The aim of the present study was to evaluate the effects of alternating red (660 nm) and blue (460 nm) light on the growth and nutritional quality of two-leaf-color pak choi (Brassica campestris L. ssp. chinensis var. communis). Four light treatments (supplemental alternating red and blue light with intervals of 0, 1, 2, and 4 hours, with a monochromatic light intensity of 100 μmol·m−2·s−1 and a cumulative lighting time of 16 hours per day) were conducted in a greenhouse under identical ambient light conditions (90 to 120 μmol·m−2·s−1 at 12:00 am) for 10 days before green- and red-leaf pak choi were harvested. The results showed that the two-leaf-color pak choi receiving alternating red and blue light exhibited more compact canopies and wider leaves than those under the control treatment, which was attributed to the shade avoidance syndrome of plants. The present study indicated that the biomass of green-leaf pak choi was much higher than that of red-leaf pak choi, but the nutritional quality of green-leaf pak choi was lower than that of red-leaf pak choi, and seemingly indicating that the regulation of metabolism for pak choi was species specific under light exposure. The trends of both biomass and the soluble sugar content were highest under the 1-hour treatment. The contents of chlorophyll a and total chlorophyll in both cultivars (green- and red-leaf pak choi) were significantly increased compared with control, without significant differences among the 1-, 2-, and 4-hour treatments, whereas chlorophyll b exhibited no significant difference in any treatment. Alternating red- and blue-light treatment significantly affected the carotenoid content, but different trends in green- and red-leaf pak choi were observed, with the highest contents being detected under the 1-hour and 4-hour treatments, respectively. With increasing time intervals, the highest soluble protein contents in two-leaf-color pak choi were observed in the 4-hour treatment, whereas nitrate contents were significantly decreased in the 4-hour treatment. Compared with 0 hours, the contents of vitamin C, phenolic compounds, flavonoids, and anthocyanins in two-leaf-color pak choi were significantly increased, but no significant differences were observed in vitamin C, phenolic compounds, and flavonoids among the 1-, 2-, and 4-hour treatments, similar to what was found for the anthocyanin content of green-leaf pak choi. However, the content of anthocyanins in red-leaf pak choi gradually increased with increasing time intervals, with the highest content being found in the 4-hour treatment. Supplemental alternating red and blue light slightly increased the antioxidant capacity [1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging rate and antioxidant power], but no significant differences were observed after 1, 2, and 4 hours of treatment. Taken together, treatment with an interval of 1 hour was the most effective for increasing the biomass of pak choi in this study, but treatment with a 4-hour interval should be considered to enhance the accumulation of health-promoting compounds.
Jing Huang, Ya-liang Xu, Fa-min Duan, Xu Du, Qi-chang Yang, and Yin-jian Zheng
Olivia M. Smith, Beverly Gerdeman, Matthew Arrington, Hollis Spitler, and Lisa Wasko DeVetter
Herbaceous flowering or woody plant borders adjacent to highbush blueberry (Vaccinium corymbosum) fields have the potential to benefit both native pollinators and species of predatory and parasitic arthropods and birds that feed on key highbush blueberry pests, such as spotted wing drosophila [SWD (Drosophila suzukii)]. However, they may also draw pollinators away from the crop, serve as overwintering and/or refugia sites for SWD, and increase the abundance of wild birds that feed on fruit and harbor foodborne pathogens. The objective of this 1-year, observational study was to explore the potential impacts of border vegetation adjacent to commercial highbush blueberry fields on pollination, crop productivity, and arthropod and bird communities within the Pacific Northwest region in the United States. The study included three highbush blueberry cultivars (Duke, Draper, and Liberty), and three field border vegetation treatments: 1) woody perennial vegetation; 2) herbaceous vegetation; and 3) medium-height grasses (control). There was one border treatment per cultivar for a total of nine sites. No cultivar effects nor interactions for any of the variables were detected, so results were combined across cultivars. No differences in pollinator abundance, pollinator visitation rates, estimated yield, berry weight, and seed number were observed across the treatments. Herbaceous borders had more natural enemies than the woody perennial borders, but both were similar to the control. This trend is attributed to higher abundances of parasitic wasps (suborder Apocrita) in the herbaceous and control borders compared with the woody perennial borders. Increased abundances of aphids (family Aphididae), a host for parasitic wasps, likely influenced these results. Differences in predatory arthropods were not observed. Insect abundances were overall low in all field sites measured in this study, likely influenced by SWD insecticide applications. There were no differences in total wild bird density by treatment except for barn swallows (Hirundo rustica), which were greatest in the control treatment. Overall, the border treatments evaluated in this study had small-to-negligible impacts on the measured variables, and there was no clear crop production benefit. Additionally, none of the investigated border treatments negatively impacted highbush blueberry production. Taken together, border vegetation treatments can provide benefits such as reducing pesticide drift, deterring trespassers, and serving as a windbreak; but any potential benefits from a pollination or biocontrol aspect are likely diminished due to current SWD management practices.
