The effects of day temperature (DT), night temperature (NT), and night length (NL) were evaluated on the flowering responses of heat-tolerant and heat-sensitive poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) cultivars Orion Red and Prestige Red, respectively. Plants were placed under 60 DT × NT × NL treatments that consisted of three DT (20, 24, 28 °C), four NT (16, 20, 24, 28 °C), and five NL (10, 11, 12, 13, 14 hours) for the first 17 days of the experiment. After 17 days, all plants were consolidated to one greenhouse with an inductive environment (14-hour NL, 24 ± 2.0 °C DT and 21.2 ± 1.4 °C NT), and the timing of first color, visible bud, and anthesis were recorded. ‘Orion Red’ reached anthesis 8 to 10 days faster than ‘Prestige Red’ across all NLs; however, in both cultivars, days to anthesis decreased in a sigmoidal pattern as NL increased. The relative rate of progress to anthesis (1/days to anthesis) under a 12-hour NL was approximately half that of plants grown at a 13- or 14-hour NL. At a 12-hour NL, the relative rate of progress to anthesis decreased linearly as DT increased for both cultivars. At 13- to 14-hour NL, DT had relatively little effect on the relative rate of progress to anthesis. Thus, high DT delayed flowering of both heat-tolerant and heat-sensitive cultivars when flower initiation occurred under NL, typical of naturally occurring NLs in September and early October (i.e., 12-hour NL), whereas high DT did not delay flowering for either cultivar under a 14-hour NL, which is typically provided under black cloth systems. In contrast, the flowering responses to NT were quite different for the two cultivars. The heat-tolerant cultivar showed relatively little change in the relative rate of progress to anthesis as NT increased from 16 to 28 °C within each NL treatment; however, the heat-sensitive cultivar displayed a large decrease in the relative rate progress to anthesis as NT increased from 20 to 28 °C within each NL treatment. Although the delayed flowering that occurred at 28 °C and 14-hour NL was significant, the relative rate of progress to anthesis at this treatment was significantly higher than the 28 °C and 12-hour NL treatment. This suggests that artificially shortening NL to 14 hours with a black cloth system does not prevent heat delay of poinsettia, but it allows for more rapid flowering than if flower initiation took place under natural NL (≈12 hours). To summarize, high DT affected flowering when flower initiation took place at 12-hour NL for heat-tolerant and heat-sensitive poinsettia cultivars, whereas high NT uniquely delayed flowering of the heat-sensitive cultivar at NL from 12 to 14 hours.
Michael Alden and James E. Faust
Catherine E. Belisle, Steven A. Sargent, Jeffrey K. Brecht, Germán V. Sandoya, and Charles A. Sims
The postharvest life of lettuce (Lactuca sativa) is variable and negatively affected by mechanical injury, incomplete cooling, and poor genetic quality. Lettuce breeders are developing cultivars with a longer shelf life and rely on subjective, destructive, and time-consuming methods for quality analysis. One method of accelerating quality evaluations is known as accelerated shelf-life testing (ASLT), which has the potential to assist breeders in assessing lettuce quality and shelf life. The objective of this research was to determine the quality traits that significantly affect shelf life to develop an ASLT procedure to rapidly assess the postharvest quality of lettuce accessions in breeding programs. In Test 1, Romaine lettuce quality was evaluated using one subjective and five objective parameters during storage at 5, 10, 15, or 20 °C. Results determined that weight loss, lightness*, and hue* angle were best correlated with the overall appearance rating, whereas storage at 10 or 15 °C differentiated the shelf-life potential quickly and without excessive deterioration. In Test 2, these objective characteristics and storage temperatures were used to study rates of quality deterioration of a commercial Romaine cultivar (Okeechobee) and a breeding line (60182), both with long shelf lives, and a Batavia lettuce cultivar (La Brillante) with a short shelf life. Lettuce was evaluated during storage at 10 °C (winter and spring seasons) or at 15 °C (winter season). Weight loss was the most appropriate quality index for lettuce at these storage temperatures for a single harvest, whereas lightness* and hue* angle were the most appropriate indices for comparing quality between harvests. To apply ASLT to postharvest assessments of lettuce, breeders and other researchers should include two controls with good and poor shelf life (similar to ‘Okeechobee’ and ‘La Brillante’, respectively) as standard baseline cultivars during storage at either 10 or 15 °C.
