Auxin resistant cropping systems will provide producers with an alternative option for weed management, but with this new technology also comes the concern of off target movement of dicamba and/or 2,4-D to susceptible crops. Research was conducted over multiple site years in order to determine the effect of soybean response to different application timings and rates of 2,4-D and dicamba. 2,4-D was applied at 1X (0.56 kg ae/ha), 1/4X, 1/16X, 1/64X, and 1/256X rates, and dicamba was applied in a separate study at 1X (0.56 kg ae/ha), 1/4X, 1/16X, 1/64X, 1/256 and 1/1024X. All rates were applied at the V3 and R1 growth stages. Greatest yield losses occurred from dicamba applied at the R1 growth stage. Additional studies were conducted to determine at which growth stage soybeans are most sensitive to 2,4-D and dicamba. Greatest yield losses occurred at the late vegetative and early reproductive growth stages for both herbicides.

Soybean accounts from more than half of the acres dedicated to row crop production in the mid-south, leading to a wide planting window from late-March through mid-July. Studies were conducted in 2013 and 2014 evaluating seven planting dates of soybean, and their impact on agronomics. As planting was delayed, plant heights significantly increased, increasing the potential for lodging. Canopy closure significantly decreased as planting was delayed, leaving soybean more vulnerable to caterpillar pests. Yield potential also significantly decreased as planting was delayed. Season long surveys of insect pests and their arthropod natural enemies were conducted from 2013 to 2014 in small plot studies, and in large plot studies from 2015 to 2016 across multiple planting dates. The most common insect pests encountered in both studies were bean leaf beetles, the stink bug complex, and soybean looper. The most common natural enemies encountered were lady beetles, spiders, and the assassin bug complex. In general, insect pests densities increased as planting was delayed, whereas natural enemies were higher in earlier plantings or had no change throughout the planting windows. With the increased difficulty of controlling some caterpillar pests such as soybean looper, new control tactics need to be evaluated. A simulated Bt treatment was evaluated against a threshold, bug only, and untreated control across multiple plantings in 2013 and 2014. The simulated Bt treatment yielded significantly higher than the untreated control at plantings from early-June through mid-July. These were the only plantings that reached action threshold for soybean looper. The simulated Bt and threshold treatments were not significantly different from one another. In 2015 and 2016, a simulated Bt treatment plus threshold was evaluated in a late planting situation. The simulated Bt plus threshold treatment yielded significantly higher than the untreated control at the early-June and early-July plantings. Also in 2015 and 2016, the simulated Bt treatment was evaluated against a grower check on producer fields at 23 locations. The simulated Bt treatment resulted in significantly higher soybean yields than the grower check.

No description available.

No description available.

The administration of raw soybeans to the diet of prepubertal gilts had no effect (p>0.05) on age to puberty, number of corpora lutea, or embryos present. Also, the number of pigs farrowed live and 28d litter weights did not differ between gilts consuming the raw soybean diet and gilts consuming the control diet. There was a reduction (p<0.05) in the number of pigs weaned in the group consuming the raw soybeans but no differences (p>0.05) in weaning weights. Gilts fed the raw soybean diet had a reduction (p=0.05) of hot carcass weights compared to gilts consuming the control diet but exhibited no differences for other carcass parameters measured. Thermal imaging was able to differentiate gilts in estrus versus diestrus. Gilts in estrus had greater (p<0.05) surface area temperatures than gilts in diestrus.

No description available.

The species of biological control agents which affect soybean pests in the Tidewater area were investigated, and their relative values were determined. Two pentatomids, <u>Podisus Macu1iventris</u> Say and <u>Stiretrus anchorago</u> F., were the only significant bio-contro1 agents which attacked the Mexican bean beetle, <u>Epi1achna varivestis</u> Mulsant. Thesepredators were not able to hold the pest population in check. A parasitic fly, <u>Trichopoda pennipes</u> F. was the only important biological control agent which attacked the green stinkbug, <u>Acrosternum hilare</u> (Say). Host and habitdt preferences of the fly suggested the presence of two strains in Virginia. Distribution of the fly was very uneven. Fungal disease was found to be an important control agent of many (larval) Lepidoptera. It was the most important control agent of <u>Plachypena scabra</u> (F.). P. <u>scabra</u> was also controlled by predation and parasitism. Nine parasites attacked the larvae and pupae. No effective biological controls were found for the corn earworm, <u>Heliothis zea</u> (Boddie). The only significant control agent, fungal disease, acted too slowly to prevent economic damage by this insect. / Master of Science

The objective of this research was to express a fungal phytase gene in transgenic soybean cells to to study the potential for improving phosphorus utilization in soybean meaL A simple and inexpensive particle inflow gene gun was constructed and bombardment was optimized as assayed by β-glucuronidase reporter gene expression. A somatic embryogenesis approach was used for soybean regeneration from culture. The efficiencies of embryo induction and embryo conversion to form roots and shoots were compared in commercial soybean cultivars to identify optimal cultivars for recovery of transgenic plants. To study the expression of a recombinant fungal phytase gene (<i>Phy</i>A from <i>Aspergillus niger</i>), four expression vectors were constructed in soybean transformation vectors. <i>Phy</i>A was placed under the control of either a constitutive cauliflower mosaic virus 35S promoter or a soybean seed specific β-conglycinin promoter, each with or without a patatin endoplasmic reticulum (ER) signal sequence. All four vectors were sequenced and introduced into 'Williams 82' suspension culture cells by particle bombardment. Stably transformed cell lines were selected and tested for stable integration by Southern analysis. The presence of the phytase protein product was detected by immunoblotting. Activity of recombinant phytase was characterized by enzyme assay. Cell lines containing the <i>phy</i>A gene under control of the CaMV 35S promoter and ER signal sequence secreted active phytase into the culture medium. The pH and temperature optima were determined for recombinant phytase. / Ph. D.

