BackgroundTomato yield is significantly reduced by root-knot nematodes (RKN; Meloidogyne spp.), particularly in tropical and subtropical regions. This study evaluated 20 bacterial isolates (B1-B20), belonging to the genera Bacillus, Lysobacter, Paenibacillus, and Streptomyces, from Sekem farms in Egypt for their potential to biocontrol RKN and stimulate plant growth in tomato 'Moneymaker.' The bacteria were compared to well-known microbial biocontrol agents (MBA), including Rhizobium etli G12 (B21), Pseudomonas trivialis 3Re2-7 (B22), Sporosarcina psychrophile Sd4-11 (B23), and B. subtilis Sb1-20 (B24), and a negative control, Escherichia coli JM109 (B25). The study involved seed-coated and -uncoated plants with bacterial isolates, planted in plastic pots, and inoculated with 1500 M. incognita J2 individuals per pot. Plants were grown in a saran-house during the 2022 and 2023 fall seasons, and their RKN-satisfying response (number of galls: NG and egg masses: NEM), vegetative growth, and metabolic activity were assessed 45 days after inoculation.ResultsIn seasons of 2022 and 2023, seed coating with bacterial isolates achieved a significant improvement in plant growth (coefficient of variation: CV ranging 26.8-120.2% in 2022 and 10.9-48.8% in 2023) and a reduction in RKN-satisfying response (CV for NG: 57.6 and 53.8%, respectively; and for NEM: 56.5 and 65.3%, respectively). Compared to uncoated-seed plants, the bacterial seed coating reduced NG by 0.66-74.09% in 2022 and 14.61-66.29% in 2023. Similarly, NEM decreased by 0.63-70.61% in 2022 and 41.91-77.46% in 2023. The coated-seed plants by Bacillus subtilis subsp. spizizenii (B5), Streptomyces subrutilus Wb2n-11 (B12), Streptomyces scabiei (B19), and Bacillus mojavensis (B20), along with the well-known MBAs B22 and B23, showed increased photosynthetic pigments, fresh weight of roots and shoots, stem size, and number of leaves. This growth has also led to higher dry weights in roots and shoots, and an increase in the root content of carbohydrates and proteins. Seed coating induced systemic RKN resistance by increasing polyphenols in the root. In contrast, uncoated-seed plants showed reduced foliar photosynthesis pigment and metabolic activity due to high RKN damage. Principal component analysis revealed significant correlations among the evaluated traits. Hierarchical clustering categorized bacteria isolates into five clusters based on their impact on estimated plant traits.ConclusionB5, B12, B19, B20, B22, and B23 demonstrated superior performance in both controlling RKN and stimulating vegetative growth in tomato 'Moneymaker' plants as known MBAs.

Soil salinity is a major abiotic stress causing severe damage to plants. Thus, proper management approaches need to be developed to lessen the detrimental effect of salinity on crop growth and productivity. The objective of this study was to investigate the potential role of exogenous salicylic acid (SA) and potassium (K+) in mitigating the adverse effects of salt stress on tomato. Salt-stressed tomato seedlings Solanum lycopersicum L. cv. Agata were exposed to 0.1 mM SA and 5 mM K+, applied individually or simultaneously for two weeks. Obtained results showed that salt stress resulted in reduced growth rate associated with accumulation of Na+ ions, reduced K+ levels, lower K+/Na+ ratio, increased oxidative damage, reduced total chlorophyll and carbohydrate contents as well as disturbed proline accumulation and disrupted antioxidant system. Nevertheless, after SA and K+ supplementation, total chlorophyll, K+, total proteins, total carbohydrates, and proline contents as well as K+/Na+ ratio were significantly increased. Additionally, exogenous SA and K+ treatments enhanced the non-enzymatic and enzymatic antioxidant system and ensured better oxidative stress tolerance, as indicated by reduced H2O2 production and membrane lipid peroxidation, resulting in an increased membrane stability index. These effects were further enhanced by the simultaneous application of SA and K+, resulting in a better growth of salt-stressed tomato seedlings compared to single applications of these two growth regulators. Taken together, the results of the current study provide evidence that SA and K+ may interact to counteract the adverse effects of salt stress on the growth of tomato seedlings by improving osmotic and ionic homeostasis and upregulating the antioxidant defense system. Therefore, the simultaneous application of SA and K+ may be suggested as a promising approach for beneficial tomato growth at the seedling stage under salt-affected soil conditions.

