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.

Surface-applied poultry litter generated using a phytase-amended diet may release less phosphorus (P) to runoff water than does litter from a conventional diet. The release of soluble reactive (SRP) and total dissolved P (TDP) from litter generated under conventional and phytase-amended diets was examined in three studies: 1) batch desorption, 2) flow-through cell, and 3) field micro-plot. In Study 1, samples of litter (10 from conventional, C, and 20 from phytase-amended, A, diets) were extracted with water at litter: water ratios from 1:5 to 1:200. Phosphorus in A litter was significantly less at the 1:10 extraction ratio; however, there was no difference at wider ratios. When desorbed P was plotted against solution concentration, all isotherms were sigmoidal. In Study 2, water was passed uniformly through samples of litter (~ 4 g in 4 cm diameter by 1 cm deep cell) at a flux of 7.5 cm h^-1 for 1.5 h and litter effluent collected in fractions for analysis. Less P was lost from the A than from the C litter, however, less P was recovered than in Study 1. Study 3 compared losses of P from litters A and C in field runoff from 324 cm² plots during a series of simulated rainfalls (7.5 cm h^-1 for 1 h each). Although significantly less P was initially lost from the A litter, P losses from the A and C litters tended to converge over the course of Study 3. Thus, whereas there was less TDP in the A than in the C litter, differences in SRP and TDP are small.

Uniola paniculata, commonly known as sea oats, is a C4 perennial grass capable of stabilizing sand dunes. The genetic relationship and diversity among U. paniculata accessions from southeastern Atlantic and Gulf coasts of the United States was established by amplified fragment length polymorphism (AFLP) analysis. One hundred ninety U. paniculata plants belonging to nineteen different accessions were selected to represent eight locations; Texas, Louisiana, Mississippi, Alabama, Florida, South Carolina, North Carolina and Virginia. Twelve AFLP EcoRI+MseI primer combinations generated a wide range of polymorphisms (42-81%) with a mean of 59%. EcoRI-CAG+MseI-CGA, EcoRI-ACT+MseI-CTC and EcoRI-CAG+MseI-ACG have the highest polymorphic rate at 81%, 75%, and 72%, respectively. A total of 703 scorable bands were identified of which 417 were polymorphic. UPGMA dendrogram using NTSYSpc version 2.10t separated U. paniculata plants into three major groups with subclusters consistent to its collection sites. All the accessions from Texas (LA2, LA5, LA9 and LA17), Louisiana (LA15 and LA16), and Virginia (LA53) were orderly clustered in Group I together with two accessions from Florida (LA35 and LA39) indicating similar genetic profiles. Group II consisted of accessions from Mississippi (LA41 and LA47), Alabama (LA19 and LA21), and the other two accessions from Florida (LA29 and LA33). Group III comprised South Carolina (NC15 and NC19) and North Carolina (NC1 and NC11) accessions. Dice similarity coefficient shows a range of genetic similarity across all plants from 64-98%. Florida has the widest range of genetic variation among its genotypes followed by Mississippi. The principal component analysis (PCA) further confirmed the three major groups. Hierarchical analysis of molecular variance (AMOVA) after 1000 permutations showed highly significant results (Fst values, p=<0.001) for all the sources of variation. The highest significant amount of genetic variation was observed at the state-level (47%) followed by among-genotypes (34%). Total variation among the accessions within a state was 19%. Calculated average molecular diversity over loci was highest in LA47 (0.07�0.04, Petit Bois Is., Mississippi), LA33 (0.07�0.04, Henderson Beach, Florida), LA15 (0.07�0.04, Fourchon Beach, Louisiana) and LA41 (0.07�0.04, West Ship Is., Mississippi). Overall, the populations of U. paniculata were genetically-diverse.

