A multi-species assessment of genetic variability in Nigerian Amaranthus accessions: potential for improving intra- and interspecies hybridization breeding

Amaranthus yields could benefit from our growing understanding of the genetic variability within and among individual species of local germplasm collections. Thirty-seven Amaranthus accessions representing three different species were evaluated for seed yield and yield components across two seasons. The objectives were to characterize the genetic variability of seed yield and its components across species and determine relationships among seed yield and its components by phenotypic correlation. Significant differences (P < 0.01) existed for all the evaluated traits among the accessions. Characters such as seed yield, stem girth and leaf length showed higher heritability estimates in A. cruentus (14) than in A. hypochondriacus (12) and A. dubius (11) accessions. Seed yield was significantly and positively correlated with stem girth and thousand seed weight. However, it was significantly and negatively correlated with number of days to flowering, plant height, leaf number, number of branches. The clustering of the accessions, which was partially in agreement with species grouping, will help in the identification of diverse parents for use in the breeding program. Enormous amount of genetic variability found in seed yield and its components among Nigerian Amaranthus accessions will offer opportunity for grain and leaf yield improvement through breeding.     

Genotype × environment interaction effects on pod yield and pod number in West African Okra

As year-to-year weather fluctuation increases, the need for better understanding of their effects on crops becomes ever more pressing. Genotype × environment (G × E) interactions for pod yield and pod number were assessed in a set of 25 West African okra genotypes that were cultivated in four successive years (otherwise called environments) through field trials, arranged in a randomized complete block design, with three replicates. Significant G × E interactions in measured traits were detected, suggesting that selection for stable genotypes, with respect to these traits must be environmental specific. Consequently, additive main effects and multiplicative interaction model was applied to dissect G × E interactions. For pod yield, the highest percentage (38.4%) of the treatment sum of square was attributable to genotypes followed by G × E interactions (36.0%) and environment (25.6%), indicating predominance of genotypic variation for this trait. Conversely, prevalence of G × E interactions was observed for pod number. The biplots of the grand mean and IPCA 1 score revealed that the environments tended to discriminate genotypes in dissimilar fashion. Rainfall, relative humidity, wind speed and soil temperature were identified as strong driving forces for development and growth, affecting pod yield. The identified genotypes could be suitable candidates for further study.     

The activation of the IFNβ induction/signaling pathway in porcine alveolar macrophages by porcine reproductive and respiratory syndrome virus is variable

Background

It has been recognized that the expression of type I interferon (IFNα/β) may be suppressed during infection with porcine reproductive, respiratory syndrome virus (PRRSV). This causes profound negative effects on both the innate and adaptive immunity of the host resulting in persistence of infection.

Objective

Test the effects of PRRSV infection of porcine alveolar macrophages (PAMs), the main target cell, on the expression of interferon beta (IFNβ) and downstream signaling events.

Methods

In order to examine those effects, PAMs harvested from lungs of healthy PRRSV-free animals were infected with virulent, attenuated, infectious clone-derived chimeric viruses, or field PRRS virus strains. Culture supernatants from the infected PAMs were tested for IFNβ protein expression by means of indirect ELISA and for bioactivity by a vesicular stomatitis virus plaque reduction assay. The expression of the Mx protein was assayed to ascertain signaling events.

Results

These experiments demonstrated that PRRSV does induce variably, the expression of bioactive IFNβ protein in the natural host cell. To further elucidate the effects of PRRSV infection on IFNβ signaling, Mx-1 an interferon stimulated gene (ISG), was also tested for expression. Interestingly, Mx-1 expression by infected PAMs generally correlated with IFNβ production.

Conclusion

The results of this study demonstrate that the induction of IFNβ and signaling in PAMs after PRRSV infection is variable.

     

Scientific critique of the paper “Climatic distribution of citrus black spot caused by <Emphasis Type="Italic">Phyllosticta citricarpa</Emphasis>. A historical analysis of disease spread in South Africa” by Martínez-Minaya et al. (2015)

The global distribution of citrus black spot (CBS) disease, caused by Phyllosticta citricarpa, is climatically constrained, which is evident from its occurrence in citrus growing areas with warm, summer rainfall and its absence from areas with cooler, Mediterranean-type winter rainfall. Various epidemiological and modelling studies have supported this observation, predominantly estimating unsuitability for P. citricarpa in Mediterranean type climates, with no more than marginal suitability estimated at a few localities within some regions with Mediterranean type climates. The study by Martínez-Minaya et al. (European Journal of Plant Pathology, 143, 69–83, 2015), describes an historic sequence of recorded CBS occurrence in parts of South Africa, conducts an autocorrelation analysis and a correlative analysis with Köppen-Geiger climate zones and makes observations about the occurrence of certain Köppen-Geiger climate zones in the European Union. The study suggests that significant portions of the European Union and the broader Mediterranean basin are climatically similar to warm, summer rainfall areas in South Africa where P. citricarpa persists and causes CBS disease and concludes that the potential distribution of P. citricarpa is less constrained by climatic factors than spatial contagion. However, in this critique we expose methodological shortcomings in the Martínez-Minaya et al. (European Journal of Plant Pathology, 143, 69–83, 2015) study and conclude that the study grossly overestimated the extent of the geographical area that could support P. citricarpa, thereby rendering the findings scientifically unreliable.     

