Virginia Agricultural Experiment Station

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The Virginia Agricultural Experiment Station conducts research on food and fiber systems, their impact on the environment, and their relation to the future needs of Virginia, the nation, and the world.

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Apple miRNAs and tasiRNAs with novel regulatory networks
Xia, Rui; Zhu, Hong; An, Yong-qiang; Beers, Eric P.; Liu, Zongrang (2012-06-15)
Background MicroRNAs (miRNAs) and their regulatory functions have been extensively characterized in model species but whether apple has evolved similar or unique regulatory features remains unknown. Results We performed deep small RNA-seq and identified 23 conserved, 10 less-conserved and 42 apple-specific miRNAs or families with distinct expression patterns. The identified miRNAs target 118 genes representing a wide range of enzymatic and regulatory activities. Apple also conserves two TAS gene families with similar but unique trans-acting small interfering RNA (tasiRNA) biogenesis profiles and target specificities. Importantly, we found that miR159, miR828 and miR858 can collectively target up to 81 MYB genes potentially involved in diverse aspects of plant growth and development. These miRNA target sites are differentially conserved among MYBs, which is largely influenced by the location and conservation of the encoded amino acid residues in MYB factors. Finally, we found that 10 of the 19 miR828-targeted MYBs undergo small interfering RNA (siRNA) biogenesis at the 3' cleaved, highly divergent transcript regions, generating over 100 sequence-distinct siRNAs that potentially target over 70 diverse genes as confirmed by degradome analysis. Conclusions Our work identified and characterized apple miRNAs, their expression patterns, targets and regulatory functions. We also discovered that three miRNAs and the ensuing siRNAs exploit both conserved and divergent sequence features of MYB genes to initiate distinct regulatory networks targeting a multitude of genes inside and outside the MYB family.
Applications of High-Resolution Imaging for Open Field Container Nursery Counting
She, Ying; Ehsani, Reza; Robbins, James; Nahún Leiva, Josué; Owen, James S. Jr. (MDPI, 2018-12-12)
Frequent inventory data of container nurseries is needed by growers to ensure proper management and marketing strategies. In this paper, inventory data are estimated from aerial images. Since there are thousands of nursery species, it is difficult to find a generic classification algorithm for all cases. In this paper, the development of classification methods was confined to three representative categories: green foliage, yellow foliage, and flowering plants. Vegetation index thresholding and the support vector machine (SVM) were used for classification. Classification accuracies greater than 97% were obtained for each case. Based on the classification results, an algorithm based on canopy area mapping was built for counting. The effects of flight altitude, container spacing, and ground cover type were evaluated. Results showed that container spacing and interaction of container spacing with ground cover type have a significant effect on counting accuracy. To mimic the practical shipping and moving process, incomplete blocks with different voids were created. Results showed that the more plants removed from the block, the higher the accuracy. The developed algorithm was tested on irregular- or regular-shaped plants and plants with and without flowers to test the stability of the algorithm, and accuracies greater than 94% were obtained.
Characterization of Glutamate-Mediated Hormonal Regulatory Pathway of the Drought Responses in Relation to Proline Metabolism in Brassica napus L.
