Histological analyses of the host response of two aspen genotypes to wounding and inoculation with Hypoxylon mammatum

Ramets derived from root sprouts of two quaking aspen (Populus tremuloides) parents were either mechanically wounded or wounded and inoculated with mycelium of Hypoxylon mammatum. Female aspen parents were considered either resistant or susceptible based on a 30-year field trial of their open-pollinated progenies that had 21% and 93% mortality, respectively, caused by H. mammatum. Each stem was wounded twice at the base and in the nonlignified zone. Samples were taken 5 mm above the site of wounding at 7 and 14 days. Histochemicals used were phloroglucinol-HCl and Sudan Black B to detect lignin and suberin, respectively. Thin sections of the resistant aspen ramets showed intensive staining phloroglucinol-HCl, which was localized along both sides of the wound margin. Collenchyma callus was well developed by day 7 and was derived from the phloem tissue internal to the cell walls staining positive for phloroglucinol-HCl, near the vascular cambium. In contrast, the tissues of susceptible aspen ramets were less stained, the stained cells were less scattered and less collenchyma callus had formed than on the resistant ramets. The presence of the fungus increased the amount of staining observed with phloroglucinol-HCl and delayed wound closure in both aspen genotypes. No distinguishing pattern could be identified between the two aspen genotypes with respect to suberin formation. When comparing stem response to phloroglucinol-HCl with respect to the tissue type on the same stem (succulent versus woody), the inoculation of older woody tissue resulted in a more defined host response and thus were better in separating the two aspen genotypes.     

Biology of Septoria musiva and Marssonina brunnea in hybrid Populus plantations and control of Septoria canker in nurseries

Spore dispersal and symptom development of Septoria musiva and Marssonina brunnea were studied in hybrid poplar plantings in the north central United States. Ascospores or conidia were present within the plantings throughout the growing season. Results of Septoria canker control in nurseries are discussed in relation to the biology of the fungus and use of resistant clones.     

Integrating food security into public health and provincial government departments in British Columbia, Canada

Food security policy, programs, and infrastructure have been incorporated into Public Health and other areas of the Provincial Government in British Columbia, including the adoption of food security as a Public Health Core Program. A policy analysis of the integration into Public Health is completed by merging findings from 48 key informant interviews conducted with government, civil society, and food supply chain representatives involved in the initiatives along with relevant documents and participant/direct observations. The paper then examines the results within the context of historic and international trends and theoretical models of food policy, community food security, and applied policy research. Public Health re-emerged as a driver of food security in BC—both as a key player and in positing the public’s health as a driver in food security and food systems. While Public Health’s lead role supported an increase in legitimacy for food security in BC, interviewees described a clash of cultures between Public Health and civil society. The clash of cultures occurred partly as a result of Public Health’s limited food security mandate and top down approach. Consequently civil society voice at the provincial level was marginalized. A social policy movement toward a new political paradigm—regulatory pluralism—calls for greater engagement of civil society, and for all sectors to work together toward common goals. A new, emerging policy map is proposed for analyzing the dynamics of food security and health promotion initiatives in BC.     

Long-term administration of the mycotoxin, ochratoxin A in chickens and the residues in the meat and animal feed]

A feeding trial was performed with chick broilers (cockerels). The feed with an addition of 850 micrograms ochratoxin A (OA) per kg was administered for six weeks. The feeding of the chicks stopped twelve hours before slaughter (in keeping with slaughter technology for chicks). Blood, liver and kidney samples were taken. At the end of trial the level of OA residues in the samples did not exceed 5 micrograms per kg. In other trials the dynamics of OA residues in the blood plasma of chicks was investigated after i.v. implantation at an amount of 2 and 20 micrograms per chick (1.5 kg lw.). An open two-compartment model was used to estimate toxicokinetic parameters. The half-time of elimination (t1/2(beta)) was about 3.3 hours. The high total clearance (CL) of 34.2 ml/min/kg lw. and apparent distribution volume (Vd(area)) of 9.8 l/kg lw. demonstrate rapid distribution to the tissues and rapid OA elimination. The results document that neither at a long-term intake of feed contaminated to the level of 850 micrograms OA per kg will the present hygienic limits of residues for foods be exceeded (5 and 20 micrograms per kg) if the principles of correct slaughter technology are observed. The blood of chicks used as feed is not an important source of OA in this case.     

Seedling response of two trembling aspen (Populus tremuloides) families to infection by Hypoxylon mammatum

Open-pollinated progenies from two trembling aspen (Populus tremuloides) families with a 30-year field history of 91% (putatively susceptible, PS) and 45% (putatively resistant, PR) mortality, respectively, caused by Hypoxylon mammatum, were grown in a greenhouse for 3 and 9 months. Seedlings were inoculated with two isolates of H. mammatum, representing high and low aggressiveness, through a stem wound. Beginning 4 days after inoculation, host responses were examined on 312 seedlings per family for a period of 5 weeks on 3- and 9-month-old seedlings. Significant differences in host responses were observed between the two isolates, with the more aggressive isolate allowing less callus formation, causing more tissue necrosis and producing longer cankers than the less aggressive isolate on both aspen families. Between-family difference was much greater than within-family difference for tissue necrosis, callus formation and canker length for both seedling ages. When the 3-month-old seedlings were challenged with H. mammatum, the PR family showed greater tissue necrosis, longer cankers, and less callus formation than the PS family. However, when the more lignifìed 9-month-old seedlings of the same families were inoculated, the PR seedlings had much less tissue necrosis, shorter cankers, more callus formation and less seedling mortality than the PS family. The results indicate that artificial inoculation of seedlings in a greenhouse can differentiate two aspen families at the seedling stage, but their correlation to field performance is highly dependent upon the seedling age. Host responses of older seedlings may be a better indicator of field performance.     

