Foram conduzidos quatro experimentos com a cultivar 'Carioca' do feijoeiro (Phaseolus vulgaris), objetivando a possibilidade de implementação de um sistema de manejo integrado da ferrugem e mancha angular do feijoeiro após a intervenção com os fungicidas oxycarboxin (Hokko Plantvax 750 - 700 gramas/ha) e trifenil hidróxido de estanho (Mertin â - 660 ml/ha), respectivamente, aplicados em diferentes épocas. Foi realizada a quantificação de danos nesses patossistemas, verificando por meio de regressões lineares e não lineares as possíveis relações existentes entre as variáveis integrais AUDPC (área sob a curva de progresso de doença)¸ HAD (duração da área foliar sadia) e HAA (absorção da área foliar sadia) e suas correspondentes HLAI (índice de área foliar sadio) e HRI (absorção da área foliar por unidade de tempo) com a produção (gramas/planta). Os melhores resultados foram obtidos com as variáveis HAD e HAA, com coeficientes de determinação (R 2 ) variáveis entre 0,19 e 0,56 para HAD e 0,23 e 0,49 para HAA. Quando as variáveis HLAI e HRI foram relacionadas com a produção, os coeficientes de determinação variaram entre 0,24 e 0,57 para HLAI e 0,28 e 0,56 para HRI. A partir das avaliações semanais de HLAI e HRI foram realizadas regressões lineares entre estas variáveis e a produção (gramas/planta). Os coeficientes angulares foram relacionados com os estádios de desenvolvimento observando-se a estabilização das curvas entre os estádios R5-R8 para o patossistema ferrugem - feijão e entre os estádios V4-R8 para o patossistema mancha angular - feijão para HLAI e HRI. Nesses experimentos foram também realizadas avaliações do Índice de Área Foliar (LAI) utilizando-se medições diretas (avaliações manuais) e indiretas com ceptômetro. As medições obtidas com o este equipamento apresentaram sensibilidade suficiente para captar as variações no índice de área foliar sadio e portanto podem ser usadas em sistemas de manejo integrado da ferrugem e da mancha angular do feijoeiro. / Four trials were carried out on dry beans (Phaseolus vulgaris), variety 'Carioca' with goal to verify the possibility of implementation of an integrated management system for rust and angular spot after the application with of oxycarboxin (Hokko Plantvax 750 - 700 g/ha) and trifenil stannic hydroxide (Mertin â - 660 ml/ha) fungicides, applied in different timings. The damage quantification in these pathosystems were done analyzing the possible existing relation among the integral variables AUPDC (Area Under Disease Progress Curve), HAD (Healthy Area Duration) and HAA (Healthy Area Absorption) and its correspondents HLAI (Healthy Leaf Area Index) and HRI (Healthy Radiation Intercept) with yield (grams/plant) through linear and non linear regression. The best results were obtained using the variables HAD and HAA with the determination coefficients (R 2 ) from 0.19 to 0.56 for HAD and 0.23 to 0.49 for HAA. When HLAI and HRI were related with yield, the determination coefficient ranged from 0.24 and 0.57 for HLAI and 0.28 to 0.56 for HRI. From weekly assessments of HLAI and HRI, linear regression analysis were done between those variables and yield (grams/plant). The angular coefficient were related with the different crop stages and the stability of curves was observed between R5-R8 stages for rust - dry bean pathosystem and between V4-V8 stages for angular spot - dry bean pathosystem when HLAI and HRI were analyzed. In these experiments, Leaf Area Indice (LAI) was also assessed with direct (manual) and indirect measures with a ceptometer. The measures obtained using this set provided necessary sensibility to catch HLAI variation and, therefore, may be used in an integrated management system of rust and angular spot in dry beans.

A demographic census and disease assessment was conducted in 2007 and 2015 in three Tennessee populations of the dioecious shrub,;Buckleya distichophylla (Santalaceae). Population sizes were relatively stable over time and plant heights and numbers of stems per clump were similar among populations. Seedlings were present in all populations, where they represented 14–19% of individuals. Two populations had an equal male:female sex ratio, but a third population was male-biased. Nonflowering individuals comprised 33–41% of individuals in a population. The majority of plants in all populations had high vigor. Spatial analyses revealed clusters of seedlings in two populations and a cluster of low-vigor plants in one population. Cronartium appalachianum, a rust fungus dependent upon;Pinus virginiana and B. distichophylla as primary and alternate hosts, respectively, was present in all populations with prevalences on B. distichophylla of 19–29%, but there was no spatial clustering of disease in populations. The tree species nearest to B. distichophyllavaried among populations with Tsuga canadensis predominant in one population, T. caroliniana in another, and P. virginiana in the third. Buckleya distichophylla in proximity to P. virginiana had a higher than expected prevalence of C. appalachianum infection.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 73-78). Also available on the World Wide Web.

