L’utilisation de molécules stimulatrices des défenses des plantes (SDP), également appelées inducteurs de résistance, constitue une alternative potentielle aux traitements fongicides conventionnels pour combattre les maladies dues à des champignons phytopathogènes. Trois SDPs, le tréhalose (TR), l’acide salicylique (SA) et l’heptanoyl d’acide salicylique (HSA), un dérivé fonctionnel du SA, protègent le blé (Triticum aestivum L.) contre l’oïdium (Blumeria graminis f.sp. tritici), lorsqu’ils sont utilisés de façon préventive. La protection obtenue n’est pas liée à un effet fongistatique direct sur la germination des spores du champignon, mais à l’induction chez le blé de défenses qui diminuent le développement de la maladie. Notre travail consistait à caractériser les mécanismes de défense mis en jeu après applications foliaires de TR, de HSA et de SA chez un cultivar de blé sensible à l’oïdium. Un suivi de l’expression de gènes marqueurs de défense, réalisé par RTqPCR, a été mené en cinétique,depuis le traitement par les SDPs jusqu'à 4 jours après infection. Les activités enzymatiques correspondantes ont été également mesurées, et l’influence indirecte des SPDs sur le processus infectieux a été observé en microscopie in planta. Ainsi, les réactions de défense déclenchées par le TR, le SA et le HSA ralentissent l’évolution de l’infection, jouant respectivement sur la germination des conidies, structures infectieuses de Bgt, sur la germination du tube germinatif appressorial (AGT) et sur la proportion d’AGTs qui parviennent à pénétrer dans les tissus foliaires. Le TR est à l’origine d’une augmentation de l’expression des gènes codant pour une lipoxygénase, une protéine de transfert des lipides et une phospholipase C, impliquées dans le métabolisme lipidique et la signalisation, et de gènes codant pour des protéines PR comme les chitinases et PR1, tous connus comme marqueurs de défense. Ainsi, les réactions déclenchées par le TR correspondent à un effet inducteur de défenseplutôt qu’à une réaction de stress osmotique. Le HSA modifie particulièrement le métabolisme lipidique, en induisant fortement et pendant toute la cinétique, l’expression du gène codant pour la LOX et l’activité correspondante, aussi bien hors contexte infectieux qu’en contexte infectieux. Cette augmentation de l’activité LOX n’est pas retrouvée chez des feuilles traitées au SA et caractérise donc le HSA. L’importance des réactions observées avec le TR, le SA et le HSA, hors contexte infectieux et en présence de Bgt amène à discuter les effets éliciteurs et potentialisateurs de ces 3 SDPs. / The use of plant elicitors, also known as resistance inducers, is an alternative to conventional fungicides to control diseases caused by phytopathogenic fungi. Three resistance inducers, trehalose (TR), salicylic acid (SA) and heptanoyl salicylic acid (HSA), a functional derivative of SA, protect wheat (Triticum aestivum L.) against powdery mildew (Blumeria graminis f . sp. tritici) when applied prior to infection. The protection obtained is not linked to any direct fungistatic effect on the fungal spore germination, but to the induction of wheat defences that impair the development of the disease. Our work aimed at characterizing the defence mechanisms triggered after foliar applications of TR, HSA and SA in a wheat cultivar susceptible to powdery mildew. Monitoring of defence markers genes expression by RTqPCR was conducted during a time-course experiment from the treatment time until 4 days after infection. Corresponding enzyme activities were also measured, and the indirect influence of elicitors on the infectious process was observed by microscopy in planta. Thus, defence responses triggered by TR, SA and HSA slow the progression of the infection, respectively altering the germination of infectious structures such as conidia, the differentiation of appressorial germ tube (AGT) and the proportion of AGTs that manage to penetrate the epidermis. TR causes an increase in the expression of genes encoding a lipoxygenase, a lipid transfer protein and a phospholipase C, which are involved in lipid metabolism and signaling, and genes encoding for PR-proteins such as chitinases and PR1, all known as markers of defence. Thus, the reactions triggered by TR match with the ones triggered during induced defence rather than during osmotic stress response. HSA specifically targeted lipid metabolism, inducing strongly and throughout the time-course, the expression ofthe gene encoding LOX and the corresponding enzyme activity, both in infectious and non-infectious contexts. This increase in LOX activity was not found in leaves treated with SA and thus characterizes HSA mode of action. The importance of the reactions observed with TR, SA and HSA, in non-infectious conditions and in the presence of Bgt have to be considered regarding either elicitation or potentiation.

