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Open access

Trent J. Davis, Miguel I. Gómez, Scott J. Harper, and Megan Twomey

Hop stunt viroid (HSVd) is one of the most important pathogens impacting hop production worldwide. It reduces yields, stunts growth, and is easily transmissible. HSVd can cause significant yield losses upward of 62% depending on the hop variety. This study uses a net present value (NPV) approach over a 6-year production cycle of one acre of hops to examine the potential economic impact of HSVd on aroma and alpha hop varieties. The estimated economic impact of HSVd ranges from about $432 (for a 1% yield reduction) to $26,795 (for a 62% yield reduction) per acre. Using the NPV approach the study then analyzes potential economic benefits of using certified disease-free planting stock as a strategy to mitigate the risk of HSVd infection. If expected yield losses of aroma and alpha hops exceed 6% and 7%, respectively, then the NPV of investing in certified clean planting stock is greater than that of the infected hops over the 6-year production cycle. Complete removal and replanting of an entire acre of aroma and alpha hops with certified clean planting stock is economically beneficial once expected yield losses exceed 35% and 36%, respectively. These findings are valuable for giving hop producers information to devise profit-maximizing planting strategies and to create incentives for extended usage of certified clean planting materials.

Open access

Lillian Hislop, Elizabeth Stephanie, Patrick Flannery, Matheus Baseggio, Michael A. Gore, and William F. Tracy

Sugarcane mosaic virus [SCMV (Potyvirus sugarcane mosaic virus)] is an ssRNA virus that negatively affects yield in maize (Zea mays) worldwide. Resistance to SCMV is controlled primarily by a single dominant gene (Scm1). The goal of this study was to identify sweet corn (Z. mays) inbreds that demonstrate resistance to SCMV, confirm the presence of genomic regions previously identified in maize associated with resistance, and identify other resistant loci in sweet corn. Eight plants from each of 563 primarily sweet corn inbred lines were tested for SCMV resistance. Plants were inoculated 14 d after planting and observed for signs of infection 24 d after planting. A subset of 420 inbred lines were genotyped using 7504 high-quality genotyping-by-sequencing single-nucleotide polymorphism markers. Population structure of the panel was observed, and a genome-wide association study was conducted to identify loci associated with SCMV resistance. Forty-six of the inbreds were found to be resistant to SCMV 10 d after inoculation. The Scm1 locus was confirmed with the presence of two significant loci on chromosome 6 (P = 2.5 × 10−8 and 1.6 × 10−8), 5 Mb downstream of the Scm1 gene previously located at Chr6: 14194429.14198587 and the surrounding 2.7-Mb presence–absence variation. We did not identify other loci associated with resistance. This research has increased information on publicly available SCMV-resistant germplasm useful to future breeding projects and demonstrated that SCMV resistance in this sweet corn panel is driven by the Scm1 gene.

Open access

Saki Toshima, Marika Fujii, Momoko Hidaka, Soya Nakagawa, Tomonari Hirano, and Hisato Kunitak

Interspecific hybridization is useful in raspberry (Rubus idaeus L. ssp. idaeus) breeding to introgression of traits such as heat or cold tolerance, and excellent fruit qualities. Rubus L. wild species in Asia, including Rubus parvifolius L., have been attracting a great deal of attention as sources of new traits in breeding raspberry and blackberry (Rubus fruticosus Agg.). We previously developed and selected IPI-1 and IPI-3 first backcross (BC1) hybrids, [‘Indian Summer’ (R. idaeus ssp. idaeus) × R. parvifolius] × ‘Indian Summer’, as raspberry cultivars adapted to the warm climate in parts of Japan. In this study, we investigated the growth, morphological traits, and fruit qualities, such as sugar, organic acid, anthocyanins, and carotenoids, of each of these IPI lines over a 2-year period to discern their potential as commercial raspberry cultivars. IPI lines had the characteristic of primocane fruit with overflowing from side buds while the parent, IP-1 (‘Indian Summer’ × R. parvifolius), did not. IPI lines showed significantly lower values in anthocyanin content than red raspberry ‘Skeena’, while showing higher carotenoid contents. This study is the first research about fruit qualities such as anthocyanin and carotenoid content of BC1 hybrids using Japanese wild Rubus species.

Open access

Martina Göttingerová, Michal Kumšta, Eliška Rampáčková, Tomáš Kiss, and Tomáš Nečas

The apricot is attractive for several reasons, with the most important being the harvest period and the significant amount of contained substances that positively affect human health. This report discusses the identification and quantification of phenolic substances in 15 selected apricots. The following 14 phenolic compounds were identified: 4aminobenzoic acid, chlorogenic acid, cinnamic acid, flavonols quercetin and quercitrin, isoquercetin (quercetin-3-β-D-glucoside), rutin, resveratrol, vanillin, phloridzin, phloretin, epicatechin, catechin, and transpiceid. Significant amounts of phytochemicals found in apricot fruits are chlorogenic acid [0.69–21.94 mg/100 g fresh weight (FW)], catechin (0.55–10.75 mg/100 g FW), epicatechin (0.04–13.52 mg/100 g FW), and rutin (1.49–20.44 mg/100 g FW). Rutin and chlorogenic acid were the dominant compounds found in the studied set of cultivars. Furthermore, other important analytical properties of fruits (total acids, vitamin C, total content of phenolic substances, flavonoids, antioxidant capacity, and carotenoids) were also determined.

