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.

Many recent additions to the US Cotton Germplasm collection are uncharacterized for common germplasm descriptors. Our objective was to evaluate a subset of this germplasm for their potential to contribute to future plant improvement efforts. One hundred fifty four cotton germplasm lines from the former USDA cotton breeding program at Shafter, California were evaluated in the field (LSU AgCenter Northeast Research Station, Saint Joseph, LA) in 2003 along with three modern commercial varieties (Delta and Pine Land �Deltapearl�, �Fibermax 958�, and �Phytogen 355�). Due to limited seed availability, an unreplicated modified augmented statistical design-2 was used, with single row plots 6.14 m long sown at a rate of 7-10 plants m-1. The following descriptors were considered: leaf and calyx pubescence; flower maturity; leaf, pollen and petal color; petal spot; glanding; presence of extra floral nectarines; bract shape. High volume instrumentation (HVI) fiber properties: length, strength, micronaire uniformity, and elongation; and cotton fiber yield. Eleven germplasm lines had yields within 10% the check average, with the top three highest yielding germplasm lines being SA 1961, 1962 and 1960 yielding 1635, 1477, and 1439 lbs acre-1, respectively. SA 2085 could be used to reduce insect damage since it was nectariless. There were 26 germplasm lines graded as having smooth leaves which could be used to reduce the ovipositing of bollworm eggs and get cleaner lint at harvest. In this germplasm, 66 % evaluated had long fiber and the top three were SA 2093, 1983, and 2091, with fiber lengths of 1.27, 1.26, and 1.25 inches, respectively. Much of this germplasm evaluated (82%) had very strong fiber and the top three were SA 2036, 2085, and 2044, with 40.5, 40.0, and 39.7 G/tex, respectively. Six germplasm lines had very high elongation and the top three were SA 2092, 1968, and 2069, with 8.4, 8.1, and 8.1 %, respectively. Over half of the germplasm evaluated (55%) had fine micronaire of between 3.8 and 4.6. In summary, these recent additions to the US Cotton Germplasm Collection present a valuable resource for improving cotton varieties with resistance to insects, yield and fiber quality.

Genetic diversity is indispensable to sustain genetic gain in breeding programs. Cultivated sugarcane is a highly heterozygous hybrid derived from crossing two highly heterozygous parents. Sugarcane breeders traditionally rely on pedigree records to select parents. Molecular markers now make it possible to assess genetic diversity at the DNA level. Sixty three sugarcane clones were characterised using Target Region Amplification Polymorphism (TRAP) markers and pedigree relationship (Coefficient of parentage (COP)). The TRAP is a PCR-based marker with a fixed primer designed from Expressed Sequence Tag (EST) sequences paired with an arbitrary primer. It is supposed to unravel trait based polymorphism in the intronic- or exonic-regions of the genome. Ten genes evidently involved in sucrose accumulation (SUC), cold tolerance (CT) and trichome development (TRICH) were paired with four arbitrary primers. A total of 3,170 bands were scored of which 2,684 (85%) were polymorphic. Cluster and Multi Dimensional Scaling (MDS) analyses revealed a very narrow genetic diversity among the entries with genetic similarity (GS) ranging from 78 to 94%. Parentage did not seem to contribute to the grouping pattern in either the overall or individual gene family (SUC, CT and TRICH) clusters which was confirmed by the lack of correlation (r = -0.008) between the TRAP and COP-derived GS matrices. The complex genome of sugarcane and the strict assumptions inherent with estimating COP may account for this disparity. Analysis of Molecular Variance (AMOVA) revealed no structure in the population with regards to era of release (Pre- versus post-1980) with among clones accounting for up to 99% of the total variation and only 1% of variation attributable to era of release. Mixed Model Analysis on the MDS axes generally revealed no significant differences among era of release. Thus, pedigree records can enhance interpretation of marker-derived information especially in an interspecific crop like sugarcane where ancestral species possess and contribute different characteristics. Results from this study needs to be supplemented with sequence analysis of TRAP fragments to definitively relate the derived information to trait variation.

