There is little information documented on the influence of soil properties on P availability of Louisiana alluvial soils thus this pot experiment was conducted in 2011 to: 1) evaluate the effect of P fertilizer rate on growth and development of corn grown on Perry clay and Commerce sl soils, 2) relate soil test P values using Mehlich-3 and Bray-2 procedures with yield, total biomass, and P uptake of corn, and 3) identify the soil properties that influence P partitioning into functional fractions of two alluvial soils. Different P fertilizer rates (0, 34, 67, 101 and 134 kg P2O5 ha-1) were applied, replicated four times and arranged in a randomized complete block design. After 30 days, corn was planted and grown until maturity. Mehlich-3 extractable-P, Bray-2, total-P and Pi fractions (labile-P, Al-P, Fe-P, reductant-P, and Ca-P) of soil samples collected at 30 DAP and at harvest were quantified. The Bray-2 P values were about six times higher than Mehlich-3 P values for Commerce sl while for Perry clay, the amounts of P extracted by these two procedures were very similar (1:1 ratio). Both Bray-2 and Mehlich-3 extractable-P of both soils increased with increasing P rate. Commerce sl and Perry clay soils tested low to medium for Mehlich-3 extractable-P but responded differently with the application of P fertilizer. Grain yield of corn grown on Perry clay significantly responded to P rate but not in Commerce sl which was testing very high for Bray-2 extractable-P. The applied P fertilizer was transformed into Ca-P for Commerce sl while Perry cl transformed into Fe- and reductant-P. Overall, the labile- and Al-P at 30 DAP increased with increasing P rate. With time across P rates, both soils showed build-up of less readily-available reductant-P. For total-P, residual-P and total-Pi components, Commerce sl and Perry clay differed significantly (P<0.05) at both 30 DAP and harvest; while total-P and residual-P of both soils were not affected. Refinement of soil test P prediction should be pursued such that P fertilizer recommendations will not be based solely on P soil test.

Sediment loading and nutrient losses from construction sites through surface runoff can have detrimental effects on nearby water bodies. Often cool-season grasses such as perennial ryegrass (Lolium perenne L.) are established for temporary coverage until environmental conditions are suitable for warm-season grass establishment. The purpose of this research was to 1) determine if higher seeding rates accelerate establishment thus reducing sediment loading and 2) determine if watering-in fertilizer applications reduces nutrient losses through surface runoff. In the first experiment trays were seeded at 0, 195, 390, or 585 kg ha-1 with 30-min rainfall simulations performed at 16.3 L per minute at 14, 28 and 42 days after seeding (DAS). Increasing seeding rates reduced total sediment loading 48% to 67% and 86% of sediment eroded from bare soil over the 42-day establishment period. Sediment losses were highest during the initial rainfall simulation at 88, 93, 83, and 62% of total sediment lost from 195, 390, or 585 kg ha-1 and bare soil controls, respectively. In the second experiment, established perennial ryegrass was fertilized at 50 kg N ha-1 with grass swards not irrigated or irrigated at 1.25 cm 48 hours prior to rainfall simulation. Thirty-minute rainfall simulations were performed 2 and 7 days after fertilization (DAF). Non-irrigated fertilizer treatments resulted in the highest TKN losses of 12.3 kg N ha-1, moderate dissolved N losses at 3.1 mg N ha-1, and highest TP losses of 2.4 P ha-1 2 DAF compared to 7.0 kg TKN ha-1, 5.2 kg DN ha-1, and 2.0 kg TP ha-1 for irrigated fertilizer treatments. At 7 DAF, iIrrigated fertilizer treatments resulted in higher dissolved N losses of 3.1 kg N ha-1 compared to 0.1 kg N ha-1 for non-irrigated treatments but similar TKN and TP losses of 0.8 kg N ha-1 and 0.4 kg P ha-1 compared to 0.9 kg N ha-1 and 0.2 kg P ha-1 lost from non-irrigated treatments. The two experiments showed increasing perennial ryegrass seeding rates during establishment can significantly reduce sediment losses; while irrigating post N fertilization of established swards may not reduce N losses during surface runoff.

