Pepper Seedlings Research Articles

Alleviating effects of exogenous melatonin on nickel toxicity in two pepper genotypes

The excessive accumulation of nickel (Ni) poses a significant threat to global agricultural productivity. In recent years, it has become clear that melatonin (ME) may play a significant role in protecting plants against heavy metal toxicity. This current study investigates the influence of exogenous ME on mitigating the adverse effects of Ni toxicity in pepper plants. The present results revealed that Ni toxicity significantly hindered pepper seedling growth, damaged the leaf photosynthetic system, impaired pigment concentration, and increased phenolic content. In contrast, ME supplementation efficiently restored seedling growth, protected the photosynthetic system, and further increased the phenolic concentration in pepper leaves. In addition, Ni toxicity considerably increased malondialdehyde (MDA) and hydrogen peroxide (H2O2) production and increased antioxidant enzymes [SOD (superoxide dismutase), CAT (catalase), POD (peroxidase), GR (glutathione reductase), APX (ascorbate peroxidase), and GST (glutathione S-transferase)] activity in pepper leaves and roots. Conversely, ME inhibited MDA and H2O2 accumulation and further increased the antioxidant enzyme activity in pepper leaves and roots. Furthermore, ME application restricted Ni accumulation from root to shoot. Collectively, the ME has shown the ability to mitigate the adverse effects of Ni toxicity in pepper plants. The findings of this study will contribute to the understanding and mitigation of the adverse impacts of Ni-induced stress on the growth and development of plants.

Discovery of Novel Small Molecule Growth Inhibitors to Manage Pseudomonas Leaf Spot Disease on Peppers (Capsicum sp.).

Pseudomonas leaf spot (PLS) disease in peppers caused by Pseudomonas syringae pv. syringae (Pss) is an emerging seedborne phytopathogen. Pss infection can severely reduce the marketable yield of peppers in favorable environmental conditions and cause significant economic losses. The intensive use of copper-sulfate and streptomycin-sulfate to control PLS and other bacterial diseases is associated with antimicrobial-resistant Pss strains, making these control methods less effective. So, there is an urgent need to develop novel antimicrobials effective against Pss in peppers. Several studies, including those done in our laboratory, have shown that small molecule (SM) antimicrobials are ideal candidates as they can be effective against multidrug resistant bacteria. Therefore, our study aims to identify novel SM growth inhibitors of Pss, assess their safety, and evaluate their efficacy on Pss-infected pepper seeds and seedlings. Using high-throughput screening, we identified 10 SMs (PC1 to PC10) that inhibited the growth of Pss strains at 200 µM or lower concentrations. These SMs were effective against both copper- and streptomycin-resistant as well as biofilm-embedded Pss. These SMs were effective against other plant pathogens (n = 22) at low concentrations (<200 μM) and had no impact on beneficial phytobacteria (n = 12). Furthermore, these SMs showed better or equivalent antimicrobial activity against Pss in infested pepper seeds and inoculated seedlings compared with copper-sulfate (200 μM) and streptomycin (200 μg/ml). Additionally, none of the SMs were toxic to pepper tissues (seeds, seedlings, or fruits), human Caco-2 cells, and pollinator honeybees at 200 μM. Overall, the SMs identified in this study are promising alternative antimicrobials for managing PLS in pepper production.

Native plant growth promoting rhizobacteria improve the growth of pepper seedlings and modify the phenolic compounds profile