A study was conducted to evaluate rice cultivar tolerance to clomazone impregnated onto urea fertilizer and applied at the rice pegging (PEG) stage. A second study was conducted to evaluate rice injury, rice yield, and weed control with clomazone applied alone or in combination with bensulfuron or halosulfuron impregnated onto urea fertilizer applied at the PEG stage. Comparison treatments for weed control were also included in the study. In addition, a study was conducted to evaluate the safening potential of bensulfuron or halosulfuron applied with clomazone on rice grown hydroponically. In the cultivar tolerance study, rice foliar bleaching was 16 to 20% at 14 d after PEG (DAPEG) for long-grain Ahrent, Cheniere, Cocodrie, Cypress, Francis, and Wells when clomazone was impregnated onto urea, and 23 and 30% for medium-grain Bengal and short-grain Pirogue, respectively. Clomazone reduced the number of tillers/m2 21 DAPEG for all cultivars. Early season height reductions occurred for all cultivars; however, Pirogue was the only cultivar shorter than the nontreated at harvest. There were no yield reductions with regard to the medium and long-grain cultivars when compared with respective nontreated cultivars. Rice foliar bleaching decreased from 42% with a single application of clomazone to 23 to 30% at 7 DAPEG when bensulfuron or halosulfuron were impregnated with clomazone. Barnyardgrass and broadleaf signalgrass control did not decrease with the addition of bensulfuron or halosulfuron to clomazone. A single application of clomazone controlled rice flatsedge 0% at 28 DAPEG; however, rice flatsedge control was greater than 76% for all bensulfuron and halosulfuron treatments at 28 DAPEG. There were no differences in rice yield between any herbicide treatments. Bensulfuron and halosulfuron applied in a hydroponic solution, safened Bengal, Cocodrie, and Pirogue at 21 d after treatment from foliar bleaching caused by clomazone. Chlorophyll content of all three rice cultivars decreased regardless of clomazone treatment. Only chlorophyll content of Cocodrie was increased by the addition of bensulfuron and halosulfuron compared with a single application of clomazone.

Irrigation to soybean can cause unintended water to pond on the soil surface for more than a desired amount of time. Most soybean acreage in Louisiana is planted on poorly drained clay soils and waterlogging of soybean can cause substantial yield reductions. Although cultural practices are available for ameliorating the adverse effects of waterlogging, little is known about genotypic tolerance, therefore our objectives were to determine if percent leaf nitrogen concentration could be used as a criterion for screening for cultivar tolerance to waterlogging and to identify waterlogging tolerance among 48 commercially available soybean cultivars. Forty-eight soybean cultivars were planted in May in 2002 and 2003 in an open- ended outdoor greenhouse at Ben Hur Research Farm near Baton Rouge, Louisiana on a Mhoon clay soil. Flooding treatment commenced the day the plants reached V4 and continued for seven consecutive days. Drained and waterlogged treatments were administered in the two halves of the greenhouse. One site received a 1-week waterlogging stress at the V4 growth stage and the other treatment received normal irrigation as necessary to avoid job stress. Each site was randomized complete block design with four replications and one factor (cultivars). Data obtained from the two year study were percent leaf nitrogen, leaf dry weight, and leaf nitrogen uptake. Analysis of variance was done by the combined analysis method of McIntosh (1983) with treatments and cultivars being fixed factors. Mean separation was accomplished by LSD (P<0.05) using appropriate LSD values to compare specific cultivars between drained and waterlogging treatments or to compare cultivars within or across drained and waterlogged treatments. Results suggested that percent leaf nitrogen concentration can be an effective parameter for screening for waterlogging tolerance. Both cultivar and drainage significantly (P<0.0001) affected yield without significant interactions with other factors. The low C.V. (7.6%) shown by percent leaf nitrogen also supports its use as a screening criterion. Cultivars showing greatest percent nitrogen were not consistent across treatments. The decline in percent leaf nitrogen between treatments was not consistent. No correlation occurred for cultivar percent leaf nitrogen between treatments.

