Socio-economic and environmental changes related to maize richness in Mexico’s central highlands

The occurrence of genetic erosion in local maize varieties in Mexico is intensely debated. Recent publications from Mexico show contradicting results about the loss of local varieties. Genetic erosion is a complex process, and well-documented examples of actual genetic erosion are not common in the literature. We worked in a region in which adoption of improved varieties was negligible, but other factors affecting maize agriculture were at play. The objectives of the study were to describe changes in maize diversity in the last 10 years and to associate them with socio-economic and environmental changes in a region in Mexico’s Central Highlands. We used richness and abundance of local varieties and diversity indices of races as indicators of maize diversity changes over time. We analyzed statistics and based on interviews we evaluated maize diversity changes between 2005 and 2015. We interviewed 113 farmers on two occasions with intervals from 5 to 10 years. According to climate statistics, rain has declined and temperature has increased. We also found a decrease in the lake level during the past 35 years. The total population in the region has doubled since the 1960s. The indigenous population has not changed significantly. Number of people working in agriculture has decreased since the 1960s. Rain fed agriculture decreased 8.1 % from 1990 to 2007. In four villages studied, farmed land area had decreased between 1995 and 2015. This reduction varies between 22 and 39 % depending on the village. Maize planted area decreased from 9675 to 8115 ha from 2003 to 2014. In the same period, avocado plantations grew from 34 to 786 ha. In despite of these changes, we did not find significant changes in average landraces per farmer (2.13 ± 0.28 in 2015) nor per village (4.15 ± 1.26 in 2015). Significant changes in maize races were not found either (1.91 ± 0.26 per farmer, 2.85 ± 0.86 per village in 2015). These results show that maize landrace diversity in the region is resilient but dynamic.     

Climate and population origin shape pine tree height-diameter allometry

Tree height-diameter allometry, the link between tree height and trunk diameter, reflects the evolutionary response of a particular species’ allocation patterns to above and belowground resources. As a result, it differs among and within species due to both local adaptation and phenotypic plasticity. These phenotypic variations in tree height-diameter allometry determine tree productivity, resistance and resilience to climate variation and, ultimately, the success of plant material used in restoration projects. We tested the effect of climate change and population origin on the phenotypic variation of tree allometry in four pine species at an early stage of development (ca. 11 years old) based upon data originated from multi-site provenance tests and planted along a wide climatic range in south-western Europe. For a representative sample of populations from each species, we used already-developed species-specific height-diameter allometric models to assess changes in allometry between present and future climatic conditions. We found that Pinus halepensis and Pinus pinaster were the most plastic species, while Pinus sylvestris and Pinus nigra showed negligible plastic responses. In addition, our models stressed that pine tree height-diameter allometry will change and phenotypic variation could increase, except in P. sylvestris, under future environmental conditions. For some of the species, this might allow the selection of phenotypes better suited to novel climatic conditions. These foreseeable changes in tree height-diameter allometry (among and within-species) could entail eco-evolutionary effects on the early forest plantation dynamics. Therefore, restoration and reforestation plans should consider these effects, as they may interfere with production and/or environmental goals.     

Sheep fed with banana leaf hay reduce ruminal protozoa population

A ciliate protozoa suppression can reduce methane production increasing the energy efficiency utilization by ruminants. The physicochemical characteristics of rumen fluid and the profile of the rumen protozoa populations were evaluated for sheep fed banana leaf hay in replacement of the Cynodon dactylon cv. vaqueiro hay. A total of 30 male sheep were raised in intensive system during 15 days of adaptation and 63 days of experimental period. The animals were distributed in a completely randomized design that included six replicates of five treatments with replacement levels (0, 25, 50, 75, and 100%) of the grass vaquero for the banana leaf hay. Samples of fluid were collected directly from the rumen with sterile catheters. Color, odor, viscosity, and the methylene blue reduction potential (MBRP) were evaluated and pH estimated using a digital potentiometer. After decimal dilutions, counts of genus protozoa were performed in Sedgewick Rafter chambers. The averages of pH, MBRP, color, odor, and viscosity were not influenced by the inclusion of the banana leaf hay. However, the total number of protozoa and Entodinium spp. population significantly decreased at 75 and 100% inclusions of banana leaf hay as roughage.     

