Genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus) revealed by DNA microsatellites

To assess the genetic diversity of Nile tilapia Oreochromis niloticus, a total of 250 fish from five Egyptian populations were genotyped using six microsatellite markers. Heterozygosity and Wright's F‐statistics (F_IS, F_ST, and F_IT) were calculated to determine the genetic variation within and between these populations. Observed heterozygosities were in the range of 0.4 (Burullus) to 0.96 (Qena), with F_IS values ranging from 0.082 to 0.282. The mean F_ST showed that approximately 96.5% of the genetic variation was within‐population and 3.5% was among populations. Standard genetic distances were used to classify the five populations into two major groups. The deeper lotic river Nile populations of Assuit and Cairo formed one group and the shallow less lotic Delta lakes populations of Manzalla and Burullus formed the second group, with the upstream Nile Qena population being an outgroup. The findings from the current study help understanding of the broad‐scale population structuring of the Nile tilapia (O. niloticus) allowing the population groupings identified to act as potential sources of genetic variation. These populations could be included in future Marker‐Assisted‐Selection programs for economically desired production traits.     

Exploring the impacts of different fasting and refeeding regimes on Nile tilapia (Oreochromis niloticus L.): growth performance,histopathological study,and expression levels of some muscle growth-related genes

Fish Physiology and Biochemistry - The current study investigated how different fasting and refeeding regimes would impact Nile tilapia growth performance, histopathological examination, and gene...     

Morphological and Genomic Differences Between Cutting and Racing Lines of Quarter Horses

To investigate morphological and genomic differences between cutting and racing lines of Quarter Horses, 120 racing and 68 cutting animals of both sexes, registered at the Brazilian Association of Quarter Horse Breeders, were used. Blood samples were collected, and the following physical traits were measured: weight; height at withers; body length; length of the shank, pastern, rump, head, and neck; and chest, shank, and hoof circumference. For analysis of genomic differences, 54,602 single-nucleotide polymorphisms (SNPs) were genotyped using the Equine SNP50 BeadChip, and the quality of individual and SNP genotype data were evaluated. The fixation index, F_ST, was used to identify genome regions that were altered in the lines by selection. The results showed significant differences between the lines in all physical traits. Quality control led to the exclusion of four cutting animals with a call rate of <0.95. After filtering, 12,544, 13,815, and 13,370 SNPs were excluded for the whole population (n = 184), the 120 racing animals, and the 64 cutting animals, respectively. The number of informative polymorphisms detected in each line and in the whole population indicated that the Equine SNP50 BeadChip can be used in genetic studies of Quarter Horses. The fixation index, F_ST, identified 2,558 genome regions that may have been modified by divergent selection.     

In vitro evaluation,in vivo quantification,and microbial diversity studies of nutritional strategies for reducing enteric methane production

The main objective of the present work was to study nutritive strategies for lessening the CH₄ formation associated to ruminant tropical diets. In vitro gas production technique was used for evaluating the effect of tannin-rich plants, essential oils, and biodiesel co-products on CH₄ formation in three individual studies and a small chamber system to measure CH₄ released by sheep for in vivo studies was developed. Microbial rumen population diversity from in vitro assays was studied using qPCR. In vitro studies with tanniniferous plants, herbal plant essential oils derived from thyme, fennel, ginger, black seed, and Eucalyptus oil (EuO) added to the basal diet and cakes of oleaginous plants (cotton, palm, castor plant, turnip, and lupine), which were included in the basal diet to replace soybean meal, presented significant differences regarding fermentation gas production and CH₄ formation. In vivo assays were performed according to the results of the in vitro assays. Mimosa caesalpineaefolia, when supplemented to a basal diet (Tifton-85 hay Cynodon sp, corn grain, soybean meal, cotton seed meal, and mineral mixture) fed to adult Santa Ines sheep reduced enteric CH₄ emission but the supplementation of the basal diet with EuO did not affect (P > 0.05) methane released. Regarding the microbial studies of rumen population diversity using qPCR with DNA samples collected from the in vitro trials, the results showed shifts in microbial communities of the tannin-rich plants in relation to control plant. This research demonstrated that tannin-rich M. caesepineapholia, essential oil from eucalyptus, and biodiesel co-products either in vitro or in vivo assays showed potential to mitigate CH₄ emission in ruminants. The microbial community study suggested that the reduction in CH₄ production may be attributed to a decrease in fermentable substrate rather than to a direct effect on methanogenesis.     

