Alleviation potential of green-synthesized selenium nanoparticles for cadmium stress in Solanum lycopersicum L: modulation of secondary metabolites and physiochemical attributes.

KEY MESSAGE: Selenium nanoparticles reduce cadmium absorption in tomato roots, mitigating heavy metal effects. SeNPs can efficiently help to enhance growth, yield, and biomolecule markers in cadmium-stressed tomato plants. In the present study, the effects of selenium nanoparticles (SeNPs) were investigated on the tomato plants grown in cadmium-contaminated soil. Nanoparticles were synthesized using water extract of Nigella sativa and were characterized for their size and shape. Two application methods (foliar spray and soil drench) with nanoparticle concentrations of 0, 100, and 300 mg/L were used to observe their effects on cadmium-stressed plants. Growth, yield, biochemical, and stress parameters were studied. Results showed that SeNPs positively affected plant growth, mitigating the negative effects of cadmium stress. Shoot length (SL), root length (RL), number of branches (NB), number of leaves per plant (NL), and leaf area (LA) were significantly reduced by cadmium stress but enhanced by 45, 51, 506, 208, and 82%, respectively, by soil drench treatment of SeNPs. Similarly, SeNPs increased the fruit yield (> 100%) and fruit weight (> 100%), and decreased the days to fruit initiation in tomato plants. Pigments were also positively affected by the SeNPs, particularly in foliar treatment. Lycopene content was also enhanced by the addition of NPs (75%). Furthermore, the addition of SeNPs improved the ascorbic acid, protein, phenolic, flavonoid, and proline contents of the tomato plants under cadmium stress, whereas stress enzymes also showed enhanced activities under cadmium stress. It is concluded from the present study that the addition of selenium nanoparticles enhanced the growth and yield of Cd-stressed plants by reducing the absorption of cadmium and increasing the stress management of plants.

Interactions between Bacillus thuringiensis and selected plant extracts for sustainable management of Phthorimaea absoluta.

Phthorimaea absoluta is a global constraint to tomato production and can cause up to 100% yield loss. Farmers heavily rely on synthetic pesticides to manage this pest. However, these pesticides are detrimental to human, animal, and environmental health. Therefore, exploring eco-friendly, sustainable Integrated Pest Management approaches, including biopesticides as potential alternatives, is of paramount importance. In this context, the present study (i) evaluated the efficacy of 10 Bacillus thuringiensis isolates, neem, garlic, and fenugreek; (ii) assessed the interactions between the most potent plant extracts and B. thuringiensis isolates, and (iii) evaluated the gut microbial diversity due to the treatments for the development of novel formulations against P. absoluta. Neem recorded the highest mortality of 93.79 ± 3.12% with an LT50 value of 1.21 ± 0.24 days, Bt HD263 induced 91.3 ± 3.68% mortality with LT50 of 2.63 ± 0.11 days, compared to both Bt 43 and fenugreek that caused < 50% mortality. Larval mortality was further enhanced to 99 ± 1.04% when Bt HD263 and neem were combined. Furthermore, the microbiome analyses showed that Klebsiella, Escherichia and Enterobacter had the highest abundance in all treatments with Klebsiella being the most abundant. In addition, a shift in the abundance of the bacterial genera due to the treatments was observed. Our findings showed that neem, garlic, and Bt HD263 could effectively control P. absoluta and be integrated into IPM programs after validation by field efficacy trials.

Green-fabricated silver nanoparticles from Quercus incana leaf extract to control the early blight of tomatoes caused by Alternaria solani.

