Capsicum Species Research Articles

Anthocyanin Content in the Capsicum Species Fruits Correlates with Expression Levels of Flavonoid Pathway Structural and Regulatory Genes

In fruits of cultivars of pepper species Capsicum annuum (Sirenevyi Cub), C. frutescens (Samotsvet) and C. chinense (Pimenta da Neyde), which differ in the pigmentation profile during maturation, the content of anthocyanins and the expression pattern of the structural and regulatory genes of anthocyanin biosynthesis were determined. Anthocyanins were found in the fruit of the Sirenevyi Cub cultivar as well as in the peel and pulp of Samotsvet and Pimenta da Neyde cultivars. In the peel of the fruits of all three analyzed cultivars, the levels of expression of structural genes for the biosynthesis of anthocyanins are two or more times higher than in the pulp. In cv. Samotsvet and Pimenta da Neyde, the expression in the pulp of CHS, F35H, DFR, ANS, and UFGT are higher than that of cv. Sirenevyi Cub. The cv. Pimenta da Neyde is characterized by a high expression of structural genes in the pulp and peel of ripe fruit. Expression of transcription factor genes anthocyanin2 (R2R3-MYB) and MYC (bHLH) was detected in the peel of fruits of cv. Sirenevyi Cub as well as in the peel and pulp of fruits of cv. Samotsvet and Pimenta da Neyde at all the analyzed stages of ripening. For all structural genes of the anthocyanin biosynthesis pathway, a high correlation was found (r = 0.54‒0.93) between the expression levels of all anthocyanin biosynthesis structural genes and anthocyanin content in fruits. High correlation (r = 0.88) is also shown for MYC. For the anthocyanin2, correlation (r = 0.85) is present only for cv. Sirenevyi Cub and Pimenta da Neyde but not for cv. Samotsvet.

SEED VIABILITY, GERMINATION, AND SEEDLING GROWTH OF CAPSICUM CULTIVATED SPECIES

Seed viability of domesticated and cultivated Capsicum species: Capsicum annuum L., Capsicum baccatum L., Capsicum chinense Jacq., Capsicum frutescens L., and Capsicum pubescens Ruiz and Pav. was tested by the tetrazolium method. The seeds were soaked in three tetrazolium salt solutions of 1, 0.5 and 0.2%, and temperature conditions of 30 - 35 C for 3 h. The percentage of seeds stained in relation to the total number of seeds was evaluated. To estimate germination, the seeds were subjected to chemical treatments with gibberellic acid (GA3) at doses of 0, 100, 200, 300, and 400 mg L-1 at room temperature for 24 h. The germination rate was estimated, while plant height was evaluated at 10, 20 and, 30 days after sowing (DAS). Capsicum seed viability fluctuated between 52.44% and 97.11%. The highest percentage of viability was obtained with the 1% dose of tetrazolium (81.63%), while the 0.2% dose resulted in the lowest average value (63.7%). In addition, C. annuum, C. baccatum and C. chinense showed high staining patterns, while most of the observed patterns in C. frutescens corresponded to non-viable seeds. After GA3 application, average seed germination was 100% in C. chinense; 75.6% in C. baccatum; 73.32% in C. annuum; and 61.5% in C. frutescens. However, the application of GA3 did not cause an additional effect on the germination of Capsicum seeds. The highest plant height at 30 DAS was observed in accessions of C. annuum (9.08 cm), while C. chinense presented the lowest value (4.49 cm).

Investigation on genetic diversity of pepper (Capsicum spp.) parents and interspecific hybrids using ISSR markers

Pepper (Capsicum) is one of the most important and widespread vegetable crops in the Balkans. Some old indigenous forms are not the focus of modern breeding but are preserved in some areas and represent valuable genetic resources. Three Bulgarian varieties (Plovdivska kapiya, Familiya and IZK Delicates) C. annuum, and two representatives of the chili pepper C. chinense and C. frutescens. Interspecific hybrids were made between sweet (C. annum) and chili pepper plants. The genetic relationships of the varieties of Capsicum species were assessed using ISSR primers. PCR amplification of isolated DNA from parental lines and interspecific hybrids revealed 65 distinct polymorphic bands. Cluster analysis clearly distinguished the parental forms and individuals from the F1 and F2 populations. The applied ISSR molecular technique can be successfully used to analyze genetic diversity in cultivars, early-stage seedlings, and interspecific hybrids, as well as to detect differences in individuals whose genomes are highly homogeneous, such as those of the genus Capsicum.

