Mapping QTLs for Witches' Broom (Crinipellis Perniciosa) Resistance in Cacao (Theobroma Cacao L.)

Molecular markers (RAPD, AFLP and microsatellites) were used to generate a linkage map and to identify QTLs associated to witches' broom (Crinipellis perniciosa) resistance in cacao (Theobroma cacao), using 82 individuals of an F₂ population derived from the clones ICS-1 (susceptible) and Scavina-6 (resistant). Fifteen evaluations of the number of brooms have been carried out in six years (1997–2002). In order to increase the precision and accuracy in the measures of resistance, each F₂ plant was cloned in three replications in a randomized block design with single-tree plots and evaluated over 2 years. Three hundred and forty-two markers were obtained, being 33 microsatellites, 77 AFLPs and 232 RAPDs. The distribution of the number of brooms in the F₂ population was skewed to resistance, suggesting the involvement of major genes controlling resistance and the repeatability estimated for resistance was 44%. A strong putative QTL was detected as being related to witches' broom resistance. Associated to this QTL, the microsatellite mTcCIR35 explained 35.5% of the phenotypic variation in resistance. This marker is being used for marker-assisted selection in Scavina-6 progenies, including those selected in private plantations, as an auxiliary tool to the phenotypic selection.     

Genetic structure, population dynamics, and conservation of Black caiman (Melanosuchus niger)

Microsatellite DNA polymorphisms were screened in seven populations of the largest Neotropical predator, the Black caiman Melanosuchus niger (n = 169), originating from Brazil, French Guiana and Ecuador. Eight loci were used, for a total of 62 alleles. The Ecuadorian population had the lowest number of alleles, heterozygosity and gene diversity; populations of the Guianas region exhibited intermediate diversities; highest values were recorded in the two populations of the Amazon and Rio Negro. During the last century Melanosuchus populations have been reduced to 1-10% of their initial levels because of hunting pressure, but no strong loss of genetic diversity was observed. Both the inter-locus g-test and the Pk distribution suggested no recent important recovery and/or expansion of current populations. On a global scale, the inter-population variation of alleles indicated strong differentiation (F_ST = 0.137).Populations were significantly isolated from each other, with rather limited gene flow; however, these gene flow levels are sufficiently high for recolonization processes to effectively act at regional scales. In French Guiana, genetic structuring is observed between populations of two geographically close but ecologically distinct habitats, an estuary and a swamp. Similar divergence is observed in Brazil between geographically proximate “black water” and “white water” populations. As a consequence, the conservation strategy of the Black caiman should include adequate ecosystem management, with strong attention to preservation of habitat integrity. Distribution of genetic diversity suggests that current populations originated from the central Amazonian region. Dispersal of the species may thus have been deeply influenced by major climatic changes during the Holocene/Pleistocene period, when the Amazonian hydrographic networks were altered. Major ecological changes such as glaciations, marine transgressions and a hypothesized presence of an Amazonian Lake could have resulted in extension of Black caiman habitats followed by isolation.     

The differential genetic signatures related to climatic landscapes for jaguars and pumas on a continental scale

Modern and paleoclimate changes may have altered species dynamics by shifting species’ niche suitability over space and time. We analyze whether the current genetic structure and isolation of the two large American felids, jaguar (Panthera onca) and puma (Puma concolor), are mediated by changes in climatic suitability and connection routes over modern and paleoclimatic landscapes. We estimate species distribution under 5 climatic landscapes (modern, Holocene, last maximum glaciations [LMG], average suitability, and climatic instability) and correlate them with individuals’ genetic isolation through causal modeling on a resemblance matrix. Both species exhibit genetic isolation patterns correlated with LMG climatic suitability, suggesting that these areas may have worked as “allele refuges.” However, the jaguar showed higher vulnerability to climate changes, responding to modern climatic suitability and connection routes, whereas the puma showed a continuous and gradual transition of genetic variation. Despite differential responsiveness to climate change, both species are subjected to the climatic effects on genetic configuration, which may make them susceptible to future climatic changes, since these are progressing faster and with higher intensity than changes in the paleoclimate. Thus, the effects of climatic changes should be considered in the design of conservation strategies to ensure evolutionary and demographic processes mediated by gene flow for both species.     

Implications of carbohydrate sources and rate of body weight gain on puberty in ewe lambs in tropical climate conditions

Tropical Animal Health and Production - The objectives were to evaluate the effects of two non-fibrous carbohydrate sources and the rate of body weight gain on puberty status in ewe lambs. Sixty...     

High Embryonic Recovery Rates with In vivo and Ex vivo Techniques in the Bitch

The embryonic collection techniques in dogs present a vast methodological variation and low recovery rates. The objectives were to compare and describe two techniques as to the recovery of canine embryos, on the 12th day after the first mating or artificial insemination. Embryos were recovered through uterine horn flushing in vivo, before performing the ovariohysterectomy (OHE) (Group 1; n = 9) or ex vivo, immediately after the OHE (Group 2; n = 9). In total, 43 and 47 embryonic structures were recovered in Groups 1 and 2, respectively. There was no significant difference (p > 0.05) between groups on recovery rates (72.8% and 81.0%, respectively). We inferred that both in vivo and ex vivo techniques allow a high rate of embryonic recovery; in the collection technique prior to the OHE, it is essential to carefully handle the reproductive system during the trans‐surgical period and that the 12th day (D12) after the first mating/artificial insemination is an efficient option for the high recovery rate of morulae and blastocysts.     

