Ivette Guzman, Danise Coon, Krystal Vargas, and Paul W. Bosland
Calen McKenzie, Ivette Guzman, Ciro Velasco-Cruz, and Paul W. Bosland
Lutescens, or lutescent, plant mutants produce leaves that are abnormally light yellow-green compared with normal plants, and are observed in multiple species of Capsicum as well as other genera such as Zea, Oryza, and Oenothera. Previous investigations into the lutescent phenotype in Capsicum have focused on genetic and transcriptomic analyses, and comparatively little is known about the phytochemical constituents of the lutescent leaf phenotype. Previous research in similar lutescent mutants in Capsicum and Oryza species has attributed their pale yellow-green leaf color and poor vigor to deficient chloroplast development. A total of 25 accessions of Capsicum lutescens mutants were phenotyped and analyzed based on a multivariate approach, using ‘Jupiter’ bell pepper (Capsicum annuum) with normal green leaves as a contextual benchmark. Photosynthetic pigments from mutant leaves were extracted and analyzed using high-performance liquid chromatography (HPLC); reflectance of the leaf material was measured with a chromameter using the L*a*b* color space. The chlorophyll a (Chl a)/b (Chl b) ratio was greater in leaves of lutescens mutants than in ‘Jupiter’. Multivariate statistical analyses revealed all lutescent mutant accessions could be distinguished from the ‘Jupiter’ contextual benchmark by variables indicating poor chloroplast development and increased photooxidative stress in lutescent mutant accessions. The lutescent leaf phenotype was not found to be caused by elevated xanthophyll or decreased chlorophyll concentrations. Furthermore, multivariate analysis revealed the lutescent mutant phenotype to be variable, with a wide range of phenotypes clustered into four major groups.
Gad G. Yousef, Mary A. Lila, Ivette Guzman, James R. Ballington, and Allan F. Brown
Blueberry (Vaccinium L. section Cyanococcus Gray), a rich source of polyphenolics with important implications for human health and chronic diseases, has become a major fruit commodity in the United States. This study was designed to assess the impact of introgression through interspecific hybridization on anthocyanin (ANC) profiles among blueberry species. Southern highbush blueberry (V. corymbosum L.) and rabbiteye blueberry (V. virgatum Ait.) commercial cultivars, North Carolina blueberry breeding selections, and blueberry breeding populations with varying degrees of introgression from multiple species were used to address this question. The breeding selections and populations were created and selected for traits not directly related to their ANC profiles and are therefore likely representative of the current selection objectives of most public and private breeding programs. Ripe fruit at a uniform stage of maturity were evaluated for ANC concentration and profile in 2 consecutive years (2010 and 2011) from all plants. Total ANC ranged from 189 to 464, 74 to 421, and 227 to 537 mg/100 g (frozen fruit) in the commercial cultivars, breeding selections, and breeding populations, respectively. Significant increases in total ANC were observed among material that represents an expanded gene pool in southern highbush blueberry (introgression from V. angustifolium Ait., V. elliottii Chap., V. myrsinites Lam., V. pallidum Ait., V. tenellum Ait., V. fuscatum Ait., V. constablaei Gray, and V. arboreum Mar.). Differences in acylation and glycosylation patterns were also observed in the same material, which may condition relative stability, absorption, and bioavailability of ANC. Results suggest that the expansion of the gene base through interspecific hybridization can have both a positive and negative impact on ANC accumulation and that breeders need to be aware of these issues early in the breeding program.
Robert F. Heyduck, Steven J. Guldan, and Ivette Guzmán
In a two-part study, we examined the effect of sowing date and harvest schedule on the yield of spinach (Spinacia oleracea) grown during the winter in 16 × 32-ft-high tunnels in northern New Mexico. Each part of the study was conducted for two growing seasons and took place between 2012 and 2015. In Study A (2012–13 and 2013–14), spinach was sown four times at roughly 2-week intervals (mid-October, early November, mid-November, and early December) and plant density (plants per square foot), plant height (centimeters), and yield (grams per square foot) were measured for three harvests in mid-January, mid-February, and mid-March. The earliest sowing date had the least-dense stands, and plant density increased with each subsequent sowing. The two earliest sowing dates had significantly higher season-long yield than the later two sowings. In Study B (2013–14 and 2014–15), all plots were sown in mid-October, but harvest schedule treatments were staggered such that harvests began at 9, 11, 13, or 15 weeks after sowing and continued at irregular intervals. Treatment 2, with harvests beginning after 11 weeks, had the greatest season-long yield, slightly greater than when harvests began at 9 weeks, and significantly more than when harvest began 13 weeks or later. More importantly, a staggered harvest schedule can provide spinach weekly for direct marketing opportunities.