Inheritance of Unilateral Incompatibility in the Genus Capsicum

Unilateral incompatibility is reported to occur between the species of Capsicum pubescens complex (Capsicum cardenasii Capsicum. eximium and Capsicum pubescens) and other species of genus Capsicum when the latter are used as the male parent. The relationship between self-incompatibility and unilateral incompatibility are yet to be resolved even in the most intensively investigated crosses within and between species of Lycopersicon and Solanum. Unilateral incompatibility in Capsicum has been less intensively studied compared to some other genus in family Solanaceae. This study was, therefore, conducted to help us to understand the genetic control of unilateral incompatibility in Capsicum. Experiment results showed that while the pistil behaviour of F1 hybrids agrees with the pistil behaviour of F1 hybrids from unilaterally incompatible crosses in other genera of Solanaceae, the pollen behaviour does not agree with data obtained from other genera of Solanaceae. No segregation ratio was obtained for unilateral incompatibility in the backcross progenies, this result does not agree with data from other genera in the Solanaceae either. Possible reasons for not obtaining segregation for unilateral incompatibility may be the small size of backcross progenies and/or distorted segregation ratios. As a conclusion it seemed more probable that, in Capsicum, unilateral incompatibility has arisen as a by-product of genetic divergence between the C. pubescens complex and the other chile peppers, not as a product of natural selection.

Chromosome-scale genome assembly of a Japanese chili pepper landrace, Capsicum annuum 'Takanotsume'.

Here, we report the genome sequence of a popular Japanese chili pepper landrace, Capsicum annuum 'Takanotsume'. We used long-read sequencing and optical mapping, together with the genetic mapping technique, to obtain the chromosome-scale genome assembly of 'Takanotsume'. The assembly consists of 12 pseudomolecules, which corresponds to the basic chromosome number of C. annuum, and is 3,058.5 Mb in size, spanning 97.0% of the estimated genome size. A total of 34,324 high-confidence genes were predicted in the genome, and 83.4% of the genome assembly was occupied by repetitive sequences. Comparative genomics of linked-read sequencing-derived de novo genome assemblies of two Capsicum chinense lines and whole-genome resequencing analysis of Capsicum species revealed not only nucleotide sequence variations but also genome structure variations (i.e. chromosomal rearrangements and transposon-insertion polymorphisms) between 'Takanotsume' and its relatives. Overall, the genome sequence data generated in this study will accelerate the pan-genomics and breeding of Capsicum, and facilitate the dissection of genetic mechanisms underlying the agronomically important traits of 'Takanotsume'.

The capsaicinoid nonivamide suppresses the inflammatory response and attenuates the progression of steatosis in a NAFLD-rat model.

Nonalcoholic fatty liver disease (NAFLD) is relatively associated with comorbidities in obesity and metabolic inflammation. Low-grade inflammation following the high-fat diet (HFD)-induced NAFLD can promote the development of nonalcoholic steatohepatitis (NASH) through particularly liver-resident immune cell recruitment and hepatic nuclear factor kappa B (NF-κB) pathway. Therefore, inflammatory intervention may contribute to NASH reduction. Pelargonic acid vanillylamide (PAVA) or nonivamide is one of the pungent capsaicinoids of Capsicum species and has been found in chili peppers. Our previous study demonstrated that PAVA improved hepatic function, decreased oxidative stress and reduced apoptotic cell death but the insight role of PAVA on NAFLD is still unclear. Thus, this study aimed to investigate the underlying anti-inflammatory mechanism of PAVA in an NAFLD-rat model. Male Sprague Dawley rats were fed with normal diet or HFD for 16 weeks. Then high-fat rats were given vehicle or PAVA (1 mg/kg/day) for another 4 weeks. We found that PAVA alleviated hepatic inflammation associated with the reducing toll-like receptor 4/NF-κB pathway, showing significantly lower recruitment of cluster of differentiation 44. PAVA also maintained activity of insulin signaling pathway, and attenuated NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome formation. NAFLD progresses to NASH through transforming growth factor (TGF-β1), and also recovery to simple stage followed by PAVA suppresses pro-inflammatory cytokines such as tumor necrosis factor-α, interleukin-1β, interleukin-6, and Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway. Therefore, our findings suggest that PAVA provides a novel therapeutic approach for NAFLD and slows the progression to NASH.

