Phytotoxic Isocassadiene-Type Diterpenoids from Tomato Fusarium Crown and Root Rot Pathogen Fusarium oxysporum f. sp. radicis-lycopersici.

Fusarium crown and root rot (FCRR) has emerged as a highly destructive soil-borne disease, posing a significant threat to the safe cultivation of tomatoes in recent years. The pathogen of tomato FCRR is Fusarium oxysporum f. sp. radicis-lycopersici (Forl). To explore potential phytotoxins from Forl, eight undescribed diterpenoids namely fusariumic acids A-H (1-8) were isolated. Their structures were elucidated by using spectroscopic data analyses, quantum chemical calculations, and X-ray crystallography. Fusariumic acids A (1) and C-H (3-8) were typical isocassadiene-type diterpenoids, while fusariumic acid B (2) contained a cage-like structure with an unusual 7,8-seco-isocassadiene skeleton. A biosynthetic pathway of 2 was proposed. Fusariumic acids A (1) and C-H (3-8) were further assessed for their phytotoxic effects on tomato seedlings at 200 µg/mL. Among them, fusariumic acid F (6) exhibited the strongest inhibition against the hypocotyl and root elongation of tomato seedlings, with inhibitory rates of 61.3 and 45.3%, respectively.

Classification of tomato leaf images for detection of plant disease using conformable polynomials image features.

Plant diseases can spread rapidly, leading to significant crop losses if not detected early. By accurately identifying diseased plants, farmers can target treatment only to the affected areas, reducing the number of pesticides or fungicides needed and minimizing environmental impact. Tomatoes are among the most significant and extensively consumed crops worldwide. The main factor affecting crop yield quantity and quality is leaf disease. Various diseases can affect tomato production, impacting both yield and quality. Automated classification of leaf images allows for the early identification of diseased plants, enabling prompt intervention and control measures. Many creative approaches to diagnosing and categorizing specific illnesses have been widely employed. The manual method is costly and labor-intensive. Without the assistance of an agricultural specialist, disease detection can be facilitated by image processing combined with machine learning algorithms. In this study, the diseases in tomato leaves will be detected using new feature extraction method using conformable polynomials image features for accurate solution and faster detection of plant diseases through a machine learning model. The methodology of this study based on:•Preprocessing, feature extraction, dimension reduction and classification modules.•Conformable polynomials method is used to extract the texture features which is passed classifier.•The proposed texture feature is constructed by two parts the enhanced based term, and the texture detail part for textual analysis.•The tomato leaf samples from the plant village image dataset were used to gather the data for this model. The disease detected are 98.80 % accurate for tomato leaf images using SVM classifier. In addition to lowering financial loss, the suggested feature extraction method can help manage plant diseases effectively, improving crop yield and food security.

Consortia of Streptomyces spp. triggers defense/PAMP genes during the interaction of Groundnut bud necrosis orthotospovirus in tomato.

In the present study, Streptomyces spp. were isolated, characterized, and the efficacy was tested against Groundnut bud necrosis orthotospovirus (GBNV) in tomato. Among the three inoculation methods viz., pre-, post-, and simultaneous inoculation, tested for antiviral efficacy, pre-inoculation spray of the three Streptomyces spp. viz., Streptomyces mutabilis, Streptomyces rochei, and Streptomyces chrestomyceticus (SAT1, SAT4, and STR2) recorded the least disease severity index (DSI) of GBNV in tomato. In the pot culture, seed treatment of liquid consortium of three Streptomyces spp. @ 2 ml/g of seeds along with seedling dip at 10 ml/lit followed by soil drenching at 10 ml/lit on 7 days after transplanting (DAT) and foliar application at 0.5% on 15 DAT, 30 DAT, and 45 DAT recorded the least GBNV infection of 15% DSI and 16.67% DSI in trial I and II respectively. Besides, under field conditions, the disease incidence was reduced to 14.44% recording a higher yield of 76.67 t/ha in the treated plants against 63.99 t/ha in control. Upregulation of defense genes viz., PR1, PR2, PR6, WRKY, MAPKK, and NPR1 during tripartite interaction between tomato, Streptomyces, and GBNV was analyzed by qRTPCR, indicating that the consortia could decrease the virus severity through induced systemic resistance pathways. Thus, it is concluded that Streptomyces spp. can be used for the management of GBNV in tomato. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-024-04030-6.

