Resistant Pepper Research Articles

CaIAA2-CaARF9 module mediates the trade-off between pepper growth and immunity.

To challenge the invasion of various pathogens, plants re-direct their resources from plant growth to an innate immune defence system. However, the underlying mechanism that coordinates the induction of the host immune response and the suppression of plant growth remains unclear. Here we demonstrate that an auxin response factor, CaARF9, has dual roles in enhancing the immune resistance to Ralstonia solanacearum infection and in retarding plant growth by repressing the expression of its target genes as exemplified by Casmc4, CaLBD37, CaAPK1b and CaRROP1. The expression of these target genes not only stimulates plant growth but also negatively impacts pepper resistance to R. solanacearum. Under normal conditions, the expression of Casmc4, CaLBD37, CaAPK1b and CaRROP1 is active when promoter-bound CaARF9 is complexed with CaIAA2. Under R. solanacearum infection, however, degradation of CaIAA2 is triggered by SA and JA-mediated signalling defence by the ubiquitin-proteasome system, which enables CaARF9 in the absence of CaIAA2 to repress the expression of Casmc4, CaLBD37, CaAPK1b and CaRROP1 and, in turn, impeding plant growth while facilitating plant defence to R. solanacearum infection. Our findings uncover an exquisite mechanism underlying the trade-off between plant growth and immunity mediated by the transcriptional repressor CaARF9 and its deactivation when complexed with CaIAA2.

Host status of melon, carrot, and Meloidogyne incognita-susceptible and -resistant cotton, cowpea, pepper, and tomato for M. floridensis from California.

The host status of carrot, melon, and susceptible and resistant cultivars of tomato, cotton, cowpea, and pepper for a California isolate of the peach root-knot nematode Meloidogyne floridensis was determined in greenhouse pot experiments. It was compared to a race 3 isolate of M. incognita. Melon was an excellent host for both isolates and roots were heavily galled after the 8-week trial. Carrot was a host for M. incognita, but a poor host for M. floridensis, although both isolates caused similar levels of galling. Susceptible cotton was a good host for M. incognita race 3, but a poor host for M. floridensis. Susceptible tomato, cowpea, and pepper were good hosts for both isolates. The M. incognita resistance in tomato and pepper was broken by M. floridensis. Resistant cowpea was a maintenance host as population levels of M. floridensis remained virtually unchanged over the trial period. We conclude that M. floridensis poses a risk to some important vegetable crops in California, as it reproduces on most vegetable crops, including some cultivars that are resistant to M. incognita. On susceptible crops, the reproduction of M. floridensis was always significantly less than that of M. incognita, and we hypothesize that in mixed species field populations, M. incognita will outcompete M. floridensis. This study demonstrates that efforts to limit the spread and prevent further introductions of M. floridensis in California are important to maintain the effectiveness of plant resistance as a nematode management strategy in vegetable crops.

Metformin blocks BIK1-mediated CPK28 phosphorylation and enhances plant immunity

IntroductionMetformin (MET), derived from Galega officinalis, stands as the primary first-line medication for the treatment of type 2 diabetes (T2D). Despite its well-documented benefits in mammalian cellular processes, its functions and underlying mechanisms in plants remain unclear. ObjectivesThis study aimed to elucidate MET’s role in inducing plant immunity and investigate the associated mechanisms. MethodsTo investigate the impact of MET on enhancing plant immune responses, we conducted assays measuring defense gene expression, reactive oxygen species (ROS) accumulation, mitogen-activated protein kinase (MAPK) phosphorylation, and pathogen infection. Additionally, surface plasmon resonance (SPR) and microscale thermophoresis (MST) techniques were employed to identify MET targets. Protein-protein interactions were analyzed using a luciferase complementation assay and a co-immunoprecipitation assay. ResultsOur findings revealed that MET boosts plant disease resistance by activating MAPKs, upregulating the expression of downstream defense genes, and fortifying the ROS burst. CALCIUM-DEPENDENT PROTEIN KINASE 28 (CPK28) was identified as a target of MET. It inhibited the interaction between BOTRYTIS-INDUCED KINASE 1 (BIK1) and CPK28, blocking CPK28 threonine 76 (T76) transphosphorylation by BIK1, and alleviating the negative regulation of immune responses by CPK28. Moreover, MET enhanced disease resistance in tomato, pepper, and soybean plants. ConclusionCollectively, our data suggest that MET enhances plant immunity by blocking BIK1-mediated CPK28 phosphorylation.