Species diversity of genus <em>Capsicum</em> using agromorphological descriptors and simple sequence repeat markers

Sustainability of crops in most demand depends upon their genetic diversity. Capsicum, commonly called chilli, is one such crop with its fruits extensively used as vegetable across the world. Knowledge on various traits is important for genetic improvement of such species. Here, we assessed the genetic diversity among 10 genotypes of six Capsicum species, namely Capsicum annuum, C. chinense, C. chacoense, C. frutescens, C. tovarii and C. galapagoense. C. annuum MS-12 is a genetic male sterile line. We used morphological descriptors and simple-sequence repeat (SSR) molecular markers for this study. Out of 60 SSR screened, 22 markers (36.66%) showed polymorphism. Alleles number per locus varied from 3 to 7. Average PIC value for 22 polymorphic markers was 0.69, and ranged from 0.54 for the primer Hpms 1-139 to 0.85 for the primer CAMS-072. Ten genotypes of Capsicum species were grouped into three major clusters such that genotypes in a single cluster had less dissimilarity matrix values among themselves than which belongs to other clusters. Range of fruit weight and pericarp thickness varied from 0.1 g (‘PAU-621’) to 2.3 g (‘MS-12’), and from 0.29 mm (‘PAU-621’) to1.09 mm (‘MS- 12’), respectively. These two genotypes can be used in hybridization or in recombinant breeding program for obtaining higher heterotic effects/ heterosis or for transgressive segregants in chilli pepper.

Nicotine content and Dietary composition of some cultivated Species of Solanaceae family

Abstract Despite the fact that vegetables are consumed in large quantities in our environment, there is a dearth of literature that focused on the optimum benefits to man especially in the management of disease like Parkinson’s Disease (PD). Nicotine, the major phyto-constituent of Nicotiana tabacum of the family Solanaceae has been reported to be present in some other species of the family. This study investigated the nicotine content and the dietary components in the leaves and fruits of selected species of cultivated vegetable plants belonging to Solanaceae family. Edible plants from Solanaceae family were grown till the fruiting stage in the experimental farm of Ekiti State University, Ado Ekiti, while Nicotiana tabacum was used as the control plant. Plants samples from mature leaves and fruits of each plant were harvested washed with de-ionized water, oven dried at 30°C. Powdered samples were analyzed for mineral and proximate components according to standard procedure and nicotine content were determined with GC-MS. Nicotine remained the major constituent of tobacco. Nicotyrine, a product of nicotine dehydrogenation was also detected in all the plant samples. Capsicum annum var. accuminatum fruit displayed the highest nicotine content (0.5543 mg/L) compared to the others with relatively lower quantities. Nicotyrine content was more available in the plant fruits than nicotine, with C. annum var abbreviatum displaying more of nicotyrine content (75.3456 mg/L). Solanum lycopersicum displayed the highest moisture contents (19.94 %), followed by tobacco leaf (11.88%). N. tabacum leaf displayed high quantity of protein (56.52%) than other members. The fruits of the solanaceae plant species were rich in carbohydrate, protein with very low amount of fat. This study revealed that the solanaceae plants contained more of nicotyrine than nicotine. In contrast to the previous studies, the nicotine content was higher in the eggplant leaves than the fruits. Eggplant and Capsicum species can be recommended for patient suffering from neurodegenerative diseases like PD.