First report of potato virus H infecting tomato (Solanum lycopersicum) in China.

Potato virus H (PVH), belonging to the genus Carlavirus in the family Betaflexiviridae, was initially discovered in potato plants in Inner Mongolia, China (Li et al., 2013). Subsequently, it was documented to infect pepino, a perennial shrub of the Solanaceae family like potatoes (Abouelnasr et al., 2014). Tomato (Solanum lycopersicum L.), a major global crop, faces threats from various plant viruses. In an open field survey in Yunnan, China during July 2023, tomatoes (cultivar: Liangsi) showed typical virus symptoms: leaf yellowing, curling, mottling, and fruit with abnormal shape and color. Eleven symptomatic tomato samples were collected for high-throughput sequencing to identify the potential pathogen. RNA sequencing libraries were prepared using the TruSeq RNA sample prep kit (Illumina, San Diego, CA, USA), followed by RNA-seq sequencing on an Illumina HiSeq4000 platform (LC Sciences, USA). Approximately 77,928,560 paired-end reads (150-bp each) were generated. After quality control, 75,808,296 reads were retained and subjected to de novo assembly using Trinity (version 2.8.5). The assembled contigs, ranging from 198 nt to 15865 nt, were used as queries to search against the NCBI non-redundant protein sequence database (NR) or nucleotide sequence database (NT) to detect the potential pathogens using BLASTx and BLASTn program with a cutoff e-value of 10-5. As a consequence, certain contigs were assigned to 3 plant viruses, including PVH (the highest RdRp blastx identity to UAD82396.1: 97.8%), Capsicum chlorosis virus (CaCV, the highest RdRp blastx identity to APQ31267.1: 98.4%), and southern tomato virus (STV, the highest CP-RdRp fusion protein blastx identity to QOW17541.1: 99.74%). The presence of the identified 3 viruses was subsequently screened in the 11 tomato samples originally collected from the corresponding field. Notably, the specific detection primers for the PVH genome was designed from the newly assembled PVH genome (Forward primer: 5'- ATAGTTGTGCACTGTGTGCCTG-3'; Reverse primer: 5'-GCTTAAGGTTCTTAGCGTATTC-3'), targeting ~1.1kb. Consequently, PVH was detected in 3 out of 11 samples: 2 leaf samples and 1 fruit sample, with one leaf sample showing a single infection. The complete genome sequence of PVH in tomatoes (PVH-tomato) was successfully obtained by assembling nine overlapping regions spanning the entire PVH-tomato genome, following the RT-PCR and the 5' RACE and 3' RACE approaches, and deposited in NCBI nucleotide database with accession number OR397130.1Phylogenetic analysis based on the full genome sequences of PVH-tomato and other publicly available PVH isolates revealed that PVH-tomato was closely related to a PVH isolate found in potatoes in Yunnan (blastn similarity: 97.76%) (Fig. S1A). To test PVH-tomato infectivity and pathogenicity, four healthy Nicotiana benthamiana and four healthy tomato plants were mechanically inoculated with PVH-infected leaf sap; controls used sap from healthy plants. Three weeks post-inoculation, all N. benthamiana (4/4) and three tomato plants (3/4) were PVH-positive by RT-PCR. Symptoms were milder in N. benthamiana, and only two tomato plants (2/4) showed leaf curling. No PVH was detected in control samples (Figure S1B, S1C). Sanger sequencing confirmed the amplicons' expected length of 1093 bp. Previously, PVH was documented only in potato and pepino. This is the first report of tomatoes as natural PVH hosts and PVH infecting N. benthamiana under lab conditions.

Evaluation of the Impact of the Ripening Stage on the Composition and Antioxidant Properties of Fruits from Organically Grown Tomato (Solanum lycopersicum L.) Spanish Varieties.

