Impacts of vertebrate herbivores and Hurricane Georges on densities of belowground plant material on shallow mudflats in the active Mississippi River Delta

Delta National Wildlife Refuge (DNWR) is located in the active Mississippi River Delta (MRD). Resource managers at DNWR are implementing a marsh creation program that consists of dredging crevasses (openings) in the natural or man-made levees of major distributaries to divert sediment rich waters in to open bays. The mudflats thus created are colonized by stands of delta duck-potato (Sagittaria platyphylla) and delta three-square (Schoenoplectus deltarum). These plant communities stabilize the mudflats and provide high quality habitat for wintering waterfowl and nutria. Two challenges for the maintenance of these plant communities is disturbance from tropical storms and intense winter grazing. Objectives for my study were to measure initial (fall) density of belowground biomass in tropical storm impact vs. non-impact years and quantify herbivore use of belowground biomass. My study was conducted in 1998-2000 following disturbance by Hurricane Georges in September 1998. Exclosures were used to prevent all grazing or limit grazing to nutria only in two treatments. The third treatment was unrestricted grazing. Twelve replicates were distributed over four crevasse/mudflat complexes. Soil cores were collected in November, January, and March to assess production and use of belowground biomass. A mixed model (PROC MIXED, SAS 1996) was used to analyze treatment effects. Production in November 1998 was less than in November 1999 in both communities. In March of 1999 and 2000, belowground biomass in no grazing treatments was different from open grazing and nutria only grazing treatments, but the open grazing and nutria only grazing treatments did not differ. Disturbance from Hurricane Georges did reduce belowground production in 1998 and winter grazing further depleted belowground biomass, but belowground production in 1999 was greater than 1998. The productivity of these plant communities was capable of sustaining heavy reduction in belowground biomass, yet return to high levels of productivity in the following year

Growth of Stuckenia pectinata under greenhouse and irrigation canal conditions in the lower valley of the Colorado River (Argentina)

Stuckenia pectinata is an invasive submerged weed in the irrigation district in the lower valley of the Colorado River, Argentina. The objective of this study was to analyze the initial growth of S. pectinata from tubers, and its annual growth cycle in irrigation canals, in order to be efficient in adapting future control techniques. Tubers were planted in aquaria in order to evaluate the effect of their size, depth of burial and below zero temperatures on the initial growth. Under field conditions, samples of plants were collected from two irrigation canals, from October to March, in two complete growth cycles. Plant height and biomass of the leaves, stems and spikes were measured. The largest tubers were able to emerge from deep burial and generated larger plants than the smallest tubers. Frozen tubers did not germinate at any burial depths. Maximum biomass in the irrigation canal reached 1660 g DM m-2 with a peak at the beginning of summer. The elimination of biomass at the end of the irrigation season would result in small tubers that would die in the winter time. The information generated could lead to more appropriate and sustainable control.Stuckenia pectinata is an invasive submerged weed in the irrigation district in the lower valley of the Colorado River, Argentina. The objective of this study was to analyze the initial growth of S. pectinata from tubers, and its annual growth cycle in irrigation canals, in order to be efficient in adapting future control techniques. Tubers were planted in aquaria in order to evaluate the effect of their size, depth of burial and below zero temperatures on the initial growth. Under field conditions, samples of plants were collected from two irrigation canals, from October to March, in two complete growth cycles. Plant height and biomass of the leaves, stems and spikes were measured. The largest tubers were able to emerge from deep burial and generated larger plants than the smallest tubers. Frozen tubers did not germinate at any burial depths. Maximum biomass in the irrigation canal reached 1660 g DM m-2 with a peak at the beginning of summer. The elimination of biomass at the end of the irrigation season would result in small tubers that would die in the winter time. The information generated could lead to more appropriate and sustainable control

Effects of Lobster Shell Meal as a Soil Amendment on Verticillium Wilt and Potato Growth