Nach den umweltpolitischen Zielsetzungen der Bundesregierung für einen integrierten Pflanzenschutz wird gefordert, Pflanzenschutzmittelapplikationen in Abhängigkeit von dem Befallsgeschehen umwelt- und ressourcenschonend durchzuführen. Der Praxis stehen bereits unterschiedliche Prognosemodelle zur Verfügung, welche das Befallsgeschehen verschiedenster Schaderreger simulieren und die dazu genutzt werden können eine Applikation optimal zu terminieren. Nach erfolgter Applikation sind Landwirte jedoch insbesondere auf ihre Erfahrung angewiesen, über die Notwendigkeit und den Zeitpunkt einer Folgeapplikation zu entscheiden. Das Ziel dieser Arbeit war deshalb die Entwicklung eines Modells zur Prognose der Wirkungsdauer von Fungiziden an Winterweizen gegen Zymoseptoria tritici. In Freiland- und Laborversuchen wurden die Wirkung und die Wirkungsdauer der Fungizide Bravo 500 (500 g/l Chlorthalonil), Epoxion (125 g/l Epoxiconazol) und Imbrex (62,5 g/l Fluxapyroxad) sowie der Mischung Epoxion+Imbrex mit wissenschaftlichen Methoden untersucht. Es wurden insgesamt neun Parzellenversuche in den Jahren 2012 bis 2014 im Freiland durchgeführt. An einem Standort erfolgte ab der Applikation zusätzlich zu den Bonituren wöchentlich eine Analyse der Wirkstoffgehalte in den Blättern. In Halbfreilandversuchen mit Winterweizen in Töpfen wurde außerdem die Wirkungsdauer der Fungizide in Abhängigkeit vom Niederschlag untersucht. Darüber hinaus wurde ein Halbfreilandversuch zur kurativen Wirkung von Epoxion und Imbrex in Abhängigkeit von der Latenzzeit von Z. tritici durchgeführt. Die Untersuchung der Einflüsse von Temperatur und Konzentration auf das Wachstum von Z. tritici und des Einflusses der Temperatur auf die Fungizide erfolgte mit Hilfe von Mikrotitertests im Labor. Für die Modellerstellung wurde eine Methode zur Berechnung der Fungizidwirkungsdauer entwickelt. Der Kernpunkt dieser Methode ist die Berechnung des Befallsanstiegs für die unbehandelte Kontrolle und die Fungizidvariante basierend auf den Ergebnissen der Parzellenversuche. Ist der Befallsanstieg beider Varianten identisch, wird die Wirkung als beendet betrachtet. Von diesem Zeitpunkt wird dann die dynamisch berechnete Latenzzeit von Z. tritici abgezogen. Auf diese Weise wird der Tag ermittelt, ab dem die Wirkung des Fungizids nicht mehr ausgereicht hat, um das Blatt vor einer Infektion zu schützen. Die berechnete Wirkungsdauer lag im Mittel je nach Fungizid zwischen 16,2 und 22,0 Tagen. Durch einen Vergleich der berechneten Wirkungsdauer mit der berechneten Infektionswahrscheinlichkeit für Z. tritici und den Wirkstoffgehalten in den Blättern zum berechneten Wirkungsende, konnte bestätigt werden, dass die mit dieser Methode berechnete Wirkungsdauer plausibel ist. Da die Methode auf allgemeinen epidemiologischen Grundlagen basiert, ist sie nicht nur für Z. tritici an Winterweizen, sondern auch auf jedes andere Pathosystem anwendbar. Die Modellierung der Fungizidwirkungsdauer erfolgte mit der berechneten Wirkungsdauer der Fungizide. Hierfür wurde die Methode der binären multiplen logistischen Regression angewendet. Mit dieser wurden die Temperatur, der Niederschlag und je nach Fungizid auch die relative Luftfeuchte als Wetterparameter mit signifikantem Einfluss auf die Wirkungsdauer identifiziert. In den Labor- beziehungsweise Halbfreilandversuchen konnte ein Einfluss von Temperatur und Niederschlag auf die Wirkungsdauer jedoch nicht nachgestellt werden. Es wurde deshalb geschlussfolgert, dass diese Faktoren in erster Linie den pflanzlichen Stoffwechsel und das Pflanzenwachstum beeinflussen. In zweiter Linie wird dadurch auch die Wirkungsdauer der Fungizide beeinflusst, wie zum Beispiel durch eine erhöhte Metabolisierung oder Verdünnung des Wirkstoffs. Insgesamt wurden drei verschiedene Modellfunktionen entwickelt. Jeweils eine für Fungizide mit “mittlerer”, “guter” und “ sehr guter” Wirkung. Damit ist es möglich das Modell nicht nur für die in dieser Arbeit untersuchten Fungizide zu nutzen, sondern für alle Fungizide und Fungizidmischungen, die