Annuum Accessions Research Articles

Genome-wide genotyping of a novel Mexican Chile Pepper collection illuminates the history of landrace differentiation after Capsicum annuum L. domestication.

Studies of genetic diversity among phenotypically distinct crop landraces improve our understanding of fruit evolution and genome structure under domestication. Chile peppers (Capsicum spp. L.) are economically valuable and culturally important species, and extensive phenotypic variation among landraces exists in southern Mexico, a center of C. annuum diversity. We collected 103 chile pepper seed accessions from 22 named landraces across 27 locations in southern Mexico. We genotyped these accessions with genotyping by sequencing (GBS), yielding 32,623 filtered single‐nucleotide polymorphisms. Afterward, we genotyped 32 additional C. annuum accessions from a global collection for comparison to the Mexican collection. Within the Mexican collection, genetic assignment analyses showed clear genetic differentiation between landraces and clarified the unique nature of the Tusta landrace. Further clustering analyses indicated that the largest fresh‐use Chile de Agua and dry‐use Costeño landraces were part of separate clades, indicating that these two landraces likely represent distinct populations. The global accessions showed considerable admixture and limited clustering, which may be due to the collapse of use‐type divisions outside of Central America. The separation of the Mexican landraces in part by fruit morphology related to use highlights the relevance of this use‐type morphological diversity for plant breeders and the utility of fruit development variation for evolutionary biologists.

Morphological and molecular characterization of two distinct chilli cultivars from North Eastern India with special reference to pungency related genes

Abstract King chilli and Dalle Khursani are the two hottest chilli (Capsicum sp.) cultivars widely grown in NE region of India but a well-organized study pertaining to King chilli and Dalle Khursani is unavailable. We have characterized twenty-two accessions of King chilli and Dalle Khursani, collected from different states of NE region with respect to 27 morphological parameters and using 30 SSR markers. The allelic status of three key pungency related genes viz, putative aminotransferase (pAmt or Pun1), acyl-CoA synthetase (Acs1) and β-ketoacyl-ACP synthase (Kas1) was also determined. Maximum morphological variation was observed for fruit traits and traits like plant growth habit, plant height, etc., which can be used to distinguish between the two cultivars. SSR markers HpmsE062 and HpmsE063 were able to distinguish between the three different cultivars (including a nonpungent bell pepper), while HpmsE116 and HpmsE139 distinguish King chilli from Dalle Khursani. Ward clustering method grouped all the eleven Dalle Khursani accessions together with non-pungent C. annuum accession in one cluster. Sequencing across Acs1 revealed total of eight SNPs and three InDels. Seven SNPs including three within exonic regions were conserved between bell pepper, Dalle Khursani and the reference pungent C. annuum accession. A 2 bp InDel at position 50–51 bp and a 3 bp InDel at position 6313–6315 bp were found to be uniquely conserved haplotypes in both Dalle Khursani and King Chilli. A total of 16 SNPs were found within the sequenced region of Pun1 gene, of which eight SNPs lie within the coding region. Three novel exonic SNPs were found in Dalle Khursani. All eight SNPs found in the intronic region for Pun1 were conserved across Dalle Khursani and the two pungent reference sequences of C. annuum. Our SSR and SNP data suggests that Dalle Khursani is genetically closer to pungent C. annuum. This work provides insights into the genotype of two hottest chillies and paves way for their utilization in chilli improvement programme.

Research Article Estimate of natural cross-pollination rate of Capsicum annuum using a codominant molecular marker associated with fruit pungency

