Effects of salinity on sexual maturity and reproduction of Poecilia velifera

Poecilia velifera is a popular fish in freshwater aquarism that naturally inhabits aquatic habitats with a wide range of salinities. Nonetheless, the effects of different salinities on the reproductive success and sex ratio of the species remain unknown. Male sex characters, sex ratio and reproductive success of P. velifera were evaluated by maintaining 160 juveniles (0.078 ± 0.011 g) in four different salinities (0; 12; 24; 36 g/L), with four replicates. The only modification observed in males was the formation of a copulatory organ from the anal fin, which was used to distinguish them from females. Timing of the formation of the male copulatory organ, and the weight and total length of males when it occurred, were recorded. Twenty‐eight fish from each treatment were euthanized after 150 day to examine the gonads and confirm sex. Eight females and four males from each treatment were then kept in their respective salinity treatments for 65 days to examine the effects of salinity on reproduction. Males were kept with females in the different treatments for 15 days, at which point they were removed. Salinity was negatively correlated with male weight and length. Salinity also affected the sex ratio, with the percentages of males and females being 32.5 and 67.5%, and 27.5 and 72.5% in the salinities of 24 and 36 g of salt/L, respectively. Fifty percent of the females kept in freshwater reproduced, while there was no reproduction in the other treatments. The maintenance of P. velifera in freshwater promoted greater reproductive success and precocity, as well as larger males.     

Characterization of antibiosis to the silverleaf whitefly Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) in cowpea entries

The silverleaf whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), is considered one of the most important pests of cowpea (Vigna unguiculata L. Walp.), limiting the productivity of this crop worldwide. Chemical control is still the main strategy for the management of populations of this insect. However, due to the harmful effects of pesticides on the environment and to humans, less injurious alternatives have been investigated. Along this line, the use of resistant genotypes can be a valuable tool for the control of the silverleaf whitefly. In this paper, we investigate some biological aspects of B. tabaci biotype B confined on 14 genotypes of cowpea. We evaluated the incubation period, egg viability, duration of nymphal stages, total duration of the juvenile phase, instar mortality and total mortality of the immature stage. The genotype MNC 99-541 F21 exhibited antibiosis against the whitefly, prolonging the lifecycle of the insect. The genotypes Canapu, BRS-Urubuquara and TE97-304 G-4 also exhibited antibiosis, causing high nymphal mortality. These results may help in breeding programmes to develop cowpea lines with resistance to B. tabaci biotype B.     

Variation in the host preferences and responses of <Emphasis Type="Italic">Ascia monuste orseis</Emphasis> Godart (Lepidoptera: Pieridae) to cultivars of collard greens <Emphasis Type="Italic">Brassica oleracea</Emphasis> (L.) var. <Emphasis Type="Italic">acephala</Emphasis>

This work evaluated the preference of Ascia monuste orseis among 29 cultivars of collard greens through free- and no-choice assays using female adults (attractiveness and oviposition) and third-instar larvae (feeding preference), in both laboratory and greenhouse conditions. In free-choice tests with female adults, the L, V, Y, H, A, and Z cultivars produced oviposition non-preference in butterflies. Cultivars R, P, C, and D produced feeding non-preference in third-instar larvae of A. monuste orseis in free- and no-choice tests. Our findings may be useful for genetic improvement focusing on the development of B. oleracea var. acephala cultivars resistant to A. monuste orseis.     

Characterization of antibiosis and antixenosis to the whitefly silverleaf <Emphasis Type="Italic">Bemisia tabaci</Emphasis> B biotype (Hemiptera: Aleyrodidae) in several squash varieties

The objective of this study was to investigate the potential resistance mechanisms to Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) B biotype, in eight Cucurbita pepo varieties. Attractivity, oviposition preference, and nymphal development were evaluated under greenhouse and laboratory conditions. Variety Bianca was the least attractive to adult whiteflies in multi-choice tests. The whiteflies showed oviposition nonpreference (antixenosis) for Novita Plus, Bianca and Sandy in multi-choice test, and similar results were observed in no-choice tests with varieties Bianca, Novita, Caserta Cac and Sandy. Sandy expressed high antibiosis levels against whitefly nymphs, leading to 63.9% mortality. The high level of resistance in variety Sandy can serve as base for genetic improvement of C. pepo focusing on the development of resistant varieties to B. tabaci B biotype.     

Effect of chicken meat replacement by spent laying hen meat on physicochemical properties and sensorial characteristics of fresh sausage

1. Sausages were used to assess the effects of chicken meat replacement by spent laying hen meat on the quality parameters and sensorial properties.