Field and greenhouse research was conducted from 1999 to 2003 to evaluate weed control in imidazolinone-tolerant (IT) rice (Oryza sativa L.) under various tillage and planting systems, tolerance of IT rice cultivars to imazethapyr rate and application timing, and the impact of IT technology and tillage systems on solids runoff in rice drainage water. In both conventional and reduced tillage systems imazethapyr applied preemergence and postemergence at 70 g ai/ha controlled red rice (Oryza sativa L.), barnyardgrass [Echinochloa crus-galli (L.) Beauv.], Amazon sprangletop [Leptochloa panicoides (Presl) Hitchc.], and rice flatsedge (Cyperus iria L.) 87 to 99%. Indian jointvetch (Aeschynomene indica L.) control with sequential applications of imazethapyr was as high as 70% in water-seeded rice but no more than 54% in drill-seeded rice. With sequential applications of imazethapyr at 70 g/ha, rice yield was 63% greater when water-seeded compared with drill-seeded. Imazethapyr applied to one- to two-leaf or three- to four-leaf rice at 70, 140, and 280 g/ha was more injurious to the IT rice cultivar �CL 161� than to �CL 121�. Shoot:root ratio for CL 161 was not affected by imazethapyr application. For CL 121, shoot:root ratio following imazethapyr application was lower than that observed for CL 161 suggesting that CL 121 shoot fresh weight was inhibited more by imazethapyr than was root fresh weight. Based on shoot fresh weight two weeks after imazethapyr application at 70 g/ha, CL 161 was 1.8 times more tolerant than CL 121 and CL 161 was 2.9 times more tolerant than CL 121 with 280 g/ha imazethapyr. In the conventional tillage and water-seeded system where soil was worked under flooded conditions one day prior to drainage, off-site movement of solids in the initial discharge of irrigation water was 1250 kg/ha. This compares with no more than 80 kg/ha for the initial drainage in reduced tillage systems where rice was water-seeded or drill-seeded. Total off-site movement of solids from initial drainage through 12 weeks totaled 2,370 kg/ha for the conventional tillage system and loss of solids was reduced by as much as 79% where reduced tillage systems were used.

Maize (Zea mays L.) kernel infection by Aspergillus flavus is a chronic problem in the southern USA. Genetic resistance to A. flavus is needed to solve this problem. To ascertain and understand the inheritance of resistance to field kernel infection by A. flavus, a five-parent diallel analysis and a half-sib family analysis of 35 maize crosses were conducted during 2003 and 2004 for percent kernel infection (PKI) rates. All parents contained the leafy gene (Lfy). From the combining ability analysis of the five maize parents and their 20 F1s, highly significant general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were found. The analysis of genetic effects showed that the parents 914 and A619 had desirable GCA effects to enhance the average performance of A. flavus resistance in hybrid progeny. The crosses 914 �� A632, 914 �� WF9, and HY �� WF9 had consistently negative SCA effects across the two years. These results suggested that resistance to kernel infection by A. flavus existed among the parents and some of their crosses. Their potential performance with desired GCAs and SCAs could be exploited to develop resistant lines in breeding programs and to produce resistant hybrids. The reciprocal effects in the crosses across years reflected the presence of maternal effects in the maize kernel. These effects were partly responsible for resistance to A. flavus and should be considered in making crosses. The cross A632 �� HY had the highest negative significant reciprocal effect, indicating that it should promote resistance to A. flavus. Analyses of the 35 half-sib crosses derived from seven maize breeding lines indicated that both the genotype and genotype-by-year effects were highly significant. Broad-sense heritability for PKI estimated from variance components was 73.8%. A North Carolina Design-II analysis of 12 crosses was used to estimate additive and dominance genetic variances. Narrow-sense heritability and the average degree of dominance for PKI were 37.6% and 1.67, respectively. A comparison of a laboratory-based infection resistance screening (LIRS) with field-based PKI demonstrated that LIRS was effective and could be used to improve maize germplasm screening and to expedite A. flavus resistance breeding.