Marc-André Sparke, Achim Wegscheider, Patrick Winterhagen, Ute Ruttensperger, Martin Hegele, and Jens Norbert Wünsche
Mechanical stimulation to produce stable and high-quality crops under greenhouse conditions is a promising alternative to chemical growth retardants. However, plant tissue damage and the lack of full automatization have been major constraints for large-scale applications. We demonstrate the potential of automated, touch-less, directed air stream application systems to control the plant height and appearance of bellflower (Campanula ‘Merrybell’), creeping inchplant (Callisia repens), and tomato (Solanum lycopersicum ‘Romello’). Plants were cultivated under greenhouse conditions and exposed to regulated air stream stimuli by three different prototype systems. Air stream stimuli of all three prototype systems significantly reduced plant height of all three plant species. Bellflower plants showed a reduction of 24% and tomato plants showed reductions of 26% to 36% compared with the respective control plants. The degree of height growth inhibition in tomato was shown to be predominantly influenced by the stimulus intensity. An air pressure prototype system was successfully implemented in a horticultural company and the height of creeping inchplant could be sufficiently reduced by 20%, on average, throughout 1 year of the experiment compared with untreated controls. Overall, no plant tissue damage of plants treated with the air stream was visible, and no difference in the number of flowers of the bellflower plants treated with the air stream and of the untreated controls was observed.
Teresita D. Amore, Peter J. Toves, Joanne L. Imamura, Janice Y. Uchida, and Chris Kadooka
Michele R. Warmund, David H. Trinklein, Mark R. Ellersieck, and Reid J. Smeda
The use of dicamba and 2,4-D products on herbicide-tolerant crops has resulted in numerous cases of off-target movement and injury to sensitive plants, including tomato (Solanum lycopersicon L.). Two greenhouse studies were conducted to determine whether ‘Big Beef’ (‘BB’) or ‘Florida 91’ (‘FL’) tomato plants pretreated with an antitranspirant, including Moisture-Loc (ML) at 100 mL·L−1, TransFilm (TF) at 50 g·L−1, or Wilt-Pruf (WP) at 100 mL·L−1, mitigated injury from synthetic auxin herbicides. Dicamba or 2,4-D was applied at a rate corresponding to 1/200 of the manufacturer’s labeled rate of 0.56 kg ae/ha or 1.06 kg ae/ha, respectively. At 2 weeks after treatment (WAT), plants treated with ML or WP before either herbicide exhibited injury symptoms, but they were always less severe than those treated with the herbicide alone for both cultivars. However, shoot length measurements indicated that none of the antitranspirants consistently provided protection against herbicide injury at 2 WAT. By 12 WAT, ML or WP used before either herbicide increased the number of live reproductive organs compared with dicamba or 2,4-D alone for both cultivars. Floral abortion on tomato plants was also reduced when ML or WP was applied before an herbicide treatment by 12 WAT. Although WP and ML did not provide complete protection against synthetic auxin herbicide injury, the concept of using film-forming barriers may be useful in mitigating some of the short-term effects of drift on plants.
Rachel Leisso, Bridgid Jarrett, Katrina Mendrey, and Zachariah Miller
Codling moth (Cydia pomonella) is a major insect pest of apple (Malus domestica). If unmanaged, then codling moth can infest nearly all apples in an orchard, where the flesh-tunneling larva leave frass-laden tracks in the fruit. Insecticide-based management requires accurate application timing (typically based on adult moth and/or degree-day monitoring) and multiple spray applications. Both the season-long commitment to codling moth monitoring and management and limited familiarity with insecticides, application tools, and proper application procedures can prevent a small-scale or backyard grower from effectively limiting fruit damage. In addition, an increasing segment of growers is interested in nonchemical alternatives. Bagging fruitlets early in the season could be a simple and effective method of codling moth management for this subset of growers. At our research orchard in Corvallis, MT, we tested a method combining fruit thinning and bagging using plastic bags the first season and nylon bags the second season. Plastic bags reduced the incidence of codling moth damage to fruit from 34% to 10%, but european earwig (Forficula auricularia) frass, which was found in more than 50% of plastic-bagged apples, made harvesting the fruit unappealing. We tested nylon fruit bags during the second year of the study. These bags did not significantly reduce the incidence of codling moth. Both the soluble solids content and titratable acidity were higher in unbagged fruit during the second year of the study, whereas color measurements indicated bagged fruit were greener on the shaded side of the fruit. Failure of the nylon bags may have been attributable to eggs laid before bagging, eggs laid or larva burrowing through bagging, or improper bag application methods. Further research could assess whole-tree bags, the addition of rubber bands or twist ties when applying nylon bags, pretreatment of fruit with horticulture oil, and/or dipping nylon bags in kaolin clay before application; however, these steps add time and increase costs, which may discourage the small-scale fruit grower. Overall, results indicate that fruit bagging holds promise for codling moth management; however, further work is needed to optimize the methodology.
