Journal Articles, Multidisciplinary Digital Publishing Institute (MDPI)

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Border Habitat Effects on Captures of Halyomorpha halys (Hemiptera: Pentatomidae) in Pheromone Traps and Fruit Injury at Harvest in Apple and Peach Orchards in the Mid-Atlantic, USA
Bergh, J. Christopher; Morrison, William R.; Stallrich, Jon W.; Short, Brent D.; Cullum, John P.; Leskey, Tracy C. (MDPI, 2021-05-08)
The invasive Halyomorpha halys invades crop fields from various bordering habitats, and its feeding on crops has caused significant economic losses. Thus, H. halys is considered a perimeter-driven threat, and research on alternative management tactics against it has focused on intervention at crop edges. Woodlands adjacent to crop fields contain many hosts of H. halys and are therefore considered “riskiest” in terms of pest pressure and crop injury. However, tree fruit orchards in the Mid-Atlantic, USA, are often bordered on one or more sides by woodlands and other habitats, including other tree fruit blocks, and field crops. Monitoring H. halys using pheromone traps has most often focused on the crop–woodland interface, but the relative effects of woodlands and other habitats bordering orchards on pest pressure and crop injury have not been examined. A two-year study comparing seasonal captures of H. halys and fruit injury among different habitats bordering commercial apple and peach orchards in the Mid-Atlantic revealed that while woodland borders often posed the greatest risk, other border habitats also contributed significantly to captures and injury in numerous instances. The relevance of these findings to refining and optimizing perimeter-based monitoring and management approaches for H. halys is discussed.
Ethylene-Mediated Modulation of Bud Phenology, Cold Hardiness, and Hormone Biosynthesis in Peach (Prunus persica)
Liu, Jianyang; Islam, Md Tabibul; Sapkota, Sangeeta; Ravindran, Pratibha; Kumar, Prakash P.; Artlip, Timothy S.; Sherif, Sherif M. (MDPI, 2021-06-22)
Spring frosts exacerbated by global climate change have become a constant threat to temperate fruit production. Delaying the bloom date by plant growth regulators (PGRs) has been proposed as a practical frost avoidance strategy. Ethephon is an ethylene-releasing PGR found to delay bloom in several fruit species, yet its use is often coupled with harmful effects, limiting its applicability in commercial tree fruit production. Little information is available regarding the mechanisms by which ethephon influences blooming and bud dormancy. This study investigated the effects of fall-applied ethephon on bud phenology, cold hardiness, and hormonal balance throughout the bud dormancy cycle in peach. Our findings concluded that ethephon could alter several significant aspects of peach bud physiology, including accelerated leaf fall, extended chilling accumulation period, increased heat requirements, improved cold hardiness, and delayed bloom date. Ethephon effects on these traits were primarily dependent on its concentration and application timing, with a high concentration (500 ppm) and an early application timing (10% leaf fall) being the most effective. Endogenous ethylene levels were induced significantly in the buds when ethephon was applied at 10% versus 90% leaf fall, indicating that leaves are essential for ethephon uptake. The hormonal analysis of buds at regular intervals of chilling hours (CH) and growing degree hours (GDH) also indicated that ethephon might exert its effects through an abscisic acid (ABA)-independent way in dormant buds. Instead, our data signifies the role of jasmonic acid (JA) in mediating budburst and bloom in peach, which also appears to be influenced by ethephon treatment. Overall, this research presents a new perspective in interpreting horticultural traits in the light of biochemical and molecular data and sheds light on the potential role of JA in bud dormancy, which deserves further attention in future studies that aim at mitigating spring frosts.
Evaluation of Blossom Thinning Spray Timing Strategies in Apple
Allen, W. Chester; Kon, Tom; Sherif, Sherif M. (MDPI, 2021-09-13)
In the eastern USA and several other apple-growing regions, apple blossom thinning using lime sulfur is a relatively new crop load management strategy. This study sought to evaluate how application timing of lime sulfur + stylet oil blossom thinning sprays would influence thinning efficacy and crop safety of ‘Gala’ apples. This project occurred at two locations in the USA, Winchester, Virginia, and Mills River, North Carolina, during the 2019 growing season. Two main timing strategies were assessed: (1) model-guided sprays with the pollen tube growth model (PTGM), (2) fixed spray intervals with the first spray applied at a specified percentage of open bloom (20% vs. 80%), and the second spray applied at a reapplication interval (48 h vs. 72 h). Model-guided and 20% open bloom + 48-h treatments reduced fruit set and increased fruit weight, diameter, and length at both sites. Treatments with a delayed first spray at 80% open bloom or a more extended second reapplication of 72 h were generally ineffective. There was no conclusive evidence that lime sulfur + stylet oil blossom thinning spray timing influenced russet incidence/severity or leaf phytotoxicity. This study demonstrated that effective and safe blossom thinning can be obtained from applying two sprays at 20% open bloom and 48 h thereafter or using the PTGM.