La, Van Hien; Lee, Bok-Rye; Islam, Md Tabibul; Al Mamun, Md; Park, Sang-Hyun; Bae, Dong-Won; Kim, Tae-Hwan (2020-04)
Proline metabolism influences the metabolic and/or signaling pathway in regulating plant stress responses. This study aimed to characterize the physiological significance of glutamate (Glu)-mediated proline metabolism in the drought stress responses, focusing on the hormonal regulatory pathway. The responses of cytosolic Ca2+ signaling, proline metabolism, and redox components to the exogenous application of Glu in well-watered or drought-stressed plants were interpreted in relation to endogenous hormone status and their signaling genes. Drought-enhanced level of abscisic acid (ABA) was concomitant with the accumulation of ROS and proline, as well as loss of reducing potential, which was assessed by measuring NAD(P)H/NAD(P)(+) and GSH/GSSG ratios. Glu application to drought-stressed plants increased both salicylic acid (SA) and cytosolic Ca2+ levels, with the highest expression of calcium-dependent protein kinase (CPK5) and salicylic acid synthesis-related ICS1. The SA-enhanced CPK5 expression was closely associated with further enhancement of proline synthesis-related genes (P5CS1, P5CS2, and P5CR) expression and a reset of reducing potential with enhanced expression of redox regulating genes (TRXh5 and GRXC9) in a SA-mediated NPR1- and/or PR1-dependent manner. These results clearly indicate that Glu-activated interplay between SA- and CPK5-signaling as well as Glu-enhanced proline synthesis are crucial in the amelioration of drought stress in Brassica napus.
Comparison of 2,4-D, dicamba and halauxifen-methyl alone or in combination with glyphosate for preplant weed control
Askew, M. Carter; Cahoon, Charles W. Jr.; York, Alan C.; Flessner, Michael L.; Langston, David B.; Ferebee, J. Harrison (2021-02)
A field study was conducted in 2017 and 2018 to determine foliar efficacy of halauxifen-methyl, 2,4-D, or dicamba applied alone and in combination with glyphosate at preplant burndown timing. Experiments were conducted near Painter, VA; Rocky Mount, NC; Jackson, NC; and Gates, NC. Control of horseweed, henbit, purple deadnettle, cutleaf evening primrose, curly dock, purple cudweed, and common chickweed were evaluated. Halauxifen-methyl applied at 5 g ae ha(-1) controlled small and large horseweed 89% and 79%, respectively, and was similar to control by dicamba applied at 280 g ae ha(-1). Both rates of 2,4-D-533 g ae ha(-1)(low rate [LR]) or 1,066 g ae ha(-1) (high rate [HR])-were less effective than halauxifen-methyl and dicamba for controlling horseweed. Halauxifen-methyl was the only auxin herbicide to control henbit (90%) and purple deadnettle (99%). Cutleaf evening primrose was controlled 74% to 85%, 51%, and 4% by 2,4-D, dicamba, and halauxifen-methyl, respectively. Dicamba and 2,4-D controlled curly dock 59% to 70% and were more effective than halauxifen-methyl (5%). Auxin herbicides applied alone controlled purple cudweed and common chickweed 21% or less. With the exception of cutleaf evening primrose (35%) and curly dock (37%), glyphosate alone provided 95% or greater control of all weeds evaluated. These experiments demonstrate halauxifen-methyl effectively (>= 79%) controls horseweed, henbit, and purple deadnettle, whereas common chickweed, curly dock, cutleaf evening primrose, and purple cudweed control by the herbicide is inadequate (<= 7%).
Compost applications increase bacterial community diversity in the apple rhizosphere
Sharaf, Hazem; Thompson, Ashley A.; Williams, Mark A.; Peck, Gregory M. (2021-03-24)
Sustainable practices are key to the improvement of soil fertility and quality in apple (Malus x domestica Borkh.) orchards. Rootstock genotype and fertilizer inputs can alter soil biology, as well as aboveground traits including nutrient acquisition. In this study, a factorial design was used to assess the interaction between two apple rootstocks, 'Geneva 41' ('G.41') and 'Malling 9' ('M.9') with four fertilizer treatments [chicken-litter compost, yardwaste compost, fertigation using Ca(NO3)(2), and an unamended control]. The bacterial community in the rhizosphere was assessed for its impact on both plant and soil properties for each rootstock x fertilizer treatment combination. The bacterial community was dominated by Acidobacteria, Proteobacteria, and Planctomycetes, but Verrucomicrobia and Chloroflexi were the most responsive to the fertilizer treatments. The chicken litter and yardwaste treatments had a greater effect on bacterial community structure than the control. Yardwaste, in particular, was associated with increased relative abundance of Chloroflexi, which was correlated with soil nutrient concentrations. Malling 9 had a greater bacterial diversity than G.41, but the rootstock treatment had no independent effect on the rhizosphere community structure. There was, however, a strong interaction between the rootstock and fertilizer treatments. Carbon cycling was the most prominent functional change associated with the soil bacterial community. These results suggest that compost amendments have a more positive effect on soil bacterial activity and nutrient availability than Ca(NO3)(2). Our work shows that waste-stream amendments can lead to multiple positive responses, such as increasing aboveground tree biomass, thus potentially improving orchard productivity.