Effects of dietary inclusion of <Emphasis Type="Italic">Moringa oleifera</Emphasis> leaves on growth and some systemic and mucosal immune parameters of seabream

The effect of the dietary incorporation of drumstick, Moringa oleifera, leaf meal (MOL; 0, 5, 10 and 15%) on the growth, feed utilization, some skin mucus and systemic immune parameters and intestinal immune-related gene expression in gilthead seabream (Sparus aurata) specimens. The experiment lasted 4 weeks. The results revealed that MOL can be incorporated in S. aurata diet up to 10% with no significant negative effect on growth and feed utilization. However, there was a significant decrease with MOL at a level of 15% after 2 weeks of feeding. The systemic immune status of fish fed with the different levels of MOL showed an improvement in head kidney leucocyte phagocytosis, respiratory burst and peroxidase activities. Also, serum humoral components, including protease, ACH₅₀ and lysozyme activities and IgM level, increased with MOL inclusion especially at the 5% level. MOL at 5% improved skin-mucosal immunity such as protease, antiprotease, peroxidase and lysozyme activities. Moreover, the feeding of MOL revealed an upregulation of the intestinal mucosal immunity genes (lyso and c3), tight junction proteins (occludin and zo-1) and anti-inflammatory cytokines (tgf-β) with a downregulation of pro-inflammatory cytokine (tnf-α). Therefore, it is recommended to incorporate MOL in S. aurata diets at a level of 5% for the best immune status or 10% for the high growth performance and acceptable immune surveillance.

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Effects of surface and subsurface water application on nitrogen and sodium relations of desert graminoids of different geographic origin

This greenhouse study evaluated nitrogen and sodium relations of three desert graminoids (Distichlis spicata, Leymus triticoides, and Juncus arcticus) as affected by availability of surface water, subsurface water or both. These species are amply distributed in desert wetlands of western USA where surface and subsurface water are differentially available. Plants of the three species were collected from two areas of ecological distribution: Bishop, California and Burns, Oregon. Because nitrogen and sodium uptake by plants is highly linked to water availability we established three general hypotheses for this study: (1) nitrogen uptake would be greater when plants have surface water available, (2) sodium uptake would be greater when plants do not have surface water available, and (3) there are populations’ differences in the response of the species to water availability. We grew plants in two-layer pots in which soil water content in the upper and lower layers was controlled independently. The first hypothesis was partially supported as only Leymus triticoides seemed to preferentially depend on the top layer for nitrogen acquisition. With respect to the second hypothesis sodium concentration was indeed greatest when plants had no surface water, but only in D. spicata. The third hypothesis was also partially supported. The Oregon population of J. arcticus had 15% more nitrogen than the California population and the California population of D. spicata had 18% more sodium than the Oregon population. Our results underline the plant nutrient uptake implications of differential availability of water pools for common desert graminoid species.     

A note on the persistence of phosfolan on cotton leaves and glass surfaces under field conditions

A study of phosfolan deposited from sprays indicated that most of it is degraded within a week in the presence of light and air. It disappears more rapidly on cotton leaves than on glass because much of it migrates into the leaf interior within 7 h of application. Degradation within the leaf proceeds more slowly than on the leaf surface or on glass.     

Bionomics and importance of two species ofChaetocnema in rice yellow mottle virus transmission in lowland rice in Tanzania

Regular samplings were done of two important vectors in farmers’ fields during the 1999/2000 and 2000/01 rice seasons at crop stages susceptible to rice yellow mottle virus (RYMV) on a traditional rice variety (‘Supa’) under rainfed lowland conditions to provide information on the bionomics and importance of these vectors in the disease transmission. The population ofChaetocnema sp. (nr.varicornis Jacoby) (Coleoptera: Chrysomelidae) was significantly higher in hotspot than non-hotspot areas. However, there was no significant difference in theC. pulla Chapuis population between these two areas. In general, theChaetocnema sp. population was higher than that ofC. pulla, and both vectors reached the peak of their population at 63 days after planting. Early planting in the hotspot areas is suggested as a disease management strategy. Both vectors are naturally infective andChaetocnema sp. proved more efficient thanC. pulla in the transmission of RYMV.     

Mechanism of resistance to quinclorac in smooth crabgrass (Digitaria ischaemum)

The mechanism of resistance to quinclorac was investigated in a smooth crabgrass biotype [Digitaria ischaemum (Schreb. ex Schweig) Schreb. ex Muhl] from Tulare County, California. Quinclorac (8.96 kg a.i. ha⁻¹) had no effect (P = 0.18) on the resistant (R) biotype, but reduced fresh weight of a susceptible (S) biotype by 93%. After treatment with 4.48 kg a.i. quinclorac ha⁻¹, the S biotype produced about three times more ethylene than the R biotype and accumulated cyanide in tissues. Similar amounts of endogenous cyanide resulting from treatment with KCN reproduced quinclorac phytotoxicity. Pre-treatment with the ACC synthase inhibitor AVG reduced quinclorac phytotoxicity by 37% and ethylene production by 89%. These data suggest a target site-based mechanism of resistance involving stimulation of ACC synthesis and accumulation of cyanide. Also, the R biotype had four times more β-cyanoalanine synthase activity than the S biotype, suggesting a higher ability to detoxify cyanide.