Onion (Allium cepa L.) bulbs produced in the Pacific Northwest of the United States in 2014 and 2015 had unusually high incidence of internal decay. This decay was not detectable externally, leading to marketing problems when bulbs were packed and shipped to markets. The onion growing seasons in 2014 and 2015 were unusually hot, suggesting a connection of heat stress to bulb internal decay. Field studies to investigate the effect of temperature on onion bulb internal decay and yield were conducted in 2016–18 with drip-irrigated onions at the Oregon State University, Malheur Experiment Station located in eastern Oregon. Two long-day onion cultivars were submitted to four cultural practice variations to affect soil and bulb temperatures: bare soil check, supplemental heat using electric heat cables, white kaolinite clay application to the bulb sides and soil surface, and wheat (Triticum aestivum L.) straw mulch. The treatments established significant midafternoon average bulb and soil surface temperature gradients in the following order of increasing temperature: straw mulch, kaolinite, check, and supplemental heat. Averaged over years and cultivars, straw-mulched onions had the highest yield of bulbs larger than 102 mm diameter. Averaged over years and cultivars, onions receiving supplemental heat had the lowest total and marketable yield with no difference among the other treatments. Straw mulched onions had higher total and marketable yield than the bare soil check treatment in 2017, the hottest year. Averaged over the 3 years and two cultivars, marketable yield and yield of bulbs larger than 102 mm diameter decreased with increasing midafternoon bulb temperatures. Kaolinite application did not increase bulb yield nor bulb size compared with the bare soil check. The incidence of internal bulb decay was low all 3 years. In 2017, onions receiving supplemental heat had the highest internal decay and the straw-mulched onions had among the lowest internal decay. There was little difference in the measured soil moisture among treatments. Straw mulching may attenuate the negative effects of excessive heat on yield and bulb internal quality for long day onion production.
Clinton C. Shock, Erik B. G. Feibert, Alicia Rivera, and Kyle D. Wieland
Chi D. Nguyen, Matthew Creech, Diying Xiang, German Sandoya, Dean Kopsell, and Heqiang Huo
Lettuce (Lactuca sativa L.) is one of the most consumed fresh vegetables in the United States. However, lettuce production is heavily limited to California and Arizona, posing a high risk to the supply chain. Hydroponic production is a soilless cultivation method and provides a sustainable alternative to growing lettuce in the field. Light is a critical factor in plant development, and light quality highly affects plant morphogenesis. The goals of this study were 2-fold, with the first to investigate the growth of 26 lettuce cultivars under a hydroponic system supplemented with fluorescent light to determine adaptability. Subsequently, the second goal was to determine how light-emitting diodes (LEDs) affect lettuce plant morphology and photosynthesis compared with fluorescent light for four lettuce cultivars. Results showed that 23 of 26 lettuce cultivars were grown successfully using a hydroponic system. However, lettuce grown under fluorescent light experienced stem elongation—a morphological response to low-light conditions known as shade avoidance syndrome. Stem elongation decreased significantly under LED light, whereas other morphological characteristics remained relatively the same between the two light treatments. Although there were no differences in dry weight and leaf area, the carbon assimilation rate increased significantly in lettuce cultivars Coastal Star, Muir, Green Butter, and Rouge d’Hiver when treated with LED light. Correspondingly, intercellular carbon dioxide (CO2) decreased in these four lettuce cultivars under the LED light treatment. Our study results indicate that LED light increased photosynthetic activity and reduced stem elongation to enhanced lettuce quality.
Dongyue Jiang, Xin Shen, and Bochun Shen
Chuan Shen and Xia Li
Amorphophallus belongs to the family Araceae and contains a high-molecular-weight polysaccharide that was originally extracted from corms called Konjac glucomannan. During the past 10 years, a vast body of research of Amorphophallus konjac has been published. Based on the Web of Science literature database, this work used Co-Occurrence, VOSviewer, and SciMAT bibliometrics analysis software tools to conduct literature analyses and big data mining of Amorphophallus Konjac research from Jan. 2012 to Dec. 2021. Therefore, the present research sorted the development process of this field and analyzed the popular changes in research topics by combing through the visualization of the analysis results to systematically review and forecast the research of Amorphophallus Konjac-related fields. This work discusses current research trends and hotspots and explores and analyzes the content that needs improvement to provide a reference for follow-up research.
