The sugar-to-acid ratio of pineapple (Ananas comosus L.) contributes toward giving the fruit its unique flavor. This ratio is an important indicator of both commercial and organoleptic ripeness, and it is useful in determining a harvest date. Citric acid is the major acid in pineapple and usually is determined by titration to a specific pH endpoint, while sugars are determined as total soluble solids by refractometry. Both acid and sugar levels vary with the season in the year-round production cycle. Acid titration is slow and difficult to perform in the field. A digital acidity meter based upon diluted juice conductivity was evaluated for potential field use. The readings obtained from the meter varied with clone and fruit potassium concentration. The meter had utility for field use to evaluate fruit quality and harvest date. Because fruit potassium levels can vary between harvests, the meter should be recalibrated on a regular schedule to adjust for potential crop management and seasonal effects.
Robert E. Paull, Gail Uruu, and Nancy Jung Chen
Guang-Lian Liao, Xiao-Biao Xu, Qing Liu, Min Zhong, Chun-Hui Huang, Dong-Feng Jia, and Xue-Yan Qu
Jinyan (Actinidia eriantha × A. chinensis) is one of the gold-fleshed kiwifruit cultivars currently being promoted in south China. However, its fruit dry matter is usually less than 16%, which seriously affects fruit quality including taste and flavor. This causes a financial loss to growers: not only are the prices paid for the fruit low because of their bad reputation for quality, but some orchards have been removed. Improvement of fruit quality is essential. In this study, a method is described for squeezing and twisting flowering shoots before flowering and removing the distal vegetative parts of flowering shoots after fruit set. The effects on fruit quality were determined. The dry matter of fruit was increased by 6.6%. Fruit size also increased as did the chlorophyll a content and the chlorophyll:carotenoid ratio. The significantly increased fruit dry matter, resulting in significant increases in fruit soluble solids concentrations (P < 0.01), thereby possibly improving fruit taste. Fruit weight, fruit length, and carotenoid and ascorbic acid concentrations were significantly enhanced in comparison with controls (P < 0.01), increasing by 20%, 7%, 12%, and 19%, respectively. However, there was no significant difference in soluble sugar concentrations, titratable acid concentrations, and the reduced chlorophyll b concentrations. This research provides a practical method to increase fruit dry matter, and hence a way to allow fruit quality to reach commercial requirements for cultivars such as Jinyan, which under previous management systems had significant shortcomings in fruit flavor and taste.
Andrea C. Landaverde, Jacob H. Shreckhise, and James E. Altland
The pour-through (PT) method is used in greenhouse and nursery production to monitor nutrient availability in soilless substrates. Efficacy of this method is based on the assumption that chemical properties of extracted solutions remain stable from the moment of collection until analysis. Extracted substrate solution can be analyzed directly in the greenhouse or sent to laboratories for complete nutritional analysis; thus, proper sample preservation methods (e.g., filtration and low temperatures) are critical for reducing sample contamination or degradation during storage. However, evidence of how these preservation methods affect chemical characteristics of PT samples is limited. The objective of this study was to evaluate the effect of storage time, storage temperature, and filtration of PT samples on pH, electrical conductivity (EC), and nutrient concentrations from pine bark– and peat-based substrates. PT extracts were obtained from liquid-fertilized fallow pots of either 100% milled pine bark (Expt. 1) or a 4 sphagnum peat: 1 perlite (by volume) substrate (Expt. 2). Aliquots of PT extract were either filtered or nonfiltered and then stored in plastic bottles at −22, 4, or 20 °C. EC, pH, and nutrient concentrations were analyzed at 0, 1, 7, and 30 days after PT sample collection. EC and pH in PT extracts of peat and pine bark, respectively, changed 1 day after collection. Storage time had the greatest effect on nutrient concentrations of samples stored at 20 °C. However, at day 30, nutrient concentrations had also changed in samples stored at 4 and −22 °C. Analytes that fluctuated most in both experiments and across all preservation treatments were dissolved organic carbon, total dissolved nitrogen, NO3 −-N, and PO4 3−-P, whereas Ca2+, Mg2+, and SO4 2−-S were more stable in PT samples. This research suggests EC and pH should be analyzed immediately, whereas samples requiring nutrient analysis should be filtered immediately after collection, stored at 4 or −22 °C (preferably −22 °C), and analyzed within 7 days of collection.
