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  • Author or Editor: John R. Stommel x
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We identified a single plant in a grow out of the eggplant (Solanum melongena L.) variety ‘Black Beauty’ bearing green fruit. ‘Black Beauty’ normally produces violet/black pigmented fruit attributed to anthocyanin accumulation. We selected the green-fruited true-breeding genotype E13GB42 from the S2 generation obtained from selfing of the S0 green-fruited color mutant. Characterization of 12 simple sequence repeat (SSR) markers, eight fruit morphological attributes and fruit yield support E13GB42 arising as a spontaneous mutant of ‘Black Beauty’. With the exception of fruit calyx prickliness, E13GB42 was not significantly different from ‘Black Beauty’ for fruit morphological attributes and yield. E13GB42 exhibited an SSR marker profile identical to that of ‘Black Beauty’ but polymorphic with that of eight violet/black-fruited modern eggplant hybrids, older open-pollinated varieties and landraces. Transcript levels of key anthocyanin biosynthetic genes (Chs, Dfr, and Ans) and regulatory genes (Myb C , Myc, and Wd) were significantly lower in the green-fruited E13GB42 mutant in comparison with the black-fruited variety ‘Black Beauty’ at various stages of fruit development ranging from small post-anthesis fruit to full-size marketable fruit. Progeny obtained from selfing of the original mutant and reciprocal crosses with ‘Black Beauty’ produced violet, green, and green with violet striped color classes that together were not compatible with one or two gene inheritance models, suggesting that the mutation responsible for the E13GB42 phenotype influences multiple genetic factors that control fruit pigmentation.

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Tomato fruit firmness is a key quality component of tomatoes produced for processing applications. Fruit firmness is generally considered a quantitatively inherited trait. Pericarp firmness of modern tomato cultivars is believed to be derived from a fairly narrow genetic background and is the result of the cumulative effort of numerous breeders over many years. Despite inferior phenotypes, wild species contain loci that can substantially increase tomato fruit quality. In the current study, inheritance of fruit firmness in firm and ultra-firm processing tomato germplasm developed from transgressive segregants of interspecific Lycopersicon esculentum × L. hirsutum and intraspecific L. esculentum crosses was characterized. Large-fruited breeding lines that varied in fruit firmness from soft to firm were identified for genetic analyses. A six-parent diallel of these advanced breeding lines was developed for field trials over multiple locations. Fruit firmness in the resulting 36 lines was determined by measuring fruit elastic properties during fruit puncture and compression. Following loading for compression, stress relaxation was recorded for 15 s. A three-parameter model was used to fit the relaxation curves. There was little correlation between firmness (maximum force) and the three relaxation parameters, i.e., firmness measured the elastic component and the relaxation parameters measured the viscous portions of the texture. General and specific combining ability for firmness derived from the respective genetic backgrounds was determined. Genetic variance components for fruit firmness were estimated using a diallel analysis and narrow sense heritability was measured using parent-offspring regression.

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Anthocyanin structural gene transcription requires the expression of at least one member of each of three transcription factor families: MYC, MYB, and WD40. These transcription factors form a complex that binds to structural gene promoters, thereby modulating gene expression. Capsicum annuum L. (pepper) displays a wide spectrum of tissue-specific anthocyanin pigmentation, making it a useful model for the study of anthocyanin accumulation. To determine the genetic basis for tissue-specific pigmentation, we used real-time polymerase chain reaction to evaluate the expression of anthocyanin biosynthetic (Chs, Dfr, and Ans) and regulatory (Myc, MybA , and Wd) genes in flower, fruit, and foliar tissue from pigmented and nonpigmented C. annuum genotypes. No differences were observed in expression of the Wd gene among these tissues. However, in all cases, biosynthetic gene transcript levels were significantly higher in anthocyanin-pigmented tissue than in nonpigmented tissues. MybA and Myc transcript levels were also substantially higher in anthocyanin-pigmented floral and fruit tissues. Our results demonstrate that differential expression of C. annuum MybA as well as Myc occurs coincident with anthocyanin accumulation in C. annuum flower and fruit tissues. In contrast to the situation in flowers and fruit, differential expression of MybA and Myc was not observed in foliar tissue, suggesting that different mechanisms contribute to the regulation of anthocyanin biosynthesis in different parts of the C. annuum plant. Cloning and sequencing of MybA genomic and cDNA clones revealed two introns of 249 and 441 bp between the R2R3 domains. Whereas the Myb R2R3 domains were conserved between C. annuum and Petunia ×hybrida Vilm., the sequence of the non-R2R3 domains was not conserved, with very little homology in these related Solanaceous species.