In the establishment of a highly productive pepper crop, obtaining quality seedlings is a decisive step. An alternative to boost rapid plant growth has been the use of plant growth promoting rhizobacteria (PGPR). The study of PGPR and its effect on different plant species has made it possible to establish, among other physiological parameters, a direct correlation between total phenolic compounds and a positive systemic response induced in plants, which could act as growth regulators. The evaluation of the phenolic compound profile and its change in relation to PGPR-pepper seedlings interaction, using liquid chromatography, has scarcely been reported. The aim of the present study was to evaluate changes in the morphology, nitrogen (N) accumulation and the phenolic compounds profile produced by the inoculation of four native PGPR strains: Pseudomonas 42P4, Cellulosimicrobium 60I, Enterobacter 64S1, and Ochrobactrum 53F during the growth of Calahorra pepper seedlings (cv. Calafyuco INTA). Our results showed that all the PGPR tested can promote growth in pepper seedlings. However, Pseudomonas 42P4 and Cellulosimicrobium 60I1 were more effective in increasing N uptake, and improving the morphological, biochemical, and physiological parameters in pepper seedlings. Flavonoids, such as naringenin, naringin, and catechin, could favor growth in plants inoculated with Pseudomonas 42P4, whereas only catechin in Cellulosimicrobium 60I1. The combined effect of gallic acid, hydroxytyrosol, tyrosol, phloridzin, and the exacerbated production of (−)-epigallocatechin gallate may contribute synergistically to limiting the growth of Control seedlings. Finally, PGPR applied in this study could be used as biofertilizers, thereby reducing the use of nitrogen fertilizers, cutting down on production time and cost, and improving the quality of seedlings for horticulturists and nurseries.

Fine mapping and identification of CaTTG1, a candidate gene that regulates the hypocotyl anthocyanin accumulation in Capsicum annuum L.

Pepper (Capsicum annuum L.) is a typical self-pollinating crop with obvious heterosis in hybrids. Consequently, the use of morphological markers during the pepper seedling stage is crucial for pepper breeding. The color of hypocotyl is widely used as a phenotypic marker in crossing studies of pepper. Pepper accessions generally have purple hypocotyls, which are mainly due to the anthocyanin accumulation in seedlings, and green hypocotyls are rarely observed in pepper. Here we reported the characterization of a green hypocotyl mutant of pepper, Cha1, which was identified from a pepper ethyl methanesulfonate (EMS) mutant library. Fine mapping revealed that the causal gene, CaTTG1, belonging to the WD40 repeat family, controlled the green hypocotyl phenotype of the mutant. Virus-induced gene silencing (VIGS) confirmed that CaTTG1 regulated anthocyanin accumulation. RNA-seq data showed that expression of structural genes CaDFR, CaANS, and CaUF3GT in the anthocyanin biosynthetic pathway was significantly decreased in Cha1 compared to the wild type. Yeast two-hybrid (Y2H) experiments also confirmed that CaTTG1 activated the synthesis of anthocyanin structural genes by forming a MBW complex with CaAN1 and CaGL3. In summary, this study provided a green hypocotyl mutant of pepper, and the Kompetitive Allele Specific PCR (KASP) marker developed based on the mutation site of the underlying gene would be helpful for pepper breeding.

Suppression of Phytophthora capsici in Chile Pepper Using Brassica juncea and Hordeum vulgare Cover Crop Residues and Trichoderma harzianum as a Biocontrol Agent.

Phytophthora blight, caused by Phytophthora capsici, is a serious disease of many vegetable crops worldwide. In New Mexico, U.S.A., the disease affects chile pepper (Capsicum annuum L.), a major crop in the state. There is no single tool that effectively controls the disease. Continuous research is needed in identifying combination of tools that can reduce the impact of Phytophthora blight. We explored the potential of combining cover crops and biocontrol agents to reduce soilborne diseases. This study aimed to evaluate the effects of Indian mustard (Brassica juncea L.) cover crop on the antagonistic ability of Trichoderma harzianum against P. capsici in vitro and to quantify the impacts of combining soil amendment with residues from B. juncea and barley (Hordeum vulgare L.) cover crops and plastic covering on infection of chile pepper seedlings by P. capsici under greenhouse conditions. Volatiles from macerated tissue of B. juncea significantly reduced P. capsici and T. harzianum growth in the absence of soil by 89.0 and 79.0%, respectively. When incorporated in soils, volatiles from macerated tissue of B. juncea significantly reduced P. capsici and T. harzianum by 33.4 and 7.8%, respectively. T. harzianum was more resilient to B. juncea biofumigation than P. capsici. Significant reduction in disease incidence was observed with B. juncea-fumigated soil, while no disease suppression was observed with soil incorporation of H. vulgare residues. Covering soil with plastic was necessary for increasing the efficacy of B. juncea biofumigation.