Dolomite and Micronutrient Fertilizer Affect Phosphorus Fate in Pine Bark Substrate used for Containerized Nursery Crop Production
Shreckhise, Jacob H.; Owen, James S. Jr.; Eick, Matthew J.; Niemiera, Alexander X.; Altland, James E.; White, Sarah A. (2019-09)
Dolomite and a micronutrient fertilizer are routinely incorporated into a pine bark-based soilless substrate when producing containerized nursery crops, yet the effect of these amendments on phosphorus (P) is not well understood. The objective of this research was to determine the effect of dolomite and micronutrient fertilizer amendments on P partitioning among four P fractions (i.e., orthophosphate-P EOM non-orthophosphate dissolved P [NODP], total dissolved P [TDP], and particulate P (PPJ) and to model potential P species in leachate of pine bark substrate. Amendment treatments incorporated into bark at experiment initiation included (1) a control (no fertilizer, dolomite, or micronutrient fertilizer), (2) controlled-release fertilizer (CRF), (3) CRF and dolomite, (4) CRF and micronutrient fertilizer, or (5) CRF, dolomite, and micronutrient fertilizer. Phosphorus fractions in leachate of irrigated pine bark columns were determined at eight sampling times over 48 days. Amending pine bark with dolomite and micronutrient fertilizer reduced leachate OP concentrations by 70% when averaged across sampling dates primarily due to retention of OP in the substrate by dolomite. The NODP fraction was unaffected by amendments, and the response of TDP was similar to that of OP. Particulate P was present throughout the study and was strongly correlated particulate Fe and DOC concentrations. Visual MINTEQ indicated MnHPO4 and Ca-5(PO4)(3)(OH) were consistently saturated with respect to their solid phase in treatments containing CRF. Results of this study suggest amending pine bark with dolomite and micronutrients is a best management practice for reducing P leaching from containerized nurseries.
Effects of horticultural oils on the photosynthesis, fruit maturity, and crop yield of winegrapes
Finger, Sarah A.; Wolf, Tony K.; Baudoin, Antonius B. (American Society for Enology and Viticulture, 2002)
The effects of horticultural oils on grapevine photosynthesis, fruit maturity, and crop yield components in field experiments were evaluated. Three applications of a 1.5% (v/v) oil/water emulsion were made to Chardonnay and Cabernet Sauvignon vine canopies at 6200 L/Ha (Chardonnay) and 2440 L/Ha (Cabernet Sauvignon) in 1998 using several horticultural oils. Net assimilation rates (NAR) and fruit soluble solids concentrations (SSC) were reduced in both cultivars by all oils, as compared to the control. In addition, berry weights, cluster weights, crop per vine, and vine pruning weights were all reduced by oil treatments to Chardonnay vines. Experiments in 1999 sought to determine if reduced spray volumes or applications to only the fruit zone minimized reductions in NAR and SSC. Chardonnay and Cabernet Sauvignon were treated twice with JMS Stylet-Oil(TM) (1.5%) using 5600 L/Ha or 1870 L/Ha applied to the whole canopy or 930 L/Ha applied only to the fruit zone. The NAR of 5600 L/Ha-treated Cabernet Sauvignon was significantly lower than the NAIR of 1870 L/Ha oil-treated vines on three of four subsequent measurement dates. The NAR of Chardonnay in either the 1870 or 5600 L/Ha whole canopy oil treatments was significantly lower than the NAR of the water treatment at all measurement dates. Oil application to only the fruit zone (930 L/Ha) reduced the negative impact on NAR. Cabernet Sauvignon fruit SSC was consistently reduced by the 5600 L/Ha and 1870 L/Ha treatments, relative to the water-treated control. Similarly, the SSC of Chardonnay fruit in the 1870 and 5600 L/Ha treatments was consistently reduced compared to controls. Oil effects on fruit pH and titratable acidity were occasionally observed. While horticultural oils may serve as effective fungicides, our results highlight the potential negative impacts they can have on fruit composition and fruitfulness if used excessively.
