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.
Ivette Guzman, Krystal Vargas, Francisco Chacon, Calen McKenzie, and Paul W. Bosland
Evan Elford, Jim Todd, Peter White, Rachel Riddle, John O’Sullivan, and Rene Van Acker
To foster development of Ontario commercial tigernut (Cyperus esculentus var. sativus) production, this study was conducted to identify cultural management practices that increase tuber yields. The agronomic practices of field preparation (hilled vs. not hilled), regular irrigation vs. natural rainfall, varying rates of nitrogen (N) fertility, and early season weed management were evaluated. Irrigation had no significant impact on total fresh weight, dry weight, and marketable yield over 2 growing seasons. Similarly, yields from plants grown in hilled rows vs. flat beds over two seasons showed no significant differences. Tigernut yields did not show a response to increasing rates of N up to 150 kg·ha−1. A critical weed-free period of 3 weeks resulted in an 844% yield increase over the nonweeded control. Overall, the results indicate that in general, tigernut requires few inputs to produce a viable commercial yield under Ontario growing conditions.
Yongjun Yue and John M. Ruter
The genus Pavonia is one of the largest genera in the Malvaceae species; it is mainly distributed in South America. Three species of Pavonia were identified based on different flower colors and potential for landscape use in the southeastern United States. These species produce a large amount of seed at the end of the blooming season, which is not ideal for ornamental use. To reduce the seed set, gamma irradiation was used for mutation induction and propensity to induce compactness and sterility. A preliminary study indicated that the seed of Pavonia hastata would germinate at irradiation rates up to 2000 Gy. Seeds of three species were treated with six different dose rates ranging from 0 Gy to 1000 Gy to determine the ideal rate for Pavonia breeding and how gamma irradiation affected seed germination. M1 (the first mutant generation) P. lasiopetala and P. missionum were sown in 2018 and planted in the field at the University of Georgia Durham Horticulture Farm on 1 May 2019, as were M2 (the second mutant generation) seeds of P. hastata. Seed germination in 2019 showed no significance due to treatment but significance due to species and species by treatment interaction. Field evaluation performed in 2019 indicated that height was not influenced by irradiation for any of the three species but that the width index was. Flower diameter and leaf area of P. missionum became smaller as the irradiation rate increased, but the other two species showed no trends. Chlorophyll mutations were observed on P. hastata at the 1500 Gy level, which has attractive traits for ornamental use.
Virginia M. Moore and William F. Tracy
Corn earworm (Helicoverpa zea) is a destructive pest with limited management options in sweet corn (Zea mays) production. Increased husk extension and the presence of the C-glycosyl flavone maysin are two proposed mechanisms for improving corn earworm resistance in corn cultivars. A factorial mating design was conducted to test hybrid combinations of sweet corn inbreds with long husks and/or maysin to identify candidates for future cultivar development. The mating design had seven male parents, including three commercial sweet corn inbreds (Wh9261, We11401, and Wt1001) and four inbreds selected for maysin content (Maysin1, 2, 3, and 4), and five female parents, including two commercial sweet corn inbreds (Ia453su and Ia5125su) and three inbreds with long, thick, tight husks (A684su, A685su, and A686su). Hybrids were evaluated for ear length, husk length, maysin content, and corn earworm resistance at six environments in 2016 and 2017. Relationships between husk extension, maysin, and corn earworm resistance were inconsistent, but five inbreds produced hybrids with significantly lower corn earworm infestation and/or damage, demonstrating potential to confer resistance to the corn earworm.
