La fonte des semis et la pourriture des racines font partie des maladies céréalières des grandes cultures au Québec. Elles sont causées par deux agents pathogènes, le Fusarium graminearum et le Bipolaris sorokiniana contaminant la semence céréalière, en particulier le blé et l’orge, ce qui entraîne à la fois une baisse de la levée et un rendement moins élevé. Des agriculteurs biologiques tentent de trouver un traitement de semences sans fongicide afin de lutter contre ces champignons, qui sont néfastes pour l’agriculture céréalière. Notre projet a comme objectif d’utiliser l’action oxydative de l’oxygène ou l’ozone humidifié pour engendrer un stress oxydatif afin de diminuer l’impact des deux agents pathogènes responsables de cette maladie, le F. graminearum et le B. sorokiniana, tout en préservant le pouvoir germinatif de ces semences. La dose en agent oxydant, le débit des gaz oxydants (ozone et /ou oxygène) ainsi que le temps d’exposition constituent les paramètres clés à optimiser pour ce traitement oxydatif et la cinétique de germination des graines céréalières traitées. Un tel traitement semblait prometteur pour la semence de blé. Il l’était toutefois un peu moins pour la semence d’orge en raison de son enveloppe assez rigide qui a rendu difficile la pénétration de l’ozone et l’oxygène. Pour remédier à ce problème, nous avons fait des tests préliminaires sur l’orge en utilisant la sonication par ultrasons comme prétraitement de l’orge avant le traitement oxydatif. Les résultats obtenus suggèrent qu’un tel traitement est prometteuret non négligeable afin d’optimiser notre traitement oxydatif et de permettre par la suite de réduire les agents responsables de la maladie sans nuire à la qualité des semences de céréales. Ce point a été abordé dans nos travaux par un test préliminaire sur l’orge, et cette approche s’annonce très prometteuse pour nos recherches futures. / Seedling blight and root rot are part of cereal diseases of field crops in Quebec. They are caused by two pathogens, Fusarium graminearum and Bipolaris sorokiniana, which contaminate the seed grain, especially wheat and barley, which causes both decreased, lift and lower performance. Organic farmers are trying to find a seed without fungicide treatment to fight against these fungi, which are harmful to cereal farming. Our project has as goal to use the oxidative action of oxygen or ozone moistened to cause oxidative stress in order to reduce the impact of the two pathogens responsible for this disease, F. graminearum and B. sorokiniana, while preserving the germinability of the seeds. The dose in oxidizing agent, the flow of oxidizing gases (ozone and/or oxygen) and the time of exposure are key parameters to optimize for this oxidative treatment and germination kinetics treated cereal seed. Such treatment looked promising for the seed of wheat. It was however a little less for the seed of barley because it’s fairly rigid envelope which made difficult the penetration of ozone and oxygen. To remedy this problem, we have preliminary tests on barley using sonication ultrasonic as pre-treatment of barley oxidative pre-treatment. The results suggest that, such treatment is promising and significant in order to optimize our oxidative treatment and subsequently, reduce the causative agents of disease without harming the quality of cereal seed. This point has been addressed in our work by a preliminary test on barley, and this approach looks very promising for our future research.

No description available.

No description available.

No description available.

Responses from pedigree selection for resistance to gibberella ear rot were assessed in four maize (Zea mays L.) populations, two selected after inoculation of Fusarium graminearum (Schwabe) macroconidia into the silk channel and two selected after inoculation into developing kernels. Responses were significant in both populations selected for silk resistance and in one of the populations selected for kernel resistance. Selection was more effective in later generations and genetic gains were associated with among-family selection but not with within-family selection. Results obtained here indicate that responses to selection could be more efficiently obtained by applying high selection intensities in advanced generations, by managing earlier generations as bulks and by reducing the number of plants per family. In another experiment, a wide sample of Argentine maize germplasm was evaluated for silk and kernel resistance to gibberella ear rot and to fusarium ear rot (caused by F. verticillioides (Saccardo) Nirenberg [=F. moniliforme (Sheldon)]. Several entries exhibited disease resistance in comparison with local check hybrids, particularly for fusarium ear rot, the most prevalent ear rot in Argentina. Results obtained in this study suggested the presence of general mechanisms controlling silk and kernel resistance to both diseases. In a supplementary study, viral diseases were surveyed in maize fields from the provinces of Ontario and Quebec in 1999 and 2000. Barley yellow dwarf was found in 1999. Sugarcane mosaic, maize dwarf mosaic and wheat streak mosaic were found in 2000. These diseases were not important for grain-maize planted in May, the most prevalent kind of maize crop in these provinces. Some of these diseases, such as sugarcane maize mosaic and maize dwarf mosaic were found important only in maize fields planted during or after the month of June, and this is of commercial relevance only for sweet corn.

