No description available.

Zugl.: Kiel, Univ., Diss., 2007

University, Diss., 2005--Kiel.

No description available.

Orientador: Paulo Cezar Ceresini / Resumo: 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 aP. grisea e com a espécie até 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 e... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In the first part of our study we described the association Pyricularia pennisetigena and P. zingibericola associated with invasive grasses from wheat cropping areas in South-Central Brazil. Howeever, the potential of P. pennisetigena and P.zingibericola as pathogens to poaceous plants of economic interest for Brazilian agriculture is still unknown. Thereforne, 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 agro-ecosystem. 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 ... (Complete abstract click electronic access below) / Doutor

<i>Gaeumannomyces graminis var. triciti (Ggt)</i>, the causal agent of take-all in wheat, is difficult to detect accurately and rapidly due to its similarity to fungi in the Gaeumannomyces-Phialophora complex. My objectives are to detect the fungus in infested plants and soil, and to predict effective combinations of bacteria as biological control agents. Detection was based on avenacinase-based primers and polymerase chain reaction (PCR) conditions specified by earlier research. PCR conditions were modified to effect detection. The annealing temperature was lowered from 68 to 62°C for plant and soil extracts, and the concentration of Taq polymerase was doubled for soil extracts. The lowest detection limit for plant extraction was with plant grown on 4 g Ggt-infested millet seed per kg soil, and that for soil extraction was 16 <span style="font-family:Symbol">m</span>g of purified Ggt DNA per g soil. Chemical and cultural control methods are currently inadequate. Biological control using bacteria is an alternative. Combinations of several bacterial strains are expected to work better than a single strain, but they may be less effective if bacteria antagonize each other or compete for the same rhizosphere habitat. Antagonism of potential biological control agents were assessed using a Petri plate assay. To estimate possible habitat competition, nutritional profiles of the strains were evaluated using the BIOLOG system. I hypothesized that bacteria not antagonistic to each other and having low coefficients of nutritional similarity would make better biological control combinations. Six bacterial combinations gave better mean root weight in the greenhouse experiment but not in the field. / Master of Science

L'utilisation de biofongicides et de molécules stimulatrices des défenses des plantes (SDP) constituent des stratégies de lutte alternative permettant la réduction de l'utilisation des fongicides conventionnels. Toutefois, il n'existe que peu de produits homologués et appliqués sur blé et encore moins contre la septoriose. Dans le cadre de cette étude, nous avons testés et mis en évidence l'efficacité de protection du blé contre Zymoseptoria tritici de plusieurs molécules. En effet, 29 molécules biosourcées dérivées de la fonctionnalisation de l'acide pyroglutamique (PGA), contenu dans les mélasses de la betterave sucrière, ont été évaluées en plus de l'acide y-aminobutyrique GABA, pour la première fois contre Z. tritici. Le GABA et 16 molécules fonctionnalisées ont réduit significativement les pourcentages de la maladie. L'absence d'effets directs sur Z. tritici vérifiée in vitro confirme que ces protections sont dues exclusivement à un effet SDP. Pour ces molécules, l'étude de la relation structure activité a mis en évidence l'importance des différents groupements chimiques impliqués dans les protections observées. D'autre part, la conjugaison du PGA avec l'acide salicylique (SA) a permis l'obtention de 5 nouvelles molécules parmi lesquelles 4 étaient plus efficaces que les molécules mères et cette efficacité semble être également due à un effet SDP. Enfin, la saccharine ainsi que trois lipopeptides cycliques produits par Bacillus subtilis (mycosubtiline, surfactine et fengycine seuls ou en mélange) ont été évalués pour la première fois sur le pathosystème blé - Z. tritici et ont conféré des protections significatives dues à des propriétés SDP, à des activités antifongiques directes ou à des effets combinés. Cette étude a donc permis d'identifier de nouvelles molécules possédant différents modes d'action et qui pourraient être envisageables en lutte alternative contre la septoriose du blé, toutefois, des analyses complémentaires sont requises. / The use of biofungicides and elicitors of plant defenses are alternative control stategies that can reduce the use of conventional fungicides. However, there are few products registered and applied on wheat and even less against Septoria tritici blotch. As part of this study, we tested and demonstrated the protective efficacity of several molecules on wheat against Zymoseptoria tritici. In fact, 29 biosourced molecules derived from the functionalization of pyroglutamic acid (PGA) contained in the molasses of sugar beet were evaluated with y-aminobutyric acid GABA, for the first time against Z. tritici. GABA and 16 functionalized molecules significantly reduced the percentages of the disease. The absence of direct effects on the fungus tested in vitro confirms that these protections are due exclusively to an elicitation of plant defense mechanisms. For these molecules, the study of the structure activity relationship has highlighted the importance of different chemical groups involved in the observed protections. On the other hand, the conjugation of PGA with salicylic acid (SA) allowed the obtention of 5 new molecules among which 4 were more effective than the parent molecules and this efficiency seems to be also due to an eliciting effect. Finally, saccharin and three cyclic lipopeptides produced by Bacillus subtilis (mycosubtilin, surfactin and fengycin alone or as mixtures) were evaluated for the first time on the pathosystem wheat - Z. tritici and conferred significant protection due to eliciting properties, direct antifungal activities or combined effects. This study has thus made it possible to identify new molecules with different modes of action and which could be considered in alternative control against wheat leaf blotch, however, additional analyses are required.