Effects of prohexadione-calcium on grape yield components and fruit and wine composition
Lo Giudice, Danielle; Wolf, Tony K.; Zoecklein, Bruce W. (American Society for Enology and Viticulture, 2004)
Prohexadione-calcium (prohexadione-Ca) was applied to field-grown Cabernet franc, Cabernet Sauvignon, Chardonnay, and Seyval to evaluate rates and timing effects on fruit yield components and on fruit and wine composition. Berries per cluster, berry weight, cluster weight, and clusters per shoot in the subsequent season were all decreased by multiple, prebloom plus postbloom, applications to Cabernet Sauvignon and Cabernet franc. Similar reductions in current season components of yield were observed with Seyval. Application (250 mg/L) to single clusters of Cabernet Sauvignon and Chardonnay at bloom, or in the one-to-two-week prebloom period decreased fruit set, whereas applications one to two weeks postbloom reduced berry weight, with no impact on fruit set. Berry weight reduction correlated to increased color intensity (420 nm + 520 nm), total anthocyanins, total phenols, and phenol-free glycosyl-glucose (PFGG) in Cabernet Sauvignon. In a separate experiment, prohexadione-Ca increased Cabernet franc must color intensity, total anthocyanins, and total phenols, despite having, minimal effects on berry weight or crop yield. Aroma and flavor triangle difference tests did not distinguish treatment differences with young Cabernet franc wines. This study of prohexadione-Ca effects on grape reproductive development illustrated that berry set and berry weight were responsive to application timing, with the one-to-two-week period after bloom most sensitive to reductions in berry weight. The concurrent effects on fruit composition were generally positive, while the full impact on wine quality remains equivocal, but worthy of further evaluation.
Evaluation of Alfalfa-Tall Fescue Mixtures across Multiple Environments
Tracy, Benjamin F.; Albrecht, Ken; Flores, Joao; Hall, Marvin; Islam, Anowarul; Jones, Gordon M.; Lamp, William O.; MacAdam, Jennifer W.; Skinner, Howard; Teutsch, Christopher D. (2016-07)
Binary grass-legume mixtures can benefit forage production systems in different ways helping growers cope both with increasing input costs (e.g., N fertilizer, herbicides) and potentially more variable weather. The main objective of this study was to evaluate alfalfa (Medicago sativa L.) and tall fescue [Schedonorus phoenix (Scop.) Holub] mixtures across a wide range of environments to assess herbage accumulation, weed suppression and fertilizer nitrogen replacement values (FNRV). A common field experiment was established in 2009 and 2010 at six study sites in the United States: Maryland, Pennsylvania, Utah, Virginia, Wisconsin, and Wyoming. Experimental treatments included an alfalfa monoculture, three alfalfa-fescue mixtures with seed ratios of 75: 25, 50: 50, and 25: 75 of alfalfa/tall fescue, and tall fescue monocultures that received nitrogen applications of 0, 50, 100, 150, 200, and 300 kg N ha(-1), respectively. Data were collected over a 2-yr period. The responses of tall fescue monocultures to N fertilization differed among sites, and this contrasted with mixture yields, which did not exhibit site x treatment interactions (P > 0.05). Herbage accumulation and weed suppression were consistently higher in mixtures compared with alfalfa monocultures and tall fescue monocultures receiving less than 100 kg N ha(-1). The FNRVs for alfalfa were within the range reported for other studies and averaged 143 kg N ha(-1). The consistent herbage accumulations across these multiple environments suggest binary mixtures of alfalfa-tall fescue may be a good option for many forage-livestock producers although yields could be improved with location specific cultivar selection.