Virulence-associated trimeric autotransporters of Haemophilus parasuis are antigenic proteins expressed in vivo

Glässer’s disease is a re-emerging swine disease characterized by a severe septicaemia. Vaccination has been widely used to control the disease, although there is a lack of extended cross-protection. Trimeric autotransporters, a family of surface exposed proteins implicated in host-pathogen interactions, are good vaccine candidates. Members of this family have been described in Haemophilus parasuis and designated as virulence-associated trimeric autotransporters (VtaA). In this work, we produced 15 recombinant VtaA passenger domains and looked for the presence of antibodies directed against them in immune sera by immunoblotting. After infection with a subclinical dose of H. parasuis Nagasaki, an IgG mediated antibody response against 6 (VtaA1, 5, 6, 8, 9 and 10) of the 13 VtaA of the Nagasaki strain was detected, indicating that they are expressed in vivo. IgA production against VtaA was detected in only one animal. VtaA were more likely to be late antigens when compared to early (Omp P5 and Omp P6) and late (YaeT) defined antigens. Antibody cross-reaction with two orthologs of Nagasaki’s VtaA5 and 6, VtaA15 and 16 of strain HP1319, was also detected. No antibodies against VtaA were detected in the sera of animals immunized with a bacterin of the Nagasaki strain, suggesting poor expression in the in vitro conditions used. Taken together, these results indicate that VtaA are good candidate immunogens that could be used to improve H. parasuis vaccines. However, their capacity to confer protective immunity needs to be further studied.     

Effect of selenium and vitamin E on oxidative stress in lambs experimentally infected with <Emphasis Type="Italic">Haemonchus contortus</Emphasis>

The objective of this study was to evaluate oxidative stress in lambs experimentally infected with Haemonchus contortus and supplemented with selenium and vitamin E. Twenty male Corriedale lambs were divided into four experimental groups with five animals each: G1 consisted of animals infected and supplemented with 0.2 mg/kg of live weight (LW) sodium selenite by intramuscular injection (IM); G2 consisted of animals infected with larvae and supplemented with 0.2 mg/kg LW sodium selenite IM and 2000 IU per animal of Vitamin E IM; G3 consisted of animals infected with larvae and supplemented with 2000 IU per animal of Vitamin E IM; and G4 consisted of animals infected with larvae. The animals were infected orally with 500 H. contortus larvae (L3) every 48 hours for 20 days. For biochemical analyses and eggs per grams of feces (EPG) evaluation, blood and feces were both collected at zero (T0), 20 (T1), 40 (T2) and 60 (T3) days. The weight of the animals was also measured at these times. Lower TBARS values were observed in the supplemented animals compared to the control group. The groups supplemented with Selenium exhibited blood GSH-Px activity higher than that of non-supplemented animals. Supplementation with selenium provided greater antioxidant protection against oxidative stress generated from experimental infection of lambs with H. contortus.     

Forest loss and fragmentation effects on woody plant species richness in Great Britain

Studies on the effect of forest loss and fragmentation on plant species richness at different spatial scales have yielded contradictory results that have been attributed to different ways to measure fragmentation. The main goal of this study was to investigate the independent and combined effects of forest loss and habitat fragmentation on woody species richness. Woody species were grouped according to their habitat requirements (forest specialists, forest generalists, non-forest and total woody species). We used regression models to investigate the effect of fragmentation and human occupation on woody species richness. The underlying factors were investigated by partitioning of the variation, i.e. decomposing the variation in species richness between the pure effects of forest loss, fragmentation and human occupation. The relationship between species richness and forest loss resulted extremely non-linear. The models for forest specialist, generalist and total woody species richness accounted for 35%, 31% and 33% of the total variance respectively. Model for non-forest species richness only accounted for 7% of the total variance. The largest fraction of variability in species richness was accounted by fragmentation variables for all groups (except for non-forest species). Results emphasize the larger independent effect of fragmentation over forest loss, suggesting that species variation is mainly conditioned by the spatial configuration of the habitat.