<p>Prouzrokovač pepelnice (Blumeria graminis f. sp. tritici) je stalni pratilac proizvodnje p&scaron;enice u agroekolo&scaron;kim uslovima Srbije. Sposobnost seksualne i aseksualne reprodukcije, kao i visok genetski protok patogena, čine da je prouzrokovač pepelnice genetski veoma divergentan, značajnog potencijala za adaptabilnost i promenu u virulentnosti populacije. Do sada je utvrđen znatan broj patotipova ovog patogena, dok se veliki broj konstantno stvara, te je efikasna otpornost p&scaron;enice kratkotrajne prirode. Rad na selekciji na otpornost p&scaron;enice prema prouzrokovaču pepelnice je važan zadatak oplemenjivačkih programa &scaron;irom sveta.&nbsp; Cilj istraživanja je bio utvrđivanje strukture virulentnosti populacije patogena B. graminis f. sp. tritici koja potiče sa teritorije Srbije, kao i dinamike njene promene tokom godina. U polnoj populaciji prouzrokovača pepelnice identifikovana je virulentnost prema svim genima p&scaron;enice za otpornost prema prouzrokovaču pepelnice (Pm geni), tokom ispitivanih godina i u svim ispitivanim lokalitetima. Utvrđene su statistički značajne razlike u virulentnosti gena patogena prema Pm genima domaćina, kao i linearni trend promene frekvencije virulentnosti gena polne populacije B. graminis f. sp. tritici. Najnižu frekvenciju virulentnosti u populaciji tokom ispitivanog perioda ispoljila je kombinacija gena V-5+6, dok je frekvencija virulentnih gena V-6 i V-7 gena bila na konstantno visokom nivou. Najznačajnija promena u populaciji je karakteristična za kombinaciju gena V-2+4b+6. U polnoj populaciji patogena u ispitivanom periodu nijedan izolat nije ispoljio virulentnost prema kombinaciji gena Pm17, Pm2+, Pm2+6 i Pm5+6. Klaster analizom utvrđen je visok stepen genetičkog diverziteta izolata u zavisnosti od godine. Analizom veze između gena avirulentnih lokusa utvrđena je pozitivna avirulentna veza između parova gena virulentnih prema Pm17 i Pm2+6, Pm2 i Pm2+; Pm2+ i Pm3a; Pm2+ i Pm1+2+9; Pm2+ i Pm2+4a+6; Pm3a i Pm8; Pm3a i Pm1+2+9; Pm3a i Pm2+6; Pm8 i Pm17; Pm17 i Pm1+2+9; Pm17 i Pm2+6 i parova gena</p><p><br /><br /><br /><br />Pm1+2+9 i Pm2+6. Piramiding ovih parova gena može biti dobra strategija za produžetak perioda efikasnosti otpornosti određene sorte. Najniža frekvencija virulentnosti polne populacije utvrđena je u lokalitetu Sremska Mitrovica. Najveći koeficijent genetičke udaljenosti utvrđen je između izolata koji potiču sa datog lokaliteta i izolata koji potiču sa ostalih ispitivanih lokaliteta. Između genetičke i geografske udaljenosti izolata prouzrokovača pepelnice za ispitivane lokalitete nije utvrđena statistički značajna linearna veza.&nbsp; Analiza strukture virulentnosti bespolne populacije ukazala je da komplekstnost patotipova prouzrokovača pepelnice raste sa porastom useva. Geni patogena za virulentnost prema genima Pm3a i Pm2+ nisu utvrđeni. Najvi&scaron;u frekvenciju virulentnosti imao je gen za virulentnost prema Mld genu za otpornost p&scaron;enice prema prouzrokovaču pepelnice. Statistički značajne korelacije su utvrđene između polne i bespolne populacije ispitivanog patogena. Istraživanja su imala za cilj i određivanje otpornosti genotipova p&scaron;enice koja je uslovljena promenom u populaciji prouzrokovača pepelnice. Visok nivo parcijalne otpornosti ispoljilo je sedam genotipova koji u svojoj genealogiji imaju roditelja sa kombinacijom gena Pm5+6, kao i kombinacijom gena&nbsp; Pm5+6 i Pm2+4b+6. Na osnovu ispitivanja strukture virulentnosti populacije prouzrokovača pepelnice smatra se da je kombinacija gena Pm5+6 nosioc otpornosti datih genotipova.</p> / <p>Powdery mildew (caused by Blumeria graminis f. sp. tritici) is the common disease of wheat in the agroecological conditions of Serbia. The ability of sexual and asexual reproduction, as well as a high genetic flow of this pathogen, make B. graminis f. sp. tritici genetically very divergent, with a significant potential for adaptability and change in the virulence of its population. So far, a large number of pathotypes of this pathogen have been identified, while a large number is constantly produced and effective resistance of wheat is short-termed. Improving wheat resistance to powdery mildew is an important task of breeding programs worldwide. The objective of this research was to determine and characterize the virulence structure of the B. graminis f. sp. tritici population that originate from the territory of Serbia, as well as the dynamics of its change over the years. During the examined period virulence of sexual stage of B. graminis f. sp. tritici population was identified for all wheat resistance genes (Pm genes) and in all investigated locations. Cluster analysis showed a high degree of genetic diversity of B. graminis f. sp. tritici isolates, depending on the year. Statistically significant differences were found between the virulence genes, as well as the linear trend of change in the virulence frequency of the genes during the investigated period. The lowest frequency of virulence in the population was found for the combination of the V-5+6 gene, while the frequency of the virulent genes V-6 and V-7 was at a consistently high level. The most significant change in the population was characteristic for the combination of the V-2+4b+6.&nbsp; Data were analyzed for associations among pairs of avirulence genes, and a positive avirulent relationship was established between the pairs of genes virulence to Pm17 and Pm2+6, Pm2 and Pm2 +; Pm2 + and Pm3a; Pm2 + and Pm1+2+9; Pm2+ and Pm2+4a+ 6; Pm3a and Pm8; Pm3a and Pm1+2+9; Pm3a and Pm2+6; Pm8 and Pm17; Pm17 and Pm1+2+9; Pm17 and Pm2 6 and gene pairs Pm1+2+9 and Pm2+6.</p><p><br /><br /><br /><br />Pyramiding these gene pairs can be a good strategy for extending the period of effectiveness of the resistance of a particular variety of wheat. The lowest frequency of virulence of the sexual stage of population was determined at the location of Sremska Mitrovica. The highest coefficient of genetic distances is established between isolates originating from a given location and isolates originating from other investigated locations. Between the genetic and geographical distance of B. graminis f. sp. tritici isolates a statistically significant linear relationship was not found. Virulence structure of the asexual population indicated that the complexity of the powdery mildew pathotypes grows with the crop growth. In this part of population the genes virulence to Pm3a and Pm2 + have not been found. The highest frequency of virulence had gene virulence to Mld resistance gene. Statistically significant correlations were found between the sexual and asexual population of the examined pathogen. The research was also aimed at determining the resistance of wheat genotypes to powdery mildew. High level of partial resistance was found in seven tested wheat genotypes whose parents have combination of the Pm5+6 gene, as well as a combination of the Pm5+6 and Pm2+4b+6 genes. Based on the study of the virulence structure of the powdery mildew population in this research, it is considered that the combination of the Pm5+6 gene is the carrier of the resistance of the given genotypes</p>