Jessa Hughes, Hamid Khazaei, and Albert Vandenberg
The horticulturally valuable traits of faba bean are poorly explored, including the available information on the genetics of flower color and pattern. This lack of understanding has reduced the inclusion of unique flower color into the horticultural-type faba bean market. The modes of inheritance of two flower colors (red petals and yellow spot on wing petals) were examined through the development of multiple F2 segregating populations. The inheritance of red flower was confirmed for two recessive genes and yellow wing spot inheritance was confirmed for a single recessive gene. These populations led to the discovery of combinations of red and yellow flower color that have not been previously reported. The solid wing petal color gene was confirmed as a single recessive gene. Understanding the inheritance of flower color in faba bean can lead to improvement of current vegetable types and opens up possibilities for ornamental markets.
Claudia Elkins and Marc W. van Iersel
Seedlings may be grown indoors where environmental conditions can be precisely controlled to ensure consistent and reliable production. The optimal spectrum for production under sole-source lighting is currently unknown. Far-red light (λ = 700–800 nm) typically is not a significant part of the spectrum of light-emitting diode (LED) grow lights. However, far-red light is photosynthetically active and can enhance leaf elongation, which may result in larger leaves and increased light interception. We hypothesized that adding far-red light to sole-source lighting would increase the growth of ‘Dalmatian Peach’ foxglove (Digitalis purpurea) seedlings grown under white LED lights, potentially shortening production times. Our objective was to evaluate the effect of far-red light intensities, ranging from 4.0 to 68.8 µmol·m−2·s−1, on the growth and morphology of foxglove seedlings. Foxglove seedlings were grown in a growth chamber with a photosynthetic photon flux density (PPFD) of 186 ± 6.4 μmol·m−2·s−1 and supplemental far-red light intensities ranging from 4.0 to 68.8 µmol·m−2·s−1. As far-red light increased, shoot dry weight, root dry weight, plant height, and plant height/number of leaves increased by 38% (P = 0.004), 20% (P = 0.029), 38% (P = 0.025), and 34% (P = 0.024), respectively, while root weight fraction decreased 16% (P = 0.034). Although we expected supplemental far-red light to induce leaf and/or stem expansion, specific leaf area and compactness (two measures of morphology) were unaffected. Because a 37% increase in total photon flux density (PPFD plus far-red light) resulted in a 34.5% increase in total plant dry weight, the increased growth likely was due to increased photosynthesis rather than a shade-acclimation response. The growth response was linear across the 4.0 to 68.8 µmol·m−2·s−1 range of far-fed light tested, so we were unable to determine a saturating far-red photon flux density.
Paige E. Boyle, Michelle M. Wisdom, and Michael D. Richardson
Most pollinating insects require a season-long succession of floral resources to fulfill life-cycle requirements. Incorporating forbs into turfgrass sites may create a season-long sequence of flowers to support foraging pollinators. However, persistence of forbs in warm-season turfgrasses such as bermudagrass (Cynodon spp.) may be affected by the competitive nature of the turfgrass and routine management practices such as mowing. A 2-year study was conducted to evaluate seven forbs (Bellis perennis L., Lotus corniculatus L., Prunella vulgaris L., Trifolium fragiferum L. ‘Fresa’, Trifolium repens L. ‘Durana’ and ‘Resolute’, Trifolium subterraneum L.) for persistence and ability to produce floral resources for pollinating insects in a low maintenance bermudagrass lawn. Plugs of each species were incorporated into ‘Riviera’ bermudagrass in Apr. 2016. Vegetative cover, flower production, flowering period and pollinator foraging were assessed. Prunella vulgaris bloomed July through August and achieved 100% cover (0% bermudagrass) by 2017. Trifolium repens achieved a more balanced competitive density with the bermudagrass and produced flowers from June through August in both years. Trifolium fragiferum persisted over two growing seasons but only bloomed in 2017. Bellis perennis, Lotus corniculatus and Trifolium subterraneum did not persist. Pollinators were observed foraging on all persistent, flowering forbs, including Trifolium repens, Prunella vulgaris, and Trifolium fragiferum. Trifolium repens and Prunella vulgaris produced the most flowers and attracted the most pollinators.
