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Browsing by Author "Copes, Warren E."

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    Comparative Analysis of Water Quality between the Runoff Entrance and Middle of Recycling Irrigation Reservoirs
    Zhang, Haibo; Richardson, Patricia A.; Belayneh, Bruk E.; Ristvey, Andrew; Lea-Cox, John; Copes, Warren E.; Moorman, Gary W.; Hong, Chuanxue (MDPI, 2015-07-14)
    Recycling irrigation reservoirs (RIRs) are an emerging aquatic ecosystem of critical importance, for conserving and protecting increasingly scarce water resources. Here, we compare water quality between runoff entrance and middle of four RIRs in nurseries in Virginia (VA) and Maryland (MD). Surface water temperature (T) and oxidation-reduction potential (ORP) were lower in the middle than at the entrance, while the trend was opposite for dissolved oxygen (DO), pH and chlorophyll a (Chla). The magnitude of these differences between the entrance and middle decreased with increasing depth. These differences were magnified by water stratification from April to October. Minimum differences were observed for electrical conductivity (EC), total dissolved solids (TDS) and turbidity (TUR). Cluster analyses were performed on water quality difference data to evaluate whether the differences vary with respect to reservoirs. Two clusters were formed with one consisting primarily of VA reservoirs, and the other consisting mostly of MD reservoirs in both years. Water quality in the middle and at the entrance of RIRs was expected to vary greatly because of runoff inflow. The two-point water quality differences observed here, although statistically significant, are not large enough to cause significant impact on crop health and productivity for most water quality parameters except pH. Additional analysis of outlet data shows that the range and magnitude of water quality difference between the middle and the outlet are comparable to those between the middle and entrance of RIRs. These results indicate that monitoring at a single point is sufficient to obtain reliable water quality estimates for most water quality parameters in RIRs except pH. This is important when considering the cost of labor and equipment necessary for documenting water quality in agricultural production systems. However, additional pH measurements are still necessary to make practical water quality management decisions.
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    New Species and Phylogeny of the Genus Phytophthora
    Yang, Xiao (Virginia Tech, 2015-01-13)
    The genus Phytophthora includes many agriculturally and ecologically important plant pathogens. Characterization of new Phytophthora species is the first and a most critical step to understanding their biology, ecology and economic importance. Six novel Phytophthora species recovered from irrigation systems at ornamental plant nurseries in Mississippi and Virginia were described based on morphological, physiological and molecular characters: 1. Phytophthora mississippiae sp. nov. produces a mix of non-papillate and semi-papillate sporangia, and catenulate hyphal swellings. It is a heterothallic species. All examined isolates of P. mississippiae are A1. When paired with A2 mating type testers, P. mississippiae produces ornamented oogonia and amphigynous antheridia. It is phylogenetically grouped in Phytophthora subclade 6b based on sequences of the rRNA internal transcribed spacer (ITS) region and the mitochondrially encoded cytochrome c oxidase 1 (cox 1) gene. 2. Phytophthora hydrogena sp. nov. is heterothallic. It produces non-caducous and non-papillate sporangia. It is characterized by frequently producing widening at the pedicel tip of sporangiophores or tapered sporangial based toward the point of attachment. This species is phylogenetically placed in a high-temperature tolerant cluster in Phytophthora clade 9. All members in this cluster grow well at 35 C. 3. Phytophthora virginiana sp. nov. is a self-sterile species. All examined isolates are silent A1. It produces non-caducous and non-papillate sporangia and is also placed in the high-temperature tolerant cluster in clade 9. Morphologically, it is characterized by producing abundant thin-walled, lateral chlamydospores in carrot agar and clarified V8 juice agar. 4. Phytophthora macilentosa sp. nov. is a heterothallic species. Only A1 isolates have been found. It produces characteristic elongated, non-papillate sporangia. It is also a member of the high-temperature cluster in clade 9. 5. Phytophthora stricta sp. nov. is a heterothallic species. It produces unique non-papillate and slightly caducous sporangia with one to three constrictions on its sporangiophore. Phylogenetically, P. stricta represents a new ITS clade within the genus. 6. Phytophthora Xstagnum nothosp. nov. is a novel hybrid species with P. taxon PgChlamydo as its paternal parent and a P. mississippiae-like species as its maternal parent. This new hybrid produces intercalary chlamydospores and catenulate hyphal swellings, which are morphological characters of P. taxon. PgChlamydo and P. mississippiae, respectively. It also produces both smooth-walled and ornamented oogonia, which may be indicative of oogonial characters of its paternal and maternal parents, respectively. By incorporating new Phytophthora species, clusters and clades, phylogenies including approximately 128 Phytophthora taxa were constructed based on sequences of five genetic markers. Among the selected genetic markers, the beta-tubulin (B-tub) gene provided the highest phylogenetic resolution. General phylogenetic structure of the B-tub phylogeny was similar to that in previous multi-locus phylogenies, except that P. cinnamomi, P. parvispora, P. quercina, P. stricta, and a provisional species, P. sp. e1, were not clustered in any of the 10 known Phytophthora clades and represented new clades. The B-tub phylogeny was also used to study the correlations between phylogeny and morphological characteristics including sporangial papillation, caducity, homothallism, and antheridial configuration, as well as maximum growth temperature. The results indicated that the character of sporangial papillation was mostly consistent among species within individual subclades. Maximum growth temperature was also generally correlated with phylogenetic positions. Consistency in caducity, homothallism or antheridial configuration was not found. A new multi-locus phylogeny based on sequences of 11 genetic markers of more than 146 Phytophthora species was proposed to validate new clades and clusters, as well as investigate detailed phylogenetic relations among species in this quickly expanding, taxonomically complex group of plant pathogens.