Open access

Bao-Zhong Yuan, Zhi-Long Bie, and Jie Sun

Cucumber (Cucumis sativus L.) is an economically important vegetable crop that is cultivated worldwide. The current study aimed to identify and analyze the 2030 articles and review article about cucumber research from the horticulture category of the VOS viewer Web of Science. Bibliometric data were analyzed by bibliometric science mapping and visualization tools. Articles mainly written in English (1884; 92.81%) were from 5630 authors, 80 countries or territories, and 1094 organizations; they were published in 46 journals and book series. The top five core journals are Scientia Horticulturae (337; 16.60%), HortScience (265; 13.05%), Journal of the American Society for Horticultural Science (239; 11.77%), European Journal of Plant Pathology (195; 9.61%), and Horticulture Journal (Journal of the Japanese Society for Horticultural Science) (157; 7.73%). These journals each published more than 157 articles. The top five countries and regions were the United States, People’s Republic of China, Japan, South Korea, and India. The top five organizations were the University of Wisconsin, North Carolina State University, U.S. Department of Agriculture–Agricultural Research Service, Michigan State University, and Nanjing Agricultural University. The top five authors are Todd C. Wehner (Wehner, TC), Jack E. Staub (Staub, JE), Yiqun Weng, R.L. Lower, and S. Tachibana; each published more than 24 articles. All keywords used for cucumber research in the horticulture category were separated into eight clusters for different research topics. Visualizations offer exploratory information regarding the current state in a scientific field or discipline as well as indicate possible developments in the future. This review could be a valuable guide for designing future studies.

Open access

Devdutt Kamath, Yun Kong, Chevonne Dayboll, and Youbin Zheng

Short campanula (Campanula portenschlagiana ‘PGM Get MEE’®) stock plants present a difficulty in machine-harvesting of cuttings. Light adjustment may be an effective approach to mediate plant elongation. Two experiments were performed to 1) investigate whether short-term (five weeks) daily 24-h dynamic lighting (DL) with red and blue light-emitting diodes (LEDs) can promote elongation without inducing flowering, and 2) explore whether DL can be used to modify stock plant morphology to improve the cutting quality and rooting success in a controlled environment. Two lighting treatments were used: concurrent lighting (CL) with red (85%) and blue (15%) LEDs (RB) at 100 µmol·m−2·s−1 and DL with red (170 µmol·m−2·s−1), blue (30 µmol·m−2·s−1), and RB (100 µmol·m−2·s−1) LEDs sequentially at three different lighting stages, respectively, in both experiments. In Expt. 1, at final harvest of stock plants, the side branches were longer under DL compared with CL, but the five (= 2 + 2 + 1) weeks of 24-h daily lighting resulted in visible flower buds under both treatments. Based on the results of Expt. 1, a second experiment (Expt. 2) was conducted with the same cultivar and experimental conditions, but with a shorter photoperiod (10 h·d−1) for 11 (= 8 + 2 + 1) weeks. In Expt. 2, at final harvest, DL compared with CL caused more upright side branches, and reduced the dry biomass of side branches with one branching order and leaf chlorophyll content. However, the harvested cutting quality and rooting success were similar between both treatments. In both experiments, side branch number under DL was greater compared with CL at the end of the first lighting stage. Stock plants under DL were taller from the second lighting stage on to final harvest compared with CL, and the final heights of stock plants under DL met the target for machine-harvest in both experiments. Therefore, if the lighting strategy is further optimized, DL can potentially benefit controlled-environment production of campanula cuttings.

Open access

Zhengnan Yan, Long Wang, Jiaxi Dai, Yufeng Liu, Duo Lin, and Yanjie Yang

Lighting strategies for morphological and physiological characteristics of horticultural crops often focus on the proper daily light integral (DLI); however, a suitable combination of photosynthetic photon flux density (PPFD) and photoperiod at the same DLI is conducive to optimize the light environment management in vegetable seedling production. In the present study, cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) were grown for 21 days under six different combinations of PPFD and photoperiod at a constant DLI of 11.5 mol⋅m−2⋅d−1, corresponding to a photoperiod of 7, 10, 13, 16, 19, and 22 h⋅d−1 provided by white light-emitting diodes (LEDs) under a controlled environment. Results showed that plant height, hypocotyl length, and specific leaf area of cucumber seedlings decreased quadratically with increasing photoperiod, and the opposite trend was observed in seedling quality index of cucumber seedlings. In general, pigment content and fresh and dry weight of cucumber seedlings increased as photoperiod increased from 7 to 16 h⋅d−1, and no significant differences were found in fresh and dry weight of shoot and root as photoperiod increased from 16 to 22 h⋅d−1. Sucrose and starch content of cucumber leaves increased by 50.6% and 32.3%, respectively, as photoperiod extended from 7 to 16 h⋅d−1. A longer photoperiod also led to higher cellulose content of cucumber seedlings, thus improving the mechanical strength of cucumber seedlings for transplanting. CsCesA1 relative expression level showed a trend similar to cellulose content. We propose that CsCesA1 is the key gene in the response to cellulose biosynthesis in cucumber seedlings grown under different combinations of PPFD and photoperiod. In summary, prolonging the photoperiod and lowering PPFD at the same DLI increased the quality of cucumber seedlings. An adaptive lighting strategy could be applied to increase seedling quality associated with the reduction of capital cost in cucumber seedling production.