Understanding the reactivity and mobility of heavy metals in soils is indispensable for assessing their potential risk to the environment. In this study, column transport and batch kinetic experiments were performed to assess the sorption-desorption and mobility of Cd, Cu, Pb, and Sn in alkaline and acidic soils. Furthermore, sequential extractions were accomplished to examine their behavior in soils. Also, the competitive reactivity of Sn and Pb in two acidic soils was quantified. Additionally, the effect of introducing Cd and Cu after a Pb pulse in calcareous soil was presented. Modeling of these heavy metals retention and transport was carried out using different models; multireaction and transport model, CXTFIT model, kinetic ion exchange formulation, and second-order two-site model. The results revealed that: 1) the studied heavy metals exhibited strong nonlinear and kinetic retention behavior; 2) Cd was nearly immobile in alkaline soil with 2.8% CaCO3, whereas 20 and 30% of the applied Cd was mobile in the acidic soil and the subsurface layer of the alkaline soil with 1.2% CaCO3, respectively; 3) for a short Cu pulse, the recoveries were <1 and 11% for alkaline and acidic soils, respectively, whereas, for the long Cu pulse, the recoveries ranged from 27 to 85% for the studied soils; 4) tin was highly sorbed in acidic soils where more than 99% of applied Sn was retained in the acidic soils columns; 5) the presence of Sn in solution reduced Pb retention in soils since the Pb recovery in the effluent solution ranged from 37.4 to 96.4%; and 6) the multireaction approach was capable of describing heavy metals retention and transport in soil columns. Moreover, a field study of the spatial distributions and the accumulation of Pb, Cd, Cu, and Ni among soil depth as consequence of irrigation with domestic wastewater were studied. The results of this research showed that Pb, Cu, and Ni had high affinity for retention in the surface soil layer whereas Cd results showed homogeneous distribution within soil depth. The impact of time scale effect on accumulation and spatial distribution of heavy metals indicated the urgent need for remediation and rational management.

As scientists work to investigate the mechanisms underlying the depletion of carbon from terrestrial ecosystems, there has been an urgent call for the development of test methods that offer reduced analysis times for soil organic carbon (SOC) determinations. Traditional laboratory techniques can be time-consuming and costly, making high-volume sample analyses problematic. Portable x-ray fluorescence spectroscopy (PXRF) provides quantitative, multi-elemental data for soil samples in as little as 60 seconds; and, unlike other spectroscopic methods, differences in elemental concentrations between field-moist and oven-dry samples are considered to be negligible when soil moisture contents are less than 20%, by weight. This study aims to evaluate the performance of various SOC prediction models, constructed from PXRF elemental data from 300 soil samples collected from alluvium and loess parent materials found in Louisiana, USA. Elemental data, in addition to pH and depth measurements, were used in the construction of prediction models using multiple linear regression (MLR) analysis and principal components analysis (PCA) statistical techniques. Previous research indicates that the use of a stability index may enhance SOC prediction modeling capabilities. Therefore, models utilized relative elemental abundances on the basis on Zr and Ti concentrations, and performances were compared to those resulting from models developed from Raw PXRF data. Results show that models constructed using field-moist PXRF elemental data provide excellent SOC prediction capabilities (R > 0.90) for both alluvium and loess datasets. Optimal performances resulted from the use of Ti as a stability index for field-moist datasets, producing accurate SOC predictions for both wet and dry validation sub-datasets. Findings indicate that PXRF elemental analysis, conducted under field conditions, provide for accurate SOC content determinations via MLR modeling of Louisiana alluvium and loess soil types examined in this study.