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    Nutrient, pH, Alkalinity, and Ionic Property Levels in Runoff Containment Basins in Alabama, Louisiana, Maryland, Mississippi, and Virginia Ornamental Plant Nurseries
    Copes, Warren E.; Zhang, Haibo; Richardson, Patricia A.; Belayneh, Bruk E.; Ristvey, Andrew; Lea-Cox, John; Hong, Chuanxue (2017-04)
    Nine runoff containment basins (RCBs), used directly or indirectly for irrigating plants in ornamental plant nurseries, and one adjacent stream were sampled for water quality between Feb. and July 2013 in Maryland (MD), Mississippi (MS), and Virginia (VA). Triplicate water samples were taken monthly. Analysis was done for 18 water quality variables including nitrate-nitrogen (NO3- L-N) and ammonium-nitrogen (NH4+-N), orthophosphate-phosphorus (PO4-P) and total-phosphorus (T-P), potassium, calcium, magnesium, sulfur, aluminum, boron (B), copper (Cu), iron (Fe), manganese, zinc (Zn), pH, total alkalinity (T-Alk), electrical conductivity (EC), and sodium. Additionally, 15 RCBs from 10 nurseries in Alabama (AL), Louisiana (LA), and MS were sampled in 2014 and 2016. Most prevalent correlations (P = 0.01) were between macronutrients, EC, B, Fe, and Zn, but none were prevalent across a majority of RCBs. Water quality parameter values were mostly present at low to preferred levels in all 25 waterways. Macronutrient levels were highest for a RCB that receives fertility from fertigation derived runoff. Water pH ranged from acidic to alkaline (> 8). Results of this study show water quality in RCBs can be suitable for promoting plant health in ornamental plant nurseries, but also shows levels will vary between individual RCBs, therefore demonstrates need to verify water quality from individual water sources.
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    Recycling Irrigation Reservoir Stratification and Implications for Crop Health and Production
    Zhang, Haibo; Richardson, Patricia A.; Belayneh, Bruk E.; Ristvey, Andrew; Lea-Cox, John; Copes, Warren E.; Moorman, Gary W.; Hong, Chuanxue (2016)
    Recycling irrigation reservoirs (RIRs) are an emerging aquatic ecosystem and water resource of global significance. This study investigated the vertical distribution of water temperature, dissolved oxygen (DO), and pH in eight RIRs at two nurseries each in Virginia and Maryland from 2011 to 2014. Monomictic thermal stratification was observed from April to October in all RIRs, despite their shallow depths (0.75-3.89 m). The strongest stratification had a top-bottom temperature difference of 21.53°C. The top-bottom temperature difference was positively correlated with water column depth, air temperature, and daily light integral (p < 0.05). Wind speed did not impact the thermal stratification, likely due to their relatively small surface areas. Thermal stratification affected the vertical distribution of DO and pH. The top-bottom differences in DO and pH were greater during stratification periods than nonstratification periods. Water pH in all RIRs was higher at the top than at the bottom with the greatest difference of 4.16 units. Discovery and characterization of thermal stratification in RIRs helps understand water quality dynamics in this novel ecosystem and promote safe and productive water reuse for irrigation. Specifically, water withdrawal depths should be adjusted according to variations in temperature, DO, and pH during the stratification and nonstratification periods to mitigate pathogen risk and improve water treatment efficacy and crop production.