The production of seeds with high genetic quality requires accurate estimates of the natural cross-pollination rate in cultivated Capsicum species. This is important in order to establish the most suitable isolation distance among fields of distinct genotypes, to minimize the risk of genetic contamination and to ensure that the agronomic and horticultural traits of an elite breeding material are preserved in a given seed lot. Cross-pollination studies in C. annuum are practically non-existent under Brazilian conditions. The objective of the present study was to estimate the natural rate of C. annuum cross-pollination in seed production fields established in the highland area of Central Brazil (“Cerrado”). A molecular marker (CA-Pun1), which allows the identification of cross-fertilization between C. annuum accessions with pungent and sweet fruits, was employed to identify hybrid seeds. This marker detects functional and non-functional alleles of an acyl-transferase (Pun1) gene, responsible to produce capsaicin (pungency) in placental tissue of C. annuum fruits. Seedlings of cultivar ‘Magali R’ (sweet fruits) were planted in the field at incremental distances from cultivar ‘BRS Garca’ (pungent fruits). Progenies obtained from ‘Magali R’ plants were genotyped with marker CA-Pun1. Approximately 10.8% of the fruits displayed at least one seed originated from cross-pollination. The overall natural cross-pollination rate in C. annuum was estimated at 1.2%, according to the percentage of hybrid seeds detected by molecular analysis. No significant differences were detected in the rate of cross-pollination among plants for distances of up to 7.2 m.

Heterosis and combining ability for ornamental chili pepper

ABSTRACT Ornamental use of Capsicum genus chili peppers has expanded due to easy seed propagation, short germination period, diversified fruit colors and harmony of potted plants. The ornamental plant sector requires cultivars adapted to different cultivation conditions in pots and gardens. Breeding programs can use heterosis and combining ability information, aiming to commercially explore hybrids or develop populations for lineage selection with desirable characteristics. However, the ornamental chili pepper field lacks studies with this data. In this study, combining ability of C. annuum accessions was determined for ornamental purposes and hybrid combinations were identified based on heterosis values. Fifteen hybrids were obtained from diallel crosses of six genotypes of C. annuum, from March to September 2014, under greenhouse conditions, grown in five-liter pots in experimental design of randomized blocks with 10 repetitions and one plant per plot. Morpho-agronomic characterization was conducted based on eight quantitative descriptors: plant height (before and after fruiting); canopy diameter; days to flourishing; days to fruiting; fruit length and diameter, and number of fruits per plant. Both additive and dominance effects play important role in controlling the studied characters, indicating hybrid exploitation as well as development of superior lineages from the progress of segregating generations. Negative heterosis values resulted in reduction in height, time for flourishing and fruiting, as well as fruit diameter and length, which are desirable for ornamental Capsicum breeding program. Considering an ideotype for ornamental chili pepper cultivars, the hybrids UENF 1626 x UENF 1750, UENF 1750 x UENF 2030 and UENF 1626 x UENF 2030 can be recommended for cultivation with ornamental purposes.

Genome-wide SNP discovery and population structure analysis in pepper (Capsicum annuum) using genotyping by sequencing.

BackgroundKnowledge on population structure and genetic diversity in vegetable crops is essential for association mapping studies and genomic selection. Genotyping by sequencing (GBS) represents an innovative method for large scale SNP detection and genotyping of genetic resources. Herein we used the GBS approach for the genome-wide identification of SNPs in a collection of Capsicum spp. accessions and for the assessment of the level of genetic diversity in a subset of 222 cultivated pepper (Capsicum annum) genotypes.ResultsGBS analysis generated a total of 7,568,894 master tags, of which 43.4% uniquely aligned to the reference genome CM334. A total of 108,591 SNP markers were identified, of which 105,184 were in C. annuum accessions. In order to explore the genetic diversity of C. annuum and to select a minimal core set representing most of the total genetic variation with minimum redundancy, a subset of 222 C. annuum accessions were analysed using 32,950 high quality SNPs. Based on Bayesian and Hierarchical clustering it was possible to divide the collection into three clusters. Cluster I had the majority of varieties and landraces mainly from Southern and Northern Italy, and from Eastern Europe, whereas clusters II and III comprised accessions of different geographical origins. Considering the genome-wide genetic variation among the accessions included in cluster I, a second round of Bayesian (K = 3) and Hierarchical (K = 2) clustering was performed. These analysis showed that genotypes were grouped not only based on geographical origin, but also on fruit-related features.ConclusionsGBS data has proven useful to assess the genetic diversity in a collection of C. annuum accessions. The high number of SNP markers, uniformly distributed on the 12 chromosomes, allowed the accessions to be distinguished according to geographical origin and fruit-related features. SNP markers and information on population structure developed in this study will undoubtedly support genome-wide association mapping studies and marker-assisted selection programs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3297-7) contains supplementary material, which is available to authorized users.