BACKGROUND: Early blight (EB) of Tomatoes, caused by Alternaria solani, is a serious fungal disease that adversely affects tomato production. Infection is characterized by dark lesions on leaves, stems, and fruits. Several agrochemicals can be used to control infection, these chemicals may disrupt environmental equilibrium. An alternative technology is needed to address this significant fungal threat. This study was designed to control the growth of EB in tomatoes caused by A. solani, using green-fabricated silver nanoparticles (Ag-NPs). RESULTS: Ag-NPs were synthesized through an environmentally friendly and cost-effective approach using leaf extract of Quercus incana Roxb. (Fagaceae). The physico-chemical characterization of the Ag-NPs was conducted through UV-visible spectroscopy, scanning electron microscopy, X-ray diffraction analysis, and Fourier transform infrared spectrometry. The Ag-NPs produced were round with a mean diameter of 27 nm. The antifungal activity of these Ag-NPs was assessed through in vitro Petri plate and in vitro leaflet assays against A. solani. The green fabricated Ag-NPs exhibited excellent antifungal activity in vitro at a concentration of 100 mg/l against A. solani, inhibiting growth by 98.27 ± 1.58% and 92.79 ± 1.33% during Petri plate and leaflet assays, respectively. CONCLUSION: In conclusion, this study suggests the practical application of green-fabricated Ag-NPs from Q. incana leaf extract against A. solani to effectively control EB disease in tomatoes.

Tomato seed extract promotes health of the gut microbiota and demonstrates a potential new way to valorize tomato waste.

The current effort to valorize waste byproducts to increase sustainability and reduce agricultural loss has stimulated interest in potential utilization of waste components as health-promoting supplements. Tomato seeds are often discarded in tomato pomace, a byproduct of tomato processing, yet these seeds are known to contain an array of compounds with biological activity and prebiotic potential. Here, extract from tomato seeds (TSE), acquired from pomace, was evaluated for their ability to effect changes on the gut microbiota using an ex vivo strategy. The results found that TSE significantly increased levels of the beneficial taxa Bifidobacteriaceae in a donor-independent manner, from a range of 18.6-24.0% to 27.0-51.6% relative abundance following treatment, yet the specific strain of Bifidobacteriaceae enhanced was inter-individually variable. These structural changes corresponded with a significant increase in total short-chain fatty acids, specifically acetate and propionate, from an average of 13.3 to 22.8 mmol/L and 4.6 to 7.4 mmol/L, respectively. Together, these results demonstrated that TSE has prebiotic potential by shaping the gut microbiota in a donor-independent manner that may be beneficial to human health. These findings provide a novel application for TSE harvested from tomato pomace and demonstrate the potential to further valorize tomato waste products.

Growth performance, plasma metabolites, meat quality, and meat and lipid health indices of New Zealand White rabbits as affected by dietary dried tomato pomace powder supplementation during the summer season.

One hundred and twenty New Zealand White rabbits (NZW) (5-week-old; 735.27 ± 27.23 g) were kept in an open-sided house during the summer season. The experiment aims to evaluate the impacts of dried tomato pomace powder (DTPP) supplementation on rabbits' performance, blood metabolites, carcass traits, meat quality, and lipid and health indices of NZW rabbits during 5-13 weeks of age. The four treatments were a standard rabbit feed (control) and the control diet supplemented with 0.5, 1.0, and 1.5% DTPP, respectively. Rabbits fed a diet containing 1.5% DTPP showed the highest growth rate through weeks 9-13 of age despite having the lowest feed intake spanning 5-13 weeks. The best feed conversion ratio (FCR) was recorded in rabbits fed with 1.5% DTPP-supplemented diet for 5-13 weeks. Diets supplemented with 0.5 or 1.0% DTPP enhanced markedly dressing %, total edible flesh, saturated (SFAs), monounsaturated (MUFAs), and polyunsaturated fatty acid (PUFAs) contents, as well as the ∑n - 6/∑n - 3 ratio and the total n - 6 of meat. Dietary supplementation with DTPP decreased kidney, abdominal, and back fat. Diets supplemented with DTTP decreased total cholesterol, triglycerides, and very low-density lipoprotein (vLDL) concentrations. The greatest levels of linoleic acid, arachidonic and water-holding capacity in meat were observed in rabbits fed 1.5% DTPP-supplemented diets. Diets containing 1 and 1.5% DTPP improved meats' atherogenic and thrombogenic indices, meat lipid quality desired fatty acids/undesired fatty acids ratio, and meat health index. Conclusively, DTPP up to 1.5% maintained the growth performance of rabbits, boosted meat quality through increasing vitamin E, reduced fat deposition, modified fatty acid composition, and improved atherogenic, thrombogenic, and hypocholesterolemic indices of rabbit meat.

