Assessment of the Nutritional Value of Traditional Vegetables from Southern Chile as Potential Sources of Natural Ingredients

Plant Foods for Human Nutrition - There is an increasing interest in consuming healthy foods motivated by the need of boosting the immune system naturally. In this sense, vegetables rich in...     

Histopathology of infection and colonization of Quercus ilex fine roots by Phytophthora cinnamomi

Quercus ilex is one of the European forest species most susceptible to root rot caused by the oomycete Phytophthora cinnamomi. This disease contributes to holm oak decline, a particularly serious problem in the ‘dehesas’ ecosystem of the southwestern Iberian Peninsula. This work describes the host–pathogen interaction of Q. ilex and P. cinnamomi, using new infection indices at the tissue level. Fine roots of 6‐month‐old saplings inoculated with P. cinnamomi were examined by light microscopy and a random pool of images was analysed in order to calculate different indices based on the measured area of pathogen structures. In the early stages of invasion, P. cinnamomi colonizes the apoplast and penetrates cortical cells with somatic structures. On reaching the parenchymatous tissues of the central cylinder, the pathogen develops different reproductive and survival structures inside the cells and then expands through the vascular system of the root. Some host responses were identified, such as cell wall thickening, accumulation of phenolic compounds in the middle lamella of sclerenchyma tissues, and mucilage secretion blocking vascular cells. New insights into the behaviour of P. cinnamomi inside fine roots are described. Host responses fail due to rapid expansion of the pathogen and a change in its behaviour from biotrophic to necrotrophic.     

Seasonal effect on infection and development of lesions caused by Cryphonectria parasitica in Castanea sativa

Seasonal variation in the development of chestnut blight, caused by Cryphonectria parasitica, was investigated by inoculating in situ chestnut trees and in vitro excised chestnut segments, at either monthly or 3‐monthly intervals throughout 30 months. Inoculations were made with conidia and mycelium of a virulent isolate and with mycelium of a hypovirulent isolate. Conidial inoculations of living sprouts or excised segments between May and July resulted in the greatest incidence of infection whereas inoculations in autumn and winter, in vitro as well as in situ, did not reveal any visible disease. However, from these symptomless inoculated stems, C. parasitica was isolated 3 months after inoculation. Inoculations with the mycelium of the virulent isolate always resulted in lesions, except in January 1999, and the greatest rate of lesion development occurred for inoculations made in the spring and summer. There was a significant seasonal effect on lesion development. Lesions caused by the hypovirulent isolate, smaller than those caused by the virulent isolate, followed a similar seasonal pattern. The same seasonal variations were observed for inoculations in vitro of excised segments. Relative water content (RWC) of chestnut bark significantly varied with bark sampling date. The rate of lesion development in sprouts significantly correlated with average minimum (ATn) and maximum (ATx) temperatures and the sum of rainfall during inoculation period, with the rate of lesion development measured in excised segments 10 days after inoculation (R10d) and with RWC measured on the day of inoculation. In multiple regression models, variables ATx and R10d best explained variation in lesion development.     

The efficiency of nitrogen in cattle manures when applied to a double‐annual forage cropping system

The use of cattle manure (CM) for fertilization presents challenges for optimizing nitrogen (N) use. Our work aimed to assess N efficiencies, in a 6‐year experiment with three biennial rotations of four crops: oat–sorghum (first year) and ryegrass–maize (second year) in a rainfed humid Mediterranean area of Spain. Fertilization treatments included the following: control (no N), 250 kg mineral N ha^?1 year^?1 (250MN), three CM rates (supplying 170, 250 and 500 kg N ha^?1 year^?1) and four treatments where the two lowest CM rates were complemented with either 80 or 160 kg mineral N ha^?1 year^?1. Treatments were distributed randomly in each of three blocks. Maximum dry‐matter yield (~44–49 t ha^?1 rotation^?1) was achieved in the third rotation, and only the control and the 170CM yielded significantly less. Within the limitations of the EU Nitrate Directive, the N steady state supply of 170CM always requires a complement of mineral N (80 kg N ha^?1) to maximize N agronomic efficiency. The maximum N‐fertilizer replacement value (250CM vs. 250MN) was 0·67, without significant differences between the two treatments in other N‐related efficiency indexes, which indicates that plants took advantage of residual‐N effects. Nitrogen losses by leaching in the 250CM treatment were around 5–7% of the N applied. This reinforces the sustainability of manure recycling in long cropping seasons.     

