Postharvest management of apple fruit ripening using controlled atmosphere (CA) storage can be enhanced because CA oxygen concentration is decreased to close to the anaerobic compensation point (ACP). Monitoring fruit chlorophyll fluorescence (CF) is a technology to assess fruit response to low pO2 as fluorescence increases as pO2 reaches a critically low concentration. This type of pO2 management has been referred to as dynamic atmosphere storage (DCA). Use of very low pO2 can enhance post-storage apple fruit quality for many cultivars, allowing better firmness retention and prevention of superficial scald, compared with fruit stored at higher pO2 during CA. ‘Honeycrisp’ is a chilling-sensitive cultivar with little risk of firmness loss or superficial scald during storage; however, other aspects of fruit-quality loss during storage, including soluble solids content (SSC), titratable acidity (TA), peel greasiness, and physiological disorder development may be impacted by pO2. A 2-year study was conducted to identify ‘Honeycrisp’ fruit-quality impacts of CA storage with a low-pO2 setpoint determined by using CF. ‘Honeycrisp’ apples were held 7 days at 10 °C after harvest, then at 3 °C. An additional treatment with 1-methylcyclopropene (1-MCP) was conducted in year two. CA was established 48 hours after transfer to 3 °C. In both years, fruit CF increased when pO2 decreased to ≈0.3 kPa O2 and then decreased after pO2 was increased to 0.5 kPa. Additional CA pO2 concentrations above 0.3 kPa were also maintained for other fruit. Fruit internal disorder incidence increased as pO2 decreased and with 1-MCP use. Changes in SSC, TA, and peel yellowing were inconsistently reduced by storage at lower pO2. Peel greasiness did not develop in either year. CA did not impact the incidence of chilling disorders regardless of pO2. Results indicate some aspects of ‘Honeycrisp’ fruit quality can be enhanced as CA pO2 decreases; however, pO2 above the low pO2 threshold did not prevent internal physiological disorder development.
Nana Millicent Duduzile Buthelezi, Tieho Paulus Mafeo, and Nhlanhla Mathaba
Preharvest factors such as poor orchard management and field sanitation can lead to pathological infection of the tree fruit being grown as well as insect pest infestation, resulting in poor postharvest fruit quality. Wind and hail damage may cause significant tree fruit abrasions and blemishes. Consequently, these preharvest factors may reduce yield and cause market and economic losses. One of the most successful methods used to manage tree fruit pathogens and insect infestation is the application of agrochemicals, predominantly fungicides and insecticides. However, this method has recently been criticized due to the adverse effects on field workers’ safety, consumers’ health, and the environment. The development and use of preharvest bagging are among the most environmentally friendly technologies intended for safe enhancement of tree fruit quality. The technique protects tree fruit against pathogens, insect pests, physiological disorders, agrochemical residues, fruit abrasions, sunburn, and bird damage, and it further modifies the microenvironment for fruit development with its various beneficial effects on its external and internal quality. Furthermore, because of the global restrictions of agrochemicals and social awareness, this technique provides extensive relief to growers and consumers. However, bagging is labor-intensive and expensive; therefore, its benefits or advantages and disadvantages must be thoroughly investigated if it is to be promoted commercially. This review examines the improvement of tree fruit quality by the application of preharvest bagging during early stages of fruit growth and development. The latest advances in the development and use of tree fruit bagging and its economic impact and cost–benefit ratio are discussed, as are recommendations for the formulation of bagging materials that could be valuable in the future.
Qiuyue Ma, Shushun Li, Jing Wen, Lu Zhu, Kunyuan Yan, Qianzhong Li, Shuxian Li, and Bin Zhang
Acer truncatum seeds are an excellent source of beneficial natural compounds, including high levels of unsaturated fatty acids (UFAs), that promote health. Recently, A. truncatum has emerged as an oil crop. Therefore, the transcriptomes of A. truncatum seeds at 70, 85, 100, 115, 145, 180 days after flowering (DAF) were analyzed to gain a better understanding of the transcriptional and translational regulation of seed development and oil biosynthesis. A total of 28,438 genes were identified, and 3069/2636, 3288/3438, 1319/2750, and 5724/5815 upregulated/downregulated genes were identified when comparing different samples with 85 DAF seeds. Sixteen lipid metabolism pathways with 754 differentially expressed genes (DEGs) were identified, including 34 DEGs associated with UFA biosynthesis. A phylogenetic analysis revealed that six putative fatty acid desaturase (FAD) genes clustered into five FAD groups. A quantitative real-time polymerase chain reaction analysis indicated that the temporal expression patterns of oil biosynthesis genes and transcription factors were largely similar to the RNA sequencing results. The results of this study will enhance the current understanding of oil metabolism in A. truncatum seeds and allow new methods of improving oil quality and seed yield in the future.