Genetic diversity of pepper (Capsicum spp.) germplasm resources in China reflects selection for cultivar types and spatial distribution

Pepper (Capsicum spp.) is an important vegetable crop in the world. Now the pepper in China contributes one-third of the world's peppers production. Genetic diversity of the pepper germplasm of China is expected interesting to know. To explore the structure of genetic diversity in Chinese pepper germplasm resources and possible relationship with cultivar types or geographic origin, we sampled and compared 372 GenBank pepper accessions (local cultivars and landraces) from 31 provinces, autonomous regions and municipalities of China and 31 additional accessions from other countries. These accessions were genotyped using 28 simple sequence repeat (SSR) markers spanning the entire pepper genome. We then investigated the genetic structure of the sampled collection using model-based analysis in STRUCTURE v2.3.4 and examined genetic relationships by the unweighted pair-group method of mathematical averages (UPGMA) in MEGA. In addition to geographic origin, we evaluated eight plant and fruit traits. In total, 363 alleles were amplified using the 28 SSR primers. Gene diversity, polymorphism information content and heterozygosity of the 28 SSR loci were estimated as 0.09–0.92, 0.08–0.92 and 0.01–0.34, respectively. The UPGMA cluster analysis clearly distinguished Capsicum annuum L. from other cultivated pepper species. Population structure analysis of the 368 C. annuum accessions uncovered three genetic groups which also corresponded to distinct cultivar types with respect to the plant and fruit descriptors. The genetic structure was also related to the geographic origin of the landraces. Overall results indicate that genetic diversity of Chinese pepper landraces were structured by migration of genotypes followed by human selection for cultivar types in agreement with consumption modes and adaptation to the highly diversified agro-climatic conditions.

Heritability of Fresh-cut Fruit Quality Attributes in Capsicum

Fresh pepper (Capsicum) fruit that are sliced and/or diced are referred to as fresh-cut products. The current report evaluates the inheritance of postharvest attributes that contribute to pepper fresh-cut quality. Marketable green fruit of large-fruited Capsicum annuum accessions with bell and related pod types (Class 1), C. annuum accessions with jalapeno and serrano pod types (Class 2), and thin-walled “aji”-like tabasco pod types from Capsicum baccatum, Capsicum frutescens, and Capsicum chinense (Class 3) were processed and stored up to 14 days in selective oxygen transmission rate packaging. Fresh-cut attributes were influenced by genotype as well as year. For all pod types, O2 and CO2 partial pressures in storage packages, tissue weight loss, and electrolyte leakage differed among accessions, days of storage, and years of testing. Percent O2 declined and CO2 and electrolyte leakage generally increased during storage. Some accessions in Class 1 and Class 2 maintained acceptable product quality during storage. Changes in fruit weight loss were small with greater weight loss observed in Class 1 accessions relative to weight loss for Class 2 and Class 3. Broad-sense heritability for fresh-cut attributes was moderate to low indicating that it will be difficult to breed for fresh-cut quality.

Etiological and epidemiological concerns about Pepper root and lower stem rot caused by Fusarium oxysporum f. sp. radicis-capsici f. sp. nova

Inoculum sources of Fusarium oxysporum f. sp. radicis-capsici and host susceptibility were studied in commercial pepper cultivars and related Capsicum spp. The pathogen could not be identified in irrigation water or in the microbiologically enriched potting medium, or associated with the seeds used in the nursery where the disease was initially reported in Spain. Although the disease was asymptomatic on older pepper plants, pathogenic strains could still be isolated from the soil of those greenhouses where the disease had been previously observed. Host susceptibility in commercial pepper cultivars and related Capsicum spp. was studied. All pepper cultivars tested (n = 19), including three rootstocks, developed symptoms when inoculated with Fusarium oxysporum f. sp. radicis-capsici. Three C. baccatum accessions and one C. annuum accession exhibited resistance, whereas two C. chinense accessions showed only partial resistance. The disease symptoms could not be distinguished from those caused by one F. oxysporum f. sp. capsici isolate, and molecular analysis also showed identical tef sequences for both formae speciales.