sich in diese Gruppen einordnen lassen. Die Einordnung der Fungizide basiert auf den Fungizidbewertungstabellen der Pflanzenschutzdienste der Länder und wird jährlich aktualisiert. Somit müssen keine aufwendigen Versuche durchgeführt werden, um das Modell zu aktualisieren. Auch eine verringerte Wirkungsdauer, wie sie zum Beispiel durch Resistenzen entsteht, wird auf diese Weise direkt berücksichtigt. Das entwickelte Modell trägt den Namen OPTIFUNG und prognostiziert in Abhängigkeit der Wetterparameter Temperatur, Niederschlag und relativer Luftfeuchte die Wirkungsdauer von Funigziden. Das Modell OPTIFUNG soll mit den Modellen SIMONTO (Ontogenesemodell) und SEPTRI (Zymoseptoria tritici-Modell) verknüpft und auf der Internetplattform www.isip.de zugänglich gemacht werden. Somit kann der Nutzer zukünftig informiert werden, wenn entweder eine neue, nicht mit behandelte Blattetage infiziert wird oder die Wirkungsdauer abgelaufen ist und die Wahrscheinlichkeit für eine neue Infektion mit Z. tritici groß ist. In dieser Arbeit wurde am Beispiel von Z. tritici eine allgemeingültige Methode zur Berechnung der Wirkungsdauer von Fungiziden entwickelt. Das daraus entstandene Modell ist durch die Bildung von Wirkungsgruppen für weitere Fungizide anwendbar und bietet dem Nutzer in Zukunft eine objektive und dynamische Unterstützung bei der Planung der Fungizidapplikationen.

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Chemical control of diseases is the most used practice in wheat. The increase in mineral nutrition with foliar fertilizers has been a promising alternative for the plant resistance against leaf diseases. However, foliar fertilizers have been applied in association with fungicides and can change the performance of the fungicide on diseases control. This study aimed to evaluate the applicability of foliar fertilizer in combination with azoxystrobin + cyproconazole fungicide in wheat, based on biochemical, physiological , nutritional and yield parameters and determine the interference caused by the fertilizer on the evolution of leaf diseases in wheat. Isolated application rates of fertilizer and application in combination with the fungicide were performed on field and in the greenhouse works. The application of fertilizer increased the plant growth, green leaves and enhanced pigments levels (Chl a, Chl b and carotenoids). When the fungicide was applied with fertilizer, it reduced the stresses effect generated by fungicide application; it increased parameters of chlorophyll fluorescence, Fv / Fm and ETR. The levels of N, P and K in the leaves increased after fertilizer application. The fertilizer mixed with fungicide did not reduce the fungicide uptake. The diseases control was better when fertilizer was mixed with fungicide. The fertilizer applied alone had no effect on the diseases. Yield parameters were increased due to application of fungicide and foliar fertilizer. / O controle químico de doenças com o uso de fungicidas é umas das práticas mais empregadas na cultura do trigo em função da eficácia de controle. Incrementos na adubação mineral com fertilizantes foliares tem sido uma alternativa promissora em busca de maior resistência as doenças. Entretanto, fertilizantes foliares são comumente aplicados associados a fungicidas e podem interferir no desempenho de controle do produto. Este trabalho teve por objetivo avaliar a aplicabilidade do fertilizante foliar em mistura com o fungicida azoxistrobina + ciproconazol na cultura do trigo, com base em parâmetros bioquímicos, fisiológicos, nutricionais e produtivos e determinar a interferência causada pelo fertilizante sobre a evolução de doenças foliares na cultura. A partir da aplicação isolada de doses do fertilizante e da aplicação em associação com o fungicida foram realizados trabalhos a campo e em casa de vegetação. A aplicação do fertilizante refletiu em maior crescimento das plantas, manutenção de folhas verdes e maiores teores de pigmentos (Chl a, Chl b e carotenóides). Quando aplicado junto ao fungicida, o