Review on toxicology and activity of tomato glycoalkaloids in immature tomatoes.

Owing to the lack of selection and limited intelligence in mechanical picking, some immature tomatoes that contain alkaloids are thrown away. Tomatine alkaloids are steroidal alkaloids naturally present in Solanaceae plants, which are distributed in small amounts in immature tomato fruits and decrease as the fruits ripen. Tomato glycoalkaloids are harmful to human health. However, in small quantities, there is some evidence that these compounds might be beneficial, as other non-antioxidant bioactivities. This article considers recent research on the biological effects of tomato glycoalkaloids in immature tomatoes, providing reference value for the potential development of these compounds.

Bactericera cockerelli Picorna-like Virus and Three New Viruses Found Circulating in Populations of Potato/Tomato Psyllids (Bactericera cockerelli).

An investigation of viruses circulating in populations of field and laboratory potato/tomato psyllids (Bactericera cockerelli) was conducted using high-throughput sequencing (HTS) technology and conventional RT-PCR. Three new viruses were discovered: one from the family Tymoviridae and two from the family Solemoviridae. A tymo-like virus sequence represented a nearly complete 6843 nt genome of a virus named Bactericera cockerelli tymo-like virus (BcTLV) that spanned five open reading frames (ORFs) which encoded RNA-dependent RNA polymerase (RdRP), helicase, protease, methyltransferase, and a capsid protein. Phylogenetic analyses placed the RdRP of BcTLV inside a divergent lineage of the viruses from the family Tymoviridae found in insect and plant hosts in a sister clade to the genera Tymovirus, Marafivirus, and Maculavirus. Four solemo-like virus sequences were identified in the HTS outputs, representing two new viruses. One virus found only in field-collected psyllids and named Bactericera cockerelli solemo-like virus 1 (BcSLV-1) had a 5479 nt genome which spanned four ORFs encoding protease and RdRP. Three solemo-like sequences displayed 87.4-99.7% nucleotide sequence identity among themselves, representing variants or strains of the same virus named Bactericera cockerelli solemo-like virus 2 (BcSLV-2). The genome of BcSLV-2 spanned only two ORFs that encoded a protease and an RdRP. Phylogenetic analysis placed the RdRPs of BcSLV-1 and BcSLV-2 in two separate lineages as sister clades to viruses from the genus Sobemovirus found in plant hosts. All three new psyllid viruses were found circulating in psyllids collected from potato fields in southern Idaho along with a previously identified Bactericera cockerelli picorna-like virus. Any possible role of the three viruses in controlling populations of the field psyllids remains to be elucidated.

Nutrient supplementation-induced metabolic profile changes and early appearance of free N-glycans in nutrient deficient tomato plants revealed by mass spectrometry.

Inorganic fertilizers are routinely used in large scale crop production for the supplementation of nitrogen, phosphorus, and potassium in nutrient poor soil. To explore metabolic changes in tomato plants grown on humic sand under different nutritional conditions, matrix-assisted laser desorption ionization (MALDI) mass spectrometry was utilized for the analysis of xylem sap. Variations in the abundances of metabolites and oligosaccharides, including free N-glycans (FNGs), were determined. Statistical analysis of the sample-related peaks revealed significant differences in the abundance ratios of multiple metabolites, including oligosaccharides, between the control plants, grown with no fertilizers, and plants raised under "ideal" and "nitrogen deficient" nutritional conditions, i.e., under the three treatment types. Among the 36 spectral features tentatively identified as oligosaccharides, the potential molecular structures for 18 species were predicted based on their accurate masses and isotope distribution patterns. To find the spectral features that account for most of the differences between the spectra corresponding to the three different treatments, multivariate statistical analysis was carried out by orthogonal partial least squares-discriminant analysis (OPLS-DA). They included both FNGs and non-FNG compounds that can be considered as early indicators of nutrient deficiency. Our results reveal that the potential nutrient deficiency indicators can be expanded to other metabolites beyond FNGs. The m/z values for 20 spectral features with the highest variable influence on projection (VIP) scores were ranked in the order of their influence on the statistical model.