Two viral outbreaks occurred 3 years apart (1997 and 2000) in the vivarium at the Pennington Biomedical Research Center. The etiology of both outbreaks was determined by enzyme-linked immunosorbent assay (ELISA) to be sialodacryoadenitis virus. The focus of this work was to fulfill Kochs postulates and definitively confirm the outbreak etiologies using 4 distinct diagnostic laboratory techniques: cell culture, indirect immunofluorescent assay (IFA), transmission electron microscopy (TEM), and reverse transcriptase polymerase chain reaction (RT-PCR). During each outbreak, infected rats were euthanatized, serum was collected by exsanguination, and infected tissues (submandibular salivary glands, Harderian glands, and lung tissue) were harvested and flash frozen in liquid nitrogen for later extraction and analysis of viral particles (field strains). The field strains were compared to the catalogued type-strain virus from the American Type Culture Collection sialodacryadenitis virus Strain 681 (the ATCC strain). Contrary to ATCC strain viral replication in culture on L2p176 (coronavirus permissive) cells, it was determined that the field strain viruses did not grow well in cell culture, but could be propagated in experimentally infected rats. IFA revealed reactivity between the infected rat serum from each outbreak and the ATCC strain, indicating marked antigenic similarity. The viral morphology, ultrastructural cellular pathology, and location of the stages of replication in field strain infected L2p176 cells examined by TEM were consistent with coronavirus infection. Genetic confirmation of the identity of the field strains was accomplished by RT-PCR. ATCC strain sequence analysis revealed a 412 base pair portion of the spike protein gene (total length: approximately 2000 base pairs) that could be amplified for sequence analysis and comparison. The amplification product, produced from each isolate, was purified, further amplified by bacterial plasmid insertion, and compared to each of the other products and to the published PubMed sequence database. Comparison of the fragments revealed homology with published data on the spike protein gene of sialodacryoadenitis virus. This study lays the groundwork for future analysis of the entire spike protein of the field strains, in comparison with the ATCC strain, to determine genetic bases for variations in infectivity and virulence of sialodacryoadenitis virus isolates.

Bacillus anthracis, the etiological agent of the disease anthrax, is a bacteria of great importance, both in the past and today. Despite this importance, many questions remain regarding defending against its use as a biological weapon, the bacteria's variation in virulence, and its epidemiology in nature. Using Etest strips (AB BIODISK, Solna, Sweden) to measure the MICs, 25 genetically diverse isolates of B. anthracis were tested to determine their susceptibility to seven clinically relevant antimicrobial agents. Using the NCCLS MIC breakpoints for staphylococci, three isolates were found to be resistant to penicillin and negative for beta-lactamase production. From a group of investigations, results indicated B. anthracis virulence is related to clonality and the copy numbers per cell of the virulence plasmids, pXO1 and pXO2. Isolates were characterized with respect to their plasmid copy number (pXO1/2) using a novel method of quantitative PCR and the numbers differ greatly from previous reports. Anthrax Vaccine with Adjuvant (AVA) vaccinated guinea pigs were challenged with 20 B. anthracis strains representative of worldwide genetic diversity. A virulence model was constructed by combining the survival, plasmid copy number, and genotyping (based on multilocus variable number tandem repeat analysis typing) data of each isolate. The model obtained was validated using a randomly chosen set of 12 B. anthracis isolates and verified model robustness. Carcass disposal methods, incineration and burial, are recommended to decrease or prevent environmental spore contamination. The extent of contamination from an anthrax carcass is almost totally unknown despite the method of disposal. Studies of environmental contamination by spores of B. anthracis from infected carcasses have only recently been possible because of new technologies. A method utilizing real-time quantitative PCR was developed to quantitate B. anthracis in environmental samples. Absolute quantitation was made possible by the use of clones. This method has allowed the evaluation of the environmental contamination by the different carcass disposal methods and by scavenging of the carcass. The results support the complete burning of a carcass soon after death as the method choice to decrease environmental contamination for the disposal of anthrax affected carcasses.