Genetic analysis and molecular mapping of quantitative trait loci in common bean against Pythium ultimum

Pythium ultimum is a soil pathogen that can cause seed decay and damage to roots in common bean. In this study, the response of a set of 40 common bean genotypes to P. ultimum and inheritance of the resistance in the 92 F? recombinant inbred lines (RIL) developed from a cross between Xana and Cornell 49242 was investigated by using emergence rate and seedling vigor. Emergence of the 40 genotypes showed a significant association between white seed coat and response to this pathogen. Among these, 11 common bean genotypes, all with colored seeds, exhibited a high percentage of emergence and seedling vigor not significantly different (P > 0.05) to noninoculated plants. Response of the RIL population revealed both qualitative and quantitative modes of inheritance. A major gene (Py-1) controlling the emergence rate was mapped in the region of the gene P, a basic color gene involved in control of seed coat color, located on LG 7. Using the RIL subpopulation with colored seeds, a significant quantitative trait loci (QTL) associated with the emergence rate (ER3(XC)) and another with seedling vigor (SV6(XC)) were identified on the LG 3 and 6, respectively. QTL SV6(XC) was mapped in the region of the gene V, another gene involved the genetic control of color. QTLs associated with seed traits were mapped in the same relative position as regions involved in responses to P. ultimum suggesting the possible implication of avoidance mechanisms in the response to this pathogen.     

Lack of biocontrol capacity in a non-pathogenic mutant of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">melonis</Emphasis>

The aim of this study was to assess the biocontrol capacity of rev157, a non-pathogenic mutant of a pathogenic strain of Fusarium oxysporum f. sp. melonis (Fom24). Inoculated in association with the virulent parental strain, the mutant rev157 did not protect the host plant (muskmelon) against infection by Fom24. Applied on flax, a non-host plant, the mutant rev157 was not able to protect it against its specific pathogen F. oxysporum f. sp. lini. On the contrary the parental strain Fom24 did protect flax as well as a soil-borne biocontrol strain (Fo47). Since the mutant rev157 was affected neither in its growth in vitro nor in its capacity to penetrate into the roots, it can be speculated that the mutation has affected traits responsible for interactions within the plant. In F. oxysporum the pair of strains Fom24/rev157 is a good candidate to identify genes involved in the biocontrol capacity of F. oxysporum and to test the hypothesis of a link between capacity to induce the disease and capacity to induce resistance in the plant.     

Ecological impacts of small hydropower plants on headwater stream fish: from individual to community effects

Hydroelectricity is increasingly used worldwide as a source of renewable energy, and many mountain ranges have dozens or hundreds of hydropower plants, with many more being under construction or planned. Although the ecological impacts of large dams are relatively well known, the effects of small hydropower plants and their weirs have been much less investigated. We studied the effects of water diversion of small hydropower plants on fish assemblages in the upper Ter river basin (Catalonia, NE Spain), which has headwater reaches with good water quality and no large dams but many of such plants. We studied fish populations and habitat features on control and impacted reaches for water diversion of 16 hydropower plants. In the impacted reaches, there was a significantly lower presence of refuges for fish, poorer habitat quality, more pools and less riffles and macrophytes, and shallower water levels. We also observed higher fish abundance, larger mean fish size and better fish condition in the control than in impacted reaches, although the results were species‐specific. Accordingly, species composition was also affected, with lower relative abundance of brown trout (Salmo trutta) and Pyrenean minnow (Phoxinus bigerri) in the impacted reaches and higher presence of stone loach (Barbatula quignardi) and Mediterranean barbel (Barbus meridionalis). Our study highlights the effects of water diversion of small hydropower plants from the individual to the population and community levels but probably underestimates them, urging for further assessment and mitigation of these ecological impacts.     

Rapid determination of inorganic and methyl mercury in fish

A method has been developed that uses a mixed solution of NaOH, NaCl and cysteine to digest fish. Inorganic Hg and MgHg were determined by cold vapor atomic absorption (CVAAS) using a selective reduction step with SnCl₂ and SnCL₂-solutions. Ethyl alcohol was satisfactorily used to prevent excessive foaming. Two optimum digestion procedures were established: (1) using a dry block heater at 90 °C for 1 hr and (2) overnight digestion at 25 to 30 °C. Differences between both were not significant (95%) in the range of 30 to 500 ng g^?1 Hg (II) and MeHg in fish. Reduction of the Hg signal due to matrix effects in different fish species was evaluated (95 to 60%). Oily fish, shrimp and lobsters gave the highest reduction. Internal calibration by addition of Hg standards are strongly recommended when exact determinations are needed. The detection limit obtained was near 10 ng g^?1. Signals were linear in the concentration range studied (30 to 500 ng g^?1). Accuracy of analyses was in the order of 5% or better, with a relative standard deviation of 5%. The method could be applied to other environmental matrices: hair, urine and blood, with some modifications.