Bimetallic nanoparticles and biochar produced by Adansonia Digitata shell and their effect against tomato pathogenic fungi.

Adansonia digitata L. is a royal tree that is highly valued in Africa for its medicinal and nutritional properties. The objective of this study was to use its fruit shell extract to develop new, powerful mono and bimetallic nanoparticles (NPs) and biochar (BC) using an eco-friendly approach. Silver (Ag), iron oxide (FeO), the bimetallic Ag-FeO NPs, as well as (BC) were fabricated by A. digitata fruit shell extract through a reduction process and biomass pyrolysis, respectively, and their activity against tomato pathogenic fungi Alternaria sp., Sclerotinia sclerotiorum, Fusarium equiseti, and Fusarium venenatum were detected by agar dilution method. The Ag, FeO, Ag-FeONPs, and BC were characterized using a range of powerful analytical techniques such as ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform-Infra Red (FT-IR), dynamic light scatter (DLS), and zeta potential analysis. The fabricated Ag, FeO and Ag-FeO NPs have demonstrated a remarkable level of effectiveness in combating fungal strains. UV-Vis spectra ofAg, FeO, Ag-FeONPs, and BC show broad exhibits peaks at 338, 352, 418, and 480 nm, respectively. The monometallic, bimetallic NPs, and biochar have indicated the presence in various forms mostly in Spherical-shaped. Their size varied from 102.3 to 183.5 nm and the corresponding FTIR spectra suggested that the specific organic functional groups from the plant extract played a significant role in the bio-reduction process. Ag and Ag-FeO NPs exhibited excellent antifungal activity against pathogenic fungi Alternaria sp., S. sclerotiorum, F. equiseti, and F. venenatum. The current study could be a significant achievement in the field of antifungal agents since has the potential to develop new approaches for treating fungal infections.

Solanum lycopersicum (Tomato)-Derived Nanovesicles Accelerate Wound Healing by Eliciting the Migration of Keratinocytes and Fibroblasts.

Plant-derived nanovesicles have been considered interesting in medicine for their breakthrough biological effects, including those relevant to wound healing. However, tomato-derived nanovesicles (TDNVs) have not been studied for their effects on wound closure yet. TDNVs were isolated from Solanum lycopersicum (var. Piccadilly) ripe tomatoes by ultracentrifugation. Extract (collected during the isolation procedure) and NVs (pellet) were characterized by transmission electron microscopy and laser Doppler electrophoresis. Wound healing in the presence of Extract or NVs was analyzed by a scratch assay with monocultures of human keratinocytes (HUKE) or NIH-3T3 mouse fibroblasts. Cell proliferation and migration were studied by MTT and agarose spot assay, respectively. The vesicles in the Extract and NV samples were nanosized with a similar mean diameter of 115 nm and 130 nm, respectively. Both Extract and NVs had already accelerated wound closure of injured HUKE and NIH-3T3 monocultures by 6 h post-injury. Although neither sample exerted a cytotoxic effect on HUKE and NIH-3T3 fibroblasts, they did not augment cell proliferation. NVs and the Extract increased cell migration of both cell types. NVs from tomatoes may accelerate wound healing by increasing keratinocyte and fibroblast migration. These results indicate the potential therapeutic usefulness of TDNVs in the treatment of chronic or hard-to-heal ulcers.

Mechanisms of cadmium mitigation in tomato plants under orthophosphate and polyphosphate fertilization regimes.