Wilfredo Seda-Martínez, Linda Wessel-Beaver, Angela Linares-Ramírez, and Jose Carlos V. Rodrigues
Infecting cucurbits around the world, Papaya ringspot virus (PRSV) and Zucchini yellow mosaic virus (ZYMV) are members of the genus Potyvirus and family Potyviridae. Tropical pumpkin is grown globally in the lowland humid tropics. In Puerto Rico, tropical pumpkin is the second most important vegetable crop in economic value. In trials in Puerto Rico in 2016 and 2017, susceptible genotypes ‘Waltham’, Mos166, ‘Taína Dorada’ (2016 only), ‘Soler’ with moderate resistance to ZYMV, and resistant ‘Menina’ and ‘Nigerian Local’ were inoculated with PRSV and ZYMV and evaluated in the greenhouse and field. Mock-inoculated (buffer) controls were included. Puerto Rico strains of PRSV and ZYMV were originally collected from plants of Cucurbita moschata in Puerto Rico. Presence of virus was determined by Double Antibody Sandwich (DAS) enzyme-linked immunosorbent assay (ELISA) and symptom severity was evaluated on a 0 to 5 scale in both trials. Days to anthesis of first staminate and pistillate flower were recorded for each plot. Number of fruits, fruit weight per plant, average fruit weight, fruit and mesocarp diameter, mesocarp color, °Brix, and percentage dry matter were measured in 2017. ‘Waltham’, Mos166, ‘Taína Dorada’, and ‘Soler’ tested positive for PRSV when inoculated with PRSV and positive for ZYMV when inoculated with ZYMV. For both PRSV and ZYMV, symptom severity was less (severity = 0) in resistant genotypes ‘Menina’ and ‘Nigerian Local’ than in all other genotypes. ‘Soler’ inoculated with ZYMV exhibited less symptom severity than that of susceptible genotypes. The degree of symptom severity of ‘Soler’ inoculated with PRSV was similar to susceptible genotypes. Symptom severity in plants inoculated with ZYMV was generally greater than when inoculated with PRSV. Compared with controls, yield per plant was unaffected by inoculation with potyvirus in resistant cultivar ‘Menina’. Unexpectedly, yield in resistant ‘Nigerian Local’ was reduced an average of 45% over control plots. Yield loss was 100% in inoculated plots of susceptible ‘Waltham’. Yield reduction ranged from 35% to 80% for susceptible Mos166 and moderately resistant ‘Soler’. There was little evidence that days to anthesis, average fruit weight, fruit diameter, and fruit quality (mesocarp thickness, chroma, hue angle, °Brix and dry matter) of plants inoculated with virus were different from that of uninoculated control plants. The exception was moderately resistant ‘Soler’ where plants inoculated with ZYMV produced fruits with a 32% reduction in average weight, as well as reductions in diameter, mesocarp thickness, and color saturation (chroma) compared with controls. This was unexpected given that ‘Soler’ has some resistance to ZYMV. Greenhouse evaluations by ELISA or symptom severity were generally useful in predicting field resistance to PRSV and ZYMV. In summary, yield reductions of up to 100% can be expected in C. moschata genotypes susceptible to PRSV or ZYMV, but fruit quality traits are usually unaffected. Moderate resistance to ZYMV in ‘Soler’ was observed to reduced symptom severity but not negative effects on yield and other traits. ‘Soler’ was not resistant to PRSV. ‘Menina’ rather than ‘Nigerian Local’ appears to be the best source of resistance because yield of the former was not impacted by inoculation with either potyvirus.
Sameer Pokhrel, Bo Meyering, Kim D. Bowman, and Ute Albrecht
Huanglongbing (HLB) is a devastating disease of citrus that is found in most citrus production areas around the world. The bacterium associated with HLB resides in and damages the phloem, restricting the movement of photosynthates throughout the plant and leading to tree decline. Considerable root loss can be observed in affected trees even when few disease symptoms are visible aboveground. Root traits can substantially influence tree performance and use of superior rootstocks is one strategy to manage tree health and reduce production losses in a disease-endemic environment. Citrus rootstocks are typically propagated by seed, but due to the increased demand for some of the best-performing cultivars, propagation by other methods is being used to overcome seed shortages. In this research, differences in root architecture and root growth of six different rootstocks propagated by seed, cuttings, and tissue culture, and their influence on the grafted ‘Valencia’ (Citrus sinensis) scion were investigated. A field trial was established in southwest Florida in 2017. Trees were evaluated for their performance during the first 2 years after planting and a subset of trees was excavated for detailed analysis of root architectures and biomass distribution. Significant differences among propagation methods were found for the rootstock trunk diameter and the lateral (structural) root length, which were largest in seed-propagated rootstocks. Most of the other horticultural and root architectural traits were not significantly influenced by the rootstock-propagation method; however, many of the measured variables were significantly influenced by the rootstock cultivar regardless of the propagation method. The results showed that rootstocks propagated by cuttings and tissue culture were similar to seed-propagated rootstocks in their influence on the grafted tree during the early years of growth in the field.
Jing Huang, Ya-liang Xu, Fa-min Duan, Xu Du, Qi-chang Yang, and Yin-jian Zheng
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.
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.