Since the beginning of mycology, studies of species concept in fungi have been mainly based on morphology, partially due to the history of mycology as part of botany. Current advances in biochemical and molecular research have provided mycologists with powerful tools that can be used for delineation of fungal taxa. Recently, an integrated approach to fungal taxonomy involving both morphological and molecular traits has found a wide application for identification of species, especially in anamorphic (mitosporic) fungi. In this thesis, I have tried to use this approach for identification of species units in two rather unrelated groups of organisms. One of the case studies concerned Colletotrichum acutatum – a worldwide economically important plant pathogenic anamorphic fungus, which is exhibiting a high level of variation in both morphological and molecular features. This fungus has been intensively studied during the past decades, and several attempts have been made to find reliable markers to separate it from other closely related species of Colletotrichum. The second case studied in this thesis was Mycelia Sterilia – an artificial group of fungi, which are deficient in production of spores of any kind, therefore lacking the main morphological feature used for assigning them to any certain fungal taxon below class level. Due to this peculiarity, Mycelia Sterilia have usually been neglected, and currently there is no working species concept applicable to these fungi. In this work, I have tried to clarify the relationships among C. acutatum and several other anamorphic (C. gloeosporioides and C. fructigenum) and teleomorphic (Glomerella acutata, G. cingulata and G. miyabeana) taxa that are closely related to each other. For this purpose, examination of morphological traits was employed in combination with comparison of DNA sequencing data from three loci and subsequent phylogenetic analysis. As a result, re-description of C. acutatum and separation of (at least) two new species was proposed. For studies of Mycelia Sterilia, a large collection of sterile strains was screened in search for biologically interesting organisms. One novel pathogen has been found, and two plant growth promoting strains with antifungal properties were selected. Attempt for tentative identification of those fungi was made based on their morphological, physiological and molecular features. Sequencing of several genes and spacers of the ribosomal DNA array revealed that the plant pathogenic strain is closely related to the teleomorphic basidiomycete genus Campanella, and plant growth-promoting isolates were identified as belonging to the anamorphic ascomycete genus Phoma. However, assigning the sterile strains to any existing species was not possible. The main conclusion of the thesis is that species in anamorphic fungi should be defined based on a combination of morphological and molecular methods, both equally important, involving as many aspects of fungal biology as is possible at our current state of knowledge.

No description available.

Lupines (Lupinus albus L.) can provide high levels of good quality protein for human and animal nutrition. Unlike soybeans, lupine seeds do not need to be processed before consumption. Being a member of the legume family, lupines improve soil structure and fertility. Lupines also have the advantage of being able to grow in cooler climates and in fields of lower fertility than soybean. Lupine production is relatively new in Eastern Canada and new diseases limit production in this region. In 1990, a Phoma sp. was isolated from diseased lupine in Quebec and Nova Scotia. This research was undertaken to acquire further knowledge about this lupine pathogen. The morphological characteristics of this fungus do not exactly fit the description of any other Phoma sp., but it is very close to P. pinodella. This Phoma sp. on lupines may be a new variety of P. pinodella affecting lupine in particular. In vitro, mycelium grew over a wide range of temperatures (5°--35°C), the optimal temperature being 25°C. Spore germination occurred under different conditions of temperature, from 10°C to 35°C, the optimum being 25°C. Spores germinated at relative humidities from 94% to 100%, (-7.027 to 0 MPa) the optimum being between 98% and 100% (-2.768 to 0 MPa). In controlled environment, disease symptoms appeared over a wide range of leaf wetness durations (8 h--36 h) and temperature regimes (15°C--30°C). The most extensive disease symptoms occurred following 36 hours of leaf wetness duration at 30°C. This Phoma sp. survived over winter in infected stubble of lupines of the previous year crop. The infected crop residue may be another source of inoculum of this seedborne pathogen.