Cadmium (Cd) is one of the most toxic elements in soil, affecting morphological, physiological, and biochemical processes in plants. Mineral plant nutrition was tested as an effective approach to mitigate Cd stress in several crop species. In this regard, the present study aimed to elucidate how different phosphorus (P) fertilization regimes can improve some bio-physiological processes in tomato plants exposed to Cd stress. In a hydroponic experiment, the impact of two phosphorus fertilizer forms (Polyphosphate (poly-P): condensed P-form with 100% polymerization rate and orthophosphate (ortho-P): from orthophosphoric acid) on the photosynthetic activity, plant growth, and nutrient uptake was assessed under three levels of Cd stress (0, 12, and 25 µM of CdCl2). The obtained results confirmed the negative effects of Cd stress on the chlorophyll content and the efficiency of the photosynthesis machinery. The application of poly-P fertilizer significantly improved the chlorophyll stability index (82%) under medium Cd stress (Cd12), as compared to the ortho-P form (55%). The analysis of the chlorophyll α fluorescence transient curve revealed that the amplitude of Cd effect on the different steps of electron transfer between PSII and PSI was significantly reduced under the poly-P fertilization regime compared to ortho-P, especially under Cd12. The evaluation of the RE0/RC parameter showed that the electron flux reducing end electron acceptors at the PSI acceptor side per reaction center was significantly improved in the poly-P treatment by 42% under Cd12 compared to the ortho-P treatment. Moreover, the use of poly-P fertilizer enhanced iron uptake and its stoichiometric homeostasis in the shoot tissue which maintained an adequate absorption of iron under Cd stress conditions. Findings from this study revealed for the first time that inorganic polyphosphate fertilizers can reduce Cd toxicity in tomato plants by enhancing photosynthesis activity, nutrient uptake, plant growth, and biomass accumulation despite the high level of cadmium accumulation in shoot tissues.

Cell wall as a barrier for protein extraction from tomato leaves: A biochemical study.

Solanum lycopersicum (Tomato) leaves and stems are considered waste. Valorization of this waste can be achieved by for example the extraction of proteins. This prospect is promising but currently not feasible, since protein extraction yields from tomato leaves are low, amongst other due to the (physical) barrier formed by the plant cell walls. However, the molecular aspects of the relationship between cell wall properties and protein extractability from tomato leaves are currently not clear and thus objective of this study. To fill this knowledge gap the biochemical composition of plant cell walls was measured and related to protein extraction yields at different plant ages, leaf positions, and across different tomato accessions, including two Solanum lycopersicum cultivars and the wildtype species S. pimpinellifolium and S. pennellii. For all genotypes, protein extraction yields from tomato leaves were the highest in young tissues, with a decreasing trend towards older plant material. This decrease of protein extraction yield was accompanied by a significant increase of arabinose and galacturonic acid content and a decrease of galactose content in the cell walls of old-vs-young tissues. This resulted in strong negative correlations between protein extraction yield and the content of arabinose and galacturonic acid in the cell wall, and a positive correlation between the content of galactose and protein extraction yield. Overall, these results point to the importance of the pectin network on protein extractability, making pectin a potential breeding target for enhancing protein extractability from tomato leaves.

Quantifying terpenes in tomato leaf extracts from different species using gas chromatography-mass spectrometry (GC-MS).

Terpenes play a vital role in plant defense; tomato plants produce a diverse range of terpenes within specialized glandular trichomes, influencing interactions with herbivores, predators, and pollinators. This study employed two distinct methods, namely leaf dip and maceration, to extract trichomes from tomato leaves. Terpene quantification was carried out using Gas Chromatography-Mass Spectrometry (GC-MS). The leaf dip method proved effective in selectively targeting trichome content, revealing unique extraction patterns compared to maceration. The GC-MS method demonstrated high linearity, accuracy, sensitivity, and low limits of detection and quantification. Application of the method to different tomato species (Solanum pennellii, Solanum pimpinellifolium, Solanum galapagense, Solanum habrochaites, and Solanum lycopersicum) identified significant variation in terpene content among these species, highlighting the potential of specific accessions for breeding programs. Notably, the terpene α-zingiberene, known for its repellency against whiteflies, was found in high quantities (211.90-9155.13 µg g-1) in Solanum habrochaites accession PI209978. These findings provide valuable insights into terpenoid diversity for plant defense mechanisms, guiding future research on developing pest-resistant tomato cultivars. Additionally, the study underscores the broader applications of terpenes in agriculture.

Acyl-CoA synthetase 1 plays an important role on pollen development and male fertility in tomato.