Soil contamination linked to anthropogenic activities has become a serious environmental problem on a global scale. It is caused by heavy metals, such as lead (Pb). Dopamine (DOP) is a biogenic amine that acts as a neurotransmitter. It is found in plant organs and induces tolerance against abiotic stresses, including contamination. 24-epibrassinolide (EBR) stimulates metabolism, positively impacting flowering and production. This research aimed to evaluate whether EBR and DOP, applied alone or combined, can mitigate the impacts caused by Pb on roots and leaves by measuring root and leaf structures and stomatal behavior. For roots, both plant growth regulators maximized the epidermis, with increases in treatments Pb2+ - DOP + EBR (45%), Pb2+ + DOP - EBR (24%), and Pb2+ + DOP + EBR (36%), when compared with equal treatment without Pb2+. To leaves, the tested molecules improved the leaf structures, significantly increasing palisade parenchyma and spongy parenchyma. Parallelly, stomatal performance was boosted after treatments with EBR and DOP, confirmed by increments in stomatal density. Our study proved that EBR and DOP, alone or combined, mitigated the damages to leaves and roots exposed to Pb stress, but better results were found when EBR was applied alone.

The root-knot nematode Meloidogyne javanica is a significant pathogen that causes substantial yield losses in tomato plants. Moroccan farmers generally lack knowledge regarding the density of this pathogen, which can trigger visible and localised symptoms. Additionally, regional studies that establish damage thresholds for this issue are scarce. This study investigated the damage threshold of M. javanica on tomato plants using nine initial population densities (Pi) of second-stage juveniles (J2s): 0, 0.5, 1, 2, 4, 8, 16, 32 and 64 J2s (g dry soil)-1. Aboveground growth (plant height and fresh and dry shoot weight) and belowground growth (root length and diameter) were assessed after 90 days. The plant growth parameters were significantly reduced at higher inoculum densities. The Seinhorst model fitting revealed the highest minimum relative yield (m) for shoot fresh weight (m = 0.761 +/- 0.012) and the lowest for root diameter (m = 0.509 +/- 0.026). The tolerance limit (T) varied, with the highest shoot dry weight (T = 1.657 +/- 0.329 J2s (g soil)-1) and lowest root diameter (T = 0.095 +/- 0.019 J2s (g soil)-1). The production of eggs by M. javanica increased significantly with increasing initial population density, rising from 211 +/- 64 eggs (g roots)-1 at 0.5 J2s (g soil)-1 to 3735 +/- 380 eggs (g roots)-1 at 64 J2s (g soil)-1, representing a 17.7-fold increase. Tomato plants exhibited the maximum galling index at lower nematode densities. Symptoms began at densities as low as 0.095 J2 (g soil)-1, with severity increasing with nematode density. Given the severe damage caused at low densities, Moroccan farmers must adopt early detection and effective management strategies.

Meloidogyne spp. are the most devastating plant-parasitic nematodes affecting tomato worldwide. Although resistant cultivars and rootstocks are used, selection for virulence occurs in the pathogen. Consequently, using other resistance sources, such as Solanum torvum, could improve resistance durability. Several experiments in microplots and plastic greenhouses were carried out to determine the potential use of S. torvum as a tomato rootstock to protect against M. incognita and M. javanica. In microplots, the relationship between nematode density at transplanting (Pi) and multiplication rate did not differ between Meloidogyne species in either ungrafted or grafted tomato. However, maximum multiplication rate and maximum density on grafted tomato were 1.27% and 2.93% those on ungrafted, respectively. The grafted tomato plants yielded between 2.9 and 7.5 more times than the ungrafted plants at Pi >= 100 eggs + J2s per 100 cm(3) of soil, but no differences were observed in plastic greenhouse where a large amount of scion-rooting occurred. In microplots, the quality of the tomato fruits of ungrafted and grafted plants was affected by the Pi. In parallel, some pot experiments were conducted on S. torvum and susceptible eggplant to determine the putative selection for nematode virulence to S. torvum and the nematode fitness cost. These showed that the nematode subpopulations infected and reproduced less on S. torvum than on eggplant. However, the female fertility was only reduced after development of three or four subpopulations on S. torvum. Finally, a histopathological study showed that nematode infection and development in S. torvum was delayed compared to eggplant.