fertilizante teve efeito mitigatório dos estresses gerados pela aplicação do fungicida, com reflexos positivos em parâmetros da fluorescência da clorofila a, Fv/Fm e ETR. Houve aumento dos teores de N, P e K nas folhas em função do fertilizante foliar. Não houve redução da absorção do ingrediente ativo azoxistrobina + ciproconazol em mistura com o fertilizante. Houve melhor resposta de controle das doenças em função da mistura do fertilizante com o fungicida. O fertilizante isolado não teve nenhum efeito sobre as doenças. Parâmetros produtivos foram incrementados em função da aplicação do fungicida e do fertilizante foliar.

Le blé dur (Triticum durum Desf, BD), tout comme le blé tendre (Triticum aestivum L. em Thell, BT), est une céréale très touchée par la septoriose, une maladie foliaire causée par le champignon hémibiotrophe Zymoseptoria tritici. D'une part, ce présent travail a permis d'étudier l'interaction compatible du blé-Z. tritici. L'étude de l'interaction compatible chez les pathosystèmes BD/St-08-46 et BT/TO1193 a révélé l'induction des mêmes voies de défense chez les deux pathosystèmes étudiés mais avec différentes intensités. Ensuite, l'étude de l'interaction de Z. tritici avec un cultivar résistant de blé dur a mis en évidence l'association de résistance au champignon est liée à l'inhibition de la pénétration directe, la sporulation et l'activité des enzymes fongiques de dégradation des parois cellulaires de la plante (endo-β-1,4-xylanase, endo-β-1,3-glucanase et protéase). Ces derniers sembleraient être fortement liés à la sévérité de Z. tritici aussi bien chez le dur que le blé tendre. En plus, on a pu démontrer moyennant des analyses qRT-PCR l'intervention de plusieurs gènes dans la résistance du blé dur à la septoriose à savoir les gènes PR2 (β-1,3-glucanase), Chi 4 precursor (précurseur de chitinase de la classe IV), Pox (peroxydase), Msr (méthionine sulfoxide réductase) et Bsil1 (inhibiteur de protéases). D'autre part, le potentiel des stimulateurs de défenses naturelles de plantes (SDPs) à protéger aussi bien le blé dur que le blé tendre contre les maladies fongiques a été évalué. Trois extraits naturels dont les matières actives sont l'acide ascorbique (AA), des oligosaccharides de parois cellulaires de plantes (Oligos) et algue brune (Ascophyllum nodosum, A. nod) ont été testés pour la première fois sur le blé. Leur effet antifongique (direct) ainsi que l'effet inducteur des mécanismes de défense du blé (indirecte) ont été bien caractérisés moyennant des analyses moléculaires, biochimiques et cytologiques. En effet, seul l'AA a montré un effet direct sur la germination des spores et la croissance mycélienne du Z. tritici associé à l'induction des mécanismes de défense du blé. Par contre, les protections obtenues par l'Oligos et l'A. nod semblent être exclusivement liées à leurs propriétés inductrices de la défense qui ont permis de ralentir le développement du champignon ainsi que d'inhiber l'activité des CWDEs fongiques et la sporulation. D'ailleurs, il s'est avéré que les SDPs testés sembleraient agir sur les mêmes mécanismes de défense chez les deux espèces de blé. Ils pourraient induire l'activation (i) des protéines PR, (ii) les enzymes antioxidants (peroxydase et catalase), (iii) les protéines PAL et LOX (enzymes clés de la voie des phénylpropanoides et la voie des octadécanoides, respectivement) et (iv) l'accumulation des H₂O₂ et le dépôt des polyphénols au niveau des sites de pénétration du champignon, ont été mis en évidence. Egalement, ils pourraient emprunter les mêmes voies utilisées par le cultivar résistant Salim en réponse à l'infection par le champignon et pourraient même induire une réponse plus importante des gènes de défense du blé dur tels que les gènes PR2, Pox, Msr, ATPase et Bsil. De même, deux applications (préventif et curatif) des SDPs testés a révélé une protection intéressante contre la maladie associée, dans le cas de l'A. nod et des AA, à une augmentation de la teneur en chlorophylle et l'amélioration de la quantité et