Tomato (Solanum lycopersicum L.) is a widely cultivated horticultural crop. It belongs to the Solanaceae family and is known for its high concentration of essential nutrients, including vitamins, minerals, and bioactive compounds with antioxidant properties. The Mediterranean countries, including Italy, Spain, and Greece, have a diverse range of tomato landraces. Assessing the nutritional and bioactive composition of different tomato varieties and their ripening stages is crucial to determine their suitability for the market. Therefore, the aim of this study was to investigate the effect of ripening on nutritional composition (including carotenoids and polyphenols content) and antioxidant activities of fruits of three specific tomato varieties grown in Spain: Josefina and Karelya, which are cherry-like tomatoes, and Muchamiel, a type of salad tomato. In addition to evaluating their characteristics and composition (including carotenoids and polyphenol content), the antioxidant activities of these varieties at three different ripening stages were quantified. As expected, the results reveal that, as the tomatoes matured, their antioxidant capacity increased along with higher levels of carotenoids and polyphenols. Interestingly, cherry-like tomatoes showed a higher antioxidant activity than the salad tomatoes. This investigation emphasizes the role of fruit ripening in increasing carotenoid levels, which contribute to the antioxidant activity of three tomato varieties.

Nematicidal Activity of Volatiles against the Rice Root-Knot Nematode and Environmental Safety in Comparison to Traditional Nematicides.

The rice root-knot nematode (RRKN), Meloidogyne graminicola Golden and Birchfield 1965, is a dangerous crop pest that affects rice production on a global scale. The largest rice-producing countries struggle with the impacts of RRKN infestation, namely, underdeveloped plants and a reduction in rice grain that can reach up to 70% of crop yield. In addition, the shift to strategies of sustainable pest management is leading to a withdrawal of some of the most effective pesticides, given the dangers they pose to the environment and human health. Volatile metabolites produced by plants can offer safer alternatives. The present study characterized the nematicidal activity of volatile phytochemicals against the RRKN and compared the most active with commercial nematicides concerning their safety to the environment and human health. Rice plants were used to grow large numbers of RRKNs for direct-contact bioassays. Mortality induced by the volatiles was followed for four days on RRKN second-stage juveniles. Of the 18 volatiles tested, carvacrol, eugenol, geraniol, and methyl salicylate showed the highest mortalities (100%) and were compared to traditional nematicides using (eco)toxicological parameters reported on freely available databases. While methyl salicylate had a faster activity, carvacrol had more lasting effects. When compared to synthetic nematicides, these volatile phytochemicals were reported to have higher thresholds of toxicity and beneficial ecotoxicological parameters. Ultimately, finding safer alternatives to traditional pesticides can lower the use of damaging chemicals in farming and leverage the transition to agricultural practices with a lower impact on biodiversity.

Optimal Planting Time for Summer Tomatoes (Lycopersicon esculentum Mill.) Cropping in Korea: Growth, Yield, and Photosynthetic Efficiency in a Semi-Closed Greenhouse.

In Korea, greenhouses are traditionally used for crop cultivation in the winter. However, due to diverse consumer demands, climate change, and advancements in agricultural technology, more farms are aiming for year-round production. Nonetheless, summer cropping poses challenges such as high temperatures, humidity from the monsoon season, and low light conditions, which make it difficult to grow crops. Therefore, this study aimed to determine the best planting time for summer tomato cultivation in a Korean semi-closed greenhouse that can be both air-conditioned and heated. The experiment was conducted in the Advanced Digital Greenhouse, built by the National Institute of Agricultural Sciences. The tomato seedlings were planted in April, May, and June 2022. Growth parameters such as stem diameter, flowering position, stem growth rate, and leaf shape index were measured, and harvesting was carried out once or twice weekly per treatment from 65 days to 265 days after planting. The light use efficiency and yield per unit area at each planting time was measured. Tomatoes planted in April showed a maximum of 42.9% higher light use efficiency for fruit production and a maximum of 33.3% higher yield. Furthermore, the growth form of the crops was closest to the reproductive growth type. Therefore, among April, May, and June, April is considered the most suitable planting time for summer cultivation, which is expected to contribute to reducing labor costs due to decreased workload and increasing farm income through increased yields. Future research should explore optimizing greenhouse microclimates and developing crop varieties tailored for summer cultivation to further enhance productivity and sustainability in year-round agricultural practices.

Enhancing Solanum lycopersicum Resilience: Bacterial Cellulose Alleviates Low Irrigation Stress and Boosts Nutrient Uptake.