Leptosphaeria maculans and L. biglobosa co-infect winter oilseed rape plants to cause phoma stem canker disease. The sexual spores of both species are produced in pseudothecia on infected winter oilseed rape stem debris after harvest and this is the most important source of inoculum for infection of newly-emerged plants in autumn. Field experiments investigated the effects of host resistance on proportions of pathogens Leptosphaeria maculans and L. biglobosa in most leaf and stem tissues during 2011/2012, 2012/2013 and 2013/2014 growing seasons and on the pseudothecial development on crop debris on nine winter oilseed rape cultivars; cvs Adriana (Rlm4 + quantitative resistance (QR)), Bilbao (Rlm4), Capitol (Rlm1), Drakkar (no R gene against L. maculans), DK Cabernet (Rlm1 + (QR), Es-Astrid (QR), Excel (Rlm7), Roxet (Rlm7) and NK Grandia (QR). Cultivars with a combination of R-gene resistance and QR [Adriana (Rlm4 + QR), DK Cabernet (Rlm1 + QR)] or cultivars with only QR [(Es-Astrid and NK Grandia)] had more numbers of L. maculans leaf spots than other cultivars in autumn but less stem canker damage. There was greater number of L. biglobosa leaf spots on leaves of cvs Roxet and Excel with resistance gene Rlm7 than those of other cultivars and later more L. biglobosa DNA was detected in their stems than in those of other cultivars. In all cultivars in the three growing seasons, there was a greater amount of L. biglobosa DNA than L. maculans DNA in basal stem canker and upper stem lesions. The cv. Drakkar (no R gene against L. maculans) was susceptible in all three growing seasons, with a great number of L. maculans and L. biglobosa leaf spots and severe stem cankers. There were four cultivars (Adriana, Bilbao, Drakkar and NK Grandia) selected for the study of pseudothecial development under natural conditions with different times of exposure and in controlled environment conditions (20oC, continuous wetness). The fastest development was on the susceptible cv. Drakkar (no R gene against L. maculans), followed by Bilbao (Rlm4), Adriana (Rlm4 + QR) and NK Grandia (QR) for stem base cankers and upper stem lesions in controlled conditions. Results for pseudothecial development on stems of the nine winter oilseed rape cultivars that were exposed in natural conditions at Bayfordbury support the controlled environment results, with pseudothecia on stems of cultivars with a combination R-gene and QR consistently maturing later than those on other cultivars, regardless of the weather conditions in three growing seasons. Ascospores produced in pseudothecia are the primary inoculum that initiate phoma stem canker epidemics in autumn. Ascospore release was later in autumn 2011 than in autumn/winter 2012/2013 or 2013/2014 because of dry weather. The pattern of ascospore release had a peak, or maximum in autumn/winter 2011/2012 (4958 spores/m-3 on 22 Jan 2012) and several maxima in autumn/winter 2012/2013 (1307 spores/m-3 on 5 Nov 2012, 1291 spores/m-3 on 15 Nov 2012, 1306 spores/m-3 on 25 Dec 2012) and 2013/2014 (4575 spores/m-3 on 27 Oct 2013, 4619 spores/m-3 on 3 Nov 2013, 3674 spores/m-3 on 9 Nov 2013, 3521 spores/m-3 on 12 Dec 2013). Results from the qPCR showed that ascospores of L. maculans were released earlier than ascospores of L. biglobosa at Bayfordbury in the 2013/2014 growing season. There were differences in phenotype of isolates amongst ninety-five isolates of L. maculans and forty-eight isolates of L. biglobosa obtained from different sources (phoma leaf spots, upper stem lesions or basal stem cankers) on different cultivars. Cotyledon tests showed that the resistance genes Rlm4, Rlm5, Rlm6 and Rlm7 are still effective in England. Most isolates from phoma leaf spots carried avirulent AvrLm4 (39 isolates; 97.5%), AvrLm5 (39 isolates; 97.5%) and AvrLm6 alleles (36 isolates; 90%) and all 40 isolates carried the avirulent allele AvrLm7 (100%). Fewer isolates from basal stem cankers carried avirulent AvrLm4 (4 isolates, 16.7%) or AvrLm6 alleles (16.7%) but all 24 isolates carried the avirulent AvrLm7 (100%). Fewer isolates from upper stem lesions carried the avirulent AvrLm4 allele (5 isolates; 16.1%), but 15 isolates carried avirulent AvrLm5 (48.4%), 21 isolates carried AvrLm6 (67.7%) and all 31 isolates carried AvrLm7 (100%). By contrast, all isolates were virulent against Rlm1, Rlm2, Rlm3 and Rlm9. This knowledge, together with knowledge about R genes present in current winter oilseed rape cultivars, should be useful to provide recommendations on cultivar selection to growers based on regional frequencies of avirulent alleles of Avr allele genes in the L. maculans populations (races) and improved understanding of the race structure of L. maculans. There is a need to further investigate any R genes that operate against L. biglobosa (possibly from wild brassicas) and to study if any R genes or QR can provide resistance against both L. maculans and L. biglobosa.

No description available.

No description available.

No description available.