Shiga-toxigenic Escherichia coli (STEC) O157:H7 is an important human pathogen. Dairy cattle, beef cattle, and white-tailed deer (WTD) are involved in STEC O157:H7 transmission to humans. We conducted cross-sectional studies in Louisiana, using sensitive microbiological methods, in dairy cattle, beef cattle, and WTD to investigate the epidemiology of STEC O157:H7. Results of the dairy studies are as follows. In the point prevalence study, summer-time prevalence in herds was 38.5%, with a cow-level prevalence of 6.5%. Among positive herds, cow-level prevalence ranged from 3%-34.6%. Three of five herds sampled in the longitudinal study were positive. Cow-level prevalence increased during spring and summer. Adult dairy cattle during the warm season had increased odds of STEC O157:H7 fecal shedding. Lactating dairy cows had increased odds of STEC O157:H7 fecal shedding compared to dry cows. In the mouth, hide, and fecal study, cow-level prevalence estimates of STEC O157:H7 in the mouth, on the dorsal hide, and from feces were 0%, 0.7%, and 25.2%, respectively. We sampled weaned beef cattle at the beginning and end of a preconditioning program. Five of twenty-nine herds were shedding STEC O157:H7 or Escherichia coli (EC) O157:H7 initially. No cattle were shedding STEC O157:H7 or EC O157:H7 at the end. We found 0.7% of weaned beef cattle shedding STEC O157:H7. The animal-level prevalence of the O157:H7 serotype, including shiga toxin (stx)-deficient isolates, was 2.5%. We expected, but did not observe, increased shedding or the spread of STEC O157:H7 subtypes. Two WTD field studies were conducted. We collected 338 fecals from hunter-harvested WTD and found one positive sample. The isolate was stx-deficient and sorbitol positive. In the second field study, we isolated STEC O157:H7 in a captive WTD herd, but were unable to demonstrate seasonal trends in fecal shedding. Louisiana reports relatively few human STEC O157:H7 cases. We detected STEC O157:H7 in each of our studies. We demonstrated high fecal prevalence, seasonal shedding, and hide contamination in dairy cattle. Epidemiologic studies in ruminant populations should be revisited using sensitive methods. Studies investigating the human incidence of STEC O157:H7 in relation to presumed ruminant reservoirs are warranted.

Osteoarthritis (OA), a non-inflammatory, degenerative disease of articular cartilages, is a common cause of poor performance and early retirement in equine athletes. Pathologically, OA is characterized by matrix degradation and decreased chondrocyte numbers. A mechanical stress is believed to be the major etiologic factor of OA development. Recent studies have indicated that apoptosis is responsible for hypocellularity in OA cartilage and that chondrocyte death by apoptosis could directly contribute to matrix degradation. Increased nitric oxide (NO), a free radical, has been implicated as a cause of chondrocyte apoptosis. No studies, however, have been performed on chondrocyte apoptosis in equine OA. We investigated chondrocyte apoptosis in equine OA cartilage and its relationship to matrix degradation and NO production. Furthermore, we studied whether mechanical stress could induce chondrocyte apoptosis and how NO production and Bcl-2 and caspase-3 proteins contribute to chondrocyte apoptosis by using a novel pressure-loading system. Five OA and three normal equine articular cartilage samples were graded histopathologically and stained with polyclonal nitrotyrosine antibody. Chondrocyte apoptosis was determined by TUNEL assay. For pressure-loading experiment, equine chondrocytes were isolated separately from superficial and deep layers of articular cartilages, embedded in alginate constructs, and intermittently pressurized at 1,000 ± 100 psi (approximately 6.8 ± 0.6 MPa) for 12 hours. TUNEL assay, immunohistochemistry with polyclonal antisera to Bcl-2 and caspase-3, and colorimetric nitrite assay were applied to the chondrocytes that adhered on glass slides by cytospin. Chondrocyte apoptosis occurred much more frequently in equine OA cartilage than in normal cartilage, and was closely correlated with matrix degradation and NO production. The cyclic hydrostatic pressure-treated chondrocytes had a higher percentage of apoptosis than the controls. The pressure-loaded chondrocytes also produced increased NO and expressed elevated Bcl-2 and caspase-3, as compared with the control groups. The present study suggests that pressure-induced NO levels play a critical role in the equine chondrocyte apoptosis process through Bcl-2 and caspase-3 pathways and mechanical stress may contribute to equine OA pathogenesis via chondrocyte apoptosis induced by endogenous NO.