The use of natural-origin biomaterials in bioengineering has led to innovative approaches in agroforestry. Bacterial cellulose (BC), sharing the same chemical formula as plant-origin cellulose (PC), exhibits significantly different biochemical properties, including a high degree of crystallinity and superior water retention capacity. Previous research showed that natural-origin glucose-based chitin enhanced plant growth in both herbaceous and non-herbaceous plants. In this study, we produced BC in the laboratory and investigated its effects on the substrate and on Solanum lycopersicum seedlings. Soil amended with BC increased root growth compared with untreated seedlings. Additionally, under limited irrigation conditions, BC increased global developmental parameters including fresh and dry weight, as well as total carbon and nitrogen content. Under non-irrigation conditions, BC contributed substantially to plant survival. RNA sequencing (Illumina®) on BC-treated seedlings revealed that BC, despite its bacterial origin, did not stress the plants, confirming its innocuous nature, and it lightly induced genes related to root development and cell division as well as inhibition of stress responses and defense. The presence of BC in the organic substrate increased soil availability of phosphorus (P), iron (Fe), and potassium (K), correlating with enhanced nutrient uptake in plants. Our results demonstrate the potential of BC for improving soil nutrient availability and plant tolerance to low irrigation, making it valuable for agricultural and forestry purposes in the context of global warming.

Flavonols improve tomato pollen thermotolerance during germination and tube elongation by maintaining ROS homeostasis.

Elevated temperatures impair pollen performance and reproductive success, resulting in lower crop yields. The tomato (Solanum lycopersicum) anthocyanin reduced (are) mutant harbors a mutation in FLAVANONE 3-HYDROXYLASE (F3H), resulting in impaired flavonol antioxidant biosynthesis. The are mutant has reduced pollen performance and seed set relative to the VF36 parental line, phenotypes that are accentuated at elevated temperatures. Transformation of are with the wild-type F3H gene, or chemical complementation with flavonols, prevented temperature-dependent reactive oxygen species (ROS) accumulation in pollen and restored the reduced viability, germination, and tube elongation of are to VF36 levels. Overexpression of F3H in VF36 prevented temperature-driven ROS increases and impaired pollen performance, revealing that flavonol biosynthesis promotes thermotolerance. Although stigmas of are had reduced flavonol and elevated ROS levels, the growth of are pollen tubes was similarly impaired in both are and VF36 pistils. RNA-seq was performed at optimal and stress temperatures in are, VF36, and the F3H overexpression line at multiple timepoints across pollen tube elongation. The number of differentially expressed genes increased over time under elevated temperatures in all genotypes, with the greatest number in are. These findings suggest potential agricultural interventions to combat the negative effects of heat-induced ROS in pollen that lead to reproductive failure.

Identification of long-chain acyl-CoA synthetase gene family reveals that SlLACS1 is essential for cuticular wax biosynthesis in tomato.

Long-chain acyl-CoA synthetases (LACSs), belonging to the acyl-activating enzyme superfamily, play crucial roles in lipid biosynthesis and fatty acid catabolism. Here, we identified 11 LACS genes in the tomato reference genome, and these genes were clustered into six subfamilies. Gene structure and conserved motif analyses indicated that LACSs from the same subfamily shared conserved gene and protein structures. Expression analysis revealed that SlLACS1 was highly expressed in the outer epidermis of tomato fruits and leaves. Subcellular localization assay results showed that SlLACS1 was located in the endoplasmic reticulum. Compared with wild-type plants, the wax content on leaves and fruits decreased by 22.5-34.2 % in SlLACS1 knockout lines, confirming that SlLACS1 was involved in wax biosynthesis in both leaves and fruits. Water loss, chlorophyll extraction, water-deficit, and toluidine blue assays suggested that cuticle permeability was elevated in SlLACS1 knockout lines, resulting in reduction in both drought stress resistance and fruit shelf-life. Overall, our analysis of the LACSs in tomato, coupled with investigations of SlLACS1 function, yielded a deeper understanding of the evolutionary patterns of LACS members and revealed the involvement of SlLACS1 in wax accumulation contribute to drought resistance and extended fruit shelf-life in tomato.