Emilee Gaulke and Irwin L. Goldman
Bacterial leaf spot (BLS) has emerged in the last few decades as an economically important disease of both table beet (Beta vulgaris ssp. vulgaris) and Swiss chard (Beta vulgaris ssp. cicla). BLS is caused by Pseudomonas syringae pv. aptata, which is spread readily on infected seeds. Symptoms appear as circular to irregular shaped, with a tan to dark brown center and a very dark border. Disease incidence and severity is dependent on cool, humid conditions and can vary widely year to year depending on the environment. Both the vegetative and reproductive phases of these biennial crops are susceptible to the pathogen. Table beet and Swiss chard commercial cultivars (n = 21), table beet breeding lines (n = 5), and table beet plant introductions (PIs) (n = 26) were screened for response to spray inoculation with P. syringae pv. aptata in a controlled greenhouse setting. Plants were rated for severity of symptoms using percent of the area of each pair of leaves (leaf set) with symptoms and an overall plant score assigned based on the scores for each leaf pair. Accessions varied in BLS susceptibility. PI accessions were most variable, with the area under the disease progress curve (AUDPC) ranging from 1.33 to 8.75. Highly significant differences among PIs were detected for disease scores in the vegetative stage, beginning 21 days after inoculation. Screens during the reproductive growth stage showed the least variation in AUDPC among PIs. Although cultivars varied less than PIs, good BLS resistance (low disease scores) was noted for ‘Touchstone Gold’, ‘Kestrel’, ‘Bull’s Blood’, ‘Rainbow’ chard, as well as PIs 222234 and NSL 28026. Accessions W451C, Red Cloud, Detroit Dark Red, and NSL 28020 were highly susceptible. There was no consistent association between disease score in the vegetative and reproductive phases, suggesting that breeders may need to screen for BLS in both phases of the biennial life cycle. The more resistant PIs or cultivars identified in this study can be used in future efforts to breed for host resistance to BLS and to establish mapping populations to better understand the genetic control of resistance, to aid in breeding efforts.
Xinwang Wang, Warren Chatwin, Keith Kubenka, Angelyn Hilton, Braden Tondre, Tommy Thompson, and LJ Grauke
Tony Reda, Pushparajah Thavarajah, William Bridges, William Whiteside, Robert Polomski, Emerson Ship, and Dil Thavarajah
Over half of global food waste occurs in retail and households, highlighting the importance of improving shelf life. Many factors affect shelf life, including storage temperature, harvest time, processing method, and packaging. Modified atmosphere packaging (MAP), such as nitrogen (N2), has been used to improve the shelf life of produce. This study aimed to determine the effect of nitrogen-enriched packaging on the shelf life of greenhouse- and garden-grown kale in raised beds outdoors. Five kale cultivars (Black Magic, Darkibor, Lacinato, Red Russian, and Westlander) were grown in the greenhouse, and four cultivars (Curly Roja, Dwarf Green Curled, Meadowlark, and Vates) outdoors in raised beds, harvested and stored in nitrogen-enriched or nonenriched bags for 6 days. Leaf water content, water activity, color, visual score, and texture were measured for each replicate. Nitrogen-enriched packaging did not affect the kale shelf life. Garden-grown kale exhibited significantly lower water activity (0.979 vs. 0.999) and noticeably lower water content (88.6 vs. 90.6%) than greenhouse-grown kale. The cultivars were significant for all factors tested except for texture on day 4 and change in light to dark (Δ L*) and blue to yellow (Δ b*) color ratios. At the end of the study, cultivars Darkibor and Curly Roja had the highest visual score (4.4) and texture (305 g), respectively. The high performance of ‘Darkibor’ and ‘Curly Roja’ in visual score and texture may be due to decreased (Δ L*) and (Δ b*) values and decreased water content and water activity values. Future breeding efforts focused on the shelf life of kale should use the top-performing cultivars identified in this study and a diverse genetic population tested in a range of environments to develop cultivars with a longer shelf life.