Open access

Sai Xu, Huazhong Lu, Xu Wang, Christopher M. Ference, Xin Liang, and Guangjun Qiu

Visible/near-infrared (VIS/NIR) spectroscopy is a powerful tool for rapid, nondestructive fruit quality detection. This technology has been widely applied for quality detection of small thin-peel fruit, although less so for large thick-peel fruit because of the low signal-to-noise ratio of the spectral signal, resulting in a reduction of accuracy. More modeling work should be focused on solving this problem. This research explored a method of spectroscopy for the total soluble solid (TSS) content and acidity detection of ‘Shatian’ pomelo, which are two major parameters of fruit internal flavor. VIS/NIR spectral signal detection of 100 pomelo samples during storage was performed. Detection based on raw data, signal jitter, and scattered light noise removal, feature extraction, and deep learning were performed and combined with modeling detection to achieve an accurate step-by-step detection. Our results showed that 600 W is the optimal light intensity for detecting the internal flavor of pomelo. The TSS content of pomelo is optimally detected using Savitzky-Golay (SG) + multiplicative scatter correction (MSC) + genetic algorithm (GA) + principal component analysis (PCA) + convolutional neural network (CNN) + partial least squares regression (PLSR); however, acidity of pomelo is optimally detected using SG + MSC + GA + PLSR. With the optimal detection method, the coefficient of determination and root mean squared error (RMSE) of the validation set for TSS detection are 0.72 and 0.49, respectively; and for acidity detection are 0.55 and 0.10, respectively. Even though the accuracy is not high, the data are still acceptable and helpful in nondestructive quality grading of large quantities postharvest fruit. Therefore, our results demonstrated that VIS/NIR was feasible for detecting the TSS content and acidity of postharvest pomelo, and for providing a possible method for the nondestructive internal quality detection of other large thick-peel fruit.

Open access

Emma K. Dawson, George E. Boyhan, Tim Coolong, Nicholas T. Basinger, and Ryan McNeill

Along with the many known benefits of cover crops, they may be an effective ecological weed management strategy in low-input agriculture. This research aimed to determine the effect of cover crops, combined with reduced-tillage and nitrogen inputs on sweet corn (Zea mays) yield and weed communities. During the 2-year study, the impact of the cover crop on yield varied. Yield within the no-till conventional treatment plots was not significantly different from the conventional treatment [6844 and 7721 lb/acre (P = 0.592)] in year 1 but differed in year 2 (P = 0.003). Weed density and experimental area covered by weeds were not significantly different between conventional and no-till conventional treatments. Multivariate analyses showed associations between specific weed species and management practices. Weeds were greatest in no-till organic treatments, and they had significantly lower yields, suggesting additional weed control beyond cover crops may be necessary for organic vegetable systems under reduced tillage.

Open access

Ronald S. Revord, J. Michael Nave, Ronald S. Revord, J. Michael Nave, Gregory Miller, Nicholas Meier, J. Bryan Webber, Michael A. Gold, and Tom Wahl

The Chinese chestnut (Castanea mollissima Blume) and other Castanea species (Castanea spp. Mill.) have been imported and circulated among growers and scientists in the United States for more than a century. Initially, importations of C. mollissima after 1914 were motivated by efforts to restore the American chestnut [Castanea dentata (Marsh.) Borkh.], with interests in timber-type characters and chestnut blight resistance. Chestnut for orchard nut production spun off from these early works. Starting in the early 20th century, open-pollinated seeds from seedlings of Chinese chestnut and other Castanea species were distributed widely to interested growers throughout much of the eastern United States to plant and evaluate. Germplasm curation and sharing increased quite robustly through grower networks over the 20th century and continues today. More than 100 cultivars have been named in the United States, although a smaller subset remains relevant for commercial production and breeding. The University of Missouri Center for Agroforestry curates and maintains a repository of more than 60 cultivars, and open-pollinated seed from this collection has been provided to growers since 2008. Currently, more than 1000 farms cultivate seedlings or grafted trees of the cultivars in this collection, and interest in participatory on-farm research is high. Here, we report descriptions of 57 of the collection’s cultivars as a comprehensive, readily accessible resource to support continued participatory research.