Mycoplasma ovis in captive cervids: prevalence, molecular characterization and phylogeny

Hemotrophic mycoplasmas (hemoplasmas) are bacteria that attach to red blood cells of mammals, leading to acute and/or subclinical disease in infected animals. It has been suggested that Mycoplasma ovis, a hemoplasma that infects sheep and goats worldwide, may also infect deer. The aim of this study was to evaluate whether South American deer are infected with M. ovis. EDTA-anticoagulated blood samples from a herd of 32 captive South American deer were collected. DNA extraction of blood samples was performed followed by PCR amplification of the 16S and 23S rRNA genes, and sequencing of products. Using M. ovis PCR, 27/31 (87%) were positive, including 21/22 Mazama nana; 2/3 Mazama americana and 4/6 Blastocerus dichotomus. Sequencing of the nearly entire 16S rRNA gene of 26/27 positive samples showed 98.2-98.8% identity to M. ovis of sheep (GenBank, AF338268) and 98.6-99.4% identity to M. ovis-like of a fawn (FJ824847); the 23S rRNA gene from one of these isolates and the fawn's had 97.6% identity. The remaining isolate had just 94.9% identity to the 16S rRNA gene of M. ovis and only 89.4% identity to the 23S rRNA gene of the fawn's M. ovis. This is the first report of M. ovis in captive South American deer, revealing a high prevalence of hemoplasma infection in these animals.     

Size Dependence of Structural Metastability in Semiconductor Nanocrystals

The kinetics of a first-order, solid-solid phase transition were investigated in the prototypical nanocrystal system CdSe as a function of crystallite size. In contrast to extended solids, nanocrystals convert from one structure to another by single nucleation events, and the transformations obey simple unimolecular kinetics. Barrier heights were observed to increase with increasing nanocrystal size, although they also depend on the nature of the nanocrystal surface. These results are analogous to magnetic phase transitions in nanocrystals and suggest general rules that may be of use in the discovery of new metastable phases.     

Evaluation of soil extractants for silicon availability for sugarcane

Adequate evaluation and interpretation of silicon (Si) phytoavailability in soil is a key to fertilizer recommendation. This study was conducted to determine the effect of soil texture on the choice of Si extractant, and provide baseline data on the relationship between extractable Si and sugarcane Si accumulation. The effects of soil texture and extractant solutions of Si were investigated on soil of nine areas of sugarcane cultivation. Si contents in clayey soils were higher than in sandy soils only in the extraction with standard calcium chloride, acetic acid, potassium chloride (KCl), and sodium acetate buffer. Other extractants failed to reveal differences in the Si availability among the three soil textures. The choice of the extractant should consider soil texture for the determination of adequate Si contents in soils planted with sugarcane, and the extractants that proved to be more efficient in the three soil textures was acetic acid and KCl.     

Effect of Different Manganese Concentrations during in vitro Maturation of Bovine Oocytes on DNA Integrity of Cumulus Cells and Subsequent Embryo Development

Manganese (Mn) is a trace element present in forages and cereals, and its concentration depends on soil status. Manganese deficiency in cattle, goats and ewes not only impairs oestrous cycle but reduces calf birth weight. The achievement of the first oestrus is delayed, and more attempts are necessary to obtain a successful conception. This study was conducted to investigate the effect of the availability of supplemental Mn during IVM on DNA damage of cumulus cells and total glutathione (GSH) content in oocytes and cumulus cells. The effect of supplementary Mn during IVM on subsequent embryo development was also studied. The results reported here indicate (i) DNA damage in cumulus cells decreased with 0, 2, 5 and 6 ng/ml Mn supplementation during IVM (p < 0.05). (ii) Intracellular GSH‐GSSG content increased (p < 0.01) with different Mn concentrations in oocytes and cumulus cells. Also, cumulus cell number per cumulus oocyte‐complexes (COC) did not differ either before or after IVM. (iii) Addition of Mn to maturation medium resulted in similar cleavage rates (p > 0.05) at 0, 2, 5 and 6 ng/ml Mn. However, subsequent embryo development to blastocyst stage was significantly higher (p < 0.01) in oocytes matured with 5 and 6 ng/ml Mn. (iv) There was also an increase (p < 0.05) in mean cell number per blastocyst obtained from oocytes matured with 5 and 6 ng/ml respect to zero Mn (IVM alone) and 2 ng/ml Mn. This study provides evidence that optimal embryo development to the blastocyst stage was partially dependent on the presence of Mn during IVM. Moreover, the availability of Mn during oocyte maturation ensures ‘normal’ intracellular GSH content in COCs and protects DNA integrity of cumulus cells.