Wayne W. Hanna and Brian M. Schwartz
Zongyu Li, R. Karina Gallardo, Vicki A. McCracken, Chengyan Yue, Ksenija Gasic, Gregory Reighard, and James R. McFerson
U.S. peach (Prunus persica) growers are challenged by the need to protect their orchards from economically damaging diseases and deliver fruit with the quality expectations of the supply chain. This study focuses on the U.S. southeastern peach sector, including North Carolina, South Carolina, Alabama, Virginia, and Georgia. This region offers a useful case to analyze growers’ preferences for both fruit quality and disease resistance. We collected primary data from peach operations in 2016 and 2018. In both surveys, a discrete choice experiment was used to advance the understanding of how peach growers in the southeastern United States value fruit quality (i.e., fruit size and external color) vs. disease resistance [i.e., brown rot (Monilinia fructicola)]. The sample of growers surveyed in 2016 growers placed a greater importance on the fruit quality attribute that would imply higher returns, that is, fruit size (expressed as fruit diameter) compared with improvements in brown rot resistance and external fruit color. Meanwhile, the sample of growers surveyed in 2018 placed a higher importance to brown rot resistance and external fruit color compared with fruit size. Findings consistent for the 2 years are that growers are willing to pay for larger rather than smaller improvements in brown rot resistance, and that a large improvement in brown rot resistance is more important than external fruit color.
Fernando Montero de Espinosa Baselga, Jonathan R. Schultheis, Michael D. Boyette, Lina M. Quesada-Ocampo, Keith D. Starke, and David W. Monks
Internal necrosis (IN) is a physiological disorder that affects Covington, the most commonly grown sweetpotato (Ipomoea batatas) cultivar in North Carolina. Because IN affects the quality of sweetpotato storage roots, studies have been conducted since the first report of IN in 2006. Field studies (three in 2016 and two in 2017) were conducted to evaluate preharvest and postharvest treatments on the occurrence of IN in ‘Covington’ storage roots. Four preharvest treatments consisted of combinations of high chlorine or minimal chlorine potash fertilizer and mowing vs. not mowing before harvest. For postharvest treatments, 30 storage roots were obtained at harvest from each preharvest treatment plot and immediately cured in 75 and 85 °F rooms for a duration of 0.5, 1, 2, 3, and 5 weeks in 2016, and 0.5, 1, and 2 weeks in 2017. Shorter curing durations (0.5 and 1 week) coincided with industry recommendations while longer durations mimicked the challenges that some commercial facilities face when cooling down temperatures of rooms after curing is supposed to be concluded. Once curing temperature and curing duration treatments were completed, roots were placed in a 58 °F storage room at 85% relative humidity until cut. A control comparison was included in which harvested roots were placed in a 58 °F storage room (no curing) immediately after harvest. The storage roots from all temperature treatments were then cut 49 to 80 days after harvest, and incidence and severity of IN visually rated. Preharvest potash fertilizer treatments had minimal or no effect on occurrence of IN. However, mowing vines before harvest in several studies reduced IN incidence when roots were cured for more than 0.5 week at temperatures of at least 75 °F. Lower temperature (75 vs. 85 °F) and shorter curing duration (0.5 vs. 1, 2, 3, or 5 weeks) resulted in reduced IN occurrence in ‘Covington’ sweetpotato.
Roxana Myers, Brian Bushe, Cathy Mello, Joanne Lichty, Arnold Hara, Koon-Hui Wang, and Brent Sipes
Burrowing nematode (Radopholus similis) causes severe stunting and yield reduction in anthurium (Anthurium andraeanum) cut flower production. Two field trials were conducted at commercial grower farms to test the efficacy of fluopyram or fluopyram + trifloxystrobin for managing burrowing nematodes. Nematode population densities in roots and cinder media were evaluated during the trial in addition to cut flower yield and canopy cover. In the first trial, the nematode population in roots was reduced by 57% after two applications of fluopyram 3 months apart. As plant health improved, the increasing anthurium root weight supported higher nematode populations. After 14 months, fluopyram-treated plots had 43% more green canopy cover and a 53% increase in flower production compared with the untreated control plots. At a second location, population densities of burrowing nematode were reduced in roots after one application of fluopyram + trifloxystrobin and remained low with quarterly applications. Nematode populations were initially reduced in fluopyram-treated plots followed by a resurgence as demonstrated in the other trial. Ten months after the initial treatment, flower yield was greater in fluopyram + trifloxystrobin-treated plots with more large and extra-large flowers produced. Canopy cover was 45% and 22% greater with fluopyram + trifloxystrobin and fluopyram applications, respectively. Fluopyram shows potential for management of burrowing nematodes in anthurium by improving plant vigor and cut flower production.