Enhancing tomato plant immune responses to Fusarium wilt disease by red seaweed Jania sp.

The novelty of this study lies in demonstrating a new approach to control wilt diseases using Jania ethyl acetate extract. In the current investigation, the potential impacts of Jania sp. ethyl acetate extract (JE) on Tomato Fusarium oxysporum wilt (FOW) have been studied. The in vitro antifungal potential of JE against F. oxysporum (FO) was examined. GC-MS investigation of the JE revealed that, the compounds possessing fungicidal action were Phenol,2-methoxy-4-(2-propenyl)-,acetate, Eugenol, Caryophyllene oxide, Isoespintanol, Cadinene, Caryophylla-4(12),8(13)-dien-5à-ol and Copaen. Jania sp. ethyl acetate extract exhibited strong antifungal potential against FO, achieving a 20 mmzone of inhibition. In the experiment, two different methods were applied: soil irrigation (SI) and foliar application (FS) of JE. The results showed that both treatments reduced disease index present DIP by 20.83% and 33.33% respectively. The findings indicated that during FOW, proline, phenolics, and the antioxidant enzymes activity increased, while growth and photosynthetic pigments decreased. The morphological features, photosynthetic pigments, total phenol content, and antioxidant enzyme activity of infected plants improved when JE was applied through soil or foliar methods. It is interesting to note that the application of JE had a substantially less negative effect on the isozymes peroxidase and polyphenol oxidase in tomato plants, compared to FOW. These reactions differed depending on whether JE was applied foliarly or via the soil. Finally, the use of Jania sp. could be utilized commercially as an ecologically acceptable method to protect tomato plants against FOW.

Genome-Wide Identification and Expression Analysis of SlNRAMP Genes in Tomato under Nutrient Deficiency and Cadmium Stress during Arbuscular Mycorrhizal Symbiosis.

Arbuscular mycorrhizal (AM) fungi are well known for enhancing phosphorus uptake in plants; however, their regulating roles in cation transporting gene family, such as natural resistance-associated macrophage protein (NRAMP), are still limited. Here, we performed bioinformatics analysis and quantitative expression assays of tomato SlNRAMP 1 to 5 genes under nutrient deficiency and cadmium (Cd) stress in response to AM symbiosis. These five SlNRAMP members are mainly located in the plasma or vacuolar membrane and can be divided into two subfamilies. Cis-element analysis revealed several motifs involved in phytohormonal and abiotic regulation in their promoters. SlNRAMP2 was downregulated by iron deficiency, while SlNRAMP1, SlNRAMP3, SlNRAMP4, and SlNRAMP5 responded positively to copper-, zinc-, and manganese-deficient conditions. AM colonization reduced Cd accumulation and expression of SlNRAMP3 but enhanced SlNRAMP1, SlNRAMP2, and SlNRMAP4 in plants under Cd stress. These findings provide valuable genetic information for improving tomato resilience to nutrient deficiency and heavy metal stress by developing AM symbiosis.

Herbivore-induced volatiles reduce the susceptibility of neighboring tomato plants to transmission of a whitefly-borne begomovirus.

Plant viruses exist in a broader ecological community, with key components include non-vector herbivores that can impact vector abundance, behavior, and virus transmission within shared host plants. However, little is known about the effects of non-vector herbivores infestation on the virus transmission by vector insects on the neighboring plants through inter-plant airborne chemicals. In this study, we investigated how volatiles emitted from tomato plants infested with the two-spotted spider mite (Tetranychus urticae) affect the infection of Tomato yellow leaf curl virus (TYLCV) transmitted by the whitefly (Bemisia tabaci) in the neighboring plants. Exposure of neighboring tomato plants to volatiles released from T. urticae-infested tomato plants reduced subsequent herbivory as well as TYLCV transmission and infection, and JA signaling pathway was essential for generation of the inter-plant defense signals. We also demonstrated that (E)-ß-Ocimene and MeSA were two volatiles induced by T. urticae that synergistically attenuated TYLCV transmission and infection in tomato. Thus, our findings suggest that plant-plant communication via volatiles likely represents a widespread defensive mechanism that substantially contributes to plant fitness. Understanding such phenomena may help us to predict the occurrence and epidemic of multiple herbivores and viruses in the agroecosystem, ultimately to manage pest and virus outbreaks.