de la qualité du rendement du cultivar sensible Karim. Par contre, pour le cultivar résistant Salim l'application des SDPs semble être inutile. En conclusion, l'application des SDPs au bon stade et avec les bonnes concentrations sur des cultivars sensibles pourraient aboutir à des résultats d'efficacité et rendement similaires à celles des cultivars résistants. Ainsi, elle pourrait remplacer l'utilisation des cultivars résistants, surtout avec l'absence de cultivars complètement résistants disponibles pour l'agriculteur en Tunisie. / The durum wheat (Triticum durum Desf, DW) as well as the bread wheat (Triticum aestivum L. em Thell, BW) is strongly affected by septoria leaf blotch (STB) caused by the hemibiotrophic fungus Zymoseptoria tritici. First, the present work was used to study of the compatible interaction wheat-Z-tritici. The study of the compatible interaction among pathosystems BD/St-08-46 Z-tritici strain an BT/TO1193 Z-tritici strain revealed the induction of defense pathways in both studied pathosystems, but with slight differences. Then, the study of the interaction of Z. tritici with a resistant durum wheat cultivar showed the fungus resistance of association is related to the inhibition of the direct penetration, sporulation and the avtivity of the fungal enzymes degrading plant cell walls (endo-β-1,4-xylanase, endo-β-1,3-glucanase and protease). They seem to be strongly related to the severity of Z. tritici in both BW and DW. In addition, this study revealed the involvement of several genes in the resistance of DW against Z. tritici such as PR2 genes (β-1,3-glucanase), Chi 4 precursor (precursor of Class IV chitinase), Pox (peroxidase), Msr (methionine sulfoxide reductase) and Bsil (protease inhibitor). On the other hand, the potential of resistance inducers (RIs) to protect BW and DW against STB disease was evaluated. Three natural extracts based on ascorbic acid (AA), plant cell wall oligosaccharides (Oligos) and brown algae (Ascophyllum nodosum, A. nod.) were tested for the first time on wheat. Their antifungal effect (direct) and the effect of inducing wheat defense mechanisms (indirect) have been well characterized through molecular, biochemical and cytological. We recorded that only AA exhibited a direct effect on spore germination and hyphal growth of Z. tritici associated to the induction of wheat defense mechanisms. However, conferred protection by Oligos and A. nod appears to be exclusively related to their plant defense inducing properties witch promoted the decrease of fungal CWDE activities and sporulation. Moreover, tested SDPs seem to enhance same defense pathways in both wheat species. They could induce the activation of (i) PR proteins, (ii) the antioxidant enzymes (catalase and peroxidase), (iii) the protein PAL and LOX (key enzymes of the phenylpropanoid and octadecanoid pathways, respectively) and (iv) the cytological accumulation of H₂O₂ and polyphenols, were highlighted. Also, they seem to use same pathways involved in durum wheat resistance mecanisms and may even induce a higher response of defense-related genes as PR2, Pox, Msr, ATPase, and Bsil. In general, protection conferred by tested RIs seems to be dependent on their composition, but it remains constant whatever of the wheat species. Similarly, in filed tested RIs conferred as interesting protection against STB associated, in the case of the A. nod and AA, with increased chlorophyll content and improving yield quantity and quality of the susceptible cultivar Karim, while in the resistant cultivar Salim, the application of RIs seems to be useless. In conclusion, protection conferred by tested RIs seems to be dependent on their composition, but it remains constant whatever of the wheat species. The use of RIs may improve the resistance level and yield of susceptible cultivars in order to obtain similar results to the resistant cultivars. Thus, it could replace the use of resistant cultivars especially with the lack of completely resistant cultivars available to farmers in Tunisia.