Brachypodium distachyon è stato recentemente proposto come pianta modello per le Triticeae che includono frumento e orzo. L’obbiettivo del presente studio è stato quello di identificare regioni genomiche associate con la resistenza quantitativa alla ruggine fogliare in Brachypodium. Le malattie causate dalle ruggini fogliari causano ingenti perdite in termini di produzione delle specie cerealicole. Una popolazione di 110 individui F2 è stata sviluppata incrociando due linee inbred di Brachypodium e una mappa di linkage di marcatori AFLP è stata create. La mappa di linkage consiste di 192 loci AFLP in dieci gruppi di linkage, e copre una lunghezza pari a 1,231 Kosambi cM. Allo scopo di identificare loci coinvolti nella resistenza quantitativa sulla mappa, i 110 individui F2 sono stati valutati per la loro reazione alla ruggine fogliare allo stadio di plantula e a quello adulto. Per confermare i risultati delle piante F2, le rispettive famiglie F3 sono state studiate per la loro resistenza alla ruggine fogliare in due esperimenti indipendenti. Due loci genomici sembrano essere maggiormente coinvolti nella resistenza. / Brachypodium distachyon has been proposed as a model species for the tribe of the Triticeae, which includes wheat and barley. The objective of our study was to identify the genomic regions associated with quantitative resistance to leaf rust in Brachypodium. Leaf rust diseases cause significant reductions annually in yield of cereal crops worldwide. An F2 mapping population of 110 individuals was generated between two Brachypodium inbred lines and a AFLP-based linkage map was developed. The linkage map consists of 192 AFLP loci in ten linkage groups, and spans a total genetic length of 1,231 Kosambi cM. To locate quantitative resistance loci on the map, the 110 F2 plants were evaluated for their reaction to the leaf rust at both seedling and adult plant stages. To improve QTL identification, F2-derived F3 families were studied for resistance to leaf rust in two independent experiments. Two major genomic regions involved in resistance to leaf rust were detected.

<p><p>Plants and their pathogens coevolve, with pathogen infection and host resistance acting in evolutionary antagonism of each other. Plant-pathogen coevolution has been shown to effect genetic divergence between populations and species, resulting in localized or specialized interactions between hosts and pathogens. Because most of the studies to date investigating plant-pathogen coevolution have been carried out in managed systems and have focused on pairwise interactions, we know little about three aspects of plant pathosystems in natural settings: 1) the role in nature of the gene-for-gene paradigm for genetic determination of resistance; 2) the relationship of host community diversity and structure, and host-pathogen interaction structure, to the coevolutionary process; and 3) the factors which underlie and drive local adaptation and specialization of interactions.</p><p><p>This dissertation constitutes the results of research in which I have begun addressing these aspects in a natural plant-fungus pathosystem comprising three <i>Ipomoea</i> host species and a single rust pathogen, <i>Coleosporium ipomoeae</i>. I have expanded previous characterization of the genetics of plant resistance in one constituent host species in the system by genetic crosses to characterize the basis of resistance in two additional species, finding support for the expectation that the gene-for-gene paradigm of interaction is important in natural systems. I conducted a cross-inoculation experiment designed to assess host and pathogen variation in infectivity and resistance, to investigate patterns of community interaction structure, and the role that antagonistic coevolution may play in structuring the communities which compose pathosystems. In these experiments I found that the coevolutionary interaction in this system leads to genetic divergence and the substantial amount of host and pathogen variation I discovered, but that it tends to preserve one pattern of community interaction structure across communities. I expanded my cross-inoculation experimental design to facilitate analysis of quantitative aspects of pathogenesis by measuring the intensity of infections, to test existing hypotheses concerning local adaptation and specialization in pathosystems. In this analysis I found strong host local adaptation and pathogen local maladaptation for the qualitative interaction trait of infectivity, and I found weak host local maladaptation and pathogen local adaptation for the quantitative interaction trait of aggressiveness. I also found host specialization among pathogens, and specialized resistance among hosts, to be common in this system. In light of these results, I hypothesize that the geographic scale of host-pathogen coevolution in this system is that of the local community, and that differences between host species result in persistent but incomplete host specialization in pathogen races.</p> / Dissertation