The development of pollen is critical to male reproduction in flowering plants. Acyl-CoA synthetase (ACOS) genes play conserved functions in regulating pollen development in various plants. Our previous work found that knockout of the SlACOS1 gene in tomato might decrease fruit setting. The current study further revealed that SlACOS1 was important to pollen development and male fertility. The SlACOS1 gene was preferentially expressed in the stamen of the flower with the highest expression at the tetrad stage of anther development. Mutation of the SlACOS1 gene by the CRISPR/Cas9-editing system reduced pollen number and viability as well as fruit setting. The tapetum layer exhibited premature degradation and the pollen showed abnormal development appearing irregular, shriveled, or anucleate in Slacos1 mutants at the tetrad stage. The fatty acid metabolism in anthers was significantly impacted by mutation of the SlACOS1 gene. Furthermore, targeted fatty acids profiling using GC-MS found that contents of most fatty acids except C18:1 and C18:2 were reduced. Yeast complementation assay demonstrated that the substrate preferences of SlACOS1 were C16:0 and C18:0 fatty acids. Male fertility of Slacos1 mutant could be slightly restored by applying exogenous palmitic acid, a type of C16:0 fatty acid. Taken together, SlACOS1 played important roles on pollen development and male fertility by regulating the fatty acid metabolism and the development of tapetum and tetrad. Our findings will facilitate unraveling the mechanism of pollen development and male fertility in tomato.

Alternaria diseases on potato and tomato.

Alternaria spp. cause different diseases in potato and tomato crops. Early blight caused by Alternaria solani and brown spot caused by Alternaria alternata are most common, but the disease complex is far more diverse. We first provide an overview of the Alternaria species infecting the two host plants to alleviate some of the confusion that arises from the taxonomic rearrangements in this fungal genus. Highlighting the diversity of Alternaria fungi on both solanaceous hosts, we review studies investigating the genetic diversity and genomes, before we present recent advances from studies elucidating host-pathogen interactions and fungicide resistances. TAXONOMY: Kingdom Fungi, Phylum Ascomycota, Class Dothideomycetes, Order Pleosporales, Family Pleosporaceae, Genus Alternaria. BIOLOGY AND HOST RANGE: Alternaria spp. adopt diverse lifestyles. We specifically review Alternaria spp. that cause disease in the two solanaceous crops potato (Solanum tuberosum) and tomato (Solanum lycopersicum). They are necrotrophic pathogens with no known sexual stage, despite some signatures of recombination. DISEASE SYMPTOMS: Symptoms of the early blight/brown spot disease complex include foliar lesions that first present as brown spots, depending on the species with characteristic concentric rings, which eventually lead to severe defoliation and considerable yield loss. CONTROL: Good field hygiene can keep the disease pressure low. Some potato and tomato cultivars show differences in susceptibility, but there are no fully resistant varieties known. Therefore, the main control mechanism is treatment with fungicides.

Impact of seed priming with Selenium nanoparticles on germination and seedlings growth of tomato.

Poor germination and seedlings growth can lead to significant economic losses for farmers, therefore, sustainable agricultural strategies to improve germination and early growth of crops are urgently needed. The objective of this work was to evaluate selenium nanoparticles (Se NPs) as nanopriming agents for tomato (Solanum lycopersicum) seeds germinated without stress conditions in both trays and Petri dishes. Germination quality, seedlings growth, synergism-antagonism of Se with other elements, and fate of Se NPs, were determined as function of different Se NPs concentrations (1, 10 and 50 ppm). Results indicated that the germination rate in Petri dishes improved with 10 ppm, while germination trays presented the best results at 1 ppm, increasing by 10 and 32.5%, respectively. Therefore, seedlings growth was measured only in germination trays. Proline content decreased up to 22.19% with 10 ppm, while for same treatment, the total antioxidant capacity (TAC) and total chlorophyll content increased up to 38.97% and 21.28%, respectively. Antagonisms between Se with Mg, K, Mn, Zn, Fe, Cu and Mo in the seed were confirmed. In the case of seedlings, the N content decreased as the Se content increased. Transmission Electron Microscopy (TEM) imaging confirmed that Se NPs surrounded the plastids of the seed cells. By this finding, it can be inferred that Se NPs can reach the embryo, which is supported by the antagonism of Se with important nutrients involved in embryogenesis, such as K, Mg and Fe, and resulted in a better germination quality. Moreover, the positive effect of Se NPs on total chlorophyll and TAC, and the negative correlation with proline content with Se content in the seed, can be explained by Se NPs interactions with proplastids and other organelles within the cells, resulting with the highest length and fresh weight when seeds were exposed to 1 ppm.

