Isolation and molecular characterization of entomopathogenic nematode,Heterorhabditis sp. from an arable land in Nigeria

The occurrence of entomopathogenic nematodes(EPNs) in arable soil samples from Nigeria was investigated using Baermann extraction tray and insect-bait(White's trap) techniques. Isolates were tested for infectivity using the larvae of Galleria mellonella(greater moth) and Tenebrio molitor(mealworm). The study revealed a new species of Heterorhabditis(MT371593) in soil samples that were randomly collected from an arable farmland cultivated with cassava TMS-30572 at the Teaching and Research Farm of Landmark University, Nigeria. Amplification of the internal transcribed spacer region(ITS) of the ribosomal DNA produced a nucleotide sequence of 933 base pairs(bp). A BLASTN search of Gen Bank showed that the sequence of the Nigerian isolate is identical at 99% similarity to that of Heterorhabditis sp. from Thailand. Infectivity test of the isolate showed 100% mortality against T. molitor larvae within 48 h of exposure while only 80% mortality was recorded for G. mellonella after 1 week of exposure. This is the first account of Heterorhabditis sp. in Nigeria. The varying degrees of infectivity against mealworm and greater moth observed in this study proved that the Nigerian isolate of Heterorhabditis sp. could potentially be an attractive option in the management of insect pests of cash crops.     

Seasonal trends in hydraulic conductance of field-grown ‘Valencia’ organge trees

Leaf water potential (ψ₁), whole tree transpiration (F) and leaf surface conductance (g), together with a number of environmental parameters, were measured from early summer until late winter in a well-watered mature ‘Valencia’ orange (Citrus sinensis (L.) Osb.) orchard during the growing season of 1977/78. F and g showed a seasonal trend, with maximum values reached during the late summer. Tree conductance (C_tree), calculated as the ratio between transpiration and the water potential difference between the wet soil and the sunlit leaves, was found to vary seasonally and showed maximum values during late summer. The soil temperature (T_s) showed a seasonal trend similar to C_tree. Analysis of this and other data from the literature confirmed that the sensitivity of tree conductance to soil temperature is related to the climatic origin of the plant species.The linear regression fitted to the relationship between C_tree and T_s was used to calculate soil temperature at apparent zero C_tree. This datum can be used as an index of plant sensitivity to root medium temperature.     

Oxidative homeostasis in oocyte competence for in vitro embryo development

The objective of this study was to evaluate the levels of reactive oxygen species (ROS) and glutathione (GSH) in oocytes from follicles of different diameters and their relevance in the in vitro production of embryos (IVPE). Bovine ovaries were aspirated according to the diameter of the follicle [2–8 (general), 4–8 (large), and 2 < 4 mm (small)]. The oocytes were evaluated for levels of ROS, GSH, in vitro maturation, and IVPE. Higher levels of ROS and GSH were observed (p < 0.05) in oocytes of the large group (85.6 ± 7.2 and 140.0 ± 9.6) followed by those in the general (81.1 ± 10.5 and 134.3 ± 7.8) and small (73.5 ± 10.1 and 125.0 ± 10.6) groups. However, the proportion of ROS/GSH did not differ (p > 0.05) between the general, large, and small groups. The maturation was higher (p < 0.05) in the large group (87.8 ± 3.0%) than in the small group (72.2 ± 5.8%), but both were similar (p > 0.05) to that in the general group (82.2 ± 2.5%), whereas the IVPE of the large group (57.3 ± 3.0%) was higher (p < 0.05) than those in the general (44.7 ± 4.4%) and small (34.0 ± 4.0%) groups. We report that oocytes from large follicles are more competent for IVPE, whereas higher levels of ROS and GSH appear to be correlated with oocyte competence, as long as oxidative homeostasis is retained.     

Associations Between Oil and Gas Wells and Arthropod and Vegetation Communities in the Southern Plains

Understanding how energy infrastructure affects local biodiversity and soil characteristics is important for informing restoration and management. However, the rapid rate of modern oil and gas development is beyond the limit of current knowledge and mitigation strategies. In a mixed-grass prairie in western Oklahoma, we assessed the presence and directionality of biodiversity and environmental gradients associated with energy development in an observational framework. Specifically, we sampled arthropods, vegetation, soil temperature, and soil moisture on the edge of active oil well pads and at 1 m, 10 m, and 100 m away from the well pad. Though variable, the abundance and biomass of most arthropod orders was lower on the pad and 1 m away compared with 10 m and 100 m away, suggesting that the pad itself negatively influenced arthropods but that these effects were limited in spatial extent. However, vegetation structure and composition varied more extensively. Vegetation height, shrub cover, and warm season grass cover increased sixfold, threefold, and fourfold, respectively, from on the oil pad to 100 m away. Forb cover was 5 × higher at 10 m from the well pad than on the pad, 1 m away, and 100 m away from the pad. Soil surface temperature was lower at sites farther from well pads, but we found no relationship between soil moisture and distance from well pad. Well pad effects on arthropods and soil temperature appear to be limited to the pad itself, though long-term changes in vegetation structure extend significantly beyond the well footprint and demand a better understanding of the effectiveness of restoration activities around well pads.     