Nebahat Sari, Emily Silverman, Danny Reiland, and Todd C. Wehner
Bottle gourd [Lagenaria siceraria (Molina) Standl.] is widely produced in some Asian and African countries as a fresh vegetable as well as for seed consumption. A major use of bottle gourd is for rootstocks in grafted watermelon production. There are several centers where bottle gourd genetic resources are maintained, with the U.S. Department of Agriculture (USDA) germplasm collection being one of the most important. There is little published information on the relationship between seed morphology and the early establishment of seedlings in bottle gourd. The objective of this study was to determine seed characterization, morphology, and cotyledon shape in 163 Lagenaria spp. accessions and measure any relationship between seed and cotyledon characteristics. In USDA Lagenaria germplasm, it has been determined that the common character in seeds was medium in terms of seed size (53% of accessions), intermediate in seed surface lustre (39% of accessions), brown in seedcoat color (89% of accessions), thin and uniform in seed margin (35% of accessions), and tan in seed margin color (64% of accessions). According to the research results, seed weight ranged from 0.11 g (PI 500820) to 0.36 g (PI 675112), seed length from 13.17 mm (PI 500820) to 23.68 mm (PI 675112), and seed width from 5.86 (PI 500808) to 11.21 mm (PI 491274). Cotyledon length ranged from 5.46 cm (PI 368640) to 2.47 cm (PI 381850). The widest cotyledon was 3.00 cm (PI 534552), and the narrowest was 1.50 cm (PI 381831). Interesting correlations were observed for seed weight with seed length (R 2 = 0.259), and cotyledon length with cotyledon width (R 2 = 0.547).
Khalid F. Almutairi, David R. Bryla, and Bernadine C. Strik
In many regions, water limitations are increasing because of frequent and persistent droughts and competition for water resources. As a result, growers in these regions, including those producing blueberries, must limit irrigation during drier years. To identify the most critical periods for irrigation, we evaluated the effects of soil water deficits during various stages of fruit development on different cultivars of northern highbush blueberry (Vaccinium corymbosum L.). The study was conducted for 2 years in western Oregon and included two early season cultivars, ‘Earliblue’ and ‘Duke’, a midseason cultivar, ‘Bluecrop’, and two late-season cultivars, ‘Elliott’ and ‘Aurora’. Volumetric soil water content and stem water potentials declined within 1 to 2 weeks with no rain or irrigation in each cultivar and were lowest during the later stages of fruit development. Water deficits reduced berry weight by 10% to 15% in ‘Earliblue’ and ‘Elliott’ when irrigation was withheld in the second year during early or late stages of fruit development and by 6% to 9% in ‘Aurora’ when irrigation was withheld in either year during the final stages of fruit development. However, water deficits only reduced yield significantly in ‘Aurora’, which produced 0.8 to 0.9 kg/plant fewer fruit per year when irrigation was withheld during fruit coloring. In many cases, water deficits also reduced fruit firmness and increased the concentration of soluble solids in the berries, but they had inconsistent effects on titratable acidity and sugar-to-acid ratios. As a rule, water deficits were most detrimental during later stages of fruit development, particularly in midseason and late-season cultivars, which ripened in July and August during the warmest and driest months of the year.