Une méthode de lutte efficace contre le phoma du colza est l'utilisation de variétés résistantes mais l'efficacité des résistances spécifiques est peu durable. D'autres méthodes de lutte peuvent être mobilisées : lutte chimique et contrôle cultural (adaptation du travail du sol, de la date et de la densité de semis, ou de l'azote organique). La combinaison spatiale et temporelle des méthodes de lutte génétique, culturale et chimique dans le paysage permet de mieux contrôler la maladie et de préserver l'efficacité des résistances spécifiques et la rentabilité économique, tout en répondant aux exigences environnementales et toxicologiques de la production intégrée. Etant données les échelles d'espace et de temps considérées et la multiplicité des techniques, il est difficile de tester expérimentalement ces stratégies. SIPPOM-WOSR a donc été développé, a Simulator for Integrated Pathogen Population Management, for Winter OilSeed Rape. Il est composé de 5 modules simulant la production d'inoculum, la dispersion des ascospores, la croissance du peuplement végétal et le rendement accessible, l'évolution de la structure génétique des populations pathogènes, et l'infection. Les sorties sont l'indice de sévérité de la maladie et les pertes de rendement associées, le rendement, la marge brute, le coût énergétique des pratiques et l'indice de fréquence de traitement, ainsi que la structure des populations pathogènes, sous l'effet de forces évolutives. Des expérimentations et analyses de données ont été réalisées pour acquérir des connaissances et compléter des formalismes, par exemple sur la récurrence de l'épidémie ou sur l'effet de la résistance quantitative sur la sévérité de la maladie. Une analyse de sensibilité a été réalisée pour étudier la sensibilité des différents modules aux variations des paramètres. Des exemples de simulation montrent l'intérêt de SIPPOM pour tester des stratégies de gestion intégrée et durable d'une maladie.

Common ragweed (Ambrosia artemisiifolia L., Asteraceae) is an annual herbacious weed that is a troublesome pest in carrot fields of Southwestern Quebec. Over the past decade, ragweed has shown resistance to linuron, the only herbicide that is registered for post-emergence control of this weed in carrots. In this research, the degree of resistance to linuron was investigated for a ragweed biotype collected from a carrot field in Sherrington, Quebec, where a decreased performance of linuron had been noted. This biotype showed a linuron resistance ratio (I50) of 9.09, when compared with ragweed plants collected from a field never sprayed with this herbicide. The fungal pathogen Phoma sp., which had been initially isolated from diseased ragweed leaves in 1993, was considered as a potentially effective biological agent for the control of common ragweed. The pathogenicity of Phoma sp. was re-evaluated during the current research. This fungus was found not to have any appreciable virulence towards common ragweed; it is likely that virulence was lost during storage. Hence, twenty other fungal species were isolated from diseased common ragweed plants and assayed to determine their potential as biological agents against this noxious weed. Varying dew periods, temperatures, spore concentrations, host growth stages, and different types of carrier were evaluated. Only isolates ATT#9, INNA4a, INNA4b, ATT#10, ISO#65, and ISO#68 were able to induce lesions on ragweed foliage at spore concentrations of 106 to 107 spores ml-1, but only after an extended dew period of 48 hrs. No interaction effects on the degree of ragweed control were found when combining five fungal isolates and the insect, Ophraella communa LeSage. However, a possible interactive effect was detected when the fungal isolate ISO#65 and linuron were used in combination.

To improve understanding of the effectiveness of host resistance against Leptosphaeria spp., three aspects of effectiveness of resistance were investigated. With focus on the major Rlm-mediated resistance against L. maculans, changes in effectiveness of Rlm7-mediated resistance to prevent initiation of disease epidemics at the leaf spot stage were investigated in winter oilseed rape field experiments at five sites in the UK over the period with the cropping seasons 2009/2010 - 2013/2014. L. maculans isolates virulent against Rlm7 were identified in the UK. This may be associated with observed changes in lesion phenotypes on the Rlm7 cultivars in field conditions. However, despite increased severity of phoma leaf spotting on Rlm7 cultivars, there was no associated increase in phoma stem canker severity at the end of the cropping seasons. The effectiveness of winter oilseed rape cultivars for control of phoma stem canker (caused by L. maculans or L. biglobosa) was affected by the coexistence of the two Leptosphaeria species in oilseed rape crops. Weather conditions influenced ascospore release of both species and favoured L. biglobosa ascospore release in 2011, resulting in subsequent increased L. biglobosa phoma leaf spotting and stem canker severity. However, coexistence of Leptosphaeria spp. on oilseed rape crops was affected by the cultivar resistance against L. maculans. CE experiments showed that there were interactions between the two Leptosphaeria spp. in planta. Their coexistence on B. napus was influenced by the different host responses that they trigger during host colonisation. Effects of increased temperature on effectiveness of resistance against L. maculans and on severity of symptoms by Leptosphaeria spp. on B. napus were investigated. Increased temperature affected both Rlm4- and Rlm7-mediated resistance, when assessed by phenotypic and molecular techniques. Increased temperature was associated with increased symptom severity, for both L. maculans and L. biglobosa lesions on plants. Cultivar quantitative resistance background increased effectiveness of resistance against phoma stem canker pathogens at increased temperature and should be deployed in in strategies for adaptation to climate change to avoid increased phoma stem canker epidemics in the future.