Control of Alternaria post-harvest infections on cherry tomato fruits by wild pepper phenolic-rich extracts

The use of plant-derived products in postharvest disease management may be a valid alternative to conventional chemical treatments. In this study, the antifungal activity of crude foliar extracts of a wild Capsicum annuum accession against Alternaria alternata was assessed. Pepper extracts affected mycelial growth and suppressed conidia germination in a dose-dependent manner. Moreover, they significantly reduced soft rot disease severity on artificially infected ripe cherry tomatoes. Extracts were characterized for their total phenolic content and antioxidant activity. UPLC–DAD analysis was also performed to obtain phenolic profiles of extracts and quantify the individual known components, including gallic acid, chlorogenic acid, catechin, caffeic acid, p-coumaric acid and ferulic acid. The putative role of this class of molecules in conferring antifungal activity to the extracts is discussed. The results indicate that extracts rich in natural phenolic compounds could be promising for sustainable applications in crop protection.

Screening of Wild and Cultivated Capsicum Germplasm Reveals New Sources of Verticillium Wilt Resistance.

Verticillium wilt caused by Verticillium dahliae is an important soilborne disease of pepper (Capsicum species) worldwide. Most commercial pepper cultivars lack resistance to this pathogen. Our objective was to identify resistance to two V. dahliae isolates in wild and cultivated Capsicum accessions from the core collection of the National Plant Germplasm System of the USDA. Screening of 397 Capsicum accessions against two V. dahliae isolates (Vdca59 and VdCf45) was performed in a greenhouse. Seventy-eight accessions selected from this screen were further evaluated in a follow-up experiment. In total, 21 (26.9%) and 13 (16.6%) Capsicum accessions tested were resistant to Verticillium wilt when inoculated with V. dahliae isolates VdCa59 and VdCf45, respectively. Eight accessions (Grif 9073, PI 281396, PI 281397, PI 438666, PI 439292, PI 439297, PI 555616, and PI 594125) were resistant to Verticillium wilt against both V. dahliae isolates. On the basis of Germplasm Resources Information Network data, two of the Capsicum annuum accessions (Grif 9073 and PI 439297) were also resistant to Phytophthora root rot disease. These sources of multiple disease resistance will be useful to pepper breeding programs.

CaAP2 transcription factor is a candidate gene for a flowering repressor and a candidate for controlling natural variation of flowering time in Capsicum annuum.

The APETALA2 transcription factor homolog CaAP2 is a candidate gene for a flowering repressor in pepper, as revealed by induced-mutation phenotype, and a candidate underlying a major QTL controlling natural variation in flowering time. To decipher the genetic control of transition to flowering in pepper (Capsicum spp.) and determine the extent of gene function conservation compared to model species, we isolated and characterized several ethyl methanesulfonate (EMS)-induced mutants that vary in their flowering time compared to the wild type. In the present study, we report on the isolation of an early-flowering mutant that flowers after four leaves on the primary stem compared to nine leaves in the wild-type 'Maor'. By genetic mapping and sequencing of putative candidate genes linked to the mutant phenotype, we identified a member of the APETALA2 (AP2) transcription factor family, CaAP2, which was disrupted in the early-flowering mutant. CaAP2 is a likely ortholog of AP2 that functions as a repressor of flowering in Arabidopsis. To test whether CaAP2 has an effect on controlling natural variation in the transition to flowering in pepper, we performed QTL mapping for flowering time in a cross between early and late-flowering C. annuum accessions. We identified a major QTL in a region of chromosome 2 in which CaAP2 was the most significant marker, explaining 52 % of the phenotypic variation of the trait. Sequence comparison of the CaAP2 open reading frames in the two parents used for QTL mapping did not reveal significant variation. In contrast, significant differences in expression level of CaAP2 were detected between near-isogenic lines that differ for the flowering time QTL, supporting the putative function of CaAP2 as a major repressor of flowering in pepper.