2. Five formulations were developed: control (CON) containing 100% chicken meat and 4 levels of chicken meat replacement with spent laying hen meat: 25% (T25), 50% (T50), 75% (T75) and 100% (T100).

3. Appearance, texture, succulence, flavour and overall consumer acceptance were analysed. Parameters such as moisture, ash, fat and protein content, pH, cooking loss and colour parameters (lightness (L*), redness (a*), yellowness (b*)) were analysed, as well as the texture properties (hardness, elasticity, cohesiveness and chewiness).

4. Statistical analysis did not reveal significant (P > 0.05) differences in chemical composition and colour parameters among formulations. On the other hand, CON treatment showed the lowest (P < 0.05) cooking loss (20.45%) that increased as spent laying hen meat increased in the formulation (24.92% vs. 27.65% vs. 28.12% vs. 33.05%, for T25, T50, T75 and T100 batches, respectively).

5. Regarding textural parameters, T75 and T100 formulations presented higher (P < 0.05) hardness and chewiness compared to the other ones.

6. Concerning to sensorial characteristics, the T100 formulation presented the lowest average scores (P < 0.05) for all attributes studied. However, the other batches (T25, T50 and T75) did not show significant differences for appearance, texture, succulence, flavour and overall acceptability attributes compared with the CON formulation.

7. The results indicated that the substitution of up to 75% of chicken meat by spent laying hen meat did not decrease the sensory acceptance of the sausages by consumers, demonstrating that this level of substitution in sausages allows better use of spent laying hen meat.     

Phloem sugars and amino acids as potential regulators of hordein expression in field grown malting barley (Hordeum vulgare L.)

The commercial quality of malting barley is dependent on the content and composition of grain proteins which are subjected to nitrogen (N) and sulfur (S) control. In nutrient deficient soils, grain protein content is mainly a consequence of the remobilization efficiency. In order to evaluate the effect of N and S soil availability on phloem amino acid and sugar export rates and B- and C-hordein gene expression during grain filling, a factorial combination of N and S fertilization assay was carried out under field conditions. Besides, several carbon (C) and N metabolites were analyzed in leaves and spikes. We observed that, even under soil N and S availabilities that do not limit yield, N and S fertilization induced significant changes in N and C metabolism. N phloem remobilization was promoted by S fertilization independently of N fertilization and C remobilization was also promoted by S fertilization but only in N fertilized plants. The B- and C-hordein gene expression correlated positively with sugar and amino acid exudation rate, respectively. Our results suggest an important role of the export rate of sugars and amino acids in the regulation of grain prolamine expression.     

Assessing the resistance of collard greens genotypes to the cabbage aphid (Brevicoryne brassicae) (Hemiptera: Aphididae)

Phytoparasitica - Severe attacks&nbsp;of Brevicoryne brassicae (Hemiptera: Aphididae) on brassica crops may lead to a significant decrease in yield and can cause plant death. Host plant...     

Low diversity in the native populations of Croton tetradenius Baill. when using SNP markers: a future crop with an insecticidal activity

Genetic Resources and Crop Evolution - Croton tetradenius Baill. is an aromatic plant species whose essential oils have high economic importance. Its incorporation into Active Germplasm Banks is...     

Preliminary study of Porcine circovirus type 2 and Torque teno sus virus coinfection frequencies in Brazilian pig herds

Torque teno sus virus (TTSuV) is emergent in swine herds. Recent studies have shown an increased frequency of TTSuV2 in Porcine circovirus type 2 (PCV2)-associated diseases (PCVAD), which are endemic in many swine-producing countries, including Brazil. Coinfection with several other viral and bacterial agents results in an increased incidence of more severe PCVAD. Given the limited information on TTSuV and PCV2 coinfection, especially in Brazilian swine herds, this study made a preliminary estimation of the occurrence of coinfection in swine herds by testing samples from different categories. Between 2008 and 2009, 111 samples of feces and 23 serum samples from 5 swine herds were tested for PCV2 and TTSuVs and the results analyzed for associations between these agents. No significant differences in coinfection frequency were observed for PCV2 + TTSuV1 or for PCV2 + TTSuV2 between nursery piglets (P = 0.730), growing pigs (P = 0.331), or sows (P = 0.472). However, a significant difference was observed for PCV2 + TTSuV1 + TTSuV2 between nursery piglets and growing pigs (P = 0.004; Fisher’s exact test). Phylogenetic studies agreed with the grouping of TTSuV1 and TTSuV2 into 2 different clades, with no distinct pattern of clustering of these isolates with the animal categories.