The breeding of Upland cotton (Gossypium hirsutum L.) cultivars that combine high yield and fiber quality is a major challenge to the breeder. The understanding of the quantitative trait loci (QTL) contributing to agronomic and fiber quality traits offers an excellent route to solve this problem. A QTL analysis was carried out after an F_2:3 population composed of 138 lines, derived from the intraspecific cross between Paymaster 54 and PeeDee 2165, was developed and a linkage map including 143 AFLP markers was constructed. The F_2:3 population was grown in two locations, Alexandria and Baton Rouge in LA. The 143 linked markers were assigned to 13 major and 15 minor linkage groups, the 28 linkage groups cover a genetic distance of 1773.2 cM. This gives coverage of 37.7% of the cotton genome (4700 cM). Single-marker analysis, including simple and logistic regression, and interval marker analysis, including interval mapping (IM) and composite interval mapping (CIM), was used. Interval mapping was used to study QTL interaction effects with the environment. For the agronomic traits, the same five QTL were detected, using a significant threshold of 2 LOD, in both IM and CIM. These include two for lint weight per boll, two for seedcotton weight per plant, and one for lint percentage, which collectively, based on IM analysis, explained 32.5%, 28.6%, and 4.4% of the phenotypic variation, respectively. In total, seven and nine different QTL were detected by IM and CIM, respectively. For the fiber quality traits, the same nine QTL were detected in both IM and CIM. These include one for fiber elongation, one for length, two for uniformity, three for strength, and two for micronaire, which collectively, based on IM analysis, explained 50.9%, 18.7%, 69%, 49.6%, and 25.3% of the phenotypic variation, respectively. In total, nine and 19 different QTL were detected in IM and CIM, respectively. Eleven QTL were found to have significant interaction effects with the two locations. Future efforts in QTL mapping should focus on developing more saturated maps, using larger population sizes, and more powerful statistical algorithms and theories for identifying QTL and elucidating QTL X environment interactions.

Wild relatives of cultivated rice varieties offer new genetic sources for enhancing economic value, but traditional interval mapping techniques have not gained widespread support among applied researchers for marker assisted selection. The objectives of this study were to detect quantitative trait loci (QTL) for agronomic traits in a hybrid mapping population and compare the non-parametric Discriminant Analysis (DA) procedure with traditional approaches for accuracy and precision. In addition, the effects of population structure on marker-assisted classification were explored. A molecular linkage map comprising 100 SSR markers that spanned the rice genome at intervals of 10.5 cM on the average was constructed based on 312 doubled haploid lines derived from the cross interspecific Oryza sativa x O. glaberrima. The mapping population was evaluated in replicated field plots in Colombia and Louisiana in 2001 and 2002, respectively. QTLs were identified for grain, milling and eating qualities and important agronomic traits such as heading date, plant height, number of tillers per plant, panicle length, grain yield and 1000-grain weight. A total of 28 QTLs were detected for 10 grain quality traits, and 22 QTLs for six agronomic traits were detected that were significant in at least one environment, but only seven were significant in both environments. SSR markers that best discriminated between pre-defined groups of high and low trait values were selected by stepwise DA. Using a k-nearest neighbor algorithm, the largest phenotypic differentiation (3 standard deviations) between two contrasting phenotypic groups resulted in 100% correct classification. Adjustments for population structure resulted in a 5-fold decrease in number of markers needed to achieve the same level of accuracy. These results demonstrated that procedures such as DA and consideration of population structure can be used for efficient marker-based allocation of the doubled haploid lines into pre-defined groups for yield and other agronomic traits. Finally, DA-selected markers pointed to the same or closely linked regions on the linkage map that in turn underscored the validity of the DA approach for genetic mapping.