Genetic diversity and assessment of markers linked to resistance and pungency genes in Capsicum germplasm

The use of germplasm as source of resistances to biotic stresses represents an important strategy in pepper in order to improve susceptible cultivars and release new resistant varieties. The study of the relationships among genotypes within germplasm collections is useful for genetic improvement as well as for the management of genetic resources. In the present study, 59 accessions belonging to nine different species have been genotyped with a set of ten simple sequence repeats (SSR) and eleven allele specific molecular markers linked to major genes and QTLs for pathogen resistance and pungency. Results allowed to select promising genotypes in terms of content of resistance alleles and to identify highly polymorphic SSR pairs which can be used for species discrimination and hybrid identification. The diversity pattern of the SSR loci revealed a number of distinct alleles per locus, ranging from 3 to 11 with an average of 6.3. Hierarchical analysis allowed to distinguish several clusters each including the different species under study with genetic similarities in the range of 7–100 %. The most distant genotypes from the C. annuum accessions belong to C. baccatum and C. pubescens. The differentiation of the accessions on the basis of the presence of resistance and pungency associated markers, allowed to identify 17 clusters in which the resistance genes were differently distributed. Tsw, L 4 and Pvr4 resulted to be most represented within the genotypes of the collection. Accessions belonging to C. chinense and C. frutescens resulted to be the most interesting ones for pyramiding multiple resistance genes, confirming the need of interspecific crosses in breeding programs in order to transfer useful alleles from domesticated Capsicum spp. to varieties and landraces of cultivated pepper.

CaDMR1 Cosegregates with QTL Pc5.1 for Resistance to Phytophthora capsici in Pepper (Capsicum annuum)

A major problem for the pepper (Capsicum annuum) industry is the root rot disease caused by Phytophthora capsici (Pc), to which all commercial varieties suffer yield losses despite good management practices and available landraces with high levels of resistance. A high‐density map with 3887 markers was generated in a set of recombinant inbred lines (RIL) derived from the highly resistant Capsicum annuum accession Criollo de Morelos‐334 and Early Jalapeño. These lines have been systematically screened for Pc resistance against a set of isolates collected from Mexico, New Mexico, New Jersey, California, Michigan and Tennessee. Quantitative trait loci (QTL) associated with effective resistance across isolates have been identified and validated with SNP markers across additional segregating populations. By leveraging transcriptomic and genomic information, we describe CaDMR1, a homoserine kinase (HSK), as a candidate gene responsible for the major QTL on chromosome P5 for resistance to Pc. SNP markers for the resistant allele were validated to facilitate gene pyramiding schemes for recurrent selection in pepper.

Genotyping a large collection of pepper (Capsicum spp.) with SSR loci brings new evidence for the wild origin of cultivated C. annuum and the structuring of genetic diversity by human selection of cultivar types

Germplasm collections of cultivated plants constitute the source for further genetic progress. These collections gained further interest with approaches for tracking allelic variants associated to phenotypic variations within core collections. In order to explore the structure of genetic variation in pepper (Capsicum spp.) and to select core-collections maximizing the genetic and the phenotypic diversity, a pepper collection including 1,352 non redundant accessions from 11 Capsicum species from 89 different countries was genotyped using 28 microsatellite (SSR) markers spanning the whole genome. Model-based analysis structured the collection into 6 clusters, with 3 clusters separating the main species complexes, including cultivated species and wild relatives, according to taxonomic classification (C. frutescens/C. chinense, C. baccatum, C. pubescens), and 3 additional clusters for C. annuum. The relationships between the cultivated C. annuum species and the wild relative (C. annnuum var. glabriusculum) was precised. The 3 C. annuum clusters were significantly distinct for plant and fruit descriptors corresponding to cultivar types, showing that the genetic structure of this cultivated species was strongly impacted by the long term human selection of landraces in primary as well as secondary diversification centres. We settled nested core-collections of 8, 16, 32, 64 and 128 C. annuum accessions capturing from 37 to 90 % of the genetic diversity for further sequencing efforts and establishment of high throughput genotyping assays. By compiling phenotypic and genotypic data, a larger core-collection of 332 accessions was established, capturing 97 % of the C. annuum genetic and phenotypic diversity for further genetic association studies.