Potatoes (Solanum tuberosum L.) are the most valuable crop in the state of Maine. Despite the crop’s success in the state, potato growers still face the challenges of various abiotic and biotic stresses, including diseases such as potato early dying, caused by the soilborne fungal pathogen, Verticillium dahliae. The disease has been controlled by soil fumigation and fungicides. As an alternative method, organic byproducts, such as lobster shell meal (LSM) or compost, can be used. The benefit of using LSM is thought to occur through the promotion of beneficial chitinolytic soil microbes which can degrade LSM. The derivatives from the LSM degradation can be a food source for some beneficial microbes that consequently suppress V. dahliae. To evaluate the efficacy of compost and LSM as a disease-suppressive tool, a greenhouse study was performed. Potato ‘Shepody’ seed pieces were planted in soil mixed with compost (10% pot volume) and/or LSM (1 lb/cu yd), with some being infested with V. dahliae. Plants were evaluated for emergence, disease symptoms, height over time, and biomass during the growth stage and after harvest. The soil was sampled from the pots during the growing period, and the survival of V. dahliae was examined using soil dilution plating and quantitative polymerase chain reaction (qPCR). Results showed there was little difference in plant emergence and plant height between treatments. However, compost with or without LSM was found to increase root biomass. LSM alone showed a decrease in the number of tubers, yet an increase in total tuber mass. Stem lesions caused by V. dahliae were larger on the compost treatments, while all treatments had similar disease ratings. Both soil plating and qPCR were inconclusive due to challenges in their protocols. Further investigation is needed to determine if LSM is a useful tool in V. dahliae management

Developing Management Recommendations for Hydrilla (Hydrilla Verticillata L.F. Royle) in the Ross Barnett Reservoir: A Community Approach

In order to develop recommendations for management of hydrilla at Ross Barnett Reservoir, Mississippi a number of techniques were utilized. Point intercept surveys were conducted within known hydrilla sites at Ross Barnett Reservoir, Mississippi in order to quantitatively assess chemical management for hydrilla control. Hydrilla tuber data were also collected during the winter and spring of 2012 and 2013. Tuber data were compared between the Ross Barnett Reservoir and Tennessee-Tombigbee Waterway in order to see the effects of chemical management on hydrilla tuber bank dynamics. Water exchange data were collected using Rhodamine WT dye at Ross Barnett Reservoir, Mississippi to determine water exchange characteristics. Dye half-life varied between the eight plots, with a minimum estimated half-life of 2.0 hours and maximum estimated half-life of 30.9 hours. Herbicide evaluations showed that bispyribac-sodium, penoxsulam, and fluridone provide the best hydrilla control 12 weeks after treatment

Development of New Platforms for Efficient Production and Purification of Recombinant Protein in Higher Plants

The world-wide demand for recombinant proteins continuously increases as new medical and industrial applications are developed. Higher plants have the potential to help meet this rising demand as green bioreactors. A major hurdle, however, is low recombinant protein yields in higher plants and, as with many production systems, high cost associated with downstream purification and the production of short peptides. The goal of this research was to address each of these problems to further increase the utility of plant bioreactors. The short antigenic peptide 277 (p277) from heat shock protein 60, which has the potential for use in the prevention of type 1 diabetes, was fused to an known adjuvant, the non-toxic B subunit of cholera toxin (CTB). The fused CTB-p277 retained the ability to form a homo-tetramer, and bound to GM1 ganglioside, allowing for the oral delivery of the fusion protein to induce mucosal tolerance and prevention of diabetes. Protein yield increases can be achieved by either increasing overall plant yield or increasing the relative accumulation of the desired protein. Using RNA interference, a knockdown of Solanum tuberosum plastidic ATP/ADP transporter, involved in energy transport into heterotrophic plastids, resulted in a 30% increase in tuber biomass, as well as a two-fold increase in soluble protein content. In addition, expression of a monoclonal antibody in the knockdown line produced double the concentration of antibody per soluble protein compared to wild-type. Taken together, this is a 4-fold yield increase compared to wild-type. Protein purification accounts for a significant portion of its production cost. We developed the recombinant production of soybean agglutinin (SBA) for potential use as an affinity tag. SBA was purified to high quality using an agarose-N-acetyl-D-galactosamine column, resulting in a 1-step purification process. Recombinant SBA performed identically to native SBA during in vitro assays, including agglutination of red blood cells (RBC). A fusion of SBA with green fluorescent protein (GFP) resulted in SBA-GFP that retained its in vivo fluorescence, purification through a 1-step process as well as the ability to agglutinate RBC and in vitro fluorescence of the agglutinated cells

Management Effects on Yam Production in Benin Republic : Experimental Analysis and Modeling

