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Derek W. Barchenger, Danise L. Coon and Paul W. Bosland

Controlled abscission of floral structures is an important horticultural technique that has many applications throughout the growing season. A novel use of chemical abscission in chile pepper (Capsicum annuum) is the removal of open flowers and fruit for the production of breeder seed. For efficiency of abscising flower buds, open flowers, and fruit of ornamental chile peppers, two foliar spray treatment levels, 1000 and 2000 ppm ethephon were tested. Ornamental chile peppers were chosen because they are prolific flower and fruit producers, making removal of potentially cross-pollinated fruit and open flowers laborious. Flower bud and flower number were reduced with both 1000- and 2000-ppm ethephon treatments, while fruit number decreased only with 2000-ppm ethephon treatment. ‘NuMex Easter’ was more sensitive to ethephon treatment as compared with ‘Chilly Chili’ and ‘Riot’. Ethephon had no negative impacts on end of the season growth index, mature fruit number, and seed number. We found ethephon can reduce numbers of flower buds, open flowers, and fruit with no long-term effect on mature fruit and seed number, making it a useful tool for the production of breeder seed in chile pepper breeding programs.

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Danise Coon, Derek W. Barchenger and Paul W. Bosland

In the past, many ornamental chile pepper (Capsicum annuum) cultivars had to be pinched or sprayed with a uniconazole foliar application to achieve a dwarf, semidwarf, or compact plant habit. This study compares 12 currently available commercial ornamental pepper cultivars considered to be compact, and introduces 13 new ornamental pepper cultivars that do not require pinching or a uniconazole foliar spray to accomplish the desired dwarf or semidwarf plant habit. All 25 cultivars evaluated in this study were given either a dwarf or semidwarf classification based on industry standards. Of the 25 cultivars evaluated, 12 originate from and are commercially available and bred by various breeding programs, whereas 13 are new cultivars bred by the New Mexico State University Chile Pepper Breeding Program with the goal of having dwarf or semidwarf growth habits. Data indicate that the 13 new ornamental chile pepper cultivars did not require pinching or a chemical foliar spray to develop a dwarf or semidwarf plant habit and have the potential for commercial container production in the greenhouse and nursery industries.

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Derek W. Barchenger, John R. Clark, Renee T. Threlfall, Luke R. Howard and Cindi R. Brownmiller

A major limiting factor in fresh-market muscadine grape (Vitis rotundifolia Michx.) commercialization is fruit deterioration during storage. Research on table grapes has shown that field fungicide applications increase storability, but little is known of their effect on muscadines. The effect of field applications of fungicides on physicochemical attributes during postharvest storage and nutraceutical content at date of harvest was evaluated on five muscadine cultivars (Nesbitt, Southern Jewel, Summit, Supreme, and Tara) and four breeding selections from the University of Arkansas Fruit Breeding Program in 2012 and 2013. There were two field treatments (no fungicide and fungicide). For the fungicide treatment, alternating applications of two fungicides were applied to the vine at 14-day intervals during berry maturation. Fruit was harvested and physicochemical attributes including berry volume, titratable acidity (TA), pH, soluble solids (%), color (L, chroma, and hue), firmness (force to penetrate berry skins and flesh), storage weight loss (%), and unmarketable fruit (%) were evaluated every 7 days for 3 weeks. Whole muscadine berries were analyzed for nutraceutical content only for the date of harvest. As a result of less decay, less weight loss, and greater firmness during storage, AM 27, ‘Southern Jewel’, and ‘Supreme’ had the highest potential for postharvest storage, whereas AM 01, AM 15, and ‘Tara’ had the least potential. Nutraceutical content varied by genotypes; overall AM 27 had the highest nutraceutical content [sum of anthocyanins, total phenolics, flavonols, resveratrol, and oxygen radical absorbane capacity (ORAC)], whereas ‘Supreme’ and AM 28 had the lowest. Total anthocyanins were only found in the black genotypes and total phenolics and resveratrol were unaffected by fungicide treatment. Total ellagitannins varied among the fungicide treatments. Total flavonols were generally greater in the no fungicide treatments, whereas ORAC was generally greater with fungicide treatments. Year of study and genotype were determined to be major contributors as sources of variation. Although field fungicide applications did not affect all postharvest attributes and nutraceutical components, differences among genotypes and fungicide treatments did occur.