Label-Free Quantitative Proteomics Analysis in Susceptible and Resistant Brassica napus Cultivars Infected with Xanthomonas campestris pv. campestris
Islam, Md Tabibul; Lee, Bok-Rye; La, Van Hien; Bae, Dong-Won; Jung, Woo-Jin; Kim, Tae-Hwan (MDPI, 2021-01-27)
Black rot, caused by Xanthomonas campestris pv. campestris (Xcc), is the main disease of cruciferous vegetables. To characterize the resistance mechanism in the Brassica napus–Xcc pathosystem, Xcc-responsive proteins in susceptible (cv. Mosa) and resistant (cv. Capitol) cultivars were investigated using gel-free quantitative proteomics and analysis of gene expression. This allowed us to identify 158 and 163 differentially expressed proteins following Xcc infection in cv. Mosa and cv. Capitol, respectively, and to classify them into five major categories including antioxidative systems, proteolysis, photosynthesis, redox, and innate immunity. All proteins involved in protein degradation such as the protease complex, proteasome subunits, and ATP-dependent Clp protease proteolytic subunits, were upregulated only in cv. Mosa, in which higher hydrogen peroxide accumulation concurred with upregulated superoxide dismutase. In cv. Capitol, photosystem II (PS II)-related proteins were downregulated (excepting PS II 22 kDa), whereas the PS I proteins, ATP synthase, and ferredoxin-NADP⁺ reductase, were upregulated. For redox-related proteins, upregulation of thioredoxin, 2-cys peroxiredoxin, and glutathione S-transferase occurred in cv. Capitol, consistent with higher NADH-, ascorbate-, and glutathione-based reducing potential, whereas the proteins involved in the C₂ oxidative cycle and glycolysis were highly activated in cv. Mosa. Most innate immunity-related proteins, including zinc finger domain (ZFD)-containing protein, glycine-rich RNA-binding protein (GRP) and mitochondrial outer membrane porin, were highly enhanced in cv. Capitol, concomitant with enhanced expression of ZFD and GRP genes. Distinguishable differences in the protein profile between the two cultivars deserves higher importance for breeding programs and understanding of disease resistance in the B. napus–Xcc pathosystem.
Physiological and Molecular Responses of Six Apple Rootstocks to Osmotic Stress
Hezema, Yasmine S.; Shukla, Mukund R.; Ayyanath, Murali M.; Sherif, Sherif M.; Saxena, Praveen K. (MDPI, 2021-07-31)
The growth and productivity of several apple rootstocks have been evaluated in various previous studies. However, limited information is available on their tolerance to osmotic stress. In the present study, the physiological and molecular responses as well as abscisic acid (ABA) levels were assessed in six apple rootstocks (M26, V3, G41, G935, B9 and B118) osmotically stressed with polyethylene glycol (PEG, 30%) application under greenhouse conditions. Our results showed that V3, G41, G935 and B9 had higher relative water content (RWC), and lower electrolyte leakage (EL) under stress conditions compared to M26 and B118. Additionally, water use efficiency (WUE) was higher in V3, G41 and B9 than M26, which might be partially due to the lower transpiration rate in these tolerant rootstocks. V3, G41 and B9 rootstocks also displayed high endogenous ABA levels which was combined with a reduction in stomatal conductance and decreased water loss. At the transcriptional level, genes involved in ABA-dependent and ABA-independent pathways, e.g., SnRK, DREB, ERD and MYC2, showed higher expression in V3, G41, G935 and B9 rootstocks compared to M26 in response to stress. In contrast, WRKY29 was down-regulated in response to stress in the tolerant rootstocks, and its expression was negatively correlated with ABA content and stomatal closure. Overall, the findings of this study showed that B9, V3 and G41 displayed better osmotic stress tolerance followed by G935 then M26 and B118 rootstocks.