Ivette Guzman, Krystal Vargas, Francisco Chacon, Calen McKenzie, and Paul W. Bosland
This study investigated the diversity of carotenoids and phenolics in germplasm from three Capsicum (chile pepper) species, Capsicum annuum, Capsicum baccatum, and Capsicum chinense. Lutein, a yellow-pigmented carotenoid, and phenolics, a group of secondary metabolites, are reported to have health-promoting properties. The germplasm studied matured to a yellow color. The hypothesis was that all yellow fruits would contain either the carotenoid lutein, a yellow pigment, or a large amount of phenolics, a group of secondary metabolites that may be yellow among other colors. Thirty-one Capsicum accessions were grown in the field over a period of two seasons. On a dry weight (DW) basis, lutein ranged from 0.14 to 94.2 μg·g−1, and total phenolics ranged from 5.79 to 15.01 mg·g−1. No lutein was detected in one accession and β-carotene, another health-promoting compound, was lacking in four accessions. Accessions were grouped into four groups according to a principal component analysis plot. Results from this study indicate that in only nine accessions, lutein represented at least 50% of the total carotenoid amounts in each accession. These accessions are desirable not only as a source of dietary lutein, a natural yellow pigment, but also as genetic material that can be used to breed for higher lutein Capsicum. Therefore, yellow color is not a good indicator of lutein content and phytochemical analysis is required to determine the content of health-promoting compounds.
Jacqueline Cormier, Robert Heyduck, Steven Guldan, Shengrui Yao, Dawn VanLeeuwen, and Ivette Guzman
A decrease in available farmland worldwide has prompted interest in polyculture systems such as intercropping where two or more crops are grown simultaneously on the same land to increase the yield per farm area. In Alcalde, NM, a year-round intercropping system was designed to evaluate organically produced blackberry cultivars (Rubus, subgenus Rubus) and winter greens in a high tunnel over a 2-year period. Two floricane fruiting blackberry cultivars, Chester Thornless and Triple Crown, were grown intercropped with ‘Red Russian’ kale (Brassica napus) and ‘Bloomsdale’ spinach (Spinacia oleracea) in a high tunnel. In an adjacent field, the planting of blackberry was repeated with no winter intercrop and no high tunnel. Both cultivars of blackberry were harvested July to September, and fresh weights were measured to determine suitability to the intercropping system in the high tunnel. Both species of winter greens were harvested January to April, and fresh yield weights were measured to discern fitness as possible intercrops in this system. Row covers were used for kale and spinach, and air temperatures were monitored November to April inside the high tunnel. High tunnel temperatures were within acceptable ranges for the production of greens with the use of rowcovers. Yield data from this study indicates that ‘Triple Crown’ blackberry outperformed ‘Chester Thornless’ blackberry in both the high tunnel and field trials with significant difference in the second season. Additionally, blackberry yields from both cultivars were observed to be higher in the field than in the high tunnel for both years. High temperature damage to high tunnel berry canes was noticed for both cultivars, with observed yield decreases in the second year in the high tunnel. Overall, this study indicates that the phenology and climate needs of the two winter greens and blackberry cultivars were not compatible for sustaining year-round organic high tunnel production.
Allan F. Brown, Gad G. Yousef, Ivette Guzman, Kranthi K. Chebrolu, Dennis J. Werner, Mike Parker, Ksenija Gasic, and Penelope Perkins-Veazie
The objective of this study was to examine the relative impact of genetics and environment on phenolic and carotenoid profiles in peach (Prunus persica) germplasm. Fully mature, (“ready-to-eat” stage) firm fruit of peach cultivars China Pearl, Contender, and Carolina Gold were collected from established trees at two North Carolina locations in 2009 and 2010. Advanced breeding selections NC Yellow and NC 97-48 were collected from a single location in both years. Using tandem extractions and chromatography analyses, 10 carotenoids and 24 phenolic compounds were quantified separately in the peel and flesh. Statistically significant differences were noted among peach cultivars and advanced selections for β-carotene, cyanidin-3-glucoside, cyanidin-3-rutinoside, cholorogenic acid, quercetin-3-glucoside, and individual procyanidins. Peel anthocyanin (ANC) concentration ranged from 183 mg/100 g in ‘Contender’ to non-detectable levels in NC97-48 and NC Yellow. ‘China Pearl’ and ‘Carolina Gold’ produced ANC levels approximately half of ‘Contender’. Chlorogenic acid concentration also fit a discrete pattern of accumulation but was not related to the accumulation of ANC. ‘China Pearl’, NC 97-48, and NC Yellow contained the highest levels of chlorogenic acid (105 to 136 mg/100 g), ‘Carolina Gold’ contained the lowest (52 mg/100 g), and ‘Contender’ represented an intermediate phenotype (70 mg/100 g). Statistically significant genetic variation was found for almost all compounds identified, whereas location and year effects tended to be compound-specific. For chlorogenic acid, 28% of the phenotypic variance was explained by location (year = nonsignificant), whereas 40% of the phenotypic variation of ANC was explained by differences in years (location = nonsignificant). Analyzing fruit from the same environment over 2 years or from two locations in the same year would not have adequately accounted for the variation associated with environment. The detailed phytochemical profile of peach reported here demonstrates the importance of multiyear, multilocation analysis in revealing accurate measures of phytochemical genetic variation and provides a comprehensive baseline analysis of phytochemicals in commonly grown peach cultivars that can be used to evaluate novel germplasm.