Triticum aestivum (bread wheat), one of the most globally important cereal crops, is vulnerable to fusarium head blight (FHB). The disease is mainly associated with the pathogen Fusarium graminearum and generates yield losses and mycotoxin contaminated grains with low quality. One possible solution to overcome this problem is the production of FHB resistant wheat varieties by crossing with strongly resistant germplasm from either wheat or closely related species. Thinopyrum elongatum is a wild grass that carries genetic resistance to FHB on the long arm of its chromosome 7E (7EL). In the first part of this research project, five Th. elongatum accessions were characterized for their response to F. graminearum infection. In the second part, BC1F4 progeny derived from the cross CS-ph1b × CS-7E(7D) were characterized to better define the 7E fragments introgressed into the 7D chromosome. Progeny were screened with a series of known 7E-specific genetic markers and for their FHB resistance. Among the 43 wheat plants tested, twelve FHB resistant progeny were shown to carry a similar, smaller 7EL introgressed fragment based on genetic marker screening. To characterize further the introgressed 7EL fragments, additional 7EL-specific markers as well as 7DL-specific markers for homoeologous wheat sequences were designed. As neither wheat nor Th. elongatum genomes were fully sequenced at the time, this made the designing procedure challenging; a cross-walking strategy between wheat and Th. elongatum draft genomic sequences was used. Twelve pairs of markers for homoeologous sequence regions of 7EL and 7DL chromosomes plus six individual 7EL- and four 7DL-specific markers were successfully designed. Nine novel 7EL-specific markers were associated with the smallest 7EL fragment carrying FHB resistance. That smallest introgressed 7EL fragment replaced approximately half of the 7DL chromosome, based on the absence of 7DL markers in some progeny. The novel 7EL- and 7DL-specific markers as well as the proposed genetic order for novel and previously designed markers contributed greatly to the characterization of the introgressed 7EL fragments in the 7DL chromosome. Further analysis of progeny from the next generations of these plants and from other families will be required to confirm the results and possibly obtain much smaller 7EL fragments.

Fusarium head blight (FHB), caused mainly by Fusarium graminearum (teleomorph: Gibberella zeae), is one of the most damaging diseases of wheat. A ‘Brio’/‘TC 67’ spring wheat population was used to map quantitative trait loci (QTLs) for resistance to FHB, and to study the association of morphological and developmental characteristics with FHB resistance. Interval mapping (IM) detected a major QTL on chromosome 5AL for resistance to disease severity (type II resistance) and Fusarium-damaged kernels (FDK) under greenhouse and field conditions, respectively. Inconsistent QTL(s) was also detected on chromosome 5BS for disease severity and index using field data. The associations of plant height and number of days to anthesis were negative with disease incidence, severity, index, and deoxynivalenol (DON) accumulation data under field conditions. However, number of days to anthesis was positively correlated with disease severity (greenhouse) and FDK (field). Awnedness had a negative effect on FHB, namely the presence of awns resulted in less disease in the population. Spike threshability also affected FHB so that the hard threshable genotypes represented lower disease. Phylogenetic relationships of putative F. graminearum isolates from different sources were characterized using Tri101 gene sequencing data. Canadian and Iranian isolates clustered in F. graminearum lineage 7 (=F. graminearum sensu stricto) within the F. graminearum clade while the isolates received from CIMMYT, Mexico were placed in F. graminearum lineage 3 (=Fusarium boothii) within the Fg clade or Fusarium cerealis. The PCR assay based on the Tri12 gene revealed the presence of the NIV, 3-ADON, and 15-ADON chemotypes with 15-ADON being the predominant chemotype. While we did not find the NIV chemotype among the Canadian isolates, it was the predominant chemotype among the Iranian isolates. High variation in aggressiveness was observed among and within Fusarium species tested, with the isolates of F. graminearum sensu stricto being the most aggressive and the NIV chemotype being the least aggressive. The interactions between Fusarium isolates and wheat genotypes from different sources were investigated by inoculating isolates of F. graminearum sensu stricto and F. boothii on wheat genotypes. Significant differences were observed among the genotypes inoculated by single isolates. Results also showed significant interactions between Fusarium isolates and wheat genotypes. The F. boothii isolates from CIMMYT produced low disease symptom and infection on wheat genotypes regardless of the origin of the genotypes while F. graminearum sensu stricto isolates from Canada and Iran resulted in higher FHB scores.

Fusarium head blight (FHB), caused mainly by Fusarium graminearum (teleomorph: Gibberella zeae), is one of the most damaging diseases of wheat. A ‘Brio’/‘TC 67’ spring wheat population was used to map quantitative trait loci (QTLs) for resistance to FHB, and to study the association of morphological and developmental characteristics with FHB resistance. Interval mapping (IM) detected a major QTL on chromosome 5AL for resistance to disease severity (type II resistance) and Fusarium-damaged kernels (FDK) under greenhouse and field conditions, respectively. Inconsistent QTL(s) was also detected on chromosome 5BS for disease severity and index using field data. The associations of plant height and number of days to anthesis were negative with disease incidence, severity, index, and deoxynivalenol (DON) accumulation data under field conditions. However, number of days to anthesis was positively correlated with disease severity (greenhouse) and FDK (field). Awnedness had a negative effect on FHB, namely the presence of awns resulted in less disease in the population. Spike threshability also affected FHB so that the hard threshable genotypes represented lower disease. Phylogenetic relationships of putative F. graminearum isolates from different sources were characterized using Tri101 gene sequencing data. Canadian and Iranian isolates clustered in F. graminearum lineage 7 (=F. graminearum sensu stricto) within the F. graminearum clade while the isolates received from CIMMYT, Mexico were placed in F. graminearum lineage 3 (=Fusarium boothii) within the Fg clade or Fusarium cerealis. The PCR assay based on the Tri12 gene revealed the presence of the NIV, 3-ADON, and 15-ADON chemotypes with 15-ADON being the predominant chemotype. While we did not find the NIV chemotype among the Canadian isolates, it was the predominant chemotype among the Iranian isolates. High variation in aggressiveness was observed among and within Fusarium species tested, with the isolates of F. graminearum sensu stricto being the most aggressive and the NIV chemotype being the least aggressive. The interactions between Fusarium isolates and wheat genotypes from different sources were investigated by inoculating isolates of F. graminearum sensu stricto and F. boothii on wheat genotypes. Significant differences were observed among the genotypes inoculated by single isolates. Results also showed significant interactions between Fusarium isolates and wheat genotypes. The F. boothii isolates from CIMMYT produced low disease symptom and infection on wheat genotypes regardless of the origin of the genotypes while F. graminearum sensu stricto isolates from Canada and Iran resulted in higher FHB scores.