Vegetable Seedlings Production Under Seed Magnetization and Use of Magnetized Water

Objective: This study aimed to evaluate the effects of seed magnetization (SM) and irrigation water (WI), using commercial (CO) and Neodymium (NEO) magnetizers, on the development of seedlings of lettuce, eggplant, cucumber, sweet pepper and okra. Method: The experiment was conducted in a randomized block design, with 5 treatments for each species, with 4 replications, being T1: irrigation with non-magnetized water; T2: SM-NEO + non-magnetized water; T3: SM-CO + non-magnetized water; T4: non-magnetized seeds + WI-NEO; and T5: non-magnetized seeds + WI-CO. The following were evaluated: emergence speed, emergence time, percentage of emergence, dry matter, root length, stem diameter, number of leaves and plant height. Result and conclusion: For lettuce, WI-NEO showed the best results and, for sweet pepper, SM-CO, irrigating with non-magnetized water. For cucumber, SM or WI provided a reduction in seedling formation time. For eggplant and okra, we recommended SM-NEO and irrigated with non-magnetized water. In general, seed magnetization caused better results than irrigation water magnetization. Implications of research: Quality seedlings produced in short time and at low cost are of great importance for the formation of vegetable crops. Originality/value: Seed magnetization and the use of magnetized water are innovative, low-cost technologies for producing seedlings of high vigor and quality.

Exogenous phthalanilic acid induces resistance to drought stress in pepper seedlings (Capsicum annuum L.).

Drought stress (DS) is one of the main abiotic negative factors for plants. Phthalanilic acid (PPA), as a plant growth regulator, can promote the growth and development of crops. In order to evaluate the ideal application concentration and frequency of PPA-induced drought resistance in pepper (Capsicum annuum) seedlings, the concentration of PPA was 133.3 mg·L-1; 200.0 mg·L-1; 266.7 mg·L-1, and some key indicators were investigated, including leaf wilting index (LWI), relative water content (RWC), and malondialdehyde (MDA). We found that the LWI and RWC in the PPA-applied pepper leaves under light drought stress (LDS) and moderate drought stress (MDS) were all elevated, while MDA contents were decreased. To better understand how PPA makes pepper drought resistant, we examined the photosynthetic characteristics, growth parameters, antioxidant activities, and osmotic substances in pepper seedlings treated twice with PPA at a concentration of 133.3 mg·L-1 under LDS, MDS, and severe drought stress (SDS). Results showed that PPA increased the chlorophyll, plant height, stem diameter, root-shoot ratio, and seedling index of pepper leaves under LDS, MDS, and SDS. The net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rates (Tr), and water-use efficiency (WUE) in the PPA-treated pepper leaves under LDS and MDS were improved, while their stomatal limitation (Ls) were reduced. PPA also boosted the activities of enzymatic antioxidants (superoxide dismutase, catalase, and peroxidase), as well as enhanced the accumulation of osmotic substances such as soluble sugar, soluble protein, and free proline in pepper leaves under LDS, MDS, and SDS. Thus, PPA can alleviate the growth inhibition and damage to pepper seedlings caused by DS, and the PPA-mediated efficacy may be associated with the improvement in PPA-mediated antioxidant activities, Pn, and accumulation of osmotic substances.