Master of Science / Department of Plant Pathology / William W. Bockus / The effects of tan spot on lipid profiles in wheat leaves were quantified by mass spectrometry. Inoculation with Pyrenophora tritici-repentis significantly reduced the amount of many lipids, including the major lipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), in leaves over time. These two lipids accounted for 89% of the mass spectral signal of detected lipids in wheat leaves. Reductions in amounts of lipids were at much higher rates over time for susceptible cultivars compared with resistant cultivars. Furthermore, data show that cultivars resistant to tan spot have different lipid profiles when compared with susceptible cultivars. Resistant cultivars had more MGDG and DGDG than susceptible ones, even in non-inoculated leaves. Using linear models that were fit to data, non-inoculated cultivars with a rating of 1 (highly resistant to tan spot) were calculated to have 66.1% more MGDG and 52.7% more DGDG signal than cultivars with a rating of 9 (highly susceptible). These latter findings are indirect evidence that the amounts of some lipids in wheat leaves may be determining factors in the resistance response of cultivars to tan spot.

During recent years the principles of Mendelism have been used extensively in the production of the new types of plants possessing resistance to various diseases. Results of this mode of attacking the disease problem have been very favorable. Old varieties are gradually giving way to newer types equal to or exceeding in quality and productivity as well as possessing resistance to one or more diseases. Loose smut (U. tritici) in wheat, while not as serious a problem in Utah as the covered smut (T. tritici), according to Tapke (14) has caused an average annual loss of between 50,000 and 100,000 bushels of wheat. these data shown in figure 1 are for the period 1917 to 1926, inclusive. The various methods advocated for the control of loose smut (U. tritici), with the exception of the use of resistant varieties and hot water treatments, either have been impradtical of application or have been ineffective in control or both (14). The modified hot water treatment of Freeman and Johnson (4), has generally been the method recommended. While this method is effective if properly executed, it is rather complicated and tedious to apply, especially for farmers who are not usually properly equipped. Because of this and the fact that the disease frequently escapes observation, seed treatment for the control of loose smut (U. tritici) is seldom practiced; as a result the smut is allowed to go unchecked. The development of a resistant variety possessing the adaptability and desirable characteristics of our locally-grown spring wheats would be a decided advantage to the farmers in combating the disease.