Effect of the genotype, developmental stage and medium composition on the in vitro culture efficiency of immature zygotic embryos from genus Capsicum

A new reliable in vitro technique for immature embryos of Capsicum spp. was developed. A collection of 10 accessions, encompassing the five cultivated species of Capsicum, and four media formulations, combining different levels of sucrose (40g/L vs. 80g/L) and MS salts (½×MS vs. 1×MS), were evaluated. In addition, the four main embryo stages (i.e. globular, heart, torpedo, early cotyledonary) were also considered. Thus, almost 2000 embryos were excised, cultured, and evaluated for germination in the present experiment. Genotype (G), media composition (M), and developmental stage (S) contributed significantly to culture efficiency. G×S and S×M interactions were also significant, although their contribution was lower than individual main factors. C. annuum accession Piquillo, C. frutescens B-144 and, particularly, C. pubescens B-61 showed the highest in vitro germination rates, while C. chinense and C. baccatum accessions showed, in general, the lowest responses. In most cases, the more advanced the embryo stage the higher the culture efficiency. However, for the first time in Capsicum globular embryos from most genotypes were germinated in vitro and also relatively high rates were achieved for heart embryos. Finally, the medium with the lowest levels of both sucrose (40g/L) and MS (½×MS) enabled, in most genotypes and stages of development, the highest in vitro germination rates. In fact, this medium allowed rates of up to 25% in globular embryos. These results provide useful information to those breeders interested on the applications of embryo culture in Capsicum peppers (e.g. shortening breeding cycles, perhaps rescue of interspecific embryos).

The disease reactions of heirloom bell pepper “California Wonder” to <i>Phytophthora capsici</i>

Greenhouse studies were performed to determine the reactions of 10 “California Wonder” (Capsicum annuum) accessions to the three forms of Phytophthora blight (root rot, stem blight and foliar blight) caused by Phytophthora capsici. Differences in root rot, stem blight and foliar blight severities among accessions were significant. The accessions consistently differentiated into two groups across the three disease syndromes. Simple sequence repeat (SSR) markers showed variability both within and between accessions of California Wonder. The variability in the responses to the three forms of Phytophthora blight does not warrant its usefulness as a standard susceptible control in studies involving the Capsicum-P. capsici patho-system.

Molecular Profiling for Genetic Variability in Capsicum Species Based on ISSR and RAPD Markers

The taxonomic identity of Capsicum species is found to be difficult as it displays variations at morpho-chemical characters. Twenty-two accessions of six Capsicum species, namely, C. annuum, C. baccatum, C. chinense, C. eximium, C. frutescens, and C. luteum were investigated for phenotypic diversity based on flower color and for genetic differences by molecular makers. The genetic cluster analyses of 27 RAPD and eight ISSR primers, respectively, revealed genetic similarities in the ranges of 23-88% and 11-96%. Principal component analysis of the pooled RAPD and ISSR data further supports the genetic similarity and groupings. Different species showed variations in relation to corolla shade of flower. C. annuum accessions formed a single cluster in the molecular analysis as maintaining their flower characteristic. C. chinense accession shared flower features with the accessions of C. frutescens and were found to be closer at genotypic level. C. luteum was found to be rather closer to C. baccatum complex, both phenotypically and genetically. The only accession of C. eximium presenting purple flowers falls apart from the groupings. The floral characteristics and the molecular markers are found to be useful toward the delineation of the species specificity in Capsicum collection and identification of genetic stock.