Rhizoengineering with biofilm producing rhizobacteria ameliorates oxidative stress and enhances bioactive compounds in tomato under nitrogen-deficient field conditions.

Nitrogen (N) deficiency limits crop productivity. In this study, rhizoengineering with biofilm producing rhizobacteria (BPR) contributing to productivity, physiology, and bioactive contents in tomato was examined under N-deficient field conditions. Here, different BPR including Leclercia adecarboxylata ESK12, Enterobacter ludwigii ESK17, Glutamicibacter arilaitensis ESM4, E. cloacae ESM12, Bacillus subtilis ESM14, Pseudomonas putida ESM17 and Exiguobacterium acetylicum ESM24 were used for the rhizoengineering of tomato plants. Rhizoengineered plants showed significant increase in growth attributes (15.73%-150.13 %) compared to the control plants. However, production of hydrogen peroxide (21.49-59.38 %), electrolyte leakage (19.5-38.07 %) and malondialdehyde accumulation (36.27-46.31 %) were increased remarkably more in the control plants than the rhizoengineered plants, thus N deficiency induced the oxidative stress. Compared to the control, photosynthetic rate, leaf temperature, stomatal conductance, intrinsic and instantaneous water use efficiency, relative water content, proline and catalase activity were incredibly enhanced in the rhizoengineered plants, suggesting both non-enzymatic and enzymatic antioxidant systems might protect tomato plants from oxidative stress under N-deficient field conditions. Yield (10.24-66.21 %), lycopene (4.8-7.94 times), flavonoids (52.32-110.46 %), phenolics (9.79-23.5 %), antioxidant activity (34.09-86.36 %) and certain minerals were significantly increased in the tomatoes from rhizoengineered plants. The principal component analysis (PCA) revealed that tomato plants treated with BPR induced distinct profiles compared to the control. Among all the applied BPR strains, ESM4 and ESM14 performed better in terms of biomass production, while ESK12 and ESK17 showed better results for reducing oxidative stress and increasing bioactive compounds in tomato, respectively. Thus, rhizoengineering with BPR can be utilized to mitigate the oxidative damage and increase the productivity and bioactive compounds in tomato under N-deficient field conditions.

Stress response in tomato as influenced by repeated waterlogging.

Introduction: Plants respond to water stress with a variety of physiological and biochemical changes, but their response varies among species, varieties and cultivars. Waterlogging in tomato reduces plant growth, degrade chlorophyll and increase concentration of oxidative parameters. Priming can alleviate stress in plants caused by waterlogging enabling plants to be more tolerant to an additional stress in the current or even subsequent generation. The aim of this study was to evaluate tomato genotypes for their sensitivity to waterlogging stress applied during early vegetative growth and at full flowering stage. Materials and methods: The study included two local genotypes, Trebinjski sitni (GB1126) and Zuti (GB1129), and the reference variety Novosadski jabucar (NJ), which is the variety most commonly used in Serbia and Bosnia and Herzegovina. The activity of class III peroxidase (POX), hydrogen peroxide (H2O2) content and malondialdehyde (MDA) content were measured spectrophotometrically, and for quantification of individual phenolic compounds, targeted approach was adopted, using UHPLC/DAD/(-)HESI-MS2 instrument (Dionex UltiMate 3000 UHPLC system with a DAD detector, configured with a triple quadrupole mass spectrometer TSQ Quantum Access Max (Thermo Fisher Scientific, Germany)). Results and discussion: Oxidative parameters (H2O2 and MDA) exhibited an increase in content in leaves of tomato plants that underwent waterlogging stress compared to control plants. Moreover, oxidative parameters showed positive correlation with proteins and phenolics content. The obtained correlations can indicate that one of the response strategies of tomato plants to waterlogging is the increased synthesis of proteins and phenolic compounds. The POX activity was not correlated with other parameters except with the polyphenols. A positive correlation was shown between POX activity and the content of phenolic compounds, indicating their independent roles in the removal of ROS. Changes in the phenolic profiles after the exposure of plants to waterlogging stress are recorded, and these changes were more severe in leaves and fruits of GB1129 and NJ genotypes than in GB1126. Thus, genotype GB1126 is the most efficient in maintaining the phenolic profiles of leaves and fruits, and therefore of the nutritive and organoleptic qualities of fruits following the exposure to waterlogging. Also, genotype GB1126 exhibited the ability to maintain the content of oxidative parameters during waterlogging at certain growth stages, implying certain waterlogging tolerance. Conclusion: Waterlogging triggered stress memory but not at all growth stages. The most pronounced stress memory was obtained in fruit samples in the phase of full fruit maturity on the 1st truss. This study shed light on the defense mechanisms of tomato plants to repeated waterlogging stress from the perspectives of the changes in the composition of major phenolics, and pointed to the 5-O-caffeoylquinic acid and rutin as the chemical markers of the waterlogging stress tolerance in tomato. However, it remains to be determined whether this modulation has a positive or negative effect on the overall plant metabolism. Further investigations are needed to fully elucidate the benefits of waterlogging pretreatment in this context.