Morphological and molecular methods to identify butternut (Juglans cinerea) and butternut hybrids: relevance to butternut conservation

Butternut (Juglans cinerea L.) is a native, cold-tolerant, hard-mast species formerly valued for its nuts and wood, which is now endangered. The most immediate threat to butternut restoration is the spread of butternut canker disease, caused by the exotic fungus Sirococcus clavigignenti-juglandacearum Nair, Kostichka & Kuntz. Other threats include the hybridization of butternut with the exotic Japanese walnut (Juglans ailantifolia Carr.) and poor regeneration. The hybrids, known as buartnuts, are vegetatively vigorous, highly fecund, more resistant than butternut to butternut canker disease and difficult to identify. We review the vegetative and reproductive morphological traits that distinguish butternut from hybrids and identify those that can be used by field biologists to separate the taxa. No single trait was sufficient to separate butternut from hybrids, but pith color, lenticel size, shape and abundance, and the presence or absence of a notch in the upper margin of leaf scars, can be used in combination with other traits to identify butternuts and exclude most hybrids. In at least one butternut population, reduced symptoms of butternut canker disease were significantly associated with a dark barked phenotype. We also describe two randomly amplified polymorphic DNA (RAPD) markers that differentiate butternuts from hybrids based on DNA polymorphism. Together, these results should assist in the identification and testing of non-hybrid butternut for breeding and reintroduction of the species to its former habitats.     

The influence of inoculum density and environment on the development of potato blackleg

Significant increases in pre-emergence seedpiece decay and preemergence shoot infection were observed asErwinia carotovora var.atroseptica inoculum density increased. As inoculum density increased, a point was reached where virtually 100 per cent of the disease was expressed as preemergence decay and no typical postemergence blackleg occurred. Soil temperature and soil moisture markedly affected blackleg incidence, especially at low inoculum densities. Increasing soil temperature (from O°C to 30°C) and soil moisture (from 65 to 100% of field capacity) usually resulted in an increased total blackleg incidence. The effect of soil temperature and soil moisture appeared to be masked at high inoculum densities. Conditions such as low inoculum density and/or cool soil temperatures and low soil moistures which apparently slowed the rate of seedpiece decay usually increased the amount of postemergence blackleg, but also reduced the total amount of disease which occurred. It is suggested that conditions which are not optimal for the pathogen result in increased amounts of typical easily diagnosed postemergence blackleg expression, whereas conditions which favor the pathogen may reduce this phase of the disease but actually increase the total loss by increasing the amount of seedpiece decay and preemergence death of potato shoots.     

Bringing home the right to food in Canada: challenges and possibilities for achieving food security

We offer a critique of Canada's approach to domestic food security with respect to international agreements, justiciability and case law, the breakdown of the public safety net, the institutionalisation of charitable approaches to food insecurity, and the need for 'joined-up' food and nutrition policies. We examined Canada's commitments to the right to food, as well as Canadian policies, case law and social trends, in order to assess Canada's performance with respect to the human right to food. We found that while Canada has been a leader in signing international human rights agreements, including those relating to the right to food, domestic action has lagged and food insecurity increased. We provide recommendations for policy changes that could deal with complex issues of state accountability, social safety nets and vulnerable populations, and joined-up policy frameworks that could help realise the right to adequate food in Canada and other developed nations.     

Diversity analysis of provitamin A maize inbred lines using single nucleotide polymorphism markers

ABSTRACT

The success of a breeding programme can be determined by the level of genetic diversity that exists among breeding materials. This study was carried out to (i) determine the level of genetic diversity that exist among the collection of tropical provitamin A maize inbred lines and (ii) evaluate the genetic structure and divergence of provitamin A maize inbred lines. Forty-six advanced provitamin A inbred lines obtained from the International Maize and Wheat Improvement Centre (CIMMYT) and International Institute of Tropical Agriculture (IITA) were genotyped using 3047 single nucleotide polymorphism (SNP) markers. Genotyping was done following an Illumina Infinium HD Assay Ultra protocol. Eight six percent of the SNPs were polymorphic with the mean polymorphic information content of 0.36. Cluster analysis displayed two distinct clusters. The average pairwise genetic distance among the inbred lines was 0.60. The average gene diversity was 0.359. Variation was partitioned into among individuals (78%), among populations (12%) and within individuals (10%). Overall results suggest the inbred lines are genetically diverse. The key implication of this study is that selection should be done from genetically diverse inbred lines in order to exploit heterosis when developing hybrids.     

Immunoenzyme detection of the mycotoxin, ochratoxin A]

Indirect, enzymoimmunological assays of the mycotoxin ochratoxin A were developed. In this technique a polyclonal (rabbit) antibody to ochratoxin A was used, along with the other, peroxidase-labelled (pig anti rabbit) antibody. The sensitivity of this method ranged around 75 pg of ochratoxin A per pit. The range of calibration curve was from 10 to 1000 pg per pit. The cross reactions with other ochratoxins made 1.4% (ochratoxin C). The ELISA test of ochratoxin A can be used as an expeditious screening method for a preliminary examination of the greater number of samples.