Entrophospora etunicata: A mycorrhizal biostimulant with the potential to enhance the production of bioactive health-promoting compounds in leaves of Capsicum chinense seedlings

Arbuscular mycorrhizal fungi (AMF) are known to benefit pepper species, but there are no reports of such efficiency in Capsicum chinense, one of the most valuable commercial plant species. Therefore, this study aimed to select an efficient mycorrhizal biostimulant to increase the production of secondary compounds and the antioxidant activity in C. chinense leaves. The experiment was conducted in a greenhouse with four mycorrhizal inoculation treatments (control without AMF, seedlings inoculated with Entrophospora etunicata, Acaulospora longula, and Gigaspora albida). After 120 days, agronomic growth parameters, production of primary and secondary metabolites, and foliar antioxidant activity were evaluated. Capsicum chinense seedlings inoculated with E. etunicata had increases in growth parameters ranging from 27 to 133% compared to the non-inoculated control, depending on the variable considered. Pepper seedlings associated with E. etunicata produced 77%, 147%, 140%, and 136% more soluble carbohydrates, total proanthocyanidins, total phenols, and total saponins, respectively, compared to those not inoculated. Such benefits were also reported for total proteins and total foliar flavonoids. On the other hand, this AMF was ineffective in enhancing the accumulation of alkaloids. It is concluded that E. etunicata is an alternative for improving the production of C. chinense seedlings and enhancing the anabolism of health-promoting bioactive compounds in the phytomass to be offered to the herbal medicine industry. This is the first report on the potential of mycorrhizal inoculation to optimize secondary anabolism in C. chinense leaves.

Exogenously applied melatonin enhanced chromium tolerance in pepper by up-regulating the photosynthetic apparatus and antioxidant machinery

Chromium (Cr) is widely recognized as a highly toxic metal pollutant that adversely affects the agricultural productivity and poses considerable risks to human health. The regulatory role of melatonin (MEL) in Cr stress is well recognized, however, the potential role of MEL in enhancing Cr stress tolerance in pepper is rarely investigated. This study examined the possible effect of MEL in alleviating the adverse effects of Cr toxicity in pepper seedlings. When pepper seedlings were exposed to Cr toxicity, they showed a significant reduction in growth traits, photosynthetic efficiency, root morphological characteristics, and biochemical attributes. Cr treatment greatly caused oxidative damage that was directly related to increased EL, H2O2, O2•−, and MDA production. Conversely, MEL supplementation significantly mitigated the phytotoxic effects of Cr on root morphology, gas exchange elements, and leaf photosynthetic capacity, and restored the growth of pepper seedlings. MEL application stimulated the plant's defense system by enhancing the modulation of antioxidant enzymes, AsA-GSH pools, maintaining the glyoxalase enzymes activity, and reducing oxidative damage. Notably, MEL supplementation significantly reduced Cr accumulation from root to shoot. Hence, MEL supplementation might be regarded as a successful approach for reducing Cr accumulation and its adverse effects in pepper seedlings cultivated in contaminated soils. The research may also provide novel perspectives on the potential application of MEL in mitigating heavy metal toxicity in pepper seedlings.

Physiological quality of ‘biquinho’ pepper seeds as a function of fruit maturation stage

The ‘biquinho’ pepper is important in Brazilian cuisine, and the production of quality seeds is necessary to guarantee the production of seedlings. Thus, the objective of this study was to determine the ideal maturation period for collecting fruits to extract seeds for seedling production, as well as to correlate the main morphological characteristics of ‘biquinho’ pepper seedlings with the Dickson quality index. The experimental design was completely randomized, with four maturation stages (1 - green fruit: completely green exocarp, 2 - orange fruit: orange exocarp, 3 - transition orange - 20% orange and 80% red, 4 - red fruit - red exocarp) and eight repetitions. Ripe fruits were harvested from the tops of three plants according to the maturation stage. Plant height, number of leaves, stem diameter, dry mass of roots and shoots, and Dickson's quality index were evaluated. Seedlings showed higher quality when seeds were collected from fruits in the orange transition stage - 20% orange and 80% red. The traits that correlate positively with Dickson's quality index are plant height, shoot dry matter, and root system dry matter.

