The carotenoid content of fresh fruits, like chiles or peppers (Capsicum annuum L.), is a desirable fruit quality trait because these compounds increase the nutritional value of the fruit. Carotenoids in general serve as antioxidants, whereas specific carotenoids are pro-vitamin A types and yet others are necessary for retinal pigments. In the plant, carotenoids function to harvest light energy during photosynthesis, act as antioxidants in multiple cell types, and pigment fruit and flowers to attract pollinators and seed dispersal agents. All of these cells presumably accumulate carotenoids through the same biosynthetic pathway. We investigated the relationship between light levels in the growth environment and the carotenoid levels that accumulated in mature fruit and leaves. Three chile cultivars with orange fruit, ‘Fogo’, ‘Orange Grande’, and ‘NuMex Sunset’, were grown under three different light conditions, shaded greenhouse, unshaded greenhouse, and field in Las Cruces, NM. Foliar carotenoid increased approximately twofold with increased light, whereas carotenoid content in fruit decreased two- to threefold with increased light. All cultivars showed identical trends with light despite having cultivar-specific carotenoid accumulation patterns in their fruit.
Neda Keyhaninejad, Richard D. Richins and Mary A. O’Connell
Junxin Huang, Robert Heyduck, Richard D. Richins, Dawn VanLeeuwen, Mary A. O’Connell and Shengrui Yao
Vitamin C profiles of 46 jujube cultivars were assessed from 2012 to 2015, and fruit nutrient dynamics of 10 cultivars during maturation were examined from 25 Aug. to 7 Oct. 2014 at 2-week intervals at New Mexico State University’s Alcalde Sustainable Agriculture Science Center and Los Lunas Agricultural Science Center. This is the first report in the United States profiling Vitamin C in jujube cultivars. The vitamin C content of mature fruit of 45 (of 46) cultivars ranged from 225 to 530 mg/100 g fresh weight (FW) plus ‘Youzao’ having the highest content of 820 mg/100 g FW at early mature stage. In general, drying cultivars had higher vitamin C content than fresh-eating cultivars whereas ‘Jinsi’ series (multipurpose) had relatively higher vitamin C content than others (>400 mg/100 g FW). Fruit vitamin C and moisture content decreased significantly during the maturation process. The average vitamin C contents of nine cultivars at Alcalde decreased more than 40% based on FW from 25 Aug. to 7 Oct. To maximize the vitamin C benefit, the ideal stage to consume fresh-eating cultivars is the creamy stage. Titratable acidity and soluble solids increased significantly during maturation. In mature jujubes, the titratable acidity and soluble solids ranged between 0.27% to 0.46% and 27.2% to 33.7%, respectively. Glucose, fructose, and sucrose content also rose significantly during ripening. Mature fruits contained 31–82 mg/g FW glucose, 32–101 mg/g FW fructose, and 53–159 mg/g FW sucrose among the cultivars tested. Based on sucrose contents, cultivars can be divided into two groups, “high-sucrose” (more sucrose than glucose or fructose) and “low-sucrose” (less sucrose than glucose or fructose). ‘Dagua’, ‘Honeyjar’, ‘Lang’, ‘Li’, ‘Maya’, ‘Sugarcane’, and ‘Sherwood’ belong to the “high-sucrose” group. Total phenolic content and 2,2-diphenyl-1-picrylhydrazyl (DPPH)-reducing capacity in fruit decreased during maturation, and the total phenolic content of mature jujube was 12–16 mg gallic acid equivalent (GAE)/g dry weight (DW). For mature fruit, ‘Li’ and ‘Li-2’ had the highest DPPH-scavenging efficiency whereas ‘Sugarcane’, ‘So’, and ‘Lang’ had the lowest at Alcalde, NM.