Xuan (Jade) Wu, Melinda J. Knuth, Charles R. Hall, and Marco A. Palma
Flower species is one of the key determinants of the aesthetic and economic value of floral products. This research study sought to evaluate whether consumer perceptions of the aesthetic appeal and monetary valuations of floral arrangements change by substituting high-cost species with low-cost species of similar appearance. In addition, the researchers explored consumer preferences for flower symmetry, which provides information to assist floral designers in choosing and using species to increase profit margins and improve the economic efficiency of the floral industry. Two experiments were administered through an online survey. For the first experiment, no difference was shown in both willingness to pay and attractiveness ratings for flowers in the high-dollar value vs. low-dollar value comparison groups. For the second experiment, roses (Rosa hybrida) were rated the highest on attractiveness, followed by dahlia (Dahlia hybrida), ranunculus (Ranunculus asiaticus), and anthurium (Anthurium sp.). Radial flowers were considered most appealing, followed by asymmetrical flowers, and last, bilaterally symmetrical flowers. The results of this study lend insight into how the general floral consumer does not differentiate between flower species that are similar in design features such as color, size, or symmetry. This information can be used by floral business operators to sell their bouquets at a higher margin by strategically using lower-cost flower inputs.
Jeff B. Million and Thomas H. Yeager
Irrigation that decreases the leaching fraction (LF; leachate/water applied) has been shown to reduce fertilizer N and P leaching during the production of sprinkler-irrigated, container-grown plants; however, little research involving outdoor production of microirrigated plants in large containers has been conducted. Two microirrigation schedules based on routine leaching fraction testing were compared to determine their effects on water use and leaching losses of N and P during the production of Dwarf Burford holly in 36-cm-diameter (trade #7) containers. Applied irrigation water and leachate were collected continuously and sampled weekly during the 12-month experiment. An irrigation schedule adjusted once every 1 to 3 weeks to a target LF of 20% resulted in the application of 36% less water (383 vs. 597 L/plant) and 43% less leachate (255 vs. 445 L/plant) than a schedule adjusted to a target LF of 40%; plant growth was unaffected (P > 0.05). Irrigation schedules had no effect (P > 0.05) on cumulative N and P leaching losses, which were attributed in large part to rain. Average leaching losses of N and P were 15.2 and 2.2 g per container (210 and 30 kg·ha−1·year−1), respectively. Both N and P leaching losses represented 35% of the 43.5 g N and 6.3 g P applied per container in two controlled-release fertilizer applications. The results support the best management practice of scheduling irrigation based on routine LF testing to reduce irrigation water use but not reduce N and P leaching.
Tran Kim Ngan Luong, Frank Forcella, Sharon A. Clay, Michael S. Douglass, and Sam E. Wortman
Abrasive weeding is a nonchemical weed control tactic that uses small, gritty materials propelled with compressed air to destroy weed seedlings. Organic fertilizers have been used successfully as abrasive grits to control weeds, but the goal for this study was to explore the effects of fertilizer grit, application rates, and background soil fertility on weeds, plant available nitrogen (N) uptake, and crop yield. Field trials were conducted in organic ‘Carmen’ sweet red pepper (Capsicum annuum) and organic ‘Gypsy’ broccoli (Brassica oleracea var. italica) and treatments included organic fertilizer grit (8N–0.9P–3.3K vs. 3N–3.1P–3.3K), grit application rates (low vs. high), compost amendments (with and without), and weedy and weed-free controls. Weed biomass was harvested at 84 days and 65 days after transplanting for pepper and broccoli, respectively. Simulated total plant available N (nitrate + ammonium) uptake was measured with ion exchange resin stakes between 7 and 49 days after the first of two grit applications. Produce was harvested at maturity, graded for marketability, and weighed. The higher grit application rate, regardless of fertilizer type, reduced the weed biomass by 75% to 89% for pepper and by 86% to 99% for broccoli. By 5 weeks after the first grit application, simulated plant N uptake was greatest following grit application with the 8% N fertilizer, followed by the 3% N fertilizer, and lowest in the weedy control. The high grit application rate of 8% N fertilizer increased pepper yield by 112% compared with the weedy control, but it was similar to that of the weed-free control. Broccoli was less responsive to abrasive grits, with yield changes ranging from no difference to up to a 36% increase (relative to the weedy control) depending on the application rate and compost amendment. This is the first evidence indicating that the nutrient composition of organic fertilizer abrasive grits can influence in-season soil N dynamics, weed competition, and crop yield. The results suggest that abrasive weeding technology could be leveraged to improve the precision of in-season fertilizer management of organic crops.