Conventional tomato production is widely threatened by environmental changes that impose increasingly frequent and severe conditions of soil salinization and water shortage. The assessment of the wild germplasm has become an appealing strategy for the stress-resilience improvement of crops. Tomato interspecific diversity encompasses wild species that are native to the dry shores and high-elevated deserts of the Andean countries, often thriving under circumstances of drought and salinity. The present work aimed to compare the effects of moderate salinity stress under different watering regimes on the ion distribution, redox homeostasis, osmoregulation, and antioxidant defenses between a domestic cultivar of tomato (Chico III) and the wild tomato species Solanum galapagense (LA1403), Solanum habrochaites (LA1223), and Solanum neorickii (LA2194). Results showed that although wild tomato plants grew slower than the cultivar, their growth was less affected by exposure to salt or to lower water availability. S. galapagense revealed a Na+ includer behavior under salt stress, increasing Na+ levels by 6-fold over control, reaching levels 4 times higher than in the cultivar. Nonetheless, H2O2-detoxifying enzymes were activated, and shoot elongation was sustained in this species, suggesting an efficient Na+ compartmentalization. On the other hand, the domestic cultivar had the highest accumulation of Na+ in roots and showed the lowest ability to sustain growth under combined stress. Leaves of S. habrochaites showed a huge proline buildup under salt stress, whereas S. neorickii and S. galapagense seemed to prevent proline accumulation. S. habrochaites also had high levels of antioxidant metabolites and superoxide dismutase activity under control conditions but downregulated further antioxidant defenses in response to stress exposure. No oxidative damages were noticed despite the almost 2-fold increase in ROS content in the leaves of S. neorickii under salt stress, which showed a negative correlation with growth traits, but an improvement in the antioxidant potential. A principal component analysis (PCA) revealed five PCs with eigenvalues >1, explaining 84 % of the total variability, and suggesting a separation of the evaluated samples mainly in accordance with the type of redox disturbances and antioxidant defenses employed, levels of photosynthetic pigments, balance between Na+ and K+ uptake and proline accumulation. These findings show that wild tomato plants respond differently than cultivated ones under moderate salinity and reduced water availability, suggesting interesting osmoregulatory and antioxidant mechanisms in S. galapagense and S. habrochaites.

Silicon (Si) and selenium (Se) can improve the tolerance of plants to NaCl-induced salt stress. However, few studies are available on their regulatory effects on plants' tolerance to calcium nitrate stress, which often occurs in protected facilities, causing secondary soil salinization. In this study, we report the effects of Si (6 mM) and Se (20 mu M) applied separately or in combination on the growth, photosynthesis, oxidative damage, and nitrogen metabolism of tomato plants, as well as fruit quality under calcium nitrate stress. The results showed that applications of Si or Se alone or in combination improved the plant growth and photosynthetic performance and reduced oxidative damage of the stressed plants. Applications of Si and Se did not decrease the calcium accumulation in leaves of the stressed plants. Under calcium nitrate stress, the concentrations of NO3-, NO2- and NH4+ in leaves were significantly increased, while the activities of nitrogen assimilation-related enzymes (including nitrate reductase, nitrite reductase, glutamine synthase, glutamine-2-oxoglutarate aminotransferase and glutamate dehydrogenase) were decreased. Applications of Si and Se, especially their combined treatment, decreased the NO3-, NO2-, and NH4+ concentrations and enhanced the activities of nitrogen assimilation -related enzymes in the stressed plants. Applied Si and Se also decreased the nitrate and titratable acid concentrations and increased vitamin levels in tomato fruits under calcium nitrate stress. It is suggested that Si and Se improved the tomato plant growth and fruit quality under calcium nitrate stress by alleviating oxidative damage and promoting both photosynthesis and nitrogen assimilation.