Diversidade genética entre acessos de pimentas e pimentões da Embrapa Clima Temperado

Os acessos de pimentas e pimentões (Capsicum annuum L.) da Embrapa Clima Temperado constituem parte dos recursos genéticos de Capsicum. Contudo, é necessário conhecer o quanto esses genótipos são divergentes para que possam ser utilizados em programas de melhoramento. Os objetivos deste trabalho foram avaliar e caracterizar a divergência genética entre os acessos de C. annuum do banco ativo de germoplasma de Capsicum da Embrapa Clima Temperado. Foram caracterizados 20 acessos com base em 36 descritores morfológicos multicategóricos. A diversidade genética foi avaliada por meio do método de agrupamento de Tocher e UPGMA. O método de Tocher formou três grupos de acessos. Pelos critérios utilizados, os dois métodos foram concordantes em agrupar isoladamente o acesso P77, que apresenta caracteres morfológicos particulares em relação aos demais. O estudo realizado evidencia a existência de variabilidade genética moderada entre os 20 acessos de C. annuum estudados e apresenta acessos com características ornamentais, os quais podem ser incorporados em programas de melhoramento.

HS-SPME Comparative Analysis of Genotypic Diversity in the Volatile Fraction and Aroma-Contributing Compounds of Capsicum Fruits from the annuum−chinense−frutescens Complex

Volatile constituents of ripe fruits of 16 Capsicum accessions from the annuum-chinense-frutescens complex, with different aroma impressions and geographical origins, were isolated by headspace-solid phase microextraction (HS-SPME) and analyzed by gas chromatography-olfactometry-mass spectrometry (GC-sniffing port-MS). More than 300 individual compounds could be detected in the studied genotypes; most of them could be identified by comparing mass spectra and retention times with authentic reference substances or literature data. Esters and terpenoids were the main groups, although other minor compounds, such as nitrogen and sulfur compounds, phenol derivatives, norcarotenoids, lipoxygenase derivatives, carbonyls, alcohols, and other hydrocarbons, were also identified. The sniffing test revealed that the diversity of aromas found among the studied cultivars is due to qualitative and quantitative differences of, at least, 23 odor-contributing volatiles (OCVs). C. chinense, and C. frutescens accessions, with fruity/exotic aromas, were characterized by a high contribution of several esters and ionones and a low or nil contribution of green/vegetable OCVs. Different combinations of fruity/exotic and green/vegetable OCVs would explain the range of aroma impressions found among C. annuum accessions. Implications of these findings for breeding and phylogeny studies in Capsicum are also discussed.

First Report of Leveillula taurica Causing Powdery Mildew on Pepper in Maryland.

Pepper plants in large experimental plots in Beltsville, MD developed widespread powdery mildew during the late summer of 2008. Infection was observed in a diversity of accessions that included Capsicum annuum, C. baccatum, C. chinense, and C. frutescens (2). The C. annuum accessions included culinary bell pepper cultivars and breeding lines as well as a diverse collection of ornamental breeding lines, heirlooms, and land races. Significant leaf damage occurred and led to partial defoliation. Extensive coverage of the abaxial surface by white patches of conidia was noted, along with chlorotic regions on the adaxial surface. Conidia were borne singly and were apically tapered, measuring 65.2 ± 3.2 × 14.9 ± 1.9 μm. Cleistothecia were not found on infected leaves (3). PCR amplification of the internal transcribed spacer (ITS) region using ITS1-2 primers yielded a band that was cloned and sequenced (4). The pathogen was identified as Leveillula taurica based on 100% homology to GenBank Accession No. AY912077. Multiple chili pepper and bell pepper plants were inoculated with conidia from an infected bell pepper plant by placement in an enclosed spore deposition chamber for 1 week, with the infected plant suspended over the test plants. Signs of powdery mildew appeared only on inoculated plants. DNA samples from these inoculated plants were analyzed and verified as L. taurica (a sequence was deposited as GenBank No. GQ167201). A second set of inoculations using the newly infected plants confirmed results of the first test, with mildew developing only on inoculated pepper plants. This disease is new to the mid-Atlantic Region of the United States. It has been reported in greenhouse peppers growing in Ontario, Canada where it has become a recurring problem requiring fungicide intervention (1). Given the wide host range of L. taurica and the systemic nature of infections, it is likely that the fungus has become established in Maryland on perennial host plants.