Unveiling molecular mechanisms of pepper resistance to Phytophthora capsici through grafting using iTRAQ-based proteomic analysis

Phytophthora blight severely threatens global pepper production. Grafting bolsters plant disease resistance, but the underlying molecular mechanisms remain unclear. In this study, we used P. capsici-resistant strain ‘ZCM334’ and susceptible strain ‘Early Calwonder’ for grafting. Compared to self-rooted ‘Early Calwonder’ plants, ‘ZCM334’ grafts exhibited delayed disease onset, elevated resistance, and reduced leaf cell damage, showcasing the potential of grafting in enhancing pepper resistance to P. capsici. Proteomic analysis via the iTRAQ technology unveiled 478 and 349 differentially expressed proteins (DEPs) in the leaves and roots, respectively, between the grafts and self-rooted plants. These DEPs were linked to metabolism and cellular processes, stimulus responses, and catalytic activity and were significantly enriched in the biosynthesis of secondary metabolites, carbon fixation in photosynthetic organizations, and pyruvate metabolism pathways. Twelve DEPs exhibiting consistent expression trends in both leaves and roots, including seven related to P. capsici resistance, were screened. qRT-PCR analysis confirmed a significant correlation between the protein and transcript levels of DEPs after P. capsici inoculation. This study highlights the molecular mechanisms whereby grafting enhances pepper resistance to Phytophthora blight. Identification of key genes provides a foundation for studying the regulatory network governing the resistance of pepper to P. capsici.

Comparative Transcriptomics Analysis Reveals the Differences in Transcription between Resistant and Susceptible Pepper (Capsicum annuum L.) Varieties in Response to Anthracnose.

Pepper (Capsicum annuum L.) is a herbaceous plant species in the family Solanaceae. Capsicum anthracnose is caused by the genus Colletotrichum. spp., which decreases pepper production by about 50% each year due to anthracnose. In this study, we evaluated the resistance of red ripe fruits from 17 pepper varieties against anthracnose fungus Colletotrichum capsici. We assessed the size of the lesion diameter and conducted significance analysis to identify the resistant variety of B158 and susceptible variety of B161. We selected a resistant cultivar B158 and a susceptible cultivar B161 of pepper and used a transcription to investigate the molecular mechanisms underlying the plant's resistance to C. capsici, of which little is known. The inoculated fruit from these two varieties were used for the comparative transcription analysis, which revealed the anthracnose-induced differential transcription in the resistant and susceptible pepper samples. In the environment of an anthrax infection, we found that there were more differentially expressed genes in resistant varieties compared to susceptible varieties. Moreover, the response to stimulus and stress ability was stronger in the KANG. The transcription analysis revealed the activation of plant hormone signaling pathways, phenylpropanoid synthesis, and metabolic processes in the defense response of peppers against anthracnose. In addition, ARR-B, AP2-EREBP, bHLH, WRKY, and NAC are associated with disease resistance to anthracnose. Notably, WRKY and NAC were found to have a potentially positive regulatory role in the defense response against anthracnose. These findings contribute to a more comprehensive understanding of the resistance mechanisms of red pepper fruit to anthracnose infection, providing valuable molecular insights for further research on the resistance mechanisms and genetic regulations during this developmental stage of pepper.

Effect of Salicylic Acid and Calcium on Growth, Yield, and Fruit Quality of Pepper (Capsicum annuum L.) Grown Hydroponically

The aim of this study was to investigate the effects of spraying plants with 0.03% salicylic acid (SA), 0.7% calcium nitrate (Ca), and 0.03% salicylic acid together with 0.7% calcium nitrate (SA + Ca) on plant growth, yield, and fruit quality of peppers grown in a mineral wool substrate. The control plants were sprayed with water (C). Two red-fruited sweet pepper cultivars were used in the study: ‘Aifos’, and ‘Palermo’, which produce fruits characterized by different shapes. Biometric measurements of the plants showed a higher growth rate of pepper plants when SA and Ca were applied foliarly compared to the control. Plants treated simultaneously with SA and Ca were characterized by the highest steady-state fluorescence yield [Fs]. The relative chlorophyll content of pepper leaves was also higher in plants sprayed with SA, Ca, and SA + Ca than in plants in the control. The analysis of pepper yield showed in both cultivars the effect of foliar treatment of plants with SA and Ca and SA + Ca on increasing pepper resistance to the occurrence of Ca deficiency on pepper fruit (Blossom end rot). Pepper fruits harvested from plants treated with SA, Ca, and SA + Ca had more juicy flesh.