Marcela Miranda, Xiuxiu Sun, Christopher Ference, Anne Plotto, Jinhe Bai, David Wood, Odílio Benedito Garrido Assis, Marcos David Ferreira, and Elizabeth Baldwin
Coatings are generally applied to fruit as microemulsions, but nanoemulsions are still experimental. ‘Nova’ mandarins (Citrus reticulata) were coated with shellac or carnauba (Copernica cerifera) microemulsions or an experimental carnauba nanoemulsion; these were compared with an uncoated control during storage for 7 days at 20 °C. Coatings were also tested on ‘Unique’ tangors (C. reticulata × C. sinensis) stored for 14 days at 10 °C followed by a simulated marketing period of 7 days at 20 °C. Fruit quality evaluations included weight loss, gloss, soluble solids (SS), titratable acidity (TA), pH, SS/TA ratio, internal CO2, O2, fruit juice ethanol, and other aroma volatile content. Sensory visual shine and tangerine (C. reticulata) flavor rank tests after storage were conducted, followed by an off-flavor rating. The carnauba waxes resulted in less weight loss compared with the uncoated control and shellac coating during both experiments. There were no differences in gloss measurements of ‘Nova’ mandarins; however, shellac-coated fruit ranked highest for shine in a sensory test. For ‘Unique’ tangors, initially, shellac showed the highest gloss (shine) measurement; however, at the end of storage, the nanoemulsion exhibited the highest gloss, although it was not different from that of the microemulsion. Similarly, after storage, the nanoemulsion ranked highest for visual shine, although it was not different from that of the microemulsion. There were only minor differences in SS, TA, pH, and SS/TA among treatments. The internal CO2 gas concentration and juice ethanol content generally increased and internal O2 decreased during storage. The highest levels of CO2 and ethanol were found for the shellac treatment, as was the lowest O2, indicating anaerobic respiration. There were only minor differences among the other coating treatments; however, they were only sometimes different from those of the control, which generally had the highest O2, lowest CO2, and lowest ethanol. Shellac and the carnauba microemulsion also altered the volatile profile more than the control and the nanoemulsion did, especially for ‘Unique’ tangors. For ‘Unique’ tangors, the control and nanoemulsion ranked highest for tangerine flavor and had the least off-flavor at the end of storage. Among the coatings tested, the carnauba emulsions demonstrated less water loss, imparted more sustainable gloss, and caused less ethanol production than shellac, with the nanoemulsion exhibiting higher gloss measurements, less modifications of the atmosphere and volatile profile, and, consequently, better flavor compared with the microemulsion.
Rachel P. Naegele and Mary K. Hausbeck
Phytophthora capsici causes root and fruit rot and foliar blight of pepper. Multiple sources of resistance to Phytophthora root rot have previously been identified, but most display only partial resistance. One source, CM334, has broad spectrum root rot resistance to multiple pathogen isolates but has only low to moderate fruit rot resistance. This study evaluated previously identified pepper lines for resistance to two P. capsici isolates, OP97 and 12889, and compared root rot resistance to fruit rot resistance and genetic structure. CM334 was confirmed as a broad spectrum resistance genotype, whereas all other sources of resistance evaluated were susceptible to infection by one or both isolates evaluated. Although not completely resistant, PI 566811 displayed moderate resistance to fruit and root rot to both P. capsici isolates. Fruit rot resistance had a significant but small to moderate positive correlation (r = 0.26–0.63) with root rot resistance depending on the isolate and length of exposure. Pepper accessions with resistance to Phytophthora root and fruit rot belonging to different genetic subpopulations were identified and could serve as candidates for partial-resistance loci to incorporate into pepper breeding programs.
Gregory E. Frey, Tarik Durmus, Erin O. Sills, Fikret Isik, and Marcus M. Comer
Shiitake (Lentinula edodes) is an edible mushroom-producing fungus. “Natural log-grown” shiitake mushrooms are favored by consumers and are often produced by small farmers and hobbyists in the United States. The tree species most often recommended as a substrate for shiitake is white oak (Quercus alba), which has many other economic uses. We tested two strains of shiitake in log substrates of three common, low-value tree species in the southeastern United States to identify potential alternatives to white oak. We found that sweetgum (Liquidambar styraciflua) was a good substitute for white oak, both in terms of mushroom production and financial returns. Red maple (Acer rubrum) had less potential, with lower production and marginal financial returns, and ailanthus (Ailanthus altissima) was not a suitable alternative substrate. Of the two shiitake strains tested, a commercially available strain performed better than a naturalized strain that was isolated from an uninoculated log. Further research is needed to identify other potential alternative substrates and production techniques in the southeastern United States and other regions.
Guirong Li, Ran Quan, Chaohui Yan, Xiaojin Hou, and Huiling Hu
Grape (Vitis vinifera) is among the world’s most important fruit crops and is a commonly used woody plant for genomics and post-genomics research. NAC transcription factors play central roles in plant growth and development, floral organ morphogenesis, and responses to biological stress. It is therefore important to identify key transcription factors from grape and clarify their mechanisms of action to generate genetic resources for grape molecular improvement. Our research group previously cloned a NAC transcription factor from V. vinifera ‘Yatomi Rosa’ [drought and leaf roll gene 1 (DRL1)] and demonstrated that it caused dwarfing of tobacco (Nicotiana benthamiana) plants when overexpressed. In the present work, we demonstrate that overexpression of DRL1 in transgenic tobacco delays flowering time and markedly reduces pollen viability. Furthermore, crosses between male DRL1 transgenic tobacco and female wild-type tobacco exhibit substantially lower fruit set, fruit and seed weights, fruit and seed shape indices, and seed germination rates than selfed wild-type plants or crosses with a transgenic female parent. DLR1 overexpression strongly influences flowering time and reproduction in transgenic tobacco, primarily through its effects on pollen development. These results provide a foundation for further functional characterization of DLR1 in grape.
