Genetic Variation Among Natural Populations of Tilletia controversa and T. bromi

ABSTRACT Isolates of Tilletia controversa and T. bromi were sampled from wheat and two Bromus species hosts, respectively, in the Pacific Northwest, and genetic variation within and among populations was determined. Fifty-one random amplified polymorphic DNA markers from eleven primers were treated as phenotypic 1 and 0 character state data to estimate similarities and analyze molecular variance (AMOVA) among populations and as putative genetic loci to carry out analyses of gene diversity. Phenotypic analysis of T. controversa and T. bromi isolates revealed two distinct clusters that were 37% similar. The T. bromi cluster was subdivided further into two groups, corresponding to host, with 40% similarity. Cluster analysis based on allele frequencies produced similar results and also supported two T. bromi groups based on host. No evidence of natural hybridization and introgression was detected between the T. controversa and T. bromi populations. Both AMOVA and gene diversity analyses detected moderate levels of differentiation among T. controversa populations, whereas T. bromi populations were highly differentiated. The level of genetic differentiation observed between the T. bromi populations on different Bromus species hosts supports the hypothesis that a high degree of host specificity exists in the wild grass-infecting smuts. We speculate that the higher level of genetic differentiation among the T. bromi populations compared with the T. controversa populations on wheat may be due to selection by a more genetically diverse host population.     

Progesterone secretion by the bovine fetoplacental unit and responsiveness of corpora lutea to steroidogenic stimuli at two stages of gestation

To evaluate the response of luteal cells to in vitro stimulation with luteinizing hormone (LH) or dibutyryl cyclic adenosine monophosphate (dbcAMP) and determine the secretion of progesterone by the fetoplacental unit, the corpora lutea were removed surgically in 10 cows (luteectomy) at 250 days (5 cows) or 270 days (5 cows) of gestation. During surgery, but before luteectomy, catheters were placed in the middle uterine artery and vein, carotid artery, and jugular vein. Blood samples were collected from all catheters just before luteectomy and at 8-hour intervals after luteectomy for 72 hours or until calving, whichever occurred first. Luteal tissue was prepared as a dispersed cell preparation and incubated with 0, 0.1, 1.0, 10, or 100 ng of LH/ml of medium or was incubated with 0, 0.5, or 2 mM dbcAMP. Synthesis of progesterone in response to LH by dispersed cells prepared from corpora lutea at 270 days was less (P less than 0.01; analysis of variance) than that by similar preparations at 250 days because a dose-response relationship was not observed for incubations of luteal tissue with LH at 270 days of gestation. Progesterone synthesis in response to the addition of dbcAMP also was less (P less than 0.01) at 270 than at 250 days of gestation. This difference in responsiveness to LH and dbcAMP between the 2 stages of gestation was not reflected by a significant difference between stages of gestation in systemic concentrations of progesterone before luteectomy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Herbicide (2,4-d) increases insect and pathogen pests on corn

Corn leaf aphids, European corn borers, and southern corn leaf blight were more abundant on corn exposed to 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide than they were on unexposed corn. Protein levels were higher in corn plants that were exposed to several dosages of 2,4-D, and this may have favored the growth of pests.     

Assessment of different ionic adjustment strategies in low-salinity water on the growth of Litopenaeus vannamei and microbial community stoichiometry in a synbiotic nursery system

The aim of this study was to evaluate different ionic adjustment strategies in oligohaline water on the growth of Litopenaeus vannamei and C:N:P stoichiometric ratios of the floc microbial community (MC) in synbiotic nursery system. A 35-day culture (2000 PL's/m³) was carried out in 60 L units in a completely randomized experimental design, with three treatments: T1—seawater diluted to a salinity of 2.5 g/L (control), T2—water with a salinity of 2.5 g/L with potassium (K?) adjusted and T3—water at a salinity of 2.5 g/L with its Ca:Mg:K ratio adjusted to 1:3:1, each treatment in triplicates. The MC of flocs and the dissolved fraction (DF) was separated by filtration, where MC >1.6 µm and DF <1.6 µm. The juveniles reached a final weight of 0.40 ± 0.09–0.49 ± 0.04 g, survival above 80% and an average yield of 0.69 ± 0.18–0.81 ± 0.02 kg/m³, without significant differences among the treatments. A stabilizing trend of C:P, C:N and N:P ratios of MC was observed considering the variations of C:N:P in the DF, indicating a homeostatic behaviour of the floc MC, as occurs in systems with high nutrient availability. Our results indicate that the major ions initial concentrations (Ca²⁺: 25.07 mg/L, Mg²⁺: 89.75 mg/L and K?: 25.00 mg/L), total alkalinity 100.00 mg/L and total hardness 433.30 mg/L provide conditions that do not limit shrimp growth in oligohaline water synbiotic nursery system.     

Biased seed rain in forest edges: Evidence from the Brazilian Atlantic forest

In this paper, we test the hypothesis that seed rain in forest edges differs from that in forest interior in terms of seed abundance, species richness, seed size, dispersal mode, and manipulation by vertebrates. The study was carried out in the Coimbra forest (3500 ha), the largest fragment currently found in the Atlantic forest of northeast Brazil. We assessed seed rain during a 1-year period by using a 1500-m long transect (with 100 sampling units) for each habitat. Seeds were categorized according to size, dispersal mode, and vertebrate manipulation. A total of 76,207 seeds belonging to 146 species were collected during the whole study and in average edge received more seeds and species per unit of area during particular periods of time. However, the analysis of all seeds and species recorded in both habitats during the 1-year period revealed that forest interior received a significant higher percentage of medium, large and very large seeds (21.8%) and species (82.6%) in comparison to edge (13.5% of seeds and 57.5% of species). The contribution of large and very large seed species dispersed by vertebrates was also lower in the edge forest as it represented 13.04% of all vertebrate-dispersed species recorded in this habitat vs. 31.5 % in the forest interior. Finally, seeds handled by vertebrates accounted for 5.9% of all seeds in forest edge, and reached 11% in the forest interior. The biased seed rain documented in the Coimbra forest raises the possibility that the creation of forest edges may alter some attributes of seed rain, particularly its content of large-seeded plants and of those dispersed by vertebrates.     

Validation of a geographic weighted regression analysis as a tool for area-wide integrated pest management programs for Ceratitis capitata Wiedemann (Diptera: Tephritidae) on Terceira Island,Azores

Extrapolation from quantitative sampling to the surrounding areas is an essential feature of many aspects of real world applications in pest management decision-making. However, these decisions are only as good as the accuracy of the methods that provided the information. The problem of estimating Mediterranean fruit fly population densities from trap grids is a specific case. The efficiency of three methods to estimate fruit flies trapped per day values for non-sampled areas in Terceira Island is evaluated, the inverse distance weighted, ordinary Kriging and the geographic weighted regression (GWR). Each method has its own specificities and merits. The results demonstrate that the GWR method is capable of estimating hotspots for the next season and can be used to identify ecological corridors over a non-sampled area. The high spatial heterogeneity and topographical conditions present on Terceira Island may explain why a more mathematically complex method is more reliable than simpler methods for use in possible future wide-area control program for medfly.