Antifungal Potential of Capsaicinoids and Capsinoids from the Capsicum Genus for the Safeguarding of Agrifood Production: Advantages and Limitations for Environmental Health.

Opportunistic pathogenic fungi arise in agricultural crops as well as in surrounding human daily life. The recent increase in antifungal-resistant strains has created the need for new effective antifungals, particularly those based on plant secondary metabolites, such as capsaicinoids and capsinoids produced by Capsicum species. The use of such natural compounds is well-aligned with the One Health approach, which tries to find an equilibrium among people, animals, and the environment. Considering this, the main objective of the present work is to review the antifungal potential of capsaicinoids and capsinoids, and to evaluate the environmental and health impacts of biofungicides based on these compounds. Overall, capsaicinoids and their analogues can be used to control pathogenic fungi growth in plant crops, as eco-friendly alternatives to pest management, and assist in the conservation and long-term storage of agrifood products. Their application in different stages of the agricultural and food production chains improves food safety, nutritional value, and overcomes antimicrobial resistance, with a lower associated risk to humans, animals, and the environment than that of synthetic fungicides and pesticides. Nevertheless, research on the effect of these compounds on bee-like beneficial insects and the development of new preservatives and packaging materials is still necessary.

Protective effects of Capsicum fruits and their constituents on damage in TNF-α-stimulated human dermal fibroblasts.

Antioxidant and anti-inflammatory effects of natural products on skin cells have been proved to be effective in improving skin damage. Capsicum species contain capsaicinoids that have antioxidant and anti-inflammatory properties, and various subspecies are cultivated. In this study, the effects of four Capsicum fruits and major constituents on oxidative stress and inflammatory reactions were measured using human dermal fibroblasts (HDFs) to verify their effects on skin damage. The inhibitory effects of nitric oxide (NO), reactive oxygen species (ROS), and prostaglandin E2 (PGE2 ) by cucumber hot pepper, red pepper (RDP), Shishito pepper (SSP), and Cheongyang pepper were determined in HDFs. RDP and SSP inhibited the production of NO, ROS, and PGE2 in tumor necrosis factor-alpha-stimulated HDFs. Additionally, SSP seeds restored tumor necrosis factor-alpha-induced increase in matrix metalloproteinase-1 and decreased procollagen I α1 (COLIA1). In high-performance liquid chromatography analysis of the capsaicinoids capsaicin (CAP) and dihydrocapsaicin (DHC), CAP was detected at a higher level than DHC in the peel and seeds of all four types of Capsicum fruits, and the total amount of capsaicinoids was the highest in SSP. CAP and DHC, which are major constituents of Capsicum fruits, also inhibited NO, ROS, and PGE2 and restored matrix metalloproteinase-1 and procollagen I α1. RDP and SSP were shown to have a significant protective effect on skin damage, including oxidative stress, inflammatory reactions, and reduction of collagens. Capsaicinoids CAP and DHC were proved as active constituents. This research may provide basic data for developing Capsicum fruits as ingredients to improve skin damage, such as inflammation and skin aging. © 2022 Society of Chemical Industry.

Genome-Wide Identification, Evolution, and Expression Characterization of the Pepper (Capsicum spp.) MADS-box Gene Family.