Elizabeth Mitcham, Claire Adkison, Nico Lingga, and Veronique Bikoba
Four cultivars of English walnut (Juglans regia) were evaluated by a trained taste panel after 6 and 12 months of storage. English walnuts were stored at 5, 15, or 25 °C, and at 40%, 60%, or 80% relative humidity within each temperature. Principal component analysis was used to compare taste, texture, and aroma attributes evaluated by the taste panel to objective indicators of English walnut quality including water activity, moisture content, free fatty acids, peroxide value, hexanal content, and kernel color. Temperature was found to significantly impact English walnut oxidation and perceived rancidity, whereas storage at high relative humidity affected English walnut texture and accelerated quality loss. Water activity was more strongly correlated to textural changes than moisture content. The effect of relative humidity was more pronounced at lower temperatures, leading to increased hydrolytic rancidity and free fatty acids. Peroxide value had higher and more significant correlation to sensory attributes related to rancidity than hexanal. Free fatty acids were not correlated to the rancid sensory attribute, but were significantly correlated to bitter. English walnuts stored at 5 °C with 40% or 60% relative humidity were associated with the sweet sensory attribute and L* value (light color). Kernel darkening was associated with bitter and rancid, but a causal relationship is unknown. Sensory quality of English walnuts is complex and requires further study to establish thresholds for chemical indices of English walnut quality loss based on organoleptic perception.
Davis D. Harmon, Darren H. Touchell, Thomas G. Ranney, Kedong Da, and Wusheng Liu
Methods of in vitro regeneration protocols were developed for three elite rose cultivars, Chewnicebell (Oso Easy Italian Ice®), Bucbi (Carefree Beauty™), and Cheweyesup (Ringo All-Star™). We evaluated the effects of different types and concentrations of auxins [dichlorophenoxyacetic acid (2,4-D) and trichlorophenoxyacetic acid (2,4,5-T)], carbohydrates [sucrose, glucose, and fructose], and cytokinins [thidiazuron (TDZ) and 6-bezylaminopurine (BAP)] on callus induction and regeneration from leaf explants. The greatest amount of regenerative callus was obtained on media containing 10 µM 2,4-D and 30 g·L−1 sucrose for Italian Ice® (40%), 10 µM 2,4-D and 60 g·L−1 glucose for Carefree Beauty™ (24%), and 5 µM 2,4,5-T and 30 g·L−1 sucrose for Ringo All-Star™ (32%). The greatest regeneration occurred when callus was transferred to media consisting of 1/2 MS media supplemented with 2.9 µM GA3 and 5 µM TDZ for Italian Ice® and Ringo All-Star™, and with 2.9 µM GA3 and 20 µM TDZ for Carefree Beauty™. Plantlets regenerated from callus were cultured on maintenance media and successfully transferred ex vitro. This study highlights the genotype-specific responses among rose cultivars and provides the first reports of in vitro regeneration for Italian Ice® and Ringo All-Star™.
Penghua Gao, Huanyu Wei, Jiani Liu, Zebin Chen, Ying Qi, Zhixing Wu, Feiyan Huang, and Lei Yu
Amorphophallus species are one of the main economic crops in the mountainous areas of southwest China. However, soft rot disease (Pectobacterium carotovorum ssp. carotovorum) is devastating for this crop. This study explored the Amorphophallus resistance mechanism against soft rot disease by analyzing transcriptome data using a weighted gene coexpression network analysis. The RNA sequencing of plants infected for 0, 12, 24, and 48 hours produced a total of 52.25 Gb of clean reads. A total of 29,096 genes were divided into 34 modules. Six modules of interest with the highest correlation with the target traits were selected to elucidate the resistance genes and pathways. The selected modules were enriched in the α-linolenic acid metabolism, phenylpropane biosynthesis, plant hormone signal transduction, and plant pathogen interaction pathways. Ultimately, AmBGLU, AmCAML, AmCDPK, AmLOX, and AmRBOHD were identified as genes of interest in the four significantly related metabolic pathways for real-time fluorescence quantitative polymerase chain reaction verification. The determination of salicylic acid (SA) and jasmonic acid (JA) in Amorphophallus muelleri and Amorphophallus konjac that suffered from soft rot disease showed that SA and JA were involved in the A. muelleri and A. konjac defense response against soft rot disease. Methyl jasmonate treatment delayed the onset of A. konjac soft rot disease. This study provides a reference for the interaction between Amorphophallus species and soft rot disease and the breeding of broad-spectrum and specific Amorphophallus cultivars that are resistant to soft rot disease.