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Fruit firmness is a key quality component of tomatoes (Lycopersicon esculentum Mill.) for fresh-market and processed product applications. We characterized inheritance of firmness in processing tomato germplasm developed from interspecific L. esculentum Mill. × L. cheesmanii f. minor (Hook. f.) C.H. Mull. and intraspecific L. esculentum crosses. Although firmness is a key quality attribute of tomato, there is no standard method for measuring it. We measured the elastic portion of firmness by compression (compression Fmax) and puncture (puncture Fmax), and the viscoelastic portion by force-relaxation. The experimental design incorporated six genotypes in a complete 6 × 6 diallel. Compression Fmax and force measurements recorded at 0.5, 1.0, 5.0, and 10.0 seconds of relaxation were strongly related to each other, while relaxation parameters (A, B, C) describing relaxation curve shape were generally independent. Compression Fmax, relaxation curve parameter A, and puncture Fmax were significantly different among hybrids. Significant differences between Maryland and Ohio environments were evident for compression Fmax and relaxation curve parameter A. The patterns of firmness means differed among firmness measurement methods, namely for compression Fmax and puncture Fmax, indicating that they measure different aspects of tomato fruit firmness. Soft-fruited parents generally exerted a negative effect on compression Fmax, whereas firm-fruited parents most often exerted a positive effect on compression Fmax. The force required for fruit compression best approximated subjective assessment of fruit firmness. Force required for fruit puncture was subject to a significant environmental × hybrid influence in the genotypes evaluated. Shape of the force relaxation curve (i.e., parameter A) was not predictive of relative fruit firmness. General combining ability (GCA) and specific combining ability were both significant with GCA being the principal source of genetic variation. In agreement with combining ability estimates, narrow-sense heritability estimates for compression Fmax and puncture Fmax were relatively high.

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During the past 40 years, the US fresh-cut product market has experienced a consistent increase in demand because consumers prioritize health and convenience. Increased interest in fresh-cut products and ready-to-eat vegetables has led to innovations in breeding, product selection, and packaging. However, despite the increased popularity of bell pepper and chile pepper (Capsicum annuum L.), research of fresh-cut jalapeño pepper is limited. This study was conducted to identify jalapeño cultivars that could be suitable as a raw fresh-cut product and explore measures beyond tissue membrane electrolyte leakage (EL) of processed products that may be useful for the identification of cultivars suitable for fresh-cut applications. A total of 22 fresh-cut parameters were examined across five cultivars of jalapeño peppers and 10 intercrosses of these cultivars, including visual quality based on an image analysis via a computer vision system, package headspace gas composition, tissue membrane EL, and texture. Based on our results, the genotypes were grouped into five clusters using a cluster analysis. Variables including tissue softening (r2 = 0.95), EL (r2 = 0.95), total energy of the mesocarp (r2 = 0.95), and package headspace carbon dioxide (CO2) partial pressure (r2 = 0.94) had strong associations with the cluster. A principal component analysis with biplots further confirmed the results. Cultivars Goliath and Emerald Fire and their hybrids in the first and second clusters showed good quality for fresh-cut applications. The fifth cluster, represented by a single cultivar, Jalapeño M, had the smallest physical size, rapid shelf-life decline, accumulated CO2 partial pressures, increased EL, and rapid tissue softening in comparison with the other genotypes. All jalapeño cultivars except Jalapeño M maintained good quality until day 14 postprocessing, and some maintained good quality until 21 days postprocessing. Hybrid crosses suggested that two of the cultivars evaluated, Goliath and Emerald Fire, were useful as parents when transferring superior fresh-cut quality traits to progeny. Traditionally, the EL level has been used as an index of freshness (or tissue deterioration). Our results showed that other quality analyses, including measurements of tissue softening via an imaging analysis, and physical analyses of tissue firmness can also be used as indices for the freshness of fresh-cut jalapeños. The results suggest that fruit size, wall thickness, and skin toughness might be useful as predictive measures in the field for the selection of jalapeño genotypes with superior fresh-cut quality.

Open Access

Ten cultivars of processing tomatoes (Lycopersicon esculentum Mill.) grown in bare soil or on black polyethylene and hairy vetch (Vicia villosa Roth.) mulches were evaluated for yield, fruit processing quality, and leaf necrosis. Yields were higher, fruit was heavier, and leaf necrosis less in hairy vetch than in bare soil or black polyethylene mulch. With the exception of pH, yield and fruit quality component responses to mulch treatments were not cultivar-dependent. Fruit pH, soluble solids concentration, and color equaled values obtained using bare soil production practices. Percent solids was highest with black polyethylene and lowest in hairy vetch. The hairy vetch mulch delayed fruit maturity compared to the bare soil and black polyethylene. The hairy vetch cultural system has the potential to increase yield of processing tomatoes.

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Pepino mosaic virus (PepMV) was first found in pepino (Solanum muricatum) growing in coastal Peru in 1974 and described in 1980; it reappeared in protected tomato (Lycopersiconesculentum) in the Netherlands in 1999. Since then, it has been reported to occur in tomato in several countries including Austria, Belgium, Canada, France, Germany, Italy, Peru, Spain and the Canary Islands, the United Kingdom, and in 11 states within the United States. Three strains of PepMV found in the United States have been cloned and sequenced. Full-length genomic sequences were obtained for two strains, PepMV-US1 and PepMV-US2, from co-infected tomato plant samples from Arizona. The 3'-end sequence of PepMV-US3 came from infected tomato fruits from Maryland. The genome organization, motifs and domains typical of the genus Potexvirus, and of other PepMV isolates, were found in full-length sequences of both US1 and US2 isolates. Direct comparison of US1 and US2 at the nucleotide level revealed an 86.3% identity; whereas, when individually compared to the French and Spanish isolates, which share ∼99% identity at the nucleotide level, US1 and US2 had 82% and 79% identities to each, respectively. Pair-wise gene-for-gene comparisons between United States and European isolates revealed a similar trend. While unique, US1 is more closely related to the previously reported European isolates than is US2. The CP of US3 is nearly identical to the European isolates at the amino acid level. None of 18 tomato germplasm accessions or 10 cultivars were resistant to mechanical inoculation with US3; in contrast, no infection was detected in nine pepper cultivars or four germplasm accessions. Plants grown from seeds of infected tomato fruits did not test positive for PepMV.

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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.

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