First Report of Klebsiella variicola Causing Tomato Pith Necrosis in Yunnan Province, China.

Tomato (Solanum lycopersicum L.) is a key vegetable crop in China. In August 2023, an outbreak of bacterial pith necrosis in tomato occurred in Lufeng County, Yunnan Province, China, affecting over 40% of the tomato plants in a greenhouse. The stems of infected plants developed a waterlogged soft rot and the disease progressed, the lower leaves and lateral branches of infected plants gradually wilted and died. A longitudinal cut of the stem revealed hollow pith with brown vascular tissue. To isolate the pathogen, the plant surface was disinfested with 75% ethanol. Then, a piece of infected tissue from the base of the stem was excised and immersed in sterile water for 2 min. A small amount of liquid was streaked onto TTC (2,3,5-triphenyltetrazolium chloride) agar medium using an inoculation loop, and plates were incubated at 28℃ for 24 h. Colonies on the TTC plate were white, indicating that the pathogen was not Ralstonia solanacearum. Colonies grown on LB (Luria-Bertani) agar medium were randomly selected and subjected to preliminary pathogenicity tests. Based on the results, a colony named Kv4 was selected and purified through six subcultures in LB agar medium. Biochemical tests showed the strain utilized D-sorbitol, raffinose and citrate but not adonitol, and was positive for methyl red, D-glucose (acid), urea hydrolysis, lysine decarboxylase, and motility, and negative for phenylalanine deaminase, H2S production, indole production, and ornithine decarboxylase. These characteristics align with Klebsiella species (Garrity et al. 2007). To determine the species of strain Kv4, partial sequences of the 16S rDNA, phoE, leuS, and rpoB genes were amplified (Barrios-Camacho et al. 2019) and sequenced. Through BLASTn analysis, strain Kv4 sequences of 16S rDNA (OR888750) had 99.47% identity (1488/1496 bp), phoE (OR899599) had 98.69% (605/613 bp) identity, leuS (OR899598) had 99.07% identity (959/968 bp), and rpoB (OR899597) had 97.69% (633/648 bp) identity with Klebsiella variicola strain FF0907. Using the ClustalW algorithm in MEGA11 for nucleotide sequence alignment, phylogenetic trees were constructed with 16S and phoE, leuS, and rpoB via the neighbor-joining method, confirming strain Kv4 as K. variicola. To test pathogenicity, the roots of 25 'Moneymaker' tomato plants with four to five true leaves were wounded, then each plant inoculated with a 15 mL bacterial suspension (OD600=0.6) of strain Kv4, while the control plants received sterile water. Plants were incubated at 28℃ with a 16 h photoperiod. Experiments were done twice. At 15 days after inoculation (DAI), all plants inoculated with Kv4 showed yellowing, unevenly distributed small black necrotic spots on the leaf surface, and purple-brown soft rot at the stem base. By 18 DAI, there was a gradual transformation of the stem bases from green to purplish brown. At 21 DAI, 60% of the inoculated plants displayed brownish soft rot at the stem base. In contrast, the control plants remained symptom-free. The pathogen was re-isolated from the stem and identified as K. variicola via sequence analysis of 16S, phoE, leuS, and rpoB. In recent years, several new bacterial pith necrosis diseases were reported in tomato (Guo et al. 2023; Ivic et al. 2023). This is the first study documenting K. variicola causing bacterial pith necrosis in tomato. Once considered a benign plant endophyte, Sun et al. (2023) reported K. variicola causing banana sheath rot in Guangdong and Guangxi Provinces, China. Malik et al. (2023) reported that K. variicola caused leaf streak in sorghum in India. This report of bacterial pith necrosis in tomato caused by K. variicola strain Kv4 underscores the escalating threat posed by emerging pathogens to agricultural production. The emergence of K. variicola as a tomato pathogen complicates plant disease management strategies.