Mycosphaerella graminicola (anamorph Septoria tritici) causes Septoria tritici blotch, a globally important disease of winter wheat. Resistance and pathogenicity generally vary quantitatively. The pathogen reproduces both sexually and asexually, and the pathogen population is highly genetically variable. Several unresolved questions about the epidemiology of this pathosystem are addressed by this research. Among them are whether cultivar-isolate specificity exists, how partial host resistance affects pathogen aggressiveness and sexual reproduction, and how host genotype mixtures influence epidemic progression and pathogenicity. At its release in 1992, the cultivar Gene was highly resistant to M. graminicola, but that resistance had substantially dissolved by 1995. Six of seven isolates collected in 1997 from field plots of Gene were virulent to Gene seedlings in the greenhouse, while 14 of 15 isolates collected from two other cultivars were avirulent to Gene. Gene apparently selected for strains of M. graminicola with specific virulence to it. In a two-year experiment, isolates were collected early and late in the growing season from field plots of three moderately resistant and three susceptible cultivars, and tested on seedlings of the same cultivars in the greenhouse. Isolates were also collected from plots of two susceptible cultivars sprayed with a fungicide to suppress epidemic development. Isolate populations were more aggressive when derived from moderately resistant than from susceptible cultivars, and more aggressive from fungicide-sprayed plots than from unsprayed plots of the same cultivars. Over 5,000 fruiting bodies were collected in three years from replicated field plots of eight cultivars with different levels of resistance. The fruiting bodies were identified as M. graminicola ascocarps or pycnidia, or other. In all three years, the frequency of ascocarps was positively correlated with cultivar susceptibility, as measured by area under the disease progress curve, and was also positively associated with epidemic intensity. For three years, four 1:1 mixtures of a moderately resistant and a susceptible wheat cultivar were planted in replicated field plots. Isolates from the plots were inoculated as bulked populations on greenhouse-grown seedlings of the same four cultivars. Mixture effects on disease progression varied among the years, and were moderately correlated with mixture effects on pathogenicity. / Graduation date: 2002

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Submitted by JULIANA TEODORA DE ASSIS REGES null (juliana.teodora@bol.com.br) on 2016-10-21T00:48:25Z No. of bitstreams: 1 Reges-Tese-DR.pdf: 2852424 bytes, checksum: e86c4e7420b8cf40a8dcc1e723431082 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-10-27T16:48:41Z (GMT) No. of bitstreams: 1 reges_jta_dr_jabo.pdf: 2852424 bytes, checksum: e86c4e7420b8cf40a8dcc1e723431082 (MD5) / Made available in DSpace on 2016-10-27T16:48:41Z (GMT). No. of bitstreams: 1 reges_jta_dr_jabo.pdf: 2852424 bytes, checksum: e86c4e7420b8cf40a8dcc1e723431082 (MD5) Previous issue date: 2016-08-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Na primeira parte de nosso estudo descrevemos a associação de Pyricularia pennisetigena e P. zingibericola a gramíneas invasoras de áreas de trigo no centro-sul do Brasil. Desconhece-se, entretanto, qual o potencial de P. pennisetigena e P. zingibericola como patógenos de poáceas de interesse econômico para a agricultura brasileira. Dessa forma, objetivamos caracterizar o espectro de patogenicidade de P. pennisetigena e P. zingibericola a braquiária, cevada e trigo e compará-lo com P. grisea e com a espécie até recentemente descrita como P. oryzae patotipo Triticum, de ocorrência generalizada no agroecossistema brasileiro. Foram testados 20 isolados de Pyricularia spp. obtidos de amostras de folhas infectadas de plantas invasoras de campos de trigo. A classificação dos isolados em espécies distintas de Pyricularia foi efetuada usando-se filogenia molecular baseada nas sequencias parciais dos genes actina e calmodulina. Pyricularia pennisetigena e P. zingibericola inoculadas em folhas, foram patogênicas a braquiária, cevada e trigo, com diferenças na agressividade entre as espécies. Pyricularia zingibericola foi a espécie mais agressiva a braquiária e cevada, enquanto P. pennisetigena foi a espécie mais agressiva em plantas jovens de trigo. Por outro lado, P. grisea isolada de Digitaria sanguinalis ou de Urochloa spp. não infectou trigo. A análise filogenética das regiões ACT e CAL concatenadas reproduziu as relações filogenéticas e a magnitude das diferenças descritas entre Pyricularia zingibericola, P. pennisetigena, P. oryzae patotipo Triticum e P. grisea. Urochloa spp. provavelmente representam fonte permanente de inóculo inicial dos patógenos da brusone do trigo entre as épocas de cultivo. Na segunda parte desta pesquisa, foi estudado a estrutura genética de populações do patógeno da brusone do trigo, o fungo Ascomiceto Pyricularia