Reinforcing Pepper (&lt;em&gt;Capsicum annuum&lt;/em&gt;) Growth by Gypsum and Salicylic Acid under Salinity Stress

Purpose: Salinity stress negatively affects plant growth, which leads to a decline in the food source. Low rainfall and high water evaporation rates in some regions are serious problems in the field of agriculture. In saline soil, plants are unable to absorb water. The aim was to find some amendments to reduce the toxic effects of saline soil. Research Method: In this study, a pot experiment was performed to study the ameliorative role of gypsum (G; 0.38 g per 200 g of soil) and salicylic acid (SA was sprayed on the leaves at two different times) on pepper growth. Two concentrations of NaCl (50mM and 100mM) were used for irrigation every two days. After 18 days, some growth characteristics, including shoot and root length, dry and fresh weight, salt tolerance index, leaf surface area, and chlorophyll content, were evaluated.Findings: The results showed that the application of gypsum alone and with foliar spray of SA was effective in reinforcing the pepper seedlings under salinity stress, regardless of salt concentration. Research limitations: Limited availability of some advanced instruments to collect more data.Originality/value: The investigated ameliorator can be used to improve plant growth under salinity stress.

Zinc oxide nanoparticle morphology modify germination and early growth of bell pepper seedlings

In recent years, interest in nutrient and nanoscale biostimulant use in agriculture to improve seed germination and crop productivity has increased. Nanoparticle seed priming has improved growth and quality in crops of agricultural value. The following study shows the effect of seed priming on bell pepper RZ F1 (35-71) with zinc oxide nanoparticles (ZnO NPs) with different morphology: spherical and hexagonal. Bell pepper seeds were primed with ZnO NPs at different doses, 50 and 100 mg L-1. The study was carried out in two phases. The first phase consisted of an in-vitro study in a germination chamber (28°C), where early growth variables were assessed: germination percentage, radicle, plumule and hypocotyl length; while the second phase was carried out under greenhouse conditions, where variables such as plant height, stem diameter, dry weight, leaf area, total chlorophyll and phenols were assessed, 45 days after sowing. Seed priming with different morphology ZnO NPs showed a positive influence, 100 mg L-1 dose giving the best results for early growth parameters, as well as for plant height, stem diameter, leaf area, total chlorophyll and phenolic content. These results suggest that ZnO NPs can be considered a promising seed preparation agent to improve germination, early growth parameters, and chlorophyll and phenolic contents.

Investigating the impact of TiO2 nanoparticles on bioactive compounds in sweet pepper seedlings: a comparison of foliar and root application methods

Engineered TiO2 nanoparticles (TiO2-NPs) are broadly produced and utilized in various consumer products. However, plant uptake of NPs may lead to disruptions in physiological and metabolic processes, particularly when the plant’s defense mechanisms are overwhelmed. In this study, sweet pepper seedlings were exposed to TiO2-NPs via foliar (2.5% suspension) and root (0.5% suspension) methods, with plants treated with distilled water serving as controls. Results showed that foliar application caused higher accumulation of Ti in leaves as compared to stems, while root exposure led to a higher increase of Ti content in stems than in leaves. Additionally, foliar application led to alterations in chemical composition of the plants, including changes in malondialdehyde (MDA), L-ascorbic acid, total phenolics content, carotenoids, in total antioxidant capacity (TAC) and antioxidant enzymes activity. Root exposure also affected enzyme activity and TAC, but also altered H2O2, MDA and glutathione content. Chlorophylls remained at stable level in the leaves of the seedlings. Overall, these studies provide important information on plant-nanoparticle interactions and the potential effects of different nanoparticle application strategies. These data indicate also that the specific nanoparticles, applied at a controlled manner, have potential to boost the plant metabolism and improve stress tolerance, which is an important factor affecting crops’ quality and productivity.