Evaluation of Hot Pepper (Capsicum annuum L.) Genotypes for Yield and Quality in Mid-hills of Bagmati Province, Nepal

The study was carried out to evaluate and select high yielding, insect pest and disease resistant hot pepper genotypes with preferred characters at open field conditions for central mid-hills of Nepal in 2018 and 2019. Seedlings of six hot pepper genotypes AVPP9905, AVPP9813, AVPP0506, Suryamukhi, Pusa Jwala and Kantipure were transplanted on April first week at Khumaltar, Lalitpur. Crop geometry was maintained with the 60 x 60 cm in randomized complete block design with three replications and fertilized with 150:120:100 NPK kg + 20 ton FYM per hectare. Observations were recorded on vegetative growth, insect pest and disease, yield attributing parameter and response of consumers and farmers. Among the tested genotypes, AVPP9905 showed superior performance that was vigoros, earliest days to flowering (41) and fruit set (47 days), least insect damage (2.0), least disease; alternaria leaf spot (1.8 ), higher number of fruits per node (1.25), superior yield (26.19 t/ha) and 960 g per plant. Consumers and farmers preference were 4.4 and 4.5.and the maximum fruit size was 18.7 g. The second superior cultivar was AVPP0506 which showed vigor (4.0), medium days to flowering (44.3) and fruit set (49 days), less insect damage (2.2), less disease; alternaria leaf spot (2.1), higher number of fruits per node (1.3), superior yield (14.28 t/ha) and 548 g per plant, consumers (3.8) and farmers preferred (4.8). Hence it could be generalized that introduced genotypes from the world Vegetable Centre, Taiwan were more promising than local check cultivars (Pusa Jwala and Kantipure) in terms of growth, fruit yield and insect pest and disease resistance, and farmers and consumers preference. These two genotypes are recommended for cultivation in central mid-hills of Bagmati Province in open field conditions.

Host suitability of pepper cultivars to (a)virulent root-knot nematodes isolates

Root-knot nematodes (RKNs) are polyphagous and cause yield losses to crops worldwide. Using the resistant plant is the most effective and environmental method to manage RKNs. Mi-1.2 gene in tomatoes is commonly used to control Meloidogyne. However, the Mi-1.2-virulent isolates can overcome this gene. In fields infested with Mi-1.2-virulent populations, plant species with different resistance genes are recommended instead of tomatoes. Therefore, investigating the host suitability of pepper cultivars to Mi-1.2-virulent RKNs is needed for management practices. This study was conducted in Akdeniz University Faculty of Agriculture Department of Plant Protection Nematology Laboratory in 2019. In this study, the response of resistant and susceptible pepper cultivars was investigated to Meloidogyne incognita (Kofoid & White,1919), Chitwood, 1949, Meloidogyne javanica (Treub, 1885) Chitwood, 1949, Meloidogyne arenaria (Neal, 1889) Chitwood, 1949, Meloidogyne luci Carneiro et al., 2014 (Tylenchida: Meloidogynidae), Mi-1.2-virulent M. incognita and Mi-1.2-virulent M. javanica. Meloidogyne arenaria, M. incognita and Mi-1.2-virulent M. incognita isolates multiplied very well on susceptible peppers but did not reproduce on resistant peppers. Mi-1.2-(a)virulent M. javanica isolates did not multiply on any pepper cultivars. Meloidogyne luci reproduced on all peppers tested. A pepper carrying N resistance gene was first tested with M. luci and did not confer resistance to M. luci. These results could be used to control RKNs in vegetable-growing areas.