The climate of Mississippi has been considered to be ideally suited for the production of soybeans. Many studies have shown the influence of weather on crops, but none that specifically attempt to pinpoint which aspects of weather have an impact on the Mississippi soybean crop. The purpose of this study was to determine what affect weather has on the phenological period length and yield of Mississippi soybeans. Data on bean phenological periods and yield used in this research were recorded as a part of soybean variety testing conducted at Delta Research and Extension Center in Stoneville, Mississippi from 1976-2000. The major statistical procedure used in this study was Pearson?s Correlation Analysis that was used to determine any significant relationships between soybeans and weather. This study found that cooler temperatures and more moist conditions positively influence yield in Mississippi soybeans, while energy is more important in determining period lengths than water.

The introduction of herbicide resistant crops offers producers many more options for weed control systems. These crops allow environmentally safe, non-selective herbicides to be used as selective herbicides, broadening the spectrum of weeds controlled, while not harming the crop. As these crops are very new on the market, investigation of their performance under various environmental conditions as well as in various weed control programs is needed. Liberty-link &reg; soybeans are resistant to the herbicide glufosinate, because of the incorporation of a gene encoding phosphinothricin acetyl-transferase (pat), which is able to detoxify glufosinate. Roundup-Ready &reg; soybeans are transformed with an altered, non-sensitive form of 5-enolpyruvylshikimate- 3-phosphate synthase (EPSPS), which confers glyphosate resistance. Field and greenhouse studies were conducted to determine the efficacy of glufosinate and glyphosate on annual and perennial weeds. Also to determine whether the use of ammonium sulfate (AMS) or pelargonic acid (PA), a 9-carbon fatty acid, as additives of glufosinate or glyphosate would increase their efficacy, while maintaining their safety on the transgenic soybeans. Three annual weeds: common lambsquarters, giant foxtail, sicklepod, as well as two perennial weeds: common milkweed and horsenettle were included in studies. Uptake, translocation, and metabolism of 14C-glufosinate + AMS or PA, were studied in the five weeds in order to determine the basis for their differential weed sensitivity to glufosinate, and the effect of the two additives. The effect of temperature on Liberty-Link &reg; and Roundup-Ready &reg; soybeans after application of glufosinate or glyphosate was investigated. Injury was quantified by measuring chlorophyll content of herbicide treated soybean trifoliolates. Uptake, translocation, and metabolism studies of 14C-glufosinate and 14C-glyphosate in transgenic soybeans were conducted to determine the potential cause for the observed temperature-dependent sensitivity. Since glufosinate is a synthetic analog of a naturally occurring bacterial toxin, it was tested for possible bactericidal activity on the soybean pathogen Pseudomonas syringae. Greenhouse and field-studies showed that the 5 weeds responded differently to glufosinate and glyphosate. Common milkweed was the most tolerant to glufosinate and common lambsquarters to glyphosate while giant foxtail was the most sensitive species to both herbicides. Some interactions between AMS or PA and glufosinate or glyphosate were also observed. Uptake and translocation studies showed that AMS increased the uptake of 14C-glufosinate in some weeds, whereas PA had only minimal effects on absorption and translocation of glufosinate. Metabolism of glufosinate was detected only in common lambsquarters. A rate dependent loss of chlorophyll in Liberty-Link &reg; soybeans treated with glufosinate was observed that was greater at 15° C than at 25° or 35° C. Metabolism studies showed a decrease in the rate of glufosinate metabolism 3 hours after treatment in Liberty-Link &reg; soybeans grown at 15° C versus 25° C. Conversely, chlorophyll loss in glyphosate-treated Roundup-Ready soybeans was greater at 35° C than at 15° or 25° C. Translocation studies showed a significantly greater percentage of absorbed 14C-glyphosate translocated to developing meristems at 35° C than at 15° C in Roundup-Ready&reg; soybeans. Glufosinate concentrations of 1 mM and higher significantly inhibited the growth of Pseudomonas syringae (L-529) in liquid media cultures. Typical field use rates of glufosinate also reduced the number of live P. syringae on Liberty-Link&reg; soybean leaves. Overall, the results of this research show that annual and perennial weeds differ in their sensitivity to glufosinate and glyphosate. Additives such as AMS and PA may enhance the efficacy of glufosinate on perennial weed species, and glyphosate in most weeds. Differences in weed sensitivity to herbicides and effects of additives can in most cases be explained by differences in absorption or metabolism. Variable temperatures may affect the engineered resistance of transgenic soybeans to the herbicides glufosinate and glyphosate. The herbicide glufosinate has some bacteriocidal activity on P. syringae. Nomenclature: Glufosinate, 2-amino-4-(hydroxymethylphosphinyl) butanoic acid; Glyphosate, N-(phosphonomethyl)glycine; PA, pelargonic acid (nanoic acid); AMS, ammonium sulfate; giant foxtail, Setaria faberi Herrm.; common lambsquarters, Chenopodium album L.; sicklepod, Cassia obtusifolia L.; horsenettle, Solanum carolinense L.; common milkweed, Ascleipias syriaca L. pat, phosphinothricin acetyl transferase; EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase. / Master of Science