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.
Evaluation of Insecticides to Control Stink Bug in Edamame, 2019
Sutton, Kemper L.; Kuhar, Thomas P.; Rideout, Steven L.; Zhang, Bo (Oxford University Press, 2020-01-01)
Exploring Rain as Source of Biological Control Agents for Fire Blight on Apple
Llontop, Marco E. Mechan; Hurley, Kelly; Tian, Long; Galeano, Vivian A. Bernal; Wildschutte, Hans K.; Marine, Sasha C.; Yoder, Keith S.; Vinatzer, Boris A. (2020-02-14)
Poor survival on plants can limit the efficacy of Biological Control Agents (BCAs) in the field. Yet bacteria survive in the atmosphere, despite their exposure to high solar radiation and extreme temperatures. If conditions in the atmosphere are similar to, or more extreme than, the environmental conditions on the plant surface, then precipitation may serve as a reservoir of robust BCAs. To test this hypothesis, two hundred and fifty-four rain-borne isolates were screened for in vitro inhibition of Erwinia amylovora, the causal agent of fire blight, as well as of other plant pathogenic bacteria, fungi and oomycetes. Two isolates showed strong activity against E. amylovora and other plant pathogenic bacteria, while other isolates showed activity against fungal and oomycete pathogens. Survival assays suggested that the two isolates that inhibited E. amylovora were able to survive on apple blossoms and branches similarly to E. amylovora. Pathogen population size and associated fire blight symptoms were significantly reduced when detached apple blossoms were treated with the two isolates before pathogen inoculation, however, disease reduction on attached blossoms within an orchard was inconsistent. Using whole genome sequencing, the isolates were identified as Pantoea agglomerans and P. ananatis, respectively. A UV-mutagenesis screen pointed to a phenazine antibiotic D-alanylgriseoluteic acid synthesis gene cluster as being at the base of the antimicrobial activity of the P. agglomerans isolate. Our work reveals the potential of precipitation as an under-explored source of BCAs, whole genome sequencing as an effective approach to precisely identify BCAs, and UV-mutagenesis as a technically simple screen to investigate the genetic basis of BCAs. More field trials are needed to determine the efficacy of the identified BCAs in fire blight control.
Fifty Years of Cereal Leaf Beetle in the U.S.: An Update on Its Biology, Management, and Current Research
Philips, Christopher R.; Herbert, D. Ames Jr.; Kuhar, Thomas P.; Reisig, Dominic D.; Thomason, Wade E.; Malone, Sean M. (Entomological Society of America, 2011-10-01)
Cereal leaf beetle, Oulema melanopus L., is an introduced insect pest of small grains first recorded in the United States in the early 1960s. Since its introduction from Europe or Asia into Michigan, cereal leaf beetle has rapidly spread and can now be found in most states. Cereal leaf beetle feeds on numerous species of grasses and is considered a major pest of oats, barley, and wheat. Although several studies have investigated cereal leaf beetle biology and population dynamics, numerous gaps remain in understanding the mechanisms that influence its spread and distribution, which makes predicting pest outbreaks difficult. Because of the difficulty in predicting when and where pest outbreaks will occur many growers in the southeast apply insecticides on a calendar basis rather than using a threshold-based integrated pest management approach. Our challenge is to develop new information and procedures that will encourage growers to reevaluate the way they are approaching spring-time insect control in wheat, and consider adoption of the integrated pest management approach. This article is a review of cereal leaf beetle biology, past and present management practices, and current research being conducted.