Study and evaluation of natural zeolite and dried zeolite for the cultivation of friggitello pepper

Research objective: The aim of this research was to evaluate whether differences exist between natural and dried chabazite zeolite in the cultivation of Friggitello peppers Materials and Methods: The experiments, which started in January 2023, were conducted in the CREA-OF greenhouses in Pescia (Pt), Tuscany, Italy (43°54′N 10°41′E) on 'Friggitello' pepper seedlings. The plants were placed in pots with a diameter of 16, 10 plants per 3 replications, for a total of 30 seedlings per experimental thesis. The pepper trial included the following theses (irrigated and fertilised): i) peat 70% + pumice 30%; ii) peat 70% + pumice 10% + natural chabazite zeolite 20%; iii) peat 70% + pumice 10% + dried chabazite zeolite 20%. Plant height, number of leaves, vegetative weight, root volume and length, number of fruits (peppers), fruit weight and the number of microorganisms in the substrate were determined on 18 July 2023. Results and Discussion: The experiment showed that the use of chabazite zeolite can indeed significantly improve the vegetative and root growth and productive and size fruits of Friggitello pepper plants (Table 1). Clear differences in growth are evident between the use of natural zeolite (ZEONAT) and dried zeolite (ZEOESS), with the natural zeolite performing better with regard to all agronomic parameters analysed. In the substrate analysis, a greater presence of microbial biomass was found in the zeolite theses than in the control theses, with greater superiority of microorganisms in the substrate with natural chabsite zeolite. Zeolites are used successfully in the cultivation of many crops. Including cereals, vegetables, grapes and other fruits. By enhancing the absorption ability of soil, zeolite enhance the long-term quality of soil by retaining nutrients. Conclusions: Due to its high absorption rate, cation exchange, catalysis, and dehydration capacity, chabazite is the most common zeolite for agricultural applications. Therefore, zeolite fertilizers are used to improve plant growth by improving their value. Additionally, they can be used as molecular sieves or filters and retain nitrogen in the manure and sludge they produce. For agricultural production, zeolites must have uniform properties and have unique properties such as cation exchange capacity, pH, and B content. Important differences exist between the use of a natural zeolite and a dried one, especially in the significant presence of useful microbiology in the interactions with the plant, in terms of growth and protection.

The Response of Chlorophyll Content and Ionic Composition in Tomato and Pepper Seedlings to Foliar Nutrition in Growing Chambers

Studies have shown that applying specific solutions to the leaves of tomato and pepper plants can boost their output by enhancing nutrient absorption. The factorial analysis of two factors was used in data collection and statistical analysis in this experiment. The first factor was the cultivar (Mobil, Korall, and Tyking F1 for tomatoes, and while cultivars of Carma, Fokusz, and Bobita F1 for sweet pepper), and the second was the spray treatment. Sprays used were sodium bicarbonate (0.52%), 50 mg·L−1 salicylic acid, and distilled water. The parameters collected were the SPAD index of chlorophyll and the plant sap’s content of calcium, potassium, and nitrates, with five observations for each record. Salicylic acid 50 mg·L−1 caused the highest multiple contents, particularly in the tomato cultivar Korall. The lowest multiple contents were for the Mobil cultivar. Spraying Mobil with salicylic acid (50 mg·L−1) and sodium bicarbonate (0.52%) produced the lowest chlorophyll and ionic content. Salicylic acid 50 mg·L−1 also led to the highest multiple values, particularly in the Carma pepper cultivar. The results revealed the multiple lowest contents of measured parameters were for the Bobita F1 cultivar. Finally, gardeners should consider growing Korall tomato and Carma pepper with a supportive spraying application of salicylic acid 50 mg·L−1 before seedlings are transferred to an open-air garden. Gardeners should consider the additional production-improving aspects described in existing research and seed manufacturer recommendations.