Powdery mildew, caused by Blumeria graminis (DC.) E.O. Speer f. sp. tritici E'm. Marchal (syn. Erysiphe graminis f. sp. tritici), is one of the major diseases of wheat (Triticum aestivum L.) worldwide. The use of cultivars with resistance to powdery mildew is an efficient, economical and environmentally safe way to control powdery mildew. Race-specific resistance has been extensively used in breeding programs; however, it is ephemeral. Adult plant resistance (APR) to powdery mildew is more durable as demonstrated by the cultivar Massey, which has maintained its APR to powdery mildew since its release in 1981. To develop an efficient breeding strategy, it is essential to understand the genetic basis of APR. The objectives of this study were to identify molecular markers associated with APR to powdery mildew in common wheat Massey and to verify their association using recombinant inbred (RI) lines. A cross was made between the powdery mildew susceptible cultivar Becker and Massey. One hundred and eighty F2:3 lines were rated for disease severity under natural pressure of powdery mildew in field. Using both restriction fragment length polymorphism (RFLP) and microsatellite markers, three quantitative trait loci (QTL), designated as QPm.vt-1B, QPm.vt-2A and QPm.vt-2B, were identified in the Becker x Massey F2:3 generation. These loci are located on chromosomes 1B, 2A and 2B, respectively, and explained 17%, 29% and 11% of the total variation among F2:3 lines for powdery mildew resistance, respectively. Cumulatively, the three QTLs explained 50% of the phenotypic variation among F2:3 lines in a multi-QTL model. The three QTLs associated with APR to powdery mildew were derived from Massey and displayed additive gene action. QPm.vt-2B also fits a recessive model for APR to powdery mildew. In the second part of this study, 97 RI lines were developed from the Becker x Massey cross. The RI lines were evaluated for APR to powdery mildew under natural disease pressure for three years. Both single marker analysis and interval mapping confirmed the presence of the three QTLs identified in the F2:3 generation. The three QTLs, QPm.vt-1B, QPm.vt-2A and QPm.vt-2B, accounted for 15%, 26% and 15% of the variation of mean powdery mildew severity of the RI lines over three years. In a multi-QTL model, the three QTLs explained 44% of the phenotypic variation of the RI lines. The RI lines were grouped according to the genotype of the three QTLs, represented by markers GWM304a, KSUD22 and PSP3100, respectively. The RI lines with Massey alleles at all three loci had a mean disease severity of 3.4%, whereas the RI lines with Becker alleles at all three loci had a mean disease severity of 22.3%. These severity values are similar to those of the corresponding parents. The molecular markers identified and verified as to their association with APR to powdery mildew in Massey have the potential for use in marker-assisted selection for resistance to powdery mildew and in pyramiding powdery mildew resistance genes, as well as facilitating a better understanding of the molecular basis of APR to powdery mildew. / Ph. D.