Bao-Zhong Yuan, Zhi-Long Bie, and Jie Sun
Muskmelon is a warm season cucurbit species that belongs to family Cucurbitaceae. We analyzed 2955 papers of global research on muskmelon (Cucumis melo L.) based on Web of Science from 1924 to 2021. Papers were mainly written in English (2766, 93.604%), from 7883 authors, 83 countries or regions, 1697 organizations, and published in 585 journals and book series. The top five journals were HortScience (334, 11.303%), Journal of the American Society for Horticultural Science (Proceedings of the American Society for Horticultural Science) (117, 3.959%), Scientia Horticulturae (109, 3.689%), Plant Disease (88, 2.978%), and Phytopathology (84, 2.843%), each of which published more than 84 papers. The top five countries or regions were the United States, PR China, Spain, Brazil, and Japan, which each published more than 168 papers. The top six organizations were U.S. Department of Agriculture Agricultural Research Service, Agricultural Research Organization, Texas A&M University, Universitat Politecnica de Valencia, University of California–Davis and Consejo Superior de Investigaciones Cientificas, each of which published more than 64 papers. The top five authors are G.D. Lester, J.D. McCreight, J. Garcia-Mas, K.M. Crosby, and T.J. Ng, who each published more than 26 papers. On the basis of the analysis of a network map of VOSviewer, there were cooperation among authors, organizations, and countries or regions. All keywords of muskmelon research were separated into eight clusters for different research topics. Visualizations offer exploratory information on the current state and indicate possible developments in the future. This work is also useful for students identifying graduate schools and researchers selecting journals.
Oleg Daugovish, Mark Gaskell, Miguel Ahumada, and Anna D. Howell
Increased productivity of recently developed primocane raspberry (Rubus idaeus) and blackberry (Rubus sp.) cultivars have been accompanied by dramatic improvements in fruit firmness, shape, size, color, and flavor. These traits have contributed to the establishment of these crops throughout California. In this study, we evaluated publically available raspberry and blackberry cultivars for fruit yields, postharvest quality, and production in response to pruning management, at two locations in the central coast of California. Among raspberries, ‘Imara’ and ‘Kweli’ were the highest yielding cultivars at both trial locations while ‘Kwanza’ produced 30% to 50% larger fruit, by weight, with postharvest shelf life superior to that of ‘Vintage’. Among blackberries, ‘Prime-Ark® 45’ was the top-yielding cultivar and had the largest fruit at both locations during both years. ‘Prime-Ark® 45’ and ‘Prime-Ark® Traveler’ had comparable weights after 13 days in cold storage in 2018, while in 2019 ‘Prime-Ark® 45’ and ‘APF 268T’ had comparable fruit weight. Greater and earlier fruit yields of both blackberries and raspberries were obtained with combined production from floricanes and primocanes compared with primocane production alone. However, increase in cane density in combined production can complicate management of pests, fertigation, and fruit harvest efficiency. With increased interest in primocane cultivars, the information generated in this study has provided new resources to guide successful production by small, independent, and direct-sale growers.
Tomohiro Jishi, Ryo Matsuda, and Kazuhiro Fujiwara
Cos lettuce was grown under different spectral photon flux density distribution (SPFD) change patterns with blue- and/or red light-emitting diode (LED) irradiation with a 24-hour cycle. Twelve treatments were designed with a combination of four relative SPFD (RSPFD) change patterns and three photosynthetic photon flux density (PPFD) levels. The RSPFD change patterns were as follows: BR/BR, simultaneous blue- and red-light irradiation (BR) for 24 h; R/BR, red-light monochromatic irradiation (R) for 12 h followed by 12 hours of BR; B/BR, blue-light monochromatic irradiation (B) for 12 hours followed by 12 hours of BR; and B/R, 12 hours of B followed by 12 hours of R. Each RSPFD change pattern was conducted at three daily average photosynthetic photon flux densities (PPFDave) of 50, 100, and 200 µmol·m−2·s−1. The RSPFD change patterns that included B (B/BR and B/R) resulted in elongated leaves. A low ratio of active phytochrome to total phytochrome under B was considered the reason for leaf elongation. Shoot dry weight was significantly greater under the RSPFD change patterns that included B when the PPFDave was 200 µmol·m−2·s−1. The leaf elongation caused by B would have increased the amount of light received and thereby promoted growth. However, excessive leaf elongation caused the plants to fall, and growth was not promoted under the RSPFD change patterns that included B when the PPFDave was 50 µmol·m−2·s−1. Thus, 12-hour B promoted growth under conditions in which leaf elongation leads to increases in the amount of light received.