Growth response of Hydrangea macrophylla and Ilex crenata cultivars to low-phosphorus controlled-release fertilizers
Shreckhise, Jacob H.; Owen, James S. Jr.; Niemiera, Alexander X. (2019-02-27)
In containerized nursery-crop production, conventional phosphorus (P) fertilization amounts are reported to be in excess of plant needs which has resulted in poor P use efficiency (PUE) and subsequent P leaching from containers. Phosphorus leaching can be reduced and PUE improved without affecting plant growth by reducing P fertilization. The objective of this study was to identify the lowest controlled-release fertilizer (CRF)-P content and subsequent pour-through-extracted substrate pore-water P (PWP) concentration that produces maximal shoot growth of two common container-grown nursery crop species, Hydrangea macrophylla 'PIIHM-II' (hydrangea) and Ilex crenata 'Helleri' (holly), in a pine bark substrate. Hydrangea and holly liners were potted into 3.8-L containers containing a pine bark substrate and grown simultaneously in two different Virginia ecoregions, Middle Atlantic Coastal Plain (MACP) and Ridge and Valley (RV). Plants were fertilized with one of five CRF formulations, each containing equal nitrogen (N) and potassium (K) and 0.4%, 0.9%, 1.3%, 1.7% or 2.6% (control) P to supply containers with 0.1, 0.2, 0.3, 0.4 or 0.6 g P, respectively. In both ecoregions, hydrangea shoot dry weight (SDW) and growth index [i.e., (widest width + perpendicular width + height) divided by 3, GI] values were maximal in plants fertilized with 0.3 to 0.4 g P or the control. The lowest CRF-P rate needed for maximal SDW and GI of holly was 0.2 g P at the RV site and 0.4 g P at the MACP site. Mean PWP concentrations that corresponded with highest SDW were as low as 0.8 and 1.2 mg L-1 for hydrangea and holly, respectively. Results from this research suggest hydrangea requires approximately half the P rate supplied by recommended rates of conventional CRFs. Since the growth response of holly to CRF-P rate at the MACP site was inconsistent with results observed at the RV site and findings in scientific literature, further research is needed to determine the minimum required CRF-P rate for this taxon.
Identification of quantitative trait loci associated with nitrogen use efficiency in winter wheat
Brasier, Kyle G.; Ward, Brian P.; Smith, Jared; Seago, John E.; Oakes, Joseph C.; Balota, Maria; Davis, Paul H.; Fountain, Myron O.; Brown-Guedira, Gina L.; Sneller, Clay H.; Thomason, Wade E.; Griffey, Carl A. (2020-02-24)
Maintaining winter wheat (Triticum aestivum L.) productivity with more efficient nitrogen (N) management will enable growers to increase profitability and reduce the negative environmental impacts associated with nitrogen loss. Wheat breeders would therefore benefit greatly from the identification and application of genetic markers associated with nitrogen use efficiency (NUE). To investigate the genetics underlying N response, two bi-parental mapping populations were developed and grown in four site-seasons under low and high N rates. The populations were derived from a cross between previously identified high NUE parents (VA05W-151 and VA09W-52) and a shared common low NUE parent, 'Yorktown.' The Yorktown x VA05W-151 population was comprised of 136 recombinant inbred lines while the Yorktown x VA09W-52 population was comprised of 138 doubled haploids. Phenotypic data was collected on parental lines and their progeny for 11 N-related traits and genotypes were sequenced using a genotyping-by-sequencing platform to detect more than 3,100 high quality single nucleotide polymorphisms in each population. A total of 130 quantitative trait loci (QTL) were detected on 20 chromosomes, six of which were associated with NUE and N-related traits in multiple testing environments. Two of the six QTL for NUE were associated with known photoperiod (Ppd-D1 on chromosome 2D) and disease resistance (FHB-4A) genes, two were reported in previous investigations, and one QTL, QNue.151-1D, was novel. The NUE QTL on 1D, 6A, 7A, and 7D had LOD scores ranging from 2.63 to 8.33 and explained up to 18.1% of the phenotypic variation. The QTL identified in this study have potential for marker-assisted breeding for NUE traits in soft red winter wheat.