Enhancing chili pepper (Capsicum annuum L.) resistance and yield against powdery mildew (Leveillula taurica) with beneficial bacteria

BackgroundLeveillula taurica is an obligate pathogen that causes powdery mildew on chili pepper (Capsicum annuum L.) which is considered one of the most serious diseases for the crop.ResultsLeveillula taurica was isolated from infected pepper plants in Assiut Governorate, Egypt. Pathogenicity test was performed, and it was found that the pathogen can cause the symptoms of powdery mildew on the pepper plant. Under greenhouse conditions, treatment with Bacillus thuringiensis MW740161.1, Pseudomonas fluorescens, and Bacillus subtilis cultures resulted in a significant reduction in conidial germination of the pathogen (69.07, 29.55, and 19.58%, respectively). Spraying chili pepper plants with the microorganisms effectively reduced the powdery mildew's disease severity. Also, treatment with the bacterial strains resulted in a significant (P 0.05%) increase in the yield of chili pepper. Based on the findings, it appears that the use of B. thuringiensis, as foliar spraying, significantly induced resistance of chili pepper plants against L. taurica and stimulated many biochemical functions in the plant. Also, it increased the crop yield compared to all other treatments.ConclusionsThis study recommends B. thuringiensis as a viable alternative to harmful pesticides, and it is feasible to formulate an appropriate fungicide for the sustainable green production of chili peppers. The B. thuringiensis can increase the resistance of chili pepper plant to L. taurica the causal pathogen of powdery mildew.

Nitrate content in roots of pepper seedlings exposed to Phytophthora capsici

Phytophthora capsici causes root rot, a deadly plant disease. Resistance to diseases is produced by the activation of many defense substances, so knowledge of this natural defense mechanism allows the development of new strategies for disease control. In this study, the response of nitrate (NO3-), which is effective in plant growth and development, in different pepper genotypes exposed to pathogen infection was investigated. For this, resistant and sensitive pepper genotypes were exposed to 102, 103, and 104 zoospore/mL of P. capsici-22 strain and changes in NO3- content were determined from root samples taken on the 2nd, 4th and 6th days after infection. All zoospore concentrations resulted in an overall increase in NO3- content in roots of CM-334 on all days. In KM-181 and SD-8 genotypes, the highest NO3- content was determined on the 6th day of 103 zoospore/mL application. In SD-8 and KM-181 genotypes, a significant decrease in the amount of NO3- was determined on the 4th and 6th days of treatment of 104 zoospore/mL. In these genotypes, a decrease in the amount of NO3- was found with the increase in infection time at high zoospore concentration. When the three pepper genotypes were compared, the highest NO3- content was determined in the resistant CM-334 genotype, which was exposed to 104 zoospore/mL on the 6th day following the infection. In this study, changes in the amount of NO3- in resistant and susceptible pepper genotypes indicated that NO3- may be effective in plant defense against P. capsici-22.

Transcriptome and metabolome analyses revealed the response mechanism of pepper roots to Phytophthora capsici infection

BackgroundPhytophthora root rot caused by the oomycete Phytophthora capsici is the most devastating disease in pepper production worldwide, and current management strategies have not been effective in preventing this disease. Therefore, the use of resistant varieties was regarded as an important part of disease management of P. capsici. However, our knowledge of the molecular mechanisms underlying the defense response of pepper roots to P. capsici infection is limited.MethodsA comprehensive transcriptome and metabolome approaches were used to dissect the molecular response of pepper to P. capsici infection in the resistant genotype A204 and the susceptible genotype A198 at 0, 24 and 48 hours post-inoculation (hpi).ResultsMore genes and metabolites were induced at 24 hpi in A204 than A198, suggesting the prompt activation of defense responses in the resistant genotype, which can attribute two proteases, subtilisin-like protease and xylem cysteine proteinase 1, involved in pathogen recognition and signal transduction in A204. Further analysis indicated that the resistant genotype responded to P. capsici with fine regulation by the Ca2+- and salicylic acid-mediated signaling pathways, and then activation of downstream defense responses, including cell wall reinforcement and defense-related genes expression and metabolites accumulation. Among them, differentially expressed genes and differentially accumulated metabolites involved in the flavonoid biosynthesis pathways were uniquely activated in the resistant genotype A204 at 24 hpi, indicating a significant role of the flavonoid biosynthesis pathways in pepper resistance to P. capsici.ConclusionThe candidate transcripts may provide genetic resources that may be useful in the improvement of Phytophthora root rot-resistant characters of pepper. In addition, the model proposed in this study provides new insight into the defense response against P. capsici in pepper, and enhance our current understanding of the interaction of pepper–P. capsici.