Rootstocks Overexpressing StNPR1 and StDREB1 Improve Osmotic Stress Tolerance of Wild-Type Scion in Transgrafted Tobacco Plants
Hezema, Yasmine S.; Shukla, Mukund R.; Goel, Alok; Ayyanath, Murali M.; Sherif, Sherif M.; Saxena, Praveen K. (MDPI, 2021-08-05)
In grafted plants, the movement of long-distance signals from rootstocks can modulate the development and function of the scion. To understand the mechanisms by which tolerant rootstocks improve scion responses to osmotic stress (OS) conditions, mRNA transport of osmotic responsive genes (ORGs) was evaluated in a tomato/potato heterograft system. In this system, Solanum tuberosum was used as a rootstock and Solanum lycopersicum as a scion. We detected changes in the gene expression levels of 13 out of the 21 ORGs tested in the osmotically stressed plants; of these, only NPR1 transcripts were transported across the graft union under both normal and OS conditions. Importantly, OS increased the abundance of StNPR1 transcripts in the tomato scion. To examine mRNA mobility in transgrafted plants, StNPR1 and StDREB1 genes representing the mobile and non-mobile transcripts, respectively, were overexpressed in tobacco (Nicotiana tabacum). The evaluation of transgenic tobacco plants indicated that overexpression of these genes enhanced the growth and improved the physiological status of transgenic plants growing under OS conditions induced by NaCl, mannitol and polyethylene glycol (PEG). We also found that transgenic tobacco rootstocks increased the OS tolerance of the WT-scion. Indeed, WT scions on transgenic rootstocks had higher ORGs transcript levels than their counterparts on non-transgenic rootstocks. However, neither StNPR1 nor StDREB1 transcripts were transported from the transgenic rootstock to the wild-type (WT) tobacco scion, suggesting that other long-distance signals downstream these transgenes could have moved across the graft union leading to OS tolerance. Overall, our results signify the importance of StNPR1 and StDREB1 as two anticipated candidates for the development of stress-resilient crops through transgrafting technology.
Seasonal Captures of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) and the Effects of Habitat Type and Tree Species on Detection Frequency
Quinn, Nicole F.; Talamas, Elijah J.; Leskey, Tracy C.; Bergh, J. Christopher (MDPI, 2021-01-29)
Trissolcus japonicus, an important egg parasitoid of Halyomorpha halys in Asia, was first detected in the USA in 2014. To evaluate the effect of habitat and the seasonality of T. japonicus detections in the USA, yellow sticky traps were placed in the canopy of Ailanthus altissima growing at the edge of isolated patches of trees, windbreaks, and woodlots in northern Virginia in 2018 and 2019. In both years, captures occurred from May to September, and peaked in July and August. While T. japonicus was detected in all habitats, there was not a consistent effect of habitat type on capture frequency. To evaluate tree species effects on T. japonicus captures, in 2017 and 2018, yellow sticky traps deployed in the canopy of A. altissima bordering apple orchards were paired with a nearby trap in one of several wild tree species along a common woods edge. In 2019, these traps were deployed in A. altissima, black walnut, and black locust growing in the same windbreaks. No consistent association between captures of T. japonicus or native parasitoids of H. halys and the tree species sampled was observed among years. Results are discussed in relation to the ecology and sampling optimization of T. japonicus.
Untargeted Metabolomics and Antioxidant Capacities of Muscadine Grape Genotypes during Berry Development
Darwish, Ahmed G.; Das, Protiva Rani; Ismail, Ahmed; Gajjar, Pranavkumar; Balasubramani, Subramani Paranthaman; Sheikh, Mehboob B.; Tsolova, Violeta; Sherif, Sherif M.; El-Sharkawy, Islam (MDPI, 2021-06-04)
Three muscadine grape genotypes (Muscadinia rotundifolia (Michx.) Small) were evaluated for their metabolite profiling and antioxidant activities at different berry developmental stages. A total of 329 metabolites were identified using UPLC-TOF-MS analysis (Ultimate 3000LC combined with Q Exactive MS and screened with ESI-MS) in muscadine genotypes throughout different developmental stages. Untargeted metabolomics study revealed the dominant chemical groups as amino acids, organic acids, sugars, and phenolics. Principal component analysis indicated that developmental stages rather than genotypes could explain the variations among the metabolic profiles of muscadine berries. For instance, catechin, epicatechin-3-gallate, and gallic acid were more accumulated in ripening seeds (RIP-S). However, tartaric acid and malonic acid were more abundant during the fruit-set (FS) stage, and malic acid was more abundant in the veraison (V) stage. The variable importance in the projection (VIP > 0.5) in partial least-squares–discriminant analysis described 27 biomarker compounds, representing the muscadine berry metabolome profiles. A heatmap of Pearson’s correlation analysis between the 27 biomarker compounds and antioxidant activities was able to identify nine antioxidant determinants; among them, gallic acid, 4-acetamidobutanoic acid, trehalose, catechine, and epicatechin-3-gallate displayed the highest correlations with different types of antioxidant activities. For instance, DPPH and FRAP conferred a similar antioxidant activity pattern and were highly correlated with gallic acid and 4-acetamidobutanoic acid. This comprehensive study of the metabolomics and antioxidant activities of muscadine berries at different developmental stages is of great reference value for the plant, food, pharmaceutical, and nutraceutical sectors.

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