Invasive dynamics of the crayfish Procambarus clarkii (Girard, 1852) in the international section of the River Minho (NW of the Iberian Peninsula)

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Variability in infection and reproduction of Meloidogyne javanica on tomato rootstocks with the Mi resistance gene

The response of 10 commercial or experimental tomato rootstocks with the Mi resistance gene to an initial inoculum of a Mi‐avirulent population of Meloidogyne javanica was determined in pot tests conducted in spring and summer. In a field test, the rootstocks were subjected to continuous exposure to high initial population densities (2050 ± 900 second‐stage juveniles (J2) per 250 cm³ soil) of the nematode. The presence of the Mi locus in the resistant rootstocks and cultivars was confirmed using the PCR co‐dominant markers REX‐1 and Mi23. Nematode infectivity (egg masses) and reproduction (eggs g^?1 root) were highly variable in the spring tests. Rootstocks PG76, Gladiator and MKT‐410 consistently responded as highly resistant, with nematode multiplication rate (Pf/Pi) < 1 and reproduction index (RI) < 10%, and they were as efficient as standard resistant tomato cultivars at nematode suppression. The relative resistance levels of rootstocks Brigeor, 42851, 43965, Big Power and He‐Man varied depending on the susceptible standard used for reference or the duration of the test. Rootstocks Beaufort and Maxifort were susceptible to M. javanica (Pf/Pi > 50 and RI > 50%). Rootstocks PG76 and He‐Man, and the resistant tomato cv. Caramba showed high levels of resistance in the test conducted in summer, whereas MKT‐410 and 42851 and the resistant tomato cv. Monika were moderately resistant. In the field, seven rootstocks showed high levels of resistance and one (He‐Man) showed an intermediate level, whereas Beaufort and Maxifort were susceptible.     

Utilization of corn gluten meal as a protein source in the diet of white shrimp Litopenaeus vannamei

A 57‐day feeding trial was designed to assess the potential of corn gluten meal (CGM) as a plant protein source in practical feeds for white shrimp Litopenaeus vannamei. Five experimental diets providing 350 g kg^?1 protein and 110 g kg^?1 lipid were prepared, where 0%, 25%, 50%, 75% and 100% of fishmeal (FM) protein was substituted by protein from CGM. The results showed that partial or complete replacement of FM with CGM did not affect survival. The growth of the shrimp declined as the levels of CGM increased, diets containing CGM showing a significantly lower final weight (3.2–5.9 g) and specific growth rates (1.7–2.7% per day) compared to those fed on the diet with 0 CGM (7.1 g and 3.0% per day). Feed conversion ratio was also significantly affected by CGM level. The inclusion of CGM resulted in a statistical decrease in the apparent digestibility (AD) of dry matter from 77.9% to 66.0% and in AD of protein from 80.5% to 52.0%, of feed. The AD of amino acids, with the exception of lysine, declined with the dietary incorporation of CGM. In summary, reduced palatability, low protein digestibility and a deficiency of lysine and methionine seem to be the major reasons behind a depressed growth in shrimp fed on CGM protein‐based diets.     

Feasibility of Cordia trichotoma (Vell.) wood and its by-products for particleboard manufacturing

The wood panel industry uses a large volume of wood and it is essential to research the use of new tree species for these types of products. As such, the aim of this study was to evaluate the feasibility of Cordia trichotoma (Vell.) wood, both on its own and as a mixture with Pinus spp., as well as to understand the effect on particleboard quality when adding the species’ bark and shavings. The experimental design included nine treatments that assessed various mixture proportations of C. trichotoma and Pinus; for example, 10% bark, and 10% shavings of C. trichotoma with Pinus spp. and C. trichotoma particles, as well as mixtures of these two species in proportions of 25/75%, 50%/50%, and 75/25%. The results indicate that the Cordia trichotoma specie is technically feasible when manufacturing particleboards in pure form. The incorporation of bark (at 10% of the mixture) is also technically feasible. It is also feasible to use the shavings of C. trichotoma. In general, all treatments produced outputs that showed dimensional stability and mechanical strength statistically equal or higher than control treatments (Pinus spp.); thus, these products may be used for non-structural applications in dry and/or moist conditions.     

Trait dissection of maize kernel weight: Towards integrating hierarchical scales using a plant growth approach

Maize (Zea mays L.) yield is a function of the number harvested kernels per unit land area and the individual kernel weight (KW). Kernel weight and its development show a wide variability due to the genotype, the environment, the crop management, and all possible interactions. Commercial maize hybrids differ markedly in the patterns (rate and duration of kernel growth) behind differences in final KW. The same can be observed when public or elite proprietary maize inbred lines are analyzed. To progress in our understanding of KW variability, we reviewed and discussed current knowledge for analyzing kernel growth as an integrated system, modulated by processes linking different levels of organization (the different kernel tissues, the whole kernel, the plant, the canopy). Ideas on how to integrate this knowledge towards the development of a multi-hierarchical scale framework for predicting KW under different growth environments are currently needed, as they have high relevance for dissecting the genetic basis of kernel growth and maize yield definition at the canopy level.     

Effects of dredging operations on sediment quality: contaminant mobilization in dredged sediments from the Port of Santos, SP, Brazil

Background, aim, and scope  

Contaminated sediments are a worldwide problem, and mobilization of contaminants is one of the most critical issues in environmental risk assessment insofar as dredging projects are concerned. The investigation of how toxic compounds are mobilized during dredging operations in the channel of the Port of Santos, Brazil, was conducted in an attempt to assess changes in the bioavailability and toxicity of these contaminants.