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Derek W. Barchenger, John R. Clark, Renee T. Threlfall, Luke R. Howard and Cindi R. Brownmiller

Muscadine grapes (Vitis rotundifolia Michx.) are native to the southeastern United States and have potential for greater fresh-market sales if postharvest storage can be improved, but limited information is available on postharvest storability. In 2012 and 2013, physiochemical and storability attributes were measured in 17 muscadine genotypes (selections and cultivars) from the muscadine breeding program at the University of Arkansas or commercial cultivars. The postharvest and physiochemical attributes of the muscadines were measured at harvest and during storage for 3 weeks at 2 °C. Nutraceutical compounds were measured initially after harvest. As a result of extreme differences in weather in 2012 and 2013, the data were analyzed by year. Genotypes significantly affected storage attributes [weight loss (%), and unmarketable berries (%)] and physiochemical attributes such as penetration force (force to penetrate berry skin), titratable acidity (TA), pH, soluble solids (%), berry color (L*, chroma, and hue) as well as the nutraceutical compounds. The postharvest attributes of weight loss and unmarketable berries and the physiochemical attribute of penetration force were significantly affected by postharvest storage, but berry composition attributes remained fairly constant during storage. Overall, University of Arkansas selections AM 04, AM 26, AM 28, and the cultivar Southern Jewel had the highest potential for postharvest storage, whereas the genotypes AM 01, AM 15, AM 18, and ‘Nesbitt’ had the least potential. Genotypes AM 03, AM 04, AM 27, and ‘Ison’ had the highest nutraceutical contents [total anthocyanins, total phenolics, total flavonols, resveratrol, and oxygen radical absorbance capacity (ORAC)], whereas AM 18, AM 28, ‘Supreme’, and ‘Tara’ had the lowest contents. Postharvest storage potential, berry composition, berry color, and nutraceutical content were genotype-specific, but commercially viable genotypes were identified that can provide genetic material for breeding programs and postharvest evaluation protocol for commercial use.

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Derek W. Barchenger, Robert A. Clark III, Paul A. Gniffke, Dolores R. Ledesma, Shih-wen Lin, Peter Hanson and Sanjeet Kumar

Multilocation trials are important for breeding programs to identify high-yielding, adapted lines for a wide range of environments. In this study, we evaluated yield and yield components (fruit weight, fruit length, and fruit width) as well as days to 50% anthesis and fruit maturity of the 10 chili pepper lines in the International Chili Pepper Nursey 15 (ICPN15) distributed by the World Vegetable Center to interested cooperators worldwide. Performance data of the ICPN15 entries were received from collaborators evaluating the set in seven different environments in five countries (Indonesia, South Korea, Thailand, Taiwan, and Vietnam). Significant genotype-by-environment (G × E) interactions were detected for all traits evaluated. Additive main effect and multiplicative interaction analyses indicated high environmental influence on yield, days to 50% anthesis, and maturity, whereas genotype was the greatest contributor to variability in the market-driven yield components of fruit length, width, and weight. Four lines (ICPN15-4, -5, -7, and -10) were identified as highly stable and could serve as sources of yield and yield component stability in either short fruit market segments (ICPN15-4) or long fruit market segments (ICPN15-5, -7, and -10). We attempted to used publicly available weather data to help in explaining the source of the environmental variability; however, differences between analyzed and observed weather were too different to be useful. This is evidence that weather data should be collected at each testing environment in future studies. This study provides a basis for future studies in the stability of important horticultural traits in pepper, and highlights the need for further work in this area.

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Derek W. Barchenger, Joseph I. Said, Yang Zhang, Mingzhou Song, Franchesca A. Ortega, Yeasong Ha, Byoung-Cheorl Kang and Paul W. Bosland

Pentatricopeptide repeat (PPR) proteins constitute one of the largest protein families in plants. They are typically targeted to the mitochondria or chloroplast and bind to one or more organellar transcripts, influencing expression. Genes responsible for inhibiting the mitochondrial genes that cause cytoplasmic male sterility (CMS), restorer-of-fertility (Rf) genes, often encode PPRs. Using in silico techniques, 552 PPR domains were identified throughout the chile pepper (Capsicum annuum) genome. The domains were mapped across 12 chromosomes and were found to be largely distally or proximally located. About 28% of the chile pepper PPR domains identified in this study have high structural similarity to previously reported PPRs in arabidopsis (Arabidopsis thaliana). In addition, 11 candidate Rf genes clustered on chromosome 6, and 1 on chromosome 1 were identified that were characterized in 16 A- (S rfrf), B- (N rfrf), and C-line (N RfRf) backgrounds. These findings support a multigene model for fertility restoration and broaden our understanding of the restoration of fertility. This may be an explanation for the lack of widely applicable molecular markers for this important trait. With this new information, specific Rf markers may be developed and will facilitate the implementation of hybrid breeding programs in chile pepper. In addition, this work provides a basis for future research in PPRs, an increasingly important gene family.