Knockout of SlDCL2b attenuates the resistance of tomato to potato spindle tuber viroid infection.

RNA interference, or RNA silencing, is an important defence mechanism against viroid infection in plants. Plants encode multiple DICER-LIKE (DCL) proteins that are key components of the RNA silencing pathway. However, the roles of different DCLs in defence responses against viroid infection remain unclear. Here, we determined the function of tomato DCL2b (SlDCL2b) in defence responses against potato spindle tuber viroid (PSTVd) infection using SlDCL2b loss-of-function tomato mutant plants. Compared with wild-type plants, mutant plants were more susceptible to PSTVd infection, developing more severe symptoms earlier and accumulating higher levels of PSTVd RNAs. Moreover, we verified the feedback mechanism for the regulation of SlDCL2b expression by miR6026. Functional blocking of tomato miR6026, by expressing its target mimics, can enhance resistance to PSTVd infection in tomato plants. These findings deepen the current understanding of RNAi-based resistance against viroid infection and provide a potentially new strategy for viroid control.

Causal agents of Stemphylium-induced foliar diseases of tomatoes and other Solanaceae hosts in Brazil.

AIM: An extensive survey was done to clarify the prevalent Stemphylium species on Solanaceae plants across Brazil, and their host ranges. METHODS AND RESULTS: Eighty nine (89) Stemphylium isolates were obtained from naturally infected tomatoes as well as S. paniculatum, potato, eggplant, scarlet eggplant (Solanum aethiopicum var. gilo), Physalis angulata, and Capsicum species. Phylogenetic analyses encompassing the ITS-5.8S rDNA and glyceraldehyde-3-phosphate dehydrogenase genomic regions placed the isolates into two distinct groupings with either Stemphylium lycopersici or S. solani. Isolates of S. lycopersici (n = 81) were obtained infecting tomato, potato, eggplant, S. paniculatum, and P. angulata. Isolates of S. solani (n = 8) were detected in natural association with scarlet eggplant and tomato. Two isolates of S. lycopersici displayed a wide experimental host range in greenhouse bioassays, infecting accessions of 12 out of 18 species. Ocimum basilicum (Lamiaceae) was the only experimental host outside the Solanaceae family.

Genetic structure and population diversity of Phytophthora infestans strains in Pacific western Canada.

Late blight caused by Phytophthora infestans is an economically important disease of potato and tomato worldwide. In Canada, an increase in late blight incidence and severity coincided with changes in genetic composition of P. infestans. We monitored late blight incidence on tomato and potato in Pacific western and eastern Canada between 2019 and 2022, identified genotypes of P. infestans, and examined their population genetic diversity. We identified four major existing genotypes US11, US17, US8, and US23 as well as 25 new genotypes. The US11 genotype was dominant in Pacific western Canada, accounting for 59% of the total population. We discovered the US17 genotype for the first time in Canada. We revealed a higher incidence of late blight and quite diverse genotypes of P. infestans in Pacific western Canada than in eastern Canada. We found high genetic diversity of P. infestans population from Pacific western Canada, as evidenced by the high number of multilocus genotypes, high values of genetic diversity indices, and emergence of 25 new genotypes. Considering the number of disease incidence, the detection of diverse known genotypes, the emergence of novel genotypes, and the high number of isolates resistant to metalaxyl-m (95%) from Pacific western Canada, the region could play a role in establishing sexual recombination and diverse populations, which could ultimately pose challenges for late blight management. Therefore, continuous monitoring of P. infestans populations in Pacific western region and across Canada is warranted. KEY POINTS: • Genotypes of P. infestans in Pacific western were quite diverse than in eastern Canada. • We discovered US17 genotype for the first time in Canada and identified 26 novel genotypes. • Approximately 95% of P. infestans isolates were resistant to metalaxyl-m.

Exogenous application of silicon and selenium improves the tolerance of tomato plants to calcium nitrate stress.

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 µM) 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.