Screening and characterization of sex-specific DNA fragments in the freshwater fish matrinchã, Brycon amazonicus (Teleostei: Characiformes: Characidae)

The matrinch? Brycon amazonicus, a commercially important freshwater fish resource, has no heteromorphic sex chromosomes so far described. In the present study, we performed a screening of sex-associated DNA markers in this species, through the use of a random amplified polymorphic DNA (RAPD) assay and a genomic DNA restriction digestion analysis. DNA digestions evidenced no differences between sexes. Sixty-six random primers were used in pooled and individual DNA samples of males and females, and the analysis of the RAPD fingerprints revealed one female sex-associated band. Cloning and sequencing of this band led to the identification of two distinct DNA segments. While one of the isolated fragments showed a significant identity with a described protein gene (phosphatidylinositol glycan anchor biosynthesis, class W), the other fragment, composed of 535?bp, corresponds to a novel DNA marker. Further experiments were performed with this second DNA fragment in order to verify its sex-specificity. Data on dot blot hybridization, using total DNA of both sexes, confirmed its female-specificity in B. amazonicus. A primer set was designed based on its sequence data and used in PCR with DNA samples of this species, leading to diagnose the animals' sexes with a 100?% overall accuracy through a sequence characterized amplified region approach. No amplification results were found for two other species of the genus-B. orbignyanus and B. lundii. The obtained data can lead to the hypothesis that B. amazonicus may present heteromorphic sex chromosomes that should be in an early phase of differentiation.     

Model legumes contribute to faba bean breeding

Faba bean is an excellent candidate crop to provide nitrogen input into temperate agricultural systems. However, its growth is hampered by several factors including environmental stresses and the presence of anti-nutritional factors. To solve these limitations, breeding programs have been initiated that were successful for monogenic traits but not so for multigenic traits. The large genome size of faba bean has slowed down breeding processes. Several other legumes have emerged as model legumes including Medicago truncatula, Lotus japonicus, Glycine max and Pisum sativum. The establishment of these models has already boosted our understanding of important processes such as the nitrogen-fixing symbiotic interaction. The high level of synteny and collinearity existing between legumes makes possible the transfer of key knowledge from model legumes to faba bean. Here we review the most recent knowledge gained from model legumes on grain quality, resistance to biotic and abiotic stresses, nitrogen-fixing symbiosis and how this knowledge can be employed for faba bean breeding.     

Genetic diversity of papaya (Carica papaya L.) F5 recombinant inbred lines using the Ward-MLM strategy

Genetic Resources and Crop Evolution - The development of segregating populations in papaya allows the development of new high fruit yield and excellent fruit quality pure line or hybrid cultivars....     

Furcation canals of the maxillary fourth premolar and the mandibular first molar teeth in cats

The furcation region morphology was evaluated in 103 mature feline carnassial teeth (54 maxillary fourth premolar and 49 mandibular first molar teeth). Patent furcation canals were present in 27.2% of teeth. No significant difference (p = 0.88) in distribution of this anatomical variation was found between maxillary fourth premolar and mandibular first molar teeth. The mean width of these furcation canals was 104.0 microns with two-thirds of the canals having a buccal orientation. The presence of furcation canals could be a factor in the etiopathogenesis of feline dental resorptive lesions, as well as a characteristic to be considered in the diagnosis, prognosis, and treatment of endodontic or periodontic-endodontic lesions in cat teeth.     

Leaf Traits as Functional Descriptors of the Intensity of Continuous Grazing in Native Grasslands in the South of Brazil

Plant functional types (PFT) have been used to describe the response of native vegetation to environmental factors (i.e., fertility) and to livestock disturbance, but rarely under conditions of continuous grazing. In this work we investigate whether the long-term response of grassland communities submitted to a gradient of continuous grazing pressure can be described with such an approach. After 15 yr of differentiation of the grazing pressure applied to native grasslands we measured leaf dry-matter content (LDMC) and specific leaf area (SLA) of Poaceae populations of the communities. A grazing pressure gradient was created by levels of daily forage allowance: 4, 8, 12, and 16 kg of dry matter per day per 100 kg of animal live weight, monitored monthly. PFTs were defined by numerical analysis, where an algorithm finds the optimal trait subset based on the agreement between matrices of species × traits, paddocks × grass biomass, and environmental variables (levels of forage allowance and soil characteristics). The results show that it is possible to describe a gradient of grazing pressure by means of LDMC and/or SLA measured only on the Poacea contributing at least 80% of the total Poaceae biomass. Four PFTs were differentiated by these leaf traits. PFTs having low LDMC and high SLA are characteristic of high intensity of use and are made up largely of stoloniferous C₄ species typical of rapid resource capture strategies. Conversely, PFTs characterized by high LDMC and low SLA include species that are representative of low grazing pressure. Variations in the aggregate value of traits are due to changes in the species proportions and not to leaf-size adaptation as hypothesized. We conclude than in the absence of a gradient of fertility, plants with strategies of resource capture tend to be more represented under high grazing pressures. This situation results in a loss of functional diversity, but in particular a reduction in forage availability, which is incompatible with high animal production.     