graminis-tritici sp. nov., no centro-sul do Brasil. Os objetivos foram responder às seguintes perguntas: As populações geograficamente distintas de P. graminis-tritici do trigo eram geneticamente subdivididas? Como se distribuía a diversidade gênica e genotípica entre as populações regionais de P. graminis-tritici, cerca de 30 anos após as primeiras epidemias de brusone no Brasil? Qual o sistema reprodutivo predominante de P. graminis-tritici no país? Conclui-se que não houve subdivisão na maioria das populações geográficas contemporâneas de P. graminis-tritici do trigo, indicando mecanismo eficiente de fluxo gênico. A magnitude e a extensão do fluxo gênico entre populações geográficas de P. graminis-tritici do trigo, o sistema reprodutivo predominantemente sexual, aliados a alta diversidade genética do fungo, indicam um patógeno com alto potencial evolutivo no agroecossistema brasileiro. Outras espécies de poáceas hospedeiras com ampla distribuição geográfica no Brasil, como por exemplo, o capim-braquiária (Urochloa brizantha), podem ter importante papel no ciclo de vida e na biologia reprodutiva, na sobrevivência e na dispersão do inóculo de P. graministritici a curta e longa distâncias, mantendo as populações geográficas do patógeno conectadas. Os padrões de fluxo gênico e genotípico entre populações hospedeiro-distintas do patógeno reforçam a hipótese de que a brusone do trigo pode ter tido origem de novo a partir de populações endêmicas de P. graminis-tritici que infectam outras espécies de poáceas (nativas ou invasoras de áreas de trigo) no país. / In the first part of our study we described the association of Pyricularia pennisetigena and P. zingibericola with invasive grasses from wheat cropping areas in South-Central Brazil. However, the potential of P. pennisetigena and P. zingibericola as pathogens to poaceous plants of economic interest for Brazilian agriculture is still unknown. Therefore, this study aimed to characterize the pathogenicity spectrum of P. pennisetigena and P. zingibericola to signal grass, barley and wheat and compare with P. grisea and with the species until recently described as P. oryzae pathotype Triticum, of widespread occurrence in the Brazilian agroecosystem. Twenty isolates of Pyricularia spp. obtained from samples of infected leaves of weed species in wheat fields were tested. Classification of isolates into different species of Pyricularia was performed using molecular phylogeny based on the partial actin and calmodulin gene sequences. Pyricularia pennisetigena and P. zingibericola inoculated on leaves were pathogenic to signal grass, barley and wheat, with differences in aggressiveness between species. Pyricularia zingibericola was the most aggressive species to signal grass and barley, while P. pennisetigena was the most aggressive species to young plants of wheat. On the other hand, P. grisea isolated from Digitaria sanguinalis or Urochloa spp. did not infect wheat. Phylogenetic analysis of the concatenated regions ACT and CAL reproduced the phylogenetic relationships and the magnitude of the differences reported between Pyricularia zingibericola, P. pennisetigena, P. oryzae pathotype Triticum and P. grisea. Urochloa spp. probably represents a permanent source of initial inoculum of the wheat blast pathogens between growing seasons. In the second part of this research, we studied the genetic structure of populations of the wheat blast pathogen, the Ascomycete fungus Pyricularia graminis - tritici sp. nov., in the South-Central Brazil. The objectives were to answer the following questions: The geographically distinct populations of P. graminis-triticiwheat were genetically subdivided? How gene and genotypic diversity were distributed among regional populations of P. graminis-tritici about 30 years after the first outbreaks of wheat blast in Brazil? What is the predominant reproductive system of P. graminis-tritici in the country? We concluded that there was no subdivision among most of the contemporary geographical populations of Pyricularia graminis- tritici from wheat fields, indicating an efficient mechanism of gene flow. The magnitude and extent of gene flow among geographical populations of P. graminis-tritici, the predominantly sexual reproductive system, coupled with high genetic diversity of the fungus, indicated a pathogen with high evolutionary potential in the Brazilian agro-ecosystem. Other species of poaceous hosts with wide geographic distribution in Brazil, for example, signal grass (Urochloa brizantha) can play an important role in the life cycle and reproductive biology, survival and spread of inoculum of P. graminis- tritici at short and long distances, keeping the geographical populations of the pathogen connected. The patterns of gene and genotypic flow between host-distinct populations of the pathogen reinforce the hypothesis that the wheat blast may had a de novo origin from endemic populations of P. graminis-tritici infecting other poaceous species (native or invasive WRwheat areas) in the country.