Rhiana F. Jones, Paul W. Bosland, Robert L. Steiner, Richard W. Jones and Mary A. O’Connell
Phytophthora capsici is responsible for multiple disease syndromes of Capsicum annuum but the resistance mechanism is still unknown. Evaluating gene expression during foliar blight can be used to identify expression patterns associated with resistance in Capsicum species. This study reports a direct comparison of gene expression changes during the foliar blight syndrome using two different races of P. capsici on C. annuum host plants with resistant and susceptible phenotypes to those races. Four genes were evaluated for differential expression following leaf inoculation with P. capsici. RNA isolated from leaves at three time points was used to quantify gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Of four genes tested, two had differential expression in response to P. capsici at 72 hours postinoculation, a xyloglucan-specific endo-β-1,4-glucanase inhibitor protein (XEGIP2) in susceptible cultivar New Mexico Heritage 6-4 (NMH6-4), and a C. annuum cell wall protein (CWP) in resistant Criollo de Morelos 334 (CM334). Both genes had a 5-fold increase in transcription in leaves over the control. These results suggest that both genes are playing a role in disease resistance to foliar blight.
Laura Rodriguez-Uribe, Luz Hernandez, James P. Kilcrease, Stephanie Walker and Mary A. O’Connell
Two key fruit qualities in Capsicum annuum are fruit pungency and color. We characterize 13 New Mexican landraces for fruit quality traits at both the chemical level measuring the capsaicinoids, dihydrocapsaicin, and capsaicin as well as five carotenoids, β-carotene, β-cryptoxanthin, zeaxanthin, violaxanthin, and capsanthin, and at the genetic level sequencing two genes in these landraces, Kas I, a capsaicinoid pathway gene, and Ccs, a carotenoid pathway gene. All of the landraces had unusually high levels of dihydrocapsaicin in comparison with capsaicin levels. The levels of the most abundant red pigment, capsanthin, ranged between 468 and 1007 μg·g−1 dry weight fruit in field-grown fruit, whereas levels of β-carotene were more similar in the landraces (13 to 22 μg·g−1 dry weight fruit). Twelve different Kas I alleles were found in the landraces, which predicted six novel KAS proteins in these landraces. Seven alleles of Ccs were found, which predicted three novel CCS proteins. These results demonstrate that the landraces under cultivation in small farms and pueblos in northern New Mexico are sources of important genetic diversity for Capsicum crops.
Richard D. Richins, Laura Hernandez, Barry Dungan, Shane Hambly, F. Omar Holguin and Mary A. O'Connell
Plant pigments represent a source of non-toxic compounds that are used as food or cosmetic coloring agents. Red-fruited varieties of Capsicum annuum can be extracted to isolate the red-colored xanthophylls, capsanthin, and capsorubin. Common commercial processes for this extraction use hexane as the extracting solvent and mild or no heat varieties of Capsicum. In this report, we describe a process for efficient extraction of these red pigments using green chemistry: CO2 supercritical fluid extraction and trapping the pigments in ethanol. Furthermore, we demonstrate that this method can be performed on hot or pungent Capsicum fruit and the resulting pigment sample has very low levels of capsaicinoids, 1 to 2 ppm. This process then can reduce the use of hazardous solvents and expand the type of fruit that can be used for the extraction of red pigments.
Andrea L. Medina-Holguín, Sandra Micheletto, F. Omar Holguín, Jaime Rodriguez, Mary A. O'Connell and Charles Martin
The climate conditions and chemical composition of root essential oils for 17 populations of Anemopsis californica in New Mexico were examined. The objective of this study was to observe the effect of environmental conditions and management conditions on essential oil composition in different populations of A. californica. Chemical concentrations of three abundant compounds—methyleugenol, thymol, and piperitone—were determined. Maximum accumulations of each compound were associated with different mean annual temperatures, precipitation, and elevation. Similar chemical profiles were detected in root samples recollected for four populations, suggesting retention of unique chemical profiles in different populations. Vegetative propagation of wild plants under cultivated conditions did not significantly alter the chemical profile of the root essential oil. The chemical concentrations for six essential oil components of A. californica roots were determined under field conditions with varying irrigation and nitrogen (N) fertilizer regimens. The concentration of only two compounds, thymol and piperitone, was increased by increasing irrigation. The concentration of all other compounds, methyeugenol, elemicin, 1,8-cineole, and myrtenol, were independent of the irrigation rates and N fertilizer rates used in the study. These results suggest that the chemical variability observed among different populations of A. californica is primarily genetically controlled and the environmental conditions in New Mexico are conducive to the production of this medicinal plant as a high-value crop.