MADS domain transcription factors play roles throughout the whole lifecycle of plants from seeding to flowering and fruit-bearing. However, systematic research into MADS-box genes of the economically important vegetable crop pepper (Capsicum spp.) is still lacking. We identified 174, 207, and 72 MADS-box genes from the genomes of C. annuum, C. baccatum, and C. chinense, respectively. These 453 MADS-box genes were divided into type I (Mα, Mβ, Mγ) and type II (MIKC* and MIKCC) based on their phylogenetic relationships. Collinearity analysis identified 144 paralogous genes and 195 orthologous genes in the three Capsicum species, and 70, 114, and 10 MADS-box genes specific to C. annuum, C. baccatum, and C. chinense, respectively. Comparative genomic analysis highlighted functional differentiation among homologous MADS-box genes during pepper evolution. Tissue expression analysis revealed three main expression patterns: highly expressed in roots, stems, leaves, and flowers (CaMADS93/CbMADS35/CcMADS58); only expressed in roots; and specifically expressed in flowers (CaMADS26/CbMADS31/CcMADS11). Protein interaction network analysis showed that type II CaMADS mainly interacted with proteins related to flowering pathway and flower organ development. This study provides the basis for an in-depth study of the evolutionary features and biological functions of pepper MADS-box genes.

Intra and interspecific morphological variations of three species of Capsicum (Solanaceae)

The widely cultivated pepper, Capsicum spp., important as a vegetable and spice crop worldwide, is one of the most diverse crops. Considerable morphological variation, especially in fruit shape, color, and size exist in the genus. The present study analysed the intra and interspecific morphological variations of three species of Capsicum (Solanaceae) using thirty nine morphological characters. Morphological variations with respect to vegetative, floral and fruit characteristics were observed among the members of the same species. Morphological data was used to obtain UPGMA derived dendrogram and the cluster analysis indicated genetic divergence among the three species. Present observations imply a great potential for chilli breeding through a hybridization programme or direct use of the varieties for the successful production of promising cultivars.

Botrytis cinerea identifies host plants via the recognition of antifungal capsidiol to induce expression of a specific detoxification gene.

The gray mold pathogen Botrytis cinerea has a broad host range, causing disease in >400 plant species, but it is not known how this pathogen evolved this polyxenous nature. Botrytis cinerea can metabolize a wide range of phytoalexins, including the stilbenoid resveratrol in grape, and the sesquiterpenoids capsidiol in tobacco and rishitin in potato and tomato. In this study, we analyzed the metabolism of sesquiterpenoid phytoalexins by B. cinerea. Capsidiol was dehydrogenated to capsenone, which was then further oxidized, while rishitin was directly oxidized to epoxy- or hydroxyrishitins, indicating that B. cinerea has separate mechanisms to detoxify structurally similar sesquiterpenoid phytoalexins. RNA-seq analysis revealed that a distinct set of genes were induced in B. cinerea when treated with capsidiol or rishitin, suggesting that B. cinerea can distinguish structurally similar phytoalexins to activate appropriate detoxification mechanisms. The gene most highly upregulated by capsidiol treatment encoded a dehydrogenase, designated Bccpdh. Heterologous expression of Bccpdh in a capsidiol-sensitive plant symbiotic fungus, Epichloë festucae, resulted in an acquired tolerance of capsidiol and the ability to metabolize capsidiol to capsenone, while B. cinerea Δbccpdh mutants became relatively sensitive to capsidiol. The Δbccpdh mutant showed reduced virulence on the capsidiol producing Nicotiana and Capsicum species but remained fully pathogenic on potato and tomato. Homologs of Bccpdh are found in taxonomically distant Ascomycota fungi but not in related Leotiomycetes species, suggesting that B. cinerea acquired the ancestral Bccpdh by horizontal gene transfer, thereby extending the pathogenic host range of this polyxenous pathogen to capsidiol-producing plant species.