Identifying Optimal Wavelengths as Disease Signatures Using Hyperspectral Sensor and Machine Learning
Wei, Xing; Johnson, Marcela A.; Langston, David B.; Mehl, Hillary L.; Li, Song (MDPI, 2021-07-19)
Hyperspectral sensors combined with machine learning are increasingly utilized in agricultural crop systems for diverse applications, including plant disease detection. This study was designed to identify the most important wavelengths to discriminate between healthy and diseased peanut (Arachis hypogaea L.) plants infected with Athelia rolfsii, the causal agent of peanut stem rot, using in-situ spectroscopy and machine learning. In greenhouse experiments, daily measurements were conducted to inspect disease symptoms visually and to collect spectral reflectance of peanut leaves on lateral stems of plants mock-inoculated and inoculated with A. rolfsii. Spectrum files were categorized into five classes based on foliar wilting symptoms. Five feature selection methods were compared to select the top 10 ranked wavelengths with and without a custom minimum distance of 20 nm. Recursive feature elimination methods outperformed the chi-square and SelectFromModel methods. Adding the minimum distance of 20 nm into the top selected wavelengths improved classification performance. Wavelengths of 501–505, 690–694, 763 and 884 nm were repeatedly selected by two or more feature selection methods. These selected wavelengths can be applied in designing optical sensors for automated stem rot detection in peanut fields. The machine-learning-based methodology can be adapted to identify spectral signatures of disease in other plant-pathogen systems.
Innovative Cover Cropping Systems for Sandy Loam Soils in the Mid-Atlantic Region, USA
Reiter, Mark S.; Wolters, B. R.; Lawrence, C. E. (2018-09-25)
Lamb performance in hardwood silvopastures, II: animal behavior in summer
Pent, Gabriel J.; Greiner, Scott P.; Munsell, John F.; Tracy, Benjamin F.; Fike, John H. (Oxford University Press, 2019-11-25)
Integrating trees into pastures, a practice known as silvopasture, may benefit livestock in the summertime through the provision of shade. The purpose of this project was to compare the behavioral patterns of sheep grazing in silvopastures and open pastures. Black walnut (Juglans nigra L.) and honeylocust (Gleditisia triacanothose L.) based silvopasture systems were compared with open pastures in a randomized complete block design with three blocks over two summers. Behavior measures were recorded within a replicate within a week, and these measures were taken sequentially within three experimental periods. Ewe lambs (n = 3) within each experimental unit were equipped with a wideband audio-recording device to detect prehension events. Time-lapse cameras documented sheep behavior every 60 s. In the silvopastures, the lambs spent over 90% of daylight hours within shade from trees. Lambs in silvopastures spent more time lying down than animals in the open pastures (P ≤ 0.01), while lambs in the open pastures spent more than 2 h longer each day standing (P < 0.0001). Lambs in the black walnut silvopastures spent more time grazing (488 ± 14 min · d⁻¹) than lambs in the honeylocust silvopastures (438 ± 14 min · d⁻¹; P = 0.0493) and lambs in the open pastures (417 ± 14 min · d⁻¹; P = 0.0026). There was no difference in grazing time for lambs in the latter two systems (P = 0.5597). Spectral analysis of the imagery revealed that the lambs in the black walnut silvopastures grazed more frequently than the lambs in the other systems for both years. The acoustic analysis, though limited by recorder durability to 47 complete recordings, revealed no difference in total bites taken per day (P ≥ 0.7222) or in the morning (P ≥ 0.2069), afternoon (P ≥ 0.5816), and evening periods (P ≥ 0.9337). Silvopastures provide an opportunity to improve lamb comfort in the summer.