Yellow rust disease is one of the most important problems in wheat production. It causes substantial yield losses throughout the world. There are resistant and susceptible wheat varieties to various yellow rust pathotypes. In this thesis genes that are induced in wheat, in virulence and avirulence conditions upon yellow rust inoculations were investigated. Consequently, it was aimed to identify genes that may be playing critical roles in the disease resistance mechanism. The strategy was to construct subtracted cDNA libraries from resistant and susceptible plants and analyse the sequences obtained from these libraries. The subtraction approach in this study differs from the common subtraction designs implicated in plant-pathogen interactions / instead of comparing a compatible or an incompatible interaction with a control, one of the subtractions in this study is done taking a compatible interaction as the tester and an incompatible one as the driver, and the second subtraction, vice versa. Therefore, it was intended to compare the transcriptomes from compatible and incompatible plant-pathogen interactions directly. Suppression Subtractive Hybridization method was used to construct subtracted cDNA libraries. Two subtractions were performed / SSH1 (D-R), taking a compatible interaction as the tester sample and an incompatible one as the driver sample, and SSH2 (R-D), taking an incompatible interaction as the tester sample and a compatible one as the driver. In the end, two subtracted cDNA libraries, SSH1 (D-R) library (1536 clones) and SSH2 (R-D) library (1152 clones) were obtained and the libraries were sequenced. Sequence results were subjected to BlastN and BlastX analysis. We looked for a group of genes that were frequently emphasized in plant disease related studies when we searched within the Blast N homology results of the two libraries. We found out that 19 such genes are present in our libraries. We discussed supposed induction of these genes in the interactions investigated in our study. The fact that these genes were found to be present in our libraries enhances the reliability of our results suggesting that the gene sequences we found indeed belong to genes differentially expressed in the respective comparisons investigated in our study. As such, it also implies that other sequences that were found similar to genes of known functions may represent candidate genes as subjects of further studies investigating wheat-yellow rust interactions.

No description available.

No description available.

Field experiments were conducted in Kentucky and Louisiana in 2008 and 2009 (split-plot in a randomized complete block design with four replications) to investigate it is possible to simulate with manual defoliation the effect of soybean rust (SBR) (Phakopsora pachyrhizi Syd. and P. Syd) injury on a healthy soybean [Glycine max, (L.) Merr.] canopy, understand how defoliation affects the growth dynamics and canopy light interception, and if defoliation affectsleaf senescence and nitrogen remobilization during the seed-filling period. Two manual defoliation treatments based on changes in effective leaf area index (ELAI) (calculated as the reduction in leaf area equivalent to SBR-induced premature leaf abscission, loss in green leaf area, and reduction in photosynthetic capacity of diseased leaves) in infected canopies in Brazil were used to simulate SBR infection at growth stage R2 (full flowering) and R5 (beginning of seed-fill). Both defoliation treatments reduced yield in all experiments and the reduction was larger for the treatments at growth stage R2. The yield losses were equivalent to that observed in infected soybean canopies in Brazil. This suggests that a system of manual defoliation to simulate changes in effective leaf area duration shows promise as a tool to simulate the impact of SBR on soybean yield. The radiation use efficiency and crop growth rate from growth stage R2 to R5 were not influenced by defoliation. Defoliation started at growth stage R2 reduced seed number per unit area, while defoliation started at growth stage R5 reduced seed size due to shortening the seed-fill duration and a lower seed growth rate. There is no evidence that manual defoliation affected leaf senescence or nitrogen redistribution to the seed. This study found that the reduction of light interception by SBR was the main reason for the reductions in soybean growth and yield.

Yellow rust, caused by Puccinia striiformis Westend. f. sp. tritici Eriksson is one of the most severe leaf diseases of wheat. Aim of this study is to illuminate the downstream signaling pathways upon incompetible infection of rust pathogen in wheat, thus to understand the genes involved in resistance mechanism. The strategy used is the dual bait yeast two-hybrid analysis which is the most powerful method for in vivo detection of protein-protein interactions. The bait proteins used are / the domains of Yr10 yellow rust resistance gene, Rad6 gene which is considered to have a critical role in R gene mediated signaling pathway, and WR5 gene fragment which is an unknown protein having homology to the WD40 repeat containing protein with apoptosis related activity. Screening of a yeast prey library with these baits revealed proteins having mostly apoptosis related functions (SRP72, POR1, CSE1), translation initiation control in response to stress conditions (Gcn2p, Eap1p), phosphorylation (SKY1) and dephosphorylation activities (GAC1), cell cycle control (FAR1), oxidative stress control (OXR1), protein degradation control (TOM1), protein folding control (CPR7) and ion homeostasis in the cell (POR1, GAC1). The significance of the study can be summarized as i) being the first yeast two hybrid analysis of a wheat R gene, ii) being able to detect interacting partners with anticipated functions, iii) most importantly, initiating further detailed analysis of the key interactors.