No description available.

4 pp. / Mesquite (Prosopis sp.) is a popular tree in landscapes in Arizona because of its drought tolerance and attractive growth habit. Powdery mildew has been observed from late summer until early spring on mesquite leaves. It has been identified as Pleochaeta polychaeta based on morphological descriptions and comparison to herbarium specimens. Surveys were conducted in fall 2008 through winter 2009 at two locations in southern Arizona to determine the susceptibility of different mesquite species to powdery mildew. Twelve mesquite trees representing two species were sampled at Texas Canyon near Willcox, AZ, and 177 trees representing eight species were sampled at the University of Arizona campus in Tucson, AZ. The North American mesquite species P. glandulosa var. glandulosa and P. velutina were infected with powdery mildew at the University of Arizona campus and P. velutina at the Texas Canyon site. No powdery mildew was observed on P. alba, P. cinerea, P. nigra, P. chilensis, P. pubescens and P. chilensis x flexuosa. The powdery mildew affects the aesthetic value of severely infected trees but seems to have little effect on long term tree health.

Thesis (Ph. D.)--University of Adelaide, 1986. / Includes bibliographical references (leaves 173-200).

Thesis (M.S.)--Missouri State University, 2009. / "May 2009." Includes bibliographical references (leaves 44-50). Also available online.

Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Resumo: O oídio em soja, trata-se de uma doença praticamente presente em todos os paises produtores. Os marcadores moleculares microssatélites ou SSR (Simple Sequence Repeat) têm sido amplamente utilizados no processo de seleção assistida de genótipos de soja. Assim, o objetivo deste estudo foi obter marcadores microssatélites próximos ao gene de resistência ao oídio em soja. O estudo foi realizado em duas populações F2, oriundas de cruzamentos entre parentais contrastantes quanto à resistência ao oídio. Para o estudo, foram selecionados marcadores microssatélites a uma distância de até 42 cM ao redor do gene Rmd (resistência ao oídio). Utilizou-se o método de BSA (Bulked Segregant Analysis) na avaliação dos marcadores, para a comparação com a análise fenotípica das populações. Na análise foram utilizados dez iniciadores SSRs para as duas populações, sendo identificados quatro marcadores polimórficos para o cruzamento 1 (MGBR95-20937 x IAC-Foscarin 31) e três para o cruzamento 2 (MGBR 46/Conquista x EMBRAPA 48). Pela análise de Qui-quadrado da avaliação fenotípica, confirmou-se à segregação esperada (3:1) de um gene dominante condicionando a resistência. Os marcadores polimórficos também segregaram conforme o esperado (1:2:1) já que possuem natureza codominante. Para as populações 1 e 2, os melhores resultados foram obtidos com os marcadores Sat_366 e Sat_393, respectivamente, localizando-se a 9,41 e 12,45 cM de distância do gene, sendo considerados promissores na seleção assistida para resistência ao oidio em soja. / Abstract: Powdery mildew in soybeans, it is a disease present in virtually all producing countries. The molecular markers microsatellites or SSR (Simple Sequence Repeat) have been widely used in the assisted selection of soybean genotypes. The objective of this study was to obtain microsatellites markers near the gene for resistance to powdery mildew in soybeans. The study was conducted in two populations F2, from crosses between contrasting parents about the resistance to powdery mildew. For the study, were selected microsatellites markers at a distance of 42 cM around the gene Rmd (resistance to powdery mildew). It was used the method of BSA (Bulked Segregant Analysis) in the evaluation of markers, for comparison with the phenotypic analysis of populations. In the analysis were used in ten initiators SSRs for the two populations, and identified four polymorphic markers for the crossing 1 (MGBR95-20937 x-IAC Foscarin 31) and three for the crossing 2 (EMBRAPA MGBR 46/Conquista x 48). For the analysis of chi-square of the phenotypic evaluation, it is confirmed the segregation expected (3:1) of a dominant gene conditioning the resistance. The polymorphic markers also segregation as expected (1:2:1) that have already codominante nature. For the populations 1 and 2, the best results were obtained with the markers Sat_366 and Sat_393, respectively, finding itself to 9.41 and 12.45 cM distance of the gene and are considered promising in assisted selection for resistance to soybean in powdery mildew. / Orientador: Antonio Orlando Di Mauro / Coorientadora: Sandra Helena Unêda Trevisoli / Banca: Eduardo Antonio Gavioli / Banca: João Carlos de Oliveira / Mestre