Preservation effect of Lactobacillus plantarum O2 fermentation supernatant on postharvest pepper and its induced resistance to Phytophthora capsici

Research of lactic acid bacteria and its metabolites on biological preservatives becomes a hot topic. Lactobacillus plantarum O2, with good inhibition on Phytophthora capsici (P. capsici), was isolated from the pickle. In this study, the effects of L. plantarum O2 fermentation supernatant (FS) on pepper postharvest preservation and its induced resistance to P. capsici were studied. Results showed that weight loss rate, rot index, respiration rate, relative electrical conductivity, loss of chlorophyll content and VC of pepper in FS treatment group were decreased by 18 %, 64 %, 15 %, 26 %, 33 % and 20 % compared with blank control (BC) after 20 d storage. L* and b*-value of pepper in FS group were lower than those in the BC group. In addition, the damage-induced resistance test found that the infection rate in the FS group was reduced by 39 %, compared with CK2 after 12 d storage. Moreover, phenylalanine ammonia-lyase activity, peroxidase activity, polyphenol oxidase activity, proline content, total phenol content and flavonoid content increased by 14 %, 9 %, 30 %, 8 %, 8 % and 9 %, respectively, while malondialdehyde content decreased by 13 %. These results indicated that FS treatment showed good fresh-keeping effects on postharvest pepper. It could enhance the tolerance of pepper under stress by improving defensive enzyme activities, slowing down the damage caused by P. capsici, and inducing pepper resistance to P. capsici. Therefore, FS can be used as a microbial source bio-preservative for postharvest pepper.

Red light induces salicylic acid accumulation by activating CaHY5 to enhance pepper resistance against Phytophthora capsici.

Pepper (Capsicum annuum L.) is frequently challenged by various pathogens, among which Phytophthora capsici is the most devastating to pepper production. Red light signal acts as a positive induction of plant resistance against multiple pathogens. However, little is known about how the red light signal affects pepper resistance to P. capsici infection (PCI). Here, we report that red light regulates salicylic acid (SA) accumulation by activating elongated hypocotyl5 (CaHY5), a basic leucine zipper (bZIP) transcription factor, thereby decreasing pepper susceptibility to PCI. Exogenous SA treatment reduced pepper susceptibility to PCI, while silencing of CaPHYB (a red light photoreceptor) increased its susceptibility. PCI significantly induced CaHY5 expression, and silencing of CaHY5 reduced SA accumulation, accompanied by decreases in the expression levels of phenylalanine ammonia-lyase 3 (CaPAL3), CaPAL7, pathogenesis-related 1 (CaPR1), and CaPR1L, which finally resulted in higher susceptibility of pepper to PCI. Moreover, CaHY5 was found to activate the expression of CaPAL3 and CaPAL7, which are essential for SA biosynthesis, by directly binding to their promoters. Further analysis revealed that exogenous SA treatment could restore the resistance of CaHY5-silenced pepper plants to PCI. Collectively, this study reveals a critical mechanism through which red light induces SA accumulation by regulating CaHY5-mediated CaPAL3 and CaPAL7 expression, leading to enhanced resistance to PCI. Moreover, red light-induced CaHY5 regulates pepper resistance to PCI, which may have implications for PCI control in protected vegetable production.

Induced Resistance Mechanism of Bacillus velezensis S3-1 Against Pepper Wilt.

In recent years, pepper wilt has emerged as a pivotal constraint on pepper yield augmentation. Bacillus velezensis S3-1, with a wide array of hosts, can be used as both a biocontrol agent and biofertilizer. Nonetheless, the precise mechanisms underpinning its employment in combating pepper wilt remain cloaked in ambiguity. In our study, we found that B. velezensis S3-1 could significantly inhibit Fusarium sp. F1T that caused pepper wilt. S3-1 could effectively inhibit both the growth and germination of F1T conidia, leading to a reduction in the spore germination percentage from 83.2 to 37.1% in vitro experiments. Additionally, leaf detachment experiments revealed that the volatile compounds produced by S3-1 could inhibit the spread of pepper leaf spot area. Moreover, we observed a significant decrease in the content of malondialdehyde (MDA) in pepper treated with S3-1, along with a significant increase in the content of soluble protein, polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL) in pepper. Furthermore, RT-PCR analysis showed that the expression of the defense genes CaPR 1 and CaPIN II in pepper after treatment with S3-1 was significantly upregulated, suggesting that S3-1 had the potential to induce systemic resistance in pepper, thereby enhancing its disease resistance. Hence, our findings suggest that S3-1 can be a promising biocontrol agent for managing pepper wilt in modern agriculture.