Open access

Derek W. Barchenger, Sopana Yule, Nakarin Jeeatid, Shih-wen Lin, Yen-wei Wang, Tsung-han Lin, Yuan-li Chan and Lawrence Kenyon

Chile pepper (Capsicum annuum L.) is an increasingly important vegetable and spice crop. Among the most devastating chile pepper–infecting viruses, especially in tropical and subtropical regions, are members of the whitefly transmitted Begomovirus, which cause pepper yellow leaf curl (PYLC). An effective PYLC management strategy is the development of resistant cultivars. However, genetic recombination, acquisition of extra DNA components, and synergistic interactions among different begomoviruses have resulted in the rapid emergence of new viruses that can infect new hosts, cause new disease symptoms, and overcome host resistance. In this project, 98 Capsicum entries comprising breeding lines, open pollinated varieties, genebank accessions, and wild species were screened for resistance to strains of Pepper yellow leaf curl Thailand virus (PepYLCThV). We used a randomized complete block design with three replications and 10 plants per replication in field net-houses at two locations (Khon Kaen and Kamphaeng Saen, Thailand) using augmented inoculation by viruliferous whiteflies. Scoring was done at ≈60, 90, and 120 days after inoculation using a standardized 6-point scale (1 = no symptoms to 6 = very severe symptoms), and the average of the scores of 10 plants within each replication was used for analysis. Although no entry was immune to the disease, the breeding line 9852-123 was highly resistant. Several accessions and lines were moderately resistant at both locations, although a high level of variability within these entries was observed. Overall, the disease severity at the Khon Kaen location was greater compared with Kamphaeng Saen, highlighting the importance of multilocation testing for disease resistance. The resistant entry identified here can be used to study gene action and to move resistance genes into well-adapted germplasm.

Open access

Derek W. Barchenger, Khin Thandar, Thain Gi Myint, Tran Ngoc Hung, Nguyen Quoc Hung, Shih-wen Lin, Yen-wei Wang and Tsung-han Lin

Chile pepper (Capsicum annuum) is an increasingly important crop worldwide, and Vietnam and Myanmar are major producing countries. The chile pepper markets in Myanmar and Vietnam are different, with production primarily for domestic consumption in Myanmar and for the export market in Vietnam. However, there is an overall lack of domestically developed cultivars in both countries. The objective of this study was to identify high-performing chile pepper entries, adapted to local conditions, for use in domestic breeding programs or direct release. Fruit length, width, weight, and yield were measured during two seasons (2016–17 and 2018–19), and the same entries were evaluated in Hanoi, Vietnam, and Nay Pyi Taw, Myanmar. However, different entries were tested in each season. During the 2016–17 season, AVPP1324 grown in Hanoi had the overall highest yield (15.3 t·ha–1), followed by AVPP1330 (15.0 t·ha–1 in Hanoi) and AVPP1111 (14.4 and 14.9 t·ha–1 in Hanoi and Nay Pyi Taw, respectively). AVPP0303 had the greatest fruit length, fruit width, and fruit weight in both Hanoi and Nay Pyi Taw during the 2016–17 season. During the 2018–19 season, AVPP1345 (24.8 t·ha–1) followed by AVPP9905 (22.5 t·ha–1) in Nay Pyi Taw, and AVPP1245 (17.4 t·ha–1) in Hanoi had the highest yield. AVPP9905 had the greatest fruit weight and width in both locations. AVPP1345 and AVPP9905 had the greatest fruit length during the 2018–19 season. There is an obvious need for domestically produced cultivars in Myanmar and Vietnam that meet local farmer and consumer preferences and that are adapted to the pests, diseases, and stress in each country. Several high-performing lines were identified that can be used as direct release or incorporated in local breeding programs for the development of inbred or F1 hybrid cultivars. This research also provides a basis for future studies on stability of yield and yield components in Southeast Asia.