The loss of Louisiana's coastal wetlands has mandated the construction of diversion structures for reintroduction of a portion of the Mississippi River into Louisiana's coastal region for slowing or reversing marsh deterioration. The Davis Pond Freshwater Diversion Structure allows for a section of the Mississippi River water to be reintroduced into Louisiana's Barataria Basin. The reintroduced Mississippi River water contains elevated levels of nitrate and other nutrients from agricultural runoff primarily from the upper reaches of the Mississippi River drainage basin. These elevated nitrate levels have raised questions of possible eutrophication effects on Louisiana estuaries. The purpose of this study is to monitor changes in concentration of nutrients as the diverted Mississippi River input moves across a 9300 acre (3800ha) of ponded, freshwater marsh. Three sampling sites, inlet, outlet, and Lake Cataouatche, were established at the Davis Pond diversion and samples were collected during various discharge or pulsing events. Change in nutrient concentrations were measured between the inlet and the outlet of the ponded freshwater marsh. Results of the study show efficiency that NO₃-N removal was affected by discharge rate entering the ponded marsh. Discharge rates of 35m³/s showed that the system effectively removed NO₃-N concentrations in diverted river water that were greater than 1 ppm. In contrast, in the month of December, a high discharge rate, even thought nitrate was removed, a significant portion of the NO₃-N passed straight through the ponded system introducing a large amount of Nitrate-N into the lake Cataouatche. Results of the study indicate that the Davis Pond Freshwater Diversion acted conservatively in relation to phosphorus with only a small amount removed. The ponded wetland system acted as a source for ammonia and organic carbon. ICP and Standard Tests for Irrigation Water analyses proved all tested nutrient elements to fall within the low to medium or high to medium when compared to threshold range. Assessments of the capacity of the system to process and assimilate nutrients in diverted Mississippi River water is multifold and longer term evaluations must be performed in order to adequately assess the future capacity of freshwater marsh to process nutrients.

Cotton (Gossypium spp) is an important world crop. Although great improvements have been achieved through traditional breeding methods, cotton breeders are facing many problems, i.e., narrow genetic base, inability to use alien genes and difficulty in breaking gene linkages. Genetic transformations and quantitative trait loci (QTL) analyses are main tools used by breeders to overcome these problems. In this dissertation, an optimized cotton regeneration system from shoot apices was developed. The regeneration rate was increased to 85% by combining rooting induction, indole acetic acid (IAA) shock and graft techniques. The regeneration system is genotype-independent and the whole process takes 12 to 16 weeks. Transgenic cotton plants were obtained via Agrobacterium-mediated transformation using shoot apices as explants. Transformation rates were 0.67% and 1.01% for LBA 4404 with β-glucuronidase (GUS) gene and EHA 105 with Bar gene, respectively. Putative transgenic plants were confirmed by leaf GUS assay, kanamycin or herbicide (Liberty) leaf test, polymerase chain reaction (PCR) and southern blot analysis. Out of 151 polymorphic markers, 53 amplified fragment-length polymorphism (AFLP) markers were assigned to individual chromosomes or chromosome arms by using a set of aneuploid genetic stock. In the QTL analysis of cotton yield and yield components was conducted on an F_2:3 population derived from the intraspecific cross. A previously developed linkage map was used based on same population covering 1733.2 cM (37.7%) cotton genome (4700 cM). A total of 47 markers associated with yield and yield component traits were detected. Nine and seven QTL detected by interval mapping (IM) and composite interval mapping (CIM) methods, respectively, four of which were detected by both methods. For lint yield, two main QTL, explaining 27% of variation, were detected via CIM method. No QTL was detected for bolls per plant by IM method and one QTL explaining 8.56% variation was detected by CIM method. For number of fibers per seed, 23.7% of variation was explained by two main QTL detected by both IM and CIM methods. For mean weight per fiber, two QTL were detected via CIM. No QTL was detected for seed number per boll via either method.