Integrated Transcriptome and Metabolome Analysis Reveals the Molecular Mechanism of Rust Resistance in Resistant (Youkang) and Susceptive (Tengjiao) Zanthoxylum armatum Cultivars.

Chinese pepper rust is a live parasitic fungal disease caused by Coleosporium zanthoxyli, which seriously affects the cultivation and industrial development of Z. armatum. Cultivating and planting resistant cultivars is considered the most economical and environmentally friendly strategy to control this disease. Therefore, the mining of excellent genes for rust resistance and the analysis of the mechanism of rust resistance are the key strategies to achieve the targeted breeding of rust resistance. However, there is no relevant report on pepper rust resistance at present. The aim of the present study was to further explore the resistance mechanism of pepper by screening the rust-resistant germplasm resources in the early stage. Combined with the analysis of plant pathology, transcriptomics, and metabolomics, we found that compared with susceptible cultivar TJ, resistant cultivar YK had 2752 differentially expressed genes (DEGs, 1253 up-, and 1499 downregulated) and 321 differentially accumulated metabolites (DAMs, 133 up- and 188 down-accumulated) after pathogen infection. And the genes and metabolites related to phenylpropanoid metabolism were highly enriched in resistant varieties, which indicated that phenylpropanoid metabolism might mediate the resistance of Z. armatum. This finding was further confirmed by a real-time quantitative polymerase chain reaction analysis, which revealed that the expression levels of core genes involved in phenylpropane metabolism in disease-resistant varieties were high. In addition, the difference in flavonoid and MeJA contents in the leaves between resistant and susceptible varieties further supported the conclusion that the flavonoid pathway and methyl jasmonate may be involved in the formation of Chinese pepper resistance. Our research results not only help to better understand the resistance mechanism of Z. armatum rust but also contribute to the breeding and utilization of resistant varieties.

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.

Effects of Potassium and Nanocapsule of Potassium on Pepper Growth and Physiological Changes in High-Temperature Stress

Abiotic stresses have been observed to cause alterations in the morphology, physiology, and biochemistry of plants. However, in recent years, the utilization of nanocompounds has emerged as a strategy to induce modifications in multiple facets of plant biology. These modifications include plant growth, nutrient absorption, the production of significant secondary metabolites, and the improvement of plants’ resistance against both abiotic and biotic stress factors. A completely randomized factorial experiment with 12 replications was created. Potassium sources including control, potassium (K), and nanocapsule-potassium (N-K) with concentration 1 µM and temperature treatments including control temperature (25 °C) and high-temperature stress (35 °C) were applied as treatments. In the control treatment, proline was increased at the high temperature, whereas proline was reduced at both treated temperatures by K and N-K. High temperature raised electrolyte leakage (EL), which peaked in the control treatment but was lowered by K and N-K. Temperature-dependent increase in glucose and fructose was observed in control and K treatments when the temperature was 35 °C, but no significant difference was observed between different levels of K at 35 °C. When K was not applied at high temperatures, the main stress indicators such as antioxidant activity (DPPH) and malondialdehyde (MDA) rose significantly, as did the water potential and linoleic acid. When high temperatures were applied, nanocapsule-potassium applied in high temperatures had the lowest stress indices. In conclusion, stress indices diminish when nanocapsule-potassium is applied under high temperatures. Additionally, nanocapsule-potassium applied at high temperatures was preferable to K applied at high temperatures in terms of pepper growth and resistance measures. Likewise, the application of nanocapsule-potassium at high temperatures alters the fatty acid composition of membranes and antioxidant enzymes.