Minicell-based fungal RNAi delivery for sustainable crop protection
Islam, Md Tabibul; Davis, Zachery; Chen, Lisa; Englaender, Jacob; Zomorodi, Sepehr; Frank, Joseph; Bartlett, Kira; Somers, Elisabeth; Carballo, Sergio M.; Kester, Mark; Shakeel, Ameer; Pourtaheri, Payam; Sherif, Sherif M. (2021-02)
Spray-induced gene silencing (SIGS) using topical dsRNA applications has risen as a promising, target-specific, and environmentally friendly disease management strategy against phytopathogenic fungi. However, dsRNA stability, efficacy, and scalability are still the main constraints facing SIGS broader application. Here we show that Escherichia coli-derived anucleated minicells can be utilized as a cost-effective, scalable platform for dsRNA production and encapsulation. We demonstrated that minicell-encapsulated dsRNA (ME-dsRNA) was shielded from RNase degradation and stabilized on strawberry surfaces, allowing dsRNA persistence in field-like conditions. ME-dsRNAs targeting chitin synthase class III (Chs3a, Chs3b) and DICER-like proteins (DCL1 and DCL2) genes of Botryotinia fuckeliana selectively knocked-down the target genes and led to significant fungal growth inhibition in vitro. We also observed a compensatory relationship between DCL1 and DCL2 gene transcripts, where the silencing of one gene upregulated the expression of the other. Contrary to naked-dsRNAs, ME-dsRNAs halted disease progression in strawberries for 12 days under greenhouse conditions. These results elucidate the potential of ME-dsRNAs to enable the commercial application of RNAi-based, species-specific biocontrols comparable in efficacy to conventional synthetics. ME-dsRNAs offer a platform that can readily be translated to large-scale production and deployed in open-field applications to control grey mould in strawberries.
Multiplexed SSR marker analysis of Diplocarpon coronariae reveals clonality within samples from Middle Europe and genetic distance from Asian and North American isolates
Oberhänsli, Thomas; Dalbosco, Anna; Leschenne, Virginie; Bohr, Anne; Buchleither, Sascha; Tamm, Lucius; Wille, Lukas; Aćimović, Srđan G.; Khodadadi, Fatemeh; Ryu, Young-Hyun; Studer, Bruno; Schärer, Hans-Jakob; Patocchi, Andrea (2021-05-29)
Background Apple blotch (AB) caused by Diplocarpon coronariae (Dc) has been established in Europe since 2010. AB is a serious apple disease, mostly in low input orchards and in cider production areas in Northern Italy, Switzerland, Austria and Germany. However, the epidemiology and population genetic structure of this pathogen is unknown. Methods We developed twelve Dc-specific microsatellite markers and screened DNA of both pure fungal isolates and infected apple leaves. The marker data of 313 European samples of Dc were compared to Dc isolates from Asia (n = 7) and the USA (n = 3). Results We found 31 distinct multilocus genotypes (MLGs) in European samples, and seven additional MLGs in the Asian and USA samples. The European samples had the typical genetic signature of a recently introduced species including high clonality, a low number of private alleles and one dominant MLG across all the sampling sites. All European MLGs were genetically distant from those MLGs of Asian and USA origin. Based on the lack of linkage disequilibrium observed, there is evidence that Dc undergoes regular cycles of sexual recombination in the European population, although the sexual stage (apothecia) has not been observed in Europe. Conclusions The twelve newly developed SSR markers reported here provide a useful tool to characterize the population genetic diversity and structure of Dc in Europe. Our study supports the hypothesis that Dc is a recently introduced pathogen in Europe, but of currently unknown origin. Dc has a large effective population size during field epidemics, so we believe that the pathogen has substantial evolutionary potential. Application of the SSR markers to large-scale and diverse Dc samples will help to better understand the epidemiology of AB, which has become a global apple disease, and will help guide effective mitigation strategies based on disease management and resistance breeding.

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