Hong Su, He Zhang, Chaoxia Wang, Jianquan Huang, Jiayin Shang, Na Zhang, Dan Wang, and Kai Li
The addition of pulverized grape pruning wood to grape soils has a positive effect on fruit quality. However, its effects on the soil microecology of the root zone and the growth of the grape plants are not fully understood. To address this, ‘Shine Muscat’ grapes were cultivated in media consisting of garden soil and crushed grape pruning material at different mass ratios [100:1 (T1), 50:1 (T2), 30:1 (T3), 20:1 (T4), and 10:1 (T5)] and in garden soil without the pruning material, as a control. The changes in the plant fresh weight, leaf area, soil and plant analyzer development (SPAD) value, root development, soil organic carbon, microbial biomass carbon, and soil enzyme activity were determined over time. High-throughput sequencing technology was used to determine the soil bacterial community structures. The pruning supplementation increased the grape plants fresh weight, leaf area, and SPAD values. The T2 and T3 treatments increased the grape root length, surface area, and the projected area and number of the root tips; the soil organic carbon content, microbial biomass carbon content, soil invertase activity, amylase activity, and β-glucosidase activity were also significantly increased. The addition of the grape pruning material was found to increase the bacterial diversity and richness 60 and 150 days after treatment. At the phylum level, Proteobacteria, Acidobacteria, and Actinobacteria were the dominant groups, and the grape pruning material increased the relative abundance of the Acidobacteria and Actinobacteria after 60 and 150 days. The relative abundance of the Actinobacteria in the T2 treatment was 1.7, 1.3, 1.5, and 1.3 times that of the control, after 60, 90, 120, and 150 days, respectively. The T2 treatment was identified as the optimal treatment for grapes in the field because it improved the soil microecology and promoted root and tree development the most compared with the other treatments tested.
Rhuanito S. Ferrarezi, Arun D. Jani, H. Thomas James III, Cristina Gil, Mark A. Ritenour, and Alan L. Wright
The prevalence of Huanglongbing (HLB) in Florida has forced growers to search for new management strategies to optimize fruit yield in young orchards and enable earlier economic returns given the likelihood of HLB-induced yield reductions during later years. There has been considerable interest in modifying orchard architecture design and fertilizer and irrigation management practices as strategies for increasing profitability. Our objectives were to evaluate how different combinations of horticultural practices including tree density, fertilization methods, and irrigation systems affect growth, foliar nutrient content, fruit yield, and fruit quality of young ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] trees during the early years of production under HLB-endemic conditions. The study was conducted in Fort Pierce, FL, from 2014 to 2020 on a 1- to 7-year-old orchard and evaluated the following treatments: standard tree density (358 trees/ha) and controlled-release fertilizer with microsprinkler irrigation (STD_dry_MS), high tree density (955 trees/ha) with fertigation and microsprinkler irrigation (HDS_fert_MS), and high tree density with fertigation and double-line drip irrigation (HDS_fert_DD). Annual foliar nutrient concentrations were usually within or higher than the recommended ranges throughout the study, with a tendency for decreases in several nutrients over time regardless of treatment, suggesting all fertilization strategies adequately met the tree nutrient demand. During fruit-bearing years, canopy volume, on a per-tree basis, was higher under STD_dry_MS (6.2–7.2 m3) than HDS_fert_MS (4.3–5.3 m3) or HDS_fert_DD (4.9–5.9 m3); however, high tree density resulted in greater canopy volume on an area basis, which explained the 86% to 300% increase in fruit yield per ha that resulted in moving from standard to high tree density. Although fruit yields per ha were generally greatest under HDS_fert_MS and HDS_fert_DD, they were lower than the 10-year Florida state average (26.5 Mg·ha−1) for standard tree density orchards, possibly due to the HLB incidence and the rootstock chosen. Although tree growth parameters and foliar nutrient concentrations varied in response to treatments, management practices that included high tree density and fertigation irrespective of irrigation systems produced the highest fruit yields and highest yield of solids. Soluble solids content (SSC) and titratable acidity (TA) were lower, and the SSC-to-TA ratio was highest under STD_dry_MS in 2016–17, with no treatment effects on quality parameters detected in other years. Both drip and microsprinkler fertigation methods sufficiently met tree nutrient demand at high tree density, but additional research is needed to determine optimal fertilization rates and better rootstock cultivars in young high-density sweet orange orchards under HLB-endemic conditions in the Indian River Citrus District.