Performance of nitrification inhibitors with different nitrogen fertilizers and soil textures

Nitrification inhibitors (NIs), DCD (dicyandiamide), and DMPP (3,4‐dimethylpyrazole phosphate), in combination with urea (UR) and ammonium sulfate nitrate (ASN) fertilizers were studied under contrasting soil textures (sand, loam, and clay) from cultivated soils collected in Brazil and Germany. Soil samples were incubated over 50 days and the content of ammonium ( ), nitrate ( ), and soil pH were measured periodically. Applied NIs delayed the nitrification process across all soil textures. Correlation analysis indicated that combining ASN with NIs resulted in higher content and efficiency in delaying the nitrification process with high N‐conversion rate (r = –0.82). The combination of ASN+ DMPP increased the efficiency of the N‐conversion rate (r = –0.86) due to H⁺ release in soil, while UR+DCD (r = –0.50) had an efficiency of the N‐conversion rate similar to UR (r = –0.42). All the NIs had a better performance in reducing formation in sandy soils as compared to the loam and clay textured soils. Use of DMPP with an N fertilizer results in a soil pH decrease and can be an option to increase the efficiency of the N‐conversion rate, reducing N losses in soil. Overall, our results suggest that NIs have a better performance in reducing formation in sandy soils as compared to that of the loam and clay textured soils. Use of DMPP with ASN results in a soil pH decrease and can be an option to reduce N losses in soil.     

Carotenoid production by the marine microalgae Nannochloropsis oculata in different low‐cost culture media

Nannochloropsis oculata (Eustigmatophyceae) is a marine microalga of great biotechnological interest, mainly due to its large production of lipids containing polyunsaturated fatty acids. In addition, this species presents a wide range of commercial interest pigments, such as zeaxanthin, beta‐carotene, and other xanthophylls, with potential for several industrial applications. However, most of the research concerning pigment production by N. oculata has been conducted by employing high‐cost laboratorial growth media, which makes large‐scale pigment production using these microalgae impractical. Considering the high interest and commercial value in microalgae pigments, this study investigates the feasibility of producing pigments by N. oculata using five different low‐cost growth media (fertilizers and aquaculture effluents). Nutrient (ammonia, nitrite and phosphate) concentrations, cell abundance, biomass, and the concentration/composition of pigments were measured. The pigment profile of N. oculata showed chlorophyll‐a as the dominant pigment, along with violaxanthin, vaucheraxanthin, and lower concentrations of antheraxanthin, zeaxanthin and beta‐carotene. Although the highest biomass (516.4 ± 76.71 mg/L) and pigment content (0.98 mg/g) were achieved in the laboratory media (f/2), the low‐cost media (containing ammonium sulfate, calcium superphosphate and urea) revealed a great potential for the production of pigments, specially chlorophyll‐a, violaxanthin and zeaxanthin, due to the high pigment content per unit of biomass.     

A genomic regulatory network for development

Development of the body plan is controlled by large networks of regulatory genes. A gene regulatory network that controls the specification of endoderm and mesoderm in the sea urchin embryo is summarized here. The network was derived from large-scale perturbation analyses, in combination with computational methodologies, genomic data, cis-regulatory analysis, and molecular embryology. The network contains over 40 genes at present, and each node can be directly verified at the DNA sequence level by cis-regulatory analysis. Its architecture reveals specific and general aspects of development, such as how given cells generate their ordained fates in the embryo and why the process moves inexorably forward in developmental time.     

General and specific combining ability in Serrasalmidae

This work was carried out to predict the combining abilities, both general and specific, for performance traits and bodily yields of Serrasalmidae. Ninety‐six 30‐day‐old juveniles were purchased from two commercial fish farms, 12 of each of the following eight genetic groups: pacu, pirapitinga, tambaqui, tambacu, tambatinga, patinga, paqui and piraqui. Six fish from each genetic group were grown in 500‐L fibreglass tanks (two tanks per genetic group) until they were 495 days old. At the end of the growth period fish were weighed, subjected to morphometric analysis and processed to obtain their bodily yields. Two nuclear markers and one mitochondrial marker were used to confirm the identity of the animals. Combining abilities were obtained using the method proposed by Griffing in 1956 (Australian Journal of Biological Science, 4, 463–493) adapted to a mixed models analysis, environmental effects were estimated by the empirical best linear unbiased estimator method and genetic effects (general and specific combining abilities) were estimated with the empirical best linear unbiased predictor. Predictions of the combining abilities of advanced hybrids were obtained by the mixed models mixture method with normal distributions. Tambaqui showed higher general and specific combining abilities than the other groups for most of the variables, making it the most important genetic group. General combining ability makes a greater contribution to phenotypic variance than specific combining ability for most variables, indicating a predominance of genes with an additive effect in the control of evaluated traits.