Effect of Pepper Variety on the Susceptibility of Pepper Weevil Parasitoids

Anthonomus eugenii Cano (Coleoptera: Curculionidae) is a key pest of cultivated peppers (Capsicum species) in tropical and subtropical America. Here we evaluated the effect of five pepper varieties on the susceptibility of A. eugenii to the parasitoids Bracon sp. (Hymenoptera: Braconidae), Eupelmus cushmani (Crawford) (Hymenoptera: Eupelmidae), and Jaliscoa hunteri Crawford (Hymenoptera: Pteromalidae). Potential parasitism was estimated by comparative analysis of parasitoid ovipositor size and the depth to which host larvae develop inside the fruit. Highest potential parasitism rates were achieved by Bracon sp. and E. cushmani on árbol and habanero peppers (84-99%) while the lowest rates were achieved by J. hunteri on serrano, bell, and jalapeño (7-18%). To validate potential parasitism rates, the actual parasitism rate by Bracon sp. and J. hunteri on three varieties of peppers was assessed. Actual parasitism rates of A. eugenii larvae in árbol were similar for Bracon sp. and J. hunteri (33%), while on bell and jalapeño Bracon sp. achieved 24% and 13% parasitism and J. hunteri achieved 14% and 8%, respectively. In most cases, actual parasitism was lower than estimated potential parasitism, although the latter had a notable predictive power (predicted R2 = 0.84). Results showed that the host was more vulnerable on small-fruited varieties because larvae were closer to the pericarp and could be reached by parasitoid ovipositors; likewise, in varieties with little placenta and seed, some larvae fed in the pericarp, where they were more vulnerable.

Identification of viral genes involved in pepper mottle virus replication and symptom development in Nicotiana benthamiana.

Pepper mottle virus (PepMoV) infects primarily Capsicum species, including pepper and bell pepper which are important vegetable and spice crops in Korea. We have previously collected 13 PepMoV isolates from nine regions comprising five provinces, causing different symptoms on inoculated indicator host plants in Korea. To further identify the responsible symptom determinant(s) and explore viral protein functions of PepMoV, two out of 13 isolates, including 134 and 205136, were used in this study. Isolate 134 causes necrosis and yellowing, while 205136 causes severe mottle and yellowing symptoms on Nicotiana benthamiana. All chimeric and site-directed mutants contain the PepMoV 134 genome as a backbone with specific regions switched for those from counterparts of PepMoV 205136. Effects of all mutants compared with 134 after inoculation onto N. benthamiana by agroinfiltration. Results from our study provide direct evidence that the helper component-proteinase (HC-Pro) and the nuclear inclusion protein b (NIb)-coat protein (CP) regions are involved in virus accumulation and symptom determinants. In addition, we mapped to amino acid residues tyrosine, glycine, and leucine at position 360, 385, and 527, respectively, in the HC-Pro region participate in faster viral accumulation or movement in the plant. The residue valine at position 2773 of NIb plays an essential role in isolate 134 symptom development. As part of this study, we seek to gain insight into viral factors involved in the PepMoV infection cycle and a better understanding of plant-virus interactions. These findings complement the insufficiency of the gene function study of the PepMoV virus and provide a novel perspective for the protein function study of the Potyvirus.

Assessment of G2P-Sol pepper core collection to Verticillium dahliae Kleb. infestation

Pepper (Capsicum spp.) is one of the major vegetable crops grown worldwide largely appreciated for its economic importance and nutritional value. The aim of study is to be assessing the G2P-Sol pepper core collection including 414 accessions from four cultivated Capsicum species to Verticillium dahliae Kleb. infestation. The use isolates VdCa13, VdCa15, VdCa17, VdCa18, VdCa19 and VdCa21, originally isolated from Capsicum annuum in the Plovdiv region, were used for inoculum. The strongest manifestation of the disease is found in accession GPC 118230 (88.54%). Among the evaluated tested accessions, 85 do not show any symptom of the disease. The average degree of attack by V. dahliae Kleb. is the highest in C. frutescens - 25.70%, and the lowest in C. chinense - 13.62%. The maximum attack index is reported in C. annuum - 89.58%, while C. annuum, C. baccatum and C. chinense all have a lack of infection. The standard deviation varied from 8.54 to 17.60. The coefficient of variation is the highest in C. annuum (106.25%), and the weakest in C. frutescens (39.08%). The percentage distribution of the tested accessions according the attack index of all examined materials is as follows: C. annuum represented 94.43%, C. baccatum - 1.77%, C. chinense - 2.78% and C. frutescens - 1.01%.

Diversification of chiles (Capsicum, Solanaceae) through time and space: New insights from genome-wide RAD-seq data.