La culture d’associations de variétés sensibles et résistantes au sein d’une même parcelle permet de réduire la propagation des maladies fongiques foliaires aériennes. L’architecture des plantes a un impact sur la dispersion de spores et le microclimat, mais est rarement prise en compte dans la conception des associations. L’objectif de cette thèse était de comprendre le rôle joué par l’architecture dans des associations de variétés différant par leur niveau de résistance à une maladie dispersée par éclaboussement, la septoriose du blé, causée par Zymoseptoria tritici. Une expérimentation en conditions contrôlées a permis de quantifier des relations entre interception de spores et architecture des couverts. Des différences de densité entre couverts purs et associés ont donné lieu à une réduction du niveau de maladie sur les plantes sensibles cultivées en association par rapport à celles cultivées pures. Lors d’une expérimentation au champ, les associations de variétés de hauteurs de tiges contrastées étaient moins malades que celles ayant des hauteurs similaires. Ces résultats ont été mis en relation avec des effets de l’architecture sur la dispersion de spores et la durée d’humectation au sein des couverts. Une approche de modélisation spatialement explicite a permis d’identifier des mécanismes de dispersion par éclaboussement liés à l’architecture des couverts associés. Dans des associations de variétés de hauteurs différentes, la quantité d’inoculum éclaboussée dépendait de la surface foliaire présente au dessus des feuilles malades (effet parapluie). La quantité d’inoculum interceptée par un étage foliaire était liée à la différence de hauteur entre la source d’inoculum et l’étage foliaire (effet hauteur). Les différences de hauteur de plantes entre variétés d’une association ont modulé l’interception de spores par des feuilles résistantes (effet barrière). Nos résultats suggèrent qu’une prise en compte de l’architecture des variétés dans la conception des associations variétales permettrait de mieux maîtriser les maladies par éclaboussement. / Growing mixtures of susceptible and resistant cultivars in the same field makes it possible to reduce the propagation of airborne fungal plant diseases. Plant architecture has an impact on spore dispersal or microclimate, but is rarely taken into account in mixture design. The objective of this work was to understand the role of canopy architecture in mixtures of cultivar of different levels of resistance to a disease dispersed by rain-splash, septoria tritici blotch, caused by Zymoseptoria tritici. A controlled conditions experiment made it possible to quantify relationships between spore interception and canopy architecture. Differences of canopy density between pure stands and mixtures led to a reduction in disease on susceptible plants grown in mixture, compared to the susceptible pure stand. During a field experiment, mixtures of cultivars with contrasted stem height were less diseased than those with similar stem height. These results were related to the effect of canopy architecture on spore dispersal and leaf wetness duration. A spatially explicit modeling approach made it possible to identify splash dispersal mechanisms related to the architecture of mixed canopies. In mixtures of cultivar with diverse plant height, the amount of splashed inoculum depended on leaf area located above diseased leaves (umbrella effect). The amount of inoculum intercepted by a leaf layer was related to its difference of height between the inoculum sources (height effect). Differences of plant height between cultivars composinga mixture modulated the interception of spores by resistant leaves, providing an increased protection of susceptible leaves (barrier effect). Our results suggest that considering cultivar architecture in the design of cultivar mixtures could make it possible to improve the management of splash-dispersed diseases.