Protein arginine methyltransferase 6 mediates antiviral immunity in plants.

Viral suppressor RNA silencing (VSR) is essential for successful infection. Nucleotide-binding and leucine-rich repeat (NLR)-based and autophagy-mediated immune responses have been reported to target VSR as counter-defense strategies. Here, we report a protein arginine methyltransferase 6 (PRMT6)-mediated defense mechanism targeting VSR. The knockout and overexpression of PRMT6 in tomato plants lead to enhanced and reduced disease symptoms, respectively, during tomato bush stunt virus (TBSV) infection. PRMT6 interacts with and inhibits the VSR function of TBSV P19 by methylating its key arginine residues R43 and R115, thereby reducing its dimerization and small RNA-binding activities. Analysis of the natural tomato population reveals that two major alleles associated with high and low levels of PRMT6 expression are significantly associated with high and low levels of viral resistance, respectively. Our study establishes PRMT6-mediated arginine methylation of VSR as a mechanism of plant immunity against viruses.

The hormone regulatory mechanism underlying parthenocarpic fruit formation in tomato.

Parthenocarpic fruits, known for their superior taste and reliable yields in adverse conditions, develop without the need for fertilization or pollination. Exploring the physiological and molecular mechanisms behind parthenocarpic fruit development holds both theoretical and practical significance, making it a crucial area of study. This review examines how plant hormones and MADS-box transcription factors control parthenocarpic fruit formation. It delves into various aspects of plant hormones-including auxin, gibberellic acid, cytokinins, ethylene, and abscisic acid-ranging from external application to biosynthesis, metabolism, signaling pathways, and their interplay in influencing parthenocarpic fruit development. The review also explores the involvement of MADS family gene functions in these processes. Lastly, we highlight existing knowledge gaps and propose directions for future research on parthenocarpy.

SlWRKY55 coordinately acts with SlVQ11 to enhance tomato thermotolerance by activating SlHsfA2.

High temperature (HT) severely restricts plant growth, development, and productivity. Plants have evolved a set of mechanisms to cope with HT, including the regulation of heat stress transcription factors (Hsfs) and heat shock proteins (Hsps). However, it is not clear how the transcriptional and translational levels of Hsfs and Hsps are controlled in tomato. Here, we reported that the HT-induced transcription factor SlWRKY55 recruited SlVQ11 to coordinately regulate defense against HT. SlWRKY55 directly bound to the promoter of SlHsfA2 and promoted its expression, which was increased by SlVQ11. Moreover, both SlWRKY55 and SlVQ11 physically interacted with SlHsfA2 to enhance the transcriptional activity of SlHsfA2. Thus, our results revealed a molecular mechanism that the SlWRKY55/SlVQ11-SlHsfA2 cascade enhanced thermotolerance and provided potential target genes for improving the adaptability of crops to HT.

Green synthesis and characterization of magnetite nanoparticles using Eucalyptus globulus leaves for water treatment and agronomic valorization.

This work presents a new process, based on the green nanoparticles Fe3O4 and magnetization coupling for the treatment of saline well water. In this context, iron nanoparticles were synthesized using Eucalyptus globulus leaves. The nanomaterials were characterized by scanning electron microscopy and infrared for identification. Batch experiments were conducted to illustrate the optimal parameters related to contact times and the mass of nanoparticles. The latter marked an optimal contact time of 100 min and a mass of 56 mg/L accompanied by a magnetic treatment for a contact time of 48 min. The results showed a significant (R2 = 0.93) water salinity reduction (67%) and a potential for improvement in the germination of tomato seeds (81%) through the investigation of the evolution of the length of the roots, the stems, and the number of germinated seeds.