations that were above the allowable levels (for human consumption) in the absence of biochar (C) or addition of SWB₁. Wastewater significantly reduced quinoa growth and photosynthetic pigments, while SWB significantly mitigated the metal toxicity and improved growth. SWB₂ significantly reduced the Pb and Cd concentrations in quinoa leaves by 29 and 30% compared with C. The Cd and Pb concentrations in quinoa seeds were safe for human consumption and below the maximum allowable limits when the soil was amended with SWB₂. SWB improved the synthesis of photosynthetic pigments and increased the activity of antioxidant enzymes such as polyphenol oxidase and ascorbate peroxidase. SWB reduced the toxic metal availability and uptake, mitigated the oxidative stress, and minimized the levels of malondialdehyde and hydrogen peroxide. The SWB addition stimulated quinoa’s antioxidant defense and protected plant cells by eliminating reactive oxygen species. The addition of 2% (w/w) shrimp waste biochar improved the quality of quinoa seeds irrigated with wastewater and decreased their toxic metal content. The obtained results contribute to sustainable development and the exploitation of wastewater to irrigate quinoa plants in arid degraded soil; additionally, it also helps in the recycling of shrimp waste.