Effective citric acid and EDTA treatments in cadmium stress tolerance in pepper (Capsicum annuum L.) seedlings by regulating specific gene expression

Soil contamination with toxic environmental pollutants [such as cadmium (Cd)] is becoming a serious global problem due to rapid development of social economy. To improve the growth and yield of a plant, various chelating agents, such as ethylenediaminetetraacetic acid (EDTA) and citric acid (CA), can be applied to the soil; such application not only increases plant uptake of metals from the soil but also promotes plant absorption of micronutrient fertilizers from the medium. For this purpose, we have conducted a pot experiment using the exogenous application of CA (2.5 mM) and EDTA (2.5 mM) in pepper (Capsicum annuum L.) seedlings grown under the varying levels of Cd (0, 50 and 100 µM) in the soil. M]. Our results depicted that Cd addition to the soil significantly (P < 0.05) decreased plant growth and biomass, gas exchange attributes, and mineral uptake by C. annuum when compared to the plants grown without the addition of Cd. However, Cd toxicity boosted the production of reactive oxygen species (ROS) by increasing the content of malondialdehyde (MDA), which is the indication of oxidative stress in C. annuum, and was also manifested by hydrogen peroxide (H2O2) content and electrolyte leakage to the membrane-bound organelles. The results showed that the activities of various antioxidative enzymes, such as superoxidase dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), and their specific gene expression and also the content of non-enzymatic antioxidants, such as phenolic, flavonoid, ascorbic acid, and anthocyanin, initially increased with an increase in the Cd concentration in the soil. The results also revealed that the levels of soluble sugar, reducing sugar, and non-reducing sugar were decreased in plants grown under elevating Cd levels, but the accumulation of the metal in the roots and shoots of C. annuum, was found to be increased. The negative impacts of Cd injury were reduced by the application of EDTA and CA, which increased plant growth and biomass, improved photosynthetic apparatus, antioxidant enzymes and their gene expression, and mineral uptake, as well as diminished the exudation of organic acids and oxidative stress indicators in C. annuum by decreasing Cd toxicity. Here, we conclude that the application of EDTA and CA under the exposure to Cd stress significantly improved plant growth and biomass, photosynthetic pigments, and gas exchange characteristics; regulated antioxidant defense system and essential nutrient uptake; and balanced organic acid exudation pattern in C. annuum.

Salicylic acid restricts mercury translocation by activating strong antioxidant defense mechanisms in sweet pepper (Capsicum annum L.)

Mercury (Hg) availability in soil and its absorption in plants is seriously concerned for plant production and human health. Salicylic acid (SA) is one of the major plant hormones involved in plant growth and development under biotic and abiotic stress conditions. So, the experiment was designed to assess the effect of SA on sweet pepper (Capsicum annum L.) seedlings grown under different Hg toxicity concentrations. Spraying of 100 μM SA at three different Hg levels, i.e., 0 μM, 50 μM, 100 μM, and 150 μM. The maximum decrease in photosynthetic machinery, plant growth attributes (shoot length, root length, no. of leaves, fresh and dry biomass (shoot and root)), and more accumulation of Hg in leaves, roots, and fruits of sweet pepper. Additionally, SA significantly reduced the reduction in photosynthetic attributes and plant growth, and increased antioxidant enzymes (SOD, POD, and CAT) under Hg toxicity. H2O2 was found to be lower in plants treated with SA under Hg toxicity than in non-treated plants. The SA application also restricts the accumulation of Hg in sweet pepper roots, leaves, and fruits. Hg translocation in leaves and fruits was also reduced under SA. These findings provide a novel perspective on Hg accumulation in sweet pepper. They open a door to identify SA signaling pathways to clarify the mechanisms of SA inhibiting Hg accumulation in leaves and fruits.

Imidacloprid-induced stress affects the growth of pepper plants by disrupting rhizosphere-plant microbial and metabolite composition