Abbas Lafta, Germán Sandoya, and Beiquan Mou
Lettuce (Lactuca sativa L.) is a cool season crop that is vulnerable to high temperature stress, which promotes bolting and decreases yield and quality. It is anticipated that climate change may lead to higher temperatures in current lettuce growing areas in the United States, thereby negatively affecting lettuce production and possibly resulting in adverse impacts on global food production. Therefore, it is important to identify lettuce germplasm with tolerance to temperatures higher than those that have occurred over the past century. We evaluated 25 crisphead lettuce cultivars for tolerance to high temperature stress in the San Joaquin, Imperial, and Salinas Valleys, CA. Genetic variation was identified for yield and horticultural traits, such as core length, head diameter, tipburn, bolting, and market maturity, of crisphead lettuce grown in warmer conditions. Significant genotype × environment interaction did not account for most of the variation; the main differences were found for environments and only a small proportion of the variation was due to genotypes. Cultivar Primetime is a good source of heat tolerance for crisphead lettuce, as it presented the best yield and exhibited other desirable characteristics across warmer conditions. These results provide insight into the cultivars that respond well to hot environments. Moreover, the data can be used by breeders to develop new heat-tolerant lettuce cultivars.
Guohui Xu, Lei Lei, Hexin Wang, and Xin Lou
Timothy P. Hartmann, Justin J. Scheiner, Larry A. Stein, Andrew R. King, and Sam E. Feagely
Two-year-old, field-grown golden kiwifruit (Actinidia chinensis) and fuzzy kiwifruit (Actinidia deliciosa) plants were evaluated for injury following an early freeze event of −4.1 °C on 14 Nov. 2018 in Burleson County, TX. Plant material included seven cultivars: one seed-propagated [Sungold™ (ZESY002)] and three cutting-propagated golden kiwifruit (AU Golden Dragon, AU Golden Sunshine, CK03), and one seed-propagated (Hayward) and two cutting-propagated fuzzy kiwifruit (AU Authur and AU Fitzgerald). Observations were made 5 weeks after the frost event. Base trunk diameter (BD) and maximum trunk diameter damaged (MDD) provided a reference of plant size and crude measurement of damage intensity, as evident by presence of water-soaked necrotic and/or dehydrated tissue following the removal of a thin slice of periderm, vascular cambium, phloem, and xylem. Percent of base diameter damaged (PBDD) was calculated as MDD divided by BD and provided an assessment of damage, unbiased by plant size. Percent of shoot damaged (PSD) was visually evaluated as the percentage of entire shoot system exhibiting damage. In addition, presence of basal damage (DB) and basal cracking (CB) were recorded. A strong cultivar response was observed for BD, MDD, PBDD, and PSD. Mean cultivar values for PSD ranged from 79% and 19% for AU Authur and Sungold™ seedlings, respectively, which represented extremes among cultivars. Fuzzy kiwifruit exhibited greater injury (PBDD, PSD, DB, and CB) as compared with golden kiwifruit cultivars. Basal damage and basal cracking proved unique to fuzzy kiwifruit, as DB ranged from 0% in Sungold™ seedlings to 100% in fuzzy kiwifruit ‘AU Authur’ and ‘AU Fitzgerald’. In spite of having greater vigor, golden kiwifruit plants sustained less injury. Method of propagation had no effect on injury. PBDD and PSD proved to be reliable field assays for documenting injury, based on their strong correlation value (r = 0.92). Greater relative autumn frost tolerance of golden kiwifruit over fuzzy kiwifruit cultivars is previously unreported.