Declining productivity in the Republic of Benin (West Africa) highlighted the need for a study to determine both the effect of fertilization on yam (Dioscorea spp.) yield and biomass production, as well as the best agronomic management options available for stabilizing yam productivity, via the modeling of yam growth and development. This study addressed the above issues by conducting plot experiments in the Benin Republic, which analyzed the effect of mineral fertilizer, manure and crop residue application on total biomass production, tuber yield and dry matter partitioning pattern, in two species of yam (Dioscorea alata var. Florido and Dioscorea rotundata var. Kokoro). Significant positive effects of mineral fertilizer were observed on yam total biomass production and tuber yield, but the magnitude of its effect were dependent on the species of yam. Crops receiving crop residues and manure also registered increases in yield, but were not significantly different from the yield under unfertilized conditions. Regarding partitioning pattern of dry matter to different plant organs, no significant difference was observed between control and fertilized treatments. An attempt has been made to simulate the effect of fertilization and fallow availability on yam (Dioscorea alata var. Florido) production by using the Environmental Policy Integrated Climate (EPIC) model. A new crop parameter file for Dioscorea alata was developed. The model accurately simulated the effect of fertilizer on the yam yield as indicated by a relatively low mean relative error (MR) ranging from 4.3 to 9.7 %. Different scenarios of fallow availability (Scenario S1 [100 % of the bush savannah is available as fallow land], Scenario S2 [50% of the bush savannah is available as fallow land] and Scenario S3 [25% of the bush savannah is available as fallow land]) were explored in the Upper Ouémé basin of Benin Republic (West Africa) by incorporating the EPIC model into the spatial decision support system (SDSS) PEDRO (Protection du sol Et Durabilité des Ressources agricoles dans le bassin versant de l'Ouémé). The best agreement between simulated and observed crop yields was found under the assumption that 50% of the bush savannah is available as fallow land under the prevailing cropping patterns. The results show the capacity of the EPIC model in connection with the SDSS PEDRO to capture both the biomass production and sensitivity of regional yields of yam to fallowing. They further reveal how a crop model can be used to analyze fallow practices at the regional scale. However, the models accuracy is most likely to be improved by a more detailed modeling of the phenological development of yam. In order to increase yam productivity and maintain soil fertility in the Upper Ouémé basin, fallowing the crop land is not a viable option due to increased demographic pressures. Mineral fertilizer application appears to be essential, but its high cost and accessibility restraints, limit its use by the farmers. The solution lies in providing mineral fertilizers to the farmers at subsidized rates. Additionally, nitrogen fixing crops could partially provide the N inputs needed, if included within crop rotations

Decline and restoration of Vallisneria americana in the Upper Mississippi River

The submersed plant Vallisneria americana declined in Upper Mississippi River backwaters after a drought in 1988. In that year overwintering tuber production may have failed when net photosynthesis declined with increasing temperatures and turbidity. To determine if light limitation and increased respiration could account for the decline, minimum seasonal light requirements were estimated for growth and tuber production, and plant respiration and photosynthetic characteristics measured;Seed bank studies were done to determine if revegetation could occur naturally from the seed banks. Sediment samples were collected from 103 sites in Lake Onalaska, Pool 7, Upper Mississippi River, and maintained in an outdoor pond. V. americana seeds germinated and produced tubers from sites throughout the lake regardless of sample location, sediment characteristics or depth. Light requirements for seedlings to produce tubers were estimated by examining seed bank samples incubated for five months in 2, 5, 9 or 25% of ambient light above the water surface. Seeds germinated in all shade treatments, but produced tubers only in 9 and 25% light;Seasonal light requirements for plants growing from tubers were measured in field transplant and pond studies. In Lake Onalaska, plants grew only at 0.5 m depth (9% of ambient light). A split-plot pond study was designed assuming light as the primary limiting factor for growth; minimum light requirements could be estimated by determining the light level above which sediment fertility significantly affected growth. Plants were grown in lake sediment, or in lake sediment diluted 1:4 with sand, with 2, 5, 9, or 25% light. Underwater light levels were measured continuously. Plant biomass was measured over 5 months. Tuber production depended primarily on light, requiring an average daily minimum photosynthetic photon flux density of 67 [mu] moles· m[superscript]-2· s[superscript]-1 at 25 C (the 5% light treatment). Above this light level plants grown in sediment with added sand senesced earlier and had lower biomass;Increasing temperature significantly increased leaf dark respiration rates. Instantaneous light compensation points (typically 10 [mu] moles· m[superscript]-2· s[superscript]-1 at 25 C) increased by a factor of 1.8 as temperature increased from 20 to 30 C. Net photosynthesis increased with increasing temperature at light levels greater than 200 [mu] moles· m[superscript]-2· s[superscript]-1. Net photosynthesis at 100 [mu] moles· m[superscript]-2· s[superscript]-1 or less decreased when temperature was increased from 20 to 30 C