Dormant Season Grazing: Effect of Supplementation Strategies on Heifer Resource Utilization and Vegetation Use

Grazing dormant forage under low-input heifer development strategies typically exposes cattle to low-quality forage. Protein supplementation while grazing dormant range can enhance heifer growth and reproductive performance. We examined resource utilization of heifers and the effects of dormant season grazing on residual vegetation characteristics under two supplementation management strategies. Approximately 100 weaned composite heifer calves were randomly selected and placed into one of two supplementation treatments in each of 2 yr, one receiving a free access 62% crude protein self-fed concentrate and the other receiving a daily hand-fed 20% crude protein cake. Grazing occurred from December (2015 and 2016) through March (2016 and 2017). Thirty transects were randomly located within each pasture for measuring vegetation quality and structure before and after grazing. Daily space use and behavior was evaluated for 21 individuals within each treatment using global positioning system (GPS) collars and resource utilization functions. Heifers supplemented with concentrated protein spent more time grazing per day than heifers supplemented with cake (6.92 ± 0.18, 6.24 ± 0.17 h). Relative use by heifers in the cake treatment was negatively related to horizontal distance from the supplement delivery site early to midwinter ($\stackrel{?}{\overline{\beta }}$ = ? 0.41 ± 0.16, ? 0.53 ± 0.17). Both treatments selected grazing locations relative to standing biomass of perennial grasses ($\stackrel{?}{\overline{\beta }}$ = 0.0005 ± 0.00004) and crude protein ($\stackrel{?}{\overline{\beta }}$ = 0.12 ± 0.007). However, resource selection was highly variable among individuals for both supplementation treatments. We found no treatment effects on pre-post grazing differences in residual cover of litter, grass, forbs and shrubs (P > 0.24). However, the time period when grazing occurred had an effect on residual vegetation conditions (P < 0.01). Our results indicate high levels of variability in grazing site selection by heifers, suggesting future research should incorporate individual animal measurements in an attempt to account for individual animal variability.     

Calculating the configurational entropy of a landscape mosaic

Background

Applications of entropy and the second law of thermodynamics in landscape ecology are rare and poorly developed. This is a fundamental limitation given the centrally important role the second law plays in all physical and biological processes. A critical first step to exploring the utility of thermodynamics in landscape ecology is to define the configurational entropy of a landscape mosaic. In this paper I attempt to link landscape ecology to the second law of thermodynamics and the entropy concept by showing how the configurational entropy of a landscape mosaic may be calculated.

Result

I begin by drawing parallels between the configuration of a categorical landscape mosaic and the mixing of ideal gases. I propose that the idea of the thermodynamic microstate can be expressed as unique configurations of a landscape mosaic, and posit that the landscape metric Total Edge length is an effective measure of configuration for purposes of calculating configurational entropy.

Conclusions

I propose that the entropy of a given landscape configuration can be calculated using the Boltzmann equation. Specifically, the configurational entropy can be defined as the logarithm of the number of ways a landscape of a given dimensionality, number of classes and proportionality can be arranged (microstates) that produce the observed amount of total edge (macrostate).

     

Genotyping strategies of selection candidates in livestock breeding programmes

Benefits of genomic selection (GS) in livestock breeding operations are well known particularly where traits are sex‐limited, hard to measure, have a low heritability and/or measured later in life. Sheep and beef breeders have a higher cost:benefit ratio for GS compared to dairy. Therefore, strategies for genotyping selection candidates should be explored to maximize the economic benefit of GS. The aim of the paper was to investigate, via simulation, the additional genetic gain achieved by selecting proportions of male selection candidates to be genotyped via truncation selection. A two‐trait selection index was used that contained an easy and early‐in‐life measurement (such as post‐weaning weight) as well as a hard‐to‐measure trait (such as intra‐muscular fat). We also evaluated the optimal proportion of female selection candidates to be genotyped in breeding programmes using natural mating and/or artificial insemination (NatAI), multiple ovulation and embryo transfer (MOET) or juvenile in vitro fertilization and embryo transfer (JIVET). The final aim of the project was to investigate the total dollars spent to increase the genetic merit by one genetic standard deviation (SD) using GS and/or reproductive technologies. For NatAI and MOET breeding programmes, females were selected to have progeny by 2 years of age, while 1‐month‐old females were required for JIVET. Genomic testing the top 20% of male selection candidates achieved 80% of the maximum benefit from GS when selection of male candidates prior to genomic testing had an accuracy of 0.36, while 54% needed to be tested to get the same benefit when the prior selection accuracy was 0.11. To achieve 80% of the maximum benefit in female, selection required 66%, 47% and 56% of female selection candidates to be genotyped in NatAI, MOET and JIVET breeding programmes, respectively. While JIVET and MOET breeding programmes achieved the highest annual genetic gain, genotyping male selection candidates provides the most economical way to increase rates of genetic gain facilitated by genomic testing.