Capsicum L. encompasses 43 American species, including the five domesticated worldwide consumed sweet and hot chiles. This study presents new, updated and age-calibrated phylogenetic hypothesis on the genus evolution incorporating nearly all currently accepted Capsicum species. A new model of spatial diversification of Capsicum is proposed based on analyses of several thousands of genome-wide RAD-seq derived SNPs. Maximum likelihood approaches were used to reconstruct phylogenies and to estimate dates of all major splits. Ancestral ranges were inferred and diversification events were modeled in a time frame using a Bayesian approach. Nine clades corresponding to genetically and (mostly) geographically well-defined lineages, which diversified starting around mid-upper Miocene, were recovered with strong support. The Northern and Central Andes were inferred to represent the most likely ancestral range of the genus Capsicum. A few early vicariant and dispersal events were estimated to have driven the geographic divergence of the main Capsicum clades. Each lineage was inferred to have diversified within a distinct region of South America and expanded geographically to different extent. Extant species diversification was inferred to have begun at the beginning of Pliocene and continued through the Pleistocene. The Central Andes, represented mainly by the territory of present-day Bolivia, were proposed to play a central role in the diversification of lineages comprising domesticated capsicums and their wild allies. The genome-wide approach allowed for high resolution and support of deep phylogenetic nodes providing novel insights into the affinities of major lineages and clades as well as on the geographic expansion of Capsicum. This study provides the first dated evolutionary history of the genus encompassing most of the chile species diversity.

Screening for resistance and genetic population structure associated with Phytophthora capsici-pepper root and crown rot

Pepper, Capsicum spp. (Solanaceae) is one of the vegetable crops with significant and multiple roles in human diet, as a vegetable, spice, food colorant and ornamental purposes worldwide. Pepper root and crown rot (RCR), and or Phytophthora-blight caused by Phytophthora capsici (Oomycetes) is one of the most destructive diseases of Capsicum species globally. To this aim, we screened 37 pepper-accessions for resistance to RCR, P. capsici and characterized their population-genetic-diversity using 21 Inter-Simple-Sequence-Repeats-(ISSR) primer-pairs, and 27 morphological-attributes. Of which, five accessions; including three-ornamental; 11BlockyP-YToran, 19OrnP-PBI, 23CherryP-Orsh, and two-longs; 32OrnP-China, 37ChilP-Paleo were resistant to RCR with the least-infection-rates, RCR <10%. To estimate the genetic-distance, based on morphological-attributes, we used simple-matching, Jaccard and Dice-similarity-coefficient-(SC), following clustering by UPGMA, and also Cophenetic-coefficient and correlation between similarity-matrices. Similarity-coefficient among genotypes was 0.26–0.93, revealed significant differences among five distinct pepper groups, predominantly in size, color, and shape of leaf and fruit. Genetic-similarity was determined by simple-matching-coefficient-(SSM), and dendrogram was constructed by clustering-analysis with un-weighted-pair-groups using arithmetic-averages-(UPGMA), showed the presence of high genetic-variability among the peppers, and assembled the peppers into five distinct genetic groups. According to ISSR analysis, the highest-resolving-power, (Rp) (≥0.77), and heterozygosity-values, Hv (≥0.26) was recorded accordingly. 19 out of 21-primers produced polymorphism, of which MBP-7, MBP -14 and MBP-18 primers (0.499) had the best performance in genetic-diversity of the related pepper population, respectively. The ISSR-assay generated 188-bands, of which 185-bands were polymorphic. Polymorphism-mean-percentage-(P%) varied from 78% to 100% with a mean of 98.5%, and an average of 9.9 bands per primer. Average polymorphism-information-content-(PIC) was 0.449, and matrix-index 4.29. Association between genotypic-phenotypic-traits-(r-0.346**), phenotypic-RCR-resistance-(r = 0.197**), and RCR-resistance-ISSR (r-0.029**) was significant, respectively. There was also a high correlation between RCR resistance and some morphological-attributes, such as node anthocyanin-pigment and its intensity (r = 0.251**), node-woolly (r = 0.255**), fruit-shape (r = 0.273**), exocarp-wavy in fruit-base-(r = 0.208**), and hollow-depth-(r = 0.358**). The genetic markers revealed much genetic variation that can be used both in genotyping and in selecting appropriate breeding strategies against P. capsici, given the documented correlations between disease resistance and certain morphological and genotyping traits.