Overusing imidacloprid (IMI) has been found to impede secondary metabolism and hinder plant growth. The impact of IMI stress on the interaction between metabolites, rhizosphere, and plant-microbe dispersion through various pathways in pepper plants has not been extensively studied. This study investigated the effects of IMI on plant signaling components, secondary metabolic pathways, and microbial communities in the rhizosphere and phyllosphere. Here, the distribution of IMI and its metabolites (6-chloronicotinic acid, IMI-desnitro, 5-hydroxy-IMI, IMI-urea, and IMI-olefin) was primarily observed in the pepper plant leaves. A rise in IMI concentration had a more significant inhibitive effect on the metabolism of pepper leaves than on pepper roots. The findings of non-target metabolomics indicated that IMI exposure primarily suppresses secondary metabolism in pepper plants, encompassing flavones, phenolic acids, and phytohormones. Notably, the IMI treatment disrupted the equilibrium between plants and microbes by decreasing the population of microorganisms such as Vicinamibacteria, Verrucomicrobiae, Gemmatimonadetes, and Gammaproteobacteria in the phyllosphere, as well as Vicinamibacteria, Gemmatimonadetes, Gammaproteobacteria, and Alphaproteobacteria in the rhizosphere of pepper plants. The study demonstrates that overexposure to IMI harms microbial composition and metabolite distribution in the rhizosphere soil and pepper seedlings, inhibiting plant growth.

Foliar Spraying of Glycine Betaine Alleviated Growth Inhibition, Photoinhibition, and Oxidative Stress in Pepper (Capsicum annuum L.) Seedlings under Low Temperatures Combined with Low Light.

Low temperature combined with low light (LL stress) is a typical environmental stress that limits peppers' productivity, yield, and quality in northwestern China. Glycine betaine (GB), an osmoregulatory substance, has increasingly valuable effects on plant stress resistance. In this study, pepper seedlings were treated with different concentrations of GB under LL stress, and 20 mM of GB was the best treatment. To further explore the mechanism of GB in response to LL stress, four treatments, including CK (normal temperature and light, 28/18 °C, 300 μmol m-2 s-1), CB (normal temperature and light + 20 mM GB), LL (10/5 °C, 100 μmol m-2 s-1), and LB (10/5 °C, 100 μmol m-2 s-1 + 20 mM GB), were investigated in terms of pepper growth, biomass accumulation, photosynthetic capacity, expression levels of encoded proteins Capsb, cell membrane permeability, antioxidant enzyme gene expression and activity, and subcellular localization. The results showed that the pre-spraying of GB under LL stress significantly alleviated the growth inhibition of pepper seedlings; increased plant height by 4.64%; increased root activity by 63.53%; and decreased photoinhibition by increasing the chlorophyll content; upregulating the expression levels of encoded proteins Capsb A, Capsb B, Capsb C, Capsb D, Capsb S, Capsb P1, and Capsb P2 by 30.29%, 36.69%, 18.81%, 30.05%, 9.01%, 6.21%, and 16.45%, respectively; enhancing the fluorescence intensity (OJIP curves), the photochemical efficiency (Fv/Fm, Fv'/Fm'), qP, and NPQ; improving the light energy distribution of PSΠ (Y(II), Y(NPQ), and Y(NO)); and increasing the photochemical reaction fraction and reduced heat dissipation, thereby increasing plant height by 4.64% and shoot bioaccumulation by 13.55%. The pre-spraying of GB under LL stress also upregulated the gene expression of CaSOD, CaPOD, and CaCAT; increased the activity of the ROS-scavenging ability in the pepper leaves; and coordinately increased the SOD activity in the mitochondria, the POD activity in the mitochondria, chloroplasts, and cytosol, and the CAT activity in the cytosol, which improved the LL resistance of the pepper plants by reducing excess H2O2, O2-, MDA, and soluble protein levels in the leaf cells, leading to reduced biological membrane damage. Overall, pre-spraying with GB effectively alleviated the negative effects of LL stress in pepper seedlings.

Diferentes substratos na produção de mudas de pimenta malagueta em Araguatins, Tocantins

The quality of seedling production is an important factor to be considered in a vegetable production system. In view of this, the objective of the study was to evaluate the effect of different alternative organic substrates on the production of chili pepper seedlings in the conditions of Araguatins, Tocantins. The treatments consisted of the following substrates: T1: 100% terra preta, T2: 100% commercial substrate (Basaplant®), T3: 50% terra preta + 50% goat manure, T4: 50% soil black + 50% swine manure, T5: 100% organic compost. The Basaplant® substrate provided lower quality seedlings. Of the alternative substrates, the organic compost provided the best development of pepper seedlings.