Genome-wide association study of resistance to anthracnose in pepper (Capsicum chinense) germplasm

BackgroundAnthracnose is a fungal disease caused by Colletotrichum spp. that has a significant impact on worldwide pepper production. Colletotrichum scovillei is the most common pathogenic anthracnose-causing species in the Republic of Korea.ResultsThe resistances of 197 pepper (Capsicum chinense) accessions deposited in Korea’s National Agrobiodiversity Center were evaluated for their response against the virulent pathogens Colletotrichum acutatum isolate ‘KSCa-1’ and C. scovillei isolate ‘Hana’) in the field and in vitro methods for three consecutive years (2018 to 2020). The severity of the disease was recorded and compared between inoculation methods. Six phenotypically resistant pepper accessions were selected based on three years of disease data. All of the selected resistant pepper accessions outperformed the control resistant pepper in terms of resistance (PI 594,137). A genome-wide association study (GWAS) was carried out to identify single nucleotide polymorphisms (SNPs) associated with anthracnose resistance. An association analysis was performed using 53,518 SNPs and the disease score of the 2020 field and in vitro experiment results. Both field and in vitro experiments revealed 25 and 32 significantly associated SNPs, respectively. These SNPs were found on all chromosomes except Ch06 and Ch07 in the field experiment, whereas in the in vitro experiment they were found on all chromosomes except Ch04 and Ch11.ConclusionIn this study, six resistant C. chinense accessions were selected. Additionally, in this study, significantly associated SNPs were found in a gene that codes for a protein kinase receptor, such as serine/threonine-protein kinase, and other genes that are known to be involved in disease resistance. This may strengthen the role of these genes in the development of anthracnose resistance in Capsicum spp. As a result, the SNPs discovered to be strongly linked in this study can be used to identify a potential marker for selecting pepper material resistant to anthracnose, which will assist in the development of resistant varieties.

PERBANDINGAN KETAHANAN DAUN CABAI RAWIT DAN TOMAT TERHADAP SERANGAN Thrips sp. BERBASIS PENGOLAHAN CITRA DIGITAL

The presence of thrips pests that attack the leaves of cayenne pepper and tomato can cause high yield losses in both crops. Plant resistance to thrips is thought to be related to the pest's preference for plant leaves. The difference in the resistance level of the two plants to thrips attack needs to be studied based on a digital image processing approach as an accurate method of assessing plant damage. This study compares the resistance of cayenne pepper and tomato leaves to thrips attack based on digital image processing. The study was designed for feed testing with the option of using cayenne pepper and tomato leaves as treatments that were placed in pairs in a testing container. There were five pairs of tests for the first and second repetitions, respectively, and each pair of tests used five individual thrips. The results showed tomato leaves were relatively more resistant to thrips attack because they tended to be less preferred than cayenne pepper. The average area of thrips attack on cayenne pepper leaves for two repetitions of testing was higher than tomato. The assessment of the extent of thrips attack tomato and cayenne pepper leaves based on image processing has high validity, characterized by the accuracy and precision of the assessment results, which reach 80-100%. However, the reliability of the assessment results for two repetitions of testing is still relatively low, especially in assessing damage to cayenne pepper leaves.

Screening native pepper, Tasmannia lanceolata (Poir.) A.C. Smith, for resistance against Phytophthora cinnamomi dieback

Tasmannia lanceolata (native pepper) has been reported as susceptible to Phytophthora cinnamomi and the objective of this study was to identify variability in native pepper resistance to P. cinnamomi. Plant material was collected from native pepper populations across Tasmania (four regions) and selected commercially grown cultivars, and 47 clones were successfully propagated. Two disease screening experiments were conducted in “soil-free plant growth system” (SPS) units. Native pepper roots were inoculated with P. cinnamomi zoospores and maintained in controlled conditions. After one week, the pathogen was re-isolated to confirm infection success, and after two weeks root discolouration was visually assessed with images, which were then analysed with an automated machine learning system, using colour thresholds. The SPS was a successful approach to screen the early response of native pepper to P. cinnamomi. Based on pathogen re-isolation success and total root discolouration percentage, clones were categorised using a susceptibility rating method across multiple categories from highly resistant to highly susceptible. In the first experiment, all 47 propagated clones were challenged with one isolate of P. cinnamomi (Pc1), and pathogen re-isolation percentage and total root discolouration (brown and black) percentage differed significantly with clone (P < 0.001). In the second experiment, three representative clones of experiment 1 were challenged with two isolates of P. cinnamomi (Pc1 and Pc2) and clone response was similar. This study has highlighted that there is a range of responses to P. cinnamomi, from highly susceptible to highly resistant, in native pepper clones from different regions of Tasmania.