Chemical Synthesis of Trans 8-Methyl-6-Nonenoyl-CoA and Functional Expression Unravel Capsaicin Synthase Activity Encoded by the Pun1 Locus.

Capsaicin, produced by diverse Capsicum species, is among the world’s most popular spices and of considerable pharmaceutical relevance. Although the capsaicinoid biosynthetic pathway has been investigated for decades, several biosynthetic steps have remained partly hypothetical. Genetic evidence suggested that the decisive capsaicin synthase is encoded by the Pun1 locus. Yet, the genetic evidence of the Pun1 locus was never corroborated by functionally active capsaicin synthase that presumably catalyzes an amide bond formation between trans 8-methyl-6-nonenoyl-CoA derived from branched-chain amino acid biosynthesis and vanilloylamine derived from the phenylpropanoid pathway. In this report, we demonstrate the enzymatic activity of a recombinant capsaicin synthase encoded by Pun1, functionally expressed in Escherichia coli, and provide information on its substrate specificity and catalytic properties. Recombinant capsaicin synthase is specific for selected aliphatic CoA-esters and highly specific for vanilloylamine. Partly purified from E. coli, the recombinant active enzyme is a monomeric protein of 51 kDa that is independent of additional co-factors or associated proteins, as previously proposed. These data can now be used to design capsaicin synthase variants with different properties and alternative substrate preferences.

Integrated omics analysis identified genes and their splice variants involved in fruit development and metabolites production in Capsicum species.

To date, several transcriptomic studies during fruit development have been reported; however, no comprehensive integrated study on expression diversity, alternative splicing, and metabolomic profiling was reported in Capsicum. This study analyzed RNA-seq data and untargeted metabolomic profiling from early green (EG), mature green (MG), and breaker (Br) fruit stages from two Capsicum species, i.e., C. annuum (Cann) and C. frutescens (Cfrut) from Northeast India. A total of 117,416 and 96,802 alternatively spliced events (AltSpli-events) were identified from Cann and Cfrut, respectively. Among AltSpli-events, intron retention (IR; 32.2% Cann and 25.75% Cfrut) followed by alternative acceptor (AA; 15.4% Cann and 18.9% Cfrut) were the most abundant in Capsicum. Around 7600 genes expressed in at least one fruit stage of Cann and Cfrut were AltSpli. The study identified spliced variants of genes including transcription factors (TFs) potentially involved in fruit development/ripening (Aux/IAA 16-like, ETR, SGR1, ARF, CaGLK2, ETR, CaAGL1, MADS-RIN, FUL1, SEPALLATA1), carotenoid (PDS, CA1, CCD4, NCED3, xanthoxin dehydrogenase, CaERF82, CabHLH100, CaMYB3R-1, SGR1, CaWRKY28, CaWRKY48, CaWRKY54), and capsaicinoids or flavonoid biosynthesis (CaMYB48, CaWRKY51), which were significantly differentially spliced (DS) between consecutive Capsicum fruit stages. Also, this study observed that differentially expressed isoforms (DEiso) from 38 genes with differentially spliced events (DSE) were significantly enriched in various metabolic pathways such as starch and sucrose metabolism, amino acid metabolism, cysteine cutin suberin and wax biosynthesis, and carotenoid biosynthesis. Furthermore, the metabolomic profiling revealed that metabolites from aforementioned pathways such as carbohydrates (mainly sugars such as D-fructose, D-galactose, maltose, and sucrose), organic acids (carboxylic acids), and peptide groups significantly altered during fruit development. Taken together, our findings could help in alternative splicing-based targeted studies of candidate genes involved in fruit development and ripening in Capsicum crop.