BackgroundSalinity is one of the most damaging abiotic stress factors in agriculture, it has a negative impact on crop growth, production, and development. It is predicted that salinity will become much more severe due to global climate change. Moreover, soil salinization affects three hectares of agricultural land every minute, increasing the salinity-affected area by 10% annually. The improvement of abiotic stress tolerance in plants was made possible by recent developments involving transgenes and the isolation of some abiotic stress tolerance genes.ObjectiveThe current study aimed to synthesize, clone and characterize two abiotic stress tolerance genes Lipid transfer protein (AtLTP1) of Arabidopsis thaliana and Stress-inducible transcription factor C-repeating binding factor (LeCBF1) of Solanum lycopersicum in Saccharomyces cerevisiae.Materials and methodsThe above-mentioned genes were synthesized, cloned into the pYES2 vector then transformed into Saccharomyces cerevisiae as a model eukaryotic system. The yeast growth was measured at (OD600 nm) in a spectrophotometer, RT-PCR expression analysis and estimation of intracellular proline content after exposure to different salt concentration were performed to characterize and evaluate the physiological roles of the selected genes in the yeast.Results and conclusionThe AtLTP1 and LeCBF1 genes were cloned into the pYES2 vector for Saccharomyces cerevisiae expression. After being exposed to increasing concentrations of sodium chloride (0, 1.7, 1.8, 1.9, 2.0, 2., 2.2, and 2.3 M) for 7 days, transgenic yeast cells were tested for their ability to survive under increasing salt-stress conditions and their growth response. A spectrophotometer was used to measure yeast growth at OD600nm. The growth of the control cells was dramatically hindered when the salt content was increased to 1.9 M NaCl. However, two transgenic yeast lines continued to grow well, at a slower rate, up to 2.3 M NaCl. The two genes' expression in transgenic yeast in response to salt stress was verified by RT-PCR. In this transgenic yeast, the precise primers of LeCBF1 and AtLTP1 amplified the genes successfully at 633 base pairs and 368 base pairs, respectively. The findings showed that increasing salinization level considerably boosted the transgenic yeast's intracellular proline accumulation. It was suggested that the possibility of utilizing these genes to produce salt tolerant transgenic plants, consequently, increase the amount of land that can be exploited for agriculture.

Using microorganisms as biocontrol agents of phytopathogens has been an alternative to synthetic fungicides. Actinomycetes isolated from soil and plants have reduced diseases caused by phytopathogens; however, microorganisms from marine environments may be an option as biocontrol agents. The tomato crop possesses an important economic impact worldwide, being Mexico the main exporter. Several species of Fusarium cause damage to tomato crops and are controlled with synthetic fungicides. The objective of this work was to determine the effect of marine actinomycetes as biocontrol on Fusarium solani in tomato plants. Four strains of marine actinomycetes (A20, A19, A18, and A15) and one terrestrial actinomycete (ED48) were used. The actinomycetes strains used, produced siderophores. The greatest inhibition of mycelial growth of F. solani due to iron competition was obtained by strain A19 with 74.28%. Only two actinomycetes showed antifungal activity by VOCs (A19 and A18), strain A19 showed the highest antagonistic activity with PICR of 76.75%. Actinomycetes treatments showed significant differences with synthetic fungicide application in growth, disease severity (SE), and disease incidence (DI) variables. The application of marine actinomycete (A19) on plants infested with F. solani increased the levels of enzyme activity (SOD, POD, CAT, and PAL) versus plants in that only F. solani and distilled water (control) were applied. Actinomycetes of marine origin are an option as biocontrol agents for F. solani .