Identification of a target‐site mutation conferring resistance to triazine herbicides in oriental mustard (Sisymbrium orientale L.) from Australia

In southern Australia, oriental mustard (Sisymbrium orientale) has been controlled successfully by triazine herbicides for several decades. The screening of 40 populations that were collected from the southern grain belt of Australia during 2010 and 2013 for resistance to six different herbicides (glyphosate, diflufenican, imazamox, chlorsulfuron, atrazine and 2,4‐dichlorophenoxyacetic acid) identified two oriental mustard populations as highly resistant to atrazine. Compared to the known oriental mustard‐susceptible populations (S1 and S2), these two resistant populations (P17 and P18) from near Horsham, Victoria, Australia, were 311‐ and 315‐fold resistant to atrazine, as determined by a comparison of the LD₅₀ values. However, there was no resistance to diuron detected in these populations. Sequencing of the chloroplast psbA gene identified a missense mutation of serine 264 to glycine in both herbicide‐resistant oriental mustard populations, which is known to confer high‐level atrazine resistance in other species.     

Enhancing the effectiveness of biological control programs of invasive species through a more comprehensive pest management approach

Invasive species are one of the greatest economic and ecological threats to agriculture and natural areas in the US and the world. Among the available management tools, biological control provides one of the most economical and long‐term effective strategies for managing widespread and damaging invasive species populations of nearly all taxa. However, integrating biological control programs in a more complete integrated pest management approach that utilizes increased information and communication, post‐release monitoring, adaptive management practices, long‐term stewardship strategies, and new and innovative ecological and genetic technologies can greatly improve the effectiveness of biological control. In addition, expanding partnerships among relevant national, regional, and local agencies, as well as academic scientists and land managers, offers far greater opportunities for long‐term success in the suppression of established invasive species. In this paper we direct our recommendations to federal agencies that oversee, fund, conduct research, and develop classical biological control programs for invasive species. By incorporating these recommendations into adaptive management strategies, private and public land managers will have far greater opportunities for long‐term success in suppression of established invasive species. © 2016 Society of Chemical Industry     

American beech leaf‐litter leachate chemistry: Effects of geography and phenophase

The decomposition of broadleaved tree leaves can contribute a substantial amount of energy to forested watersheds via dissolved organic matter (DOM), nutrients, and biological activity. Less is known about how these inputs may vary within a single tree species that is known to have two genetically distinct and geographically separate populations, or how these inputs may change throughout autumn senescence and abscission. It is often implicitly assumed that intraspecific differences in leaf‐litter leachate chemistry do not significantly differ geographically. We analyzed the morphological and chemical leaf traits and leachates from Fagus grandifolia (American beech) leaves (n = 360) during three phenophases: fresh green leaves, senescing leaves, and fallen leaves. During each phenophase, leaves were collected from four sites along a geographic transect stretching from Vermont to North Carolina (over 1400 km), with two sites representing each genetic population and differing climatic conditions. Leachates were analyzed for routine solutes and nutrients, as well as fluorescent and UV‐visible absorbance indices. Amounts of macro‐ and micronutrients were highly variable among sites and phenophases but tended to be lowest during the fallen‐leaf phase, while measured fluorescence and absorbance indices tended to increase during the senescing‐leaf phase and plateau. Results suggest significant differences in leached nutrients among sites, and optical properties and nutrients among phenophases. Aromaticity and molecular weight of DOM in leachates was generally low, and aromaticity and humification of leachates both increased over time with leaf age. These results also suggest that geographically (or genetically) separate populations of the same species do not experience senescence in the same way and that implicit assumptions of intraspecific uniformity of leaf‐litter leachate chemistry for a given tree species may be invalid.     

Growth and fillet quality attributes of five genetic strains of rainbow trout (Oncorhynchus mykiss) reared in a partial water reuse system and harvested at different sizes

Genetics and harvest size influence fish growth performance and product quality attributes, making selection of fish strain and harvest size critical for optimizing quality. Definition of performance and quality outcomes in a recirculating aquaculture system (RAS) environment may guide selection of fish stocks best suited for RAS farmers to meet production and product quality goals. Accordingly, five genetic lines of rainbow trout, Oncorhynchus mykiss were reared to 3 kg in a partial water reuse system and sampled at common harvest sizes (0.5, 1, 2 and 3 kg) to compare growth performance and product quality attributes. Fish weight affected fish processing yields and cook yields. Genetic line affected fish weight. When correcting for fish size, differences in fillet yields due to genetic line were present. Both fish weight and genetic line affected different organ indices, fillet colour scores and mortality. Muscle composition and texture were similar at each harvest, but changed with increasing fish size over time. Differences in growth performance and product quality traits due to genetic line identify variation in available fish stocks, and balancing change to these traits due to fish size can guide producer selection of fish stocks and optimal harvest size to meet individual production goals.