Master of Science

Grapevine powdery mildew is caused by Erysiphe necator, an Ascomycete fungus and an obligate biotroph restricted to growth on its grapevine host. Biotrophic pathogens form a stable association with host cells without directly causing cell death, and take up nutrients from, in the case of powdery mildew ( PM ), host epidermal cells ( Rumbolz et al., 2000 ). As the fungus grows, its increasing biomass becomes a strong nutrient sink capable of altering assimilate flow and storage in the host. To identify host genes that may mediate nutrient delivery to powdery mildew infected tissues and therefore may contribute to disease susceptibility, a candidate gene approach using degenerate and RT - PCR, and a nontargeted approach using microarray analysis was instigated. Once identified, " susceptibility genes " could be targeted for manipulation to provide alternative resistance strategies based on reduced susceptibility in the future. In addition to genes encoding pathogenesis and stress related proteins, microarray analysis revealed that transcript levels of a putative metal transporter and a cell wall structural protein were elevated in infected berry skin, while aquaporin water channels and genes associated with photosynthesis were generally repressed. Degenerate PCR was used to isolated new cell wall invertase, monosaccharide and amino acid transporter genes and initial RT - PCR revealed that expression of genes involved in sugar mobilisation were the most significantly modulated by powdery mildew infection. Previously unreported hexose transporters ( HTs ), ( VvHT3, VvHT4 and VvHT5 ) and a cwINV ( VvcwINV ) had been isolated from cDNA prepared from powdery mildew infected grapevine leaves. Full length clones of grapevine HTs and cwINV were obtained by RACE PCR. Heterologous expression of the three new HTs in yeast confirmed that VvHT4 and VvHT5 mediated glucose uptake, while VvHT3 did not function in the yeast system. However, transient expression of a translational fusion of the VvHT3 protein with green florescence protein in onion epidermal cells indicated that it is targeted to the plasma membrane of plant cells. Quantitative RT - PCR analysis of these new genes, together with previously reported grapevine HTs and cytoplasmic and vacuolar invertases, indicated that expression of VvcwINV and VvHT5, were significantly up - regulated by PM infection, while a vacuolar invertase was strongly down - regulated by PM infection. Invertase activity assays were in agreement with these findings, showing elevated sucrolytic activity in insoluble fractions and reduced sucrolytic activity in soluble fractions. These results suggest that apoplasmic phloem unloading of sucrose in the infected leaf is elevated and that VvHT5 is induced to recover the additional hexoses from the apoplasm. Basic localisation studies indicated that VvHT5 and VvcwINV are not induced specifically in powdery mildew infected leaf regions, but are induced in a more diffuse distribution within infected leaves. To determine if induction of VvHT5 and VvcwINV is specific to PM infection or if other stimuli may also mediate these responses, leaves were inoculated with downy mildew or stressed by wounding. Transcript levels of VvHT5 and VvcwINV were elevated by wounding and downy mildew infection, suggesting that the induction of these genes may be part of a general stress response. To explore the signalling pathways that may underlie these responses, leaves were treated with the plant growth regulators ethylene, jasmonate and abscisic acid. Exogenous application of ethylene and methyl jasmonate only marginally affected the expression of the genes studied, however foliar application of abscisic acid ( ABA ) induced gene expression changes similar to those observed in response to powdery mildew infection and wounding. Promoter sequences of VvHT3, VvHT4, VvHT5 and VvcwINV were isolated and analysed for the presence of regulatory elements. Compared with the promoters of VvHTs that were not induced by pathogen infection or wounding, the VvHT5 and VvcwINV promoters contained numerous motifs associated with induction by ABA including ABRE, Myc and Myb binding elements. The path of sugar loading into the mesocarp of grape berries during ripening is still poorly understood and few molecular components associated with this process have been described. Quantitative RT - PCR was used to monitor the expression of five HTs and VvcwINV during Cabernet sauvignon and Shiraz berry development and ripening. Of the three new HTs reported here, the expression of VvHT3 is most consistent with a potential role in sugar loading, while VvHT5 is induced late in this process. VvcwINV transcript levels were high pre - ripening and also during the later stages of ripening, therefore based on this expression pattern, a role for this enzyme during ripening is not clearly evident. These results are discussed in terms of an apoplasmic step in phloem unloading in ripening grape berries. This study has provided new insights into the molecular and biochemical processes associated with the formation of carbohydrate sink metabolism in response to stress stimuli, and sugar delivery to grape berries during ripening. ABA - dependant pathways may mediate the stress - associated induction of VvcwINV and VvHT5, presumably to recruit additional carbohydrates to the affected organ to energise repair and defence responses. At this stage it is unknown if this response is beneficial to pathogen nutrition, however potentially, modification of genes associated with carbohydrate sink metabolism could provide an alternative way to engineer resistance to this pathogen. / Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.

Bibliography: leaves 148-166. This study identifies genetic variation in Australian Uncinula necator populations. Techniques were developed for molecular and phenotypic markers for U. necator. Mating types of Australian clonal lines were identified and viable cleistothecia and infective ascospores were produced in vitro. The study establishes the foundation for investigating the population biology of U. necator, by identifying two distinct genetic groups, A and B, and micro-geographical variation among 35 clonal lines from various Australian viticultural regions.

Bibliography: leaves 148-166. / vi, 169, [4] leaves, [20] leaves of plates : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study identifies genetic variation in Australian Uncinula necator populations. Techniques were developed for molecular and phenotypic markers for U. necator. Mating types of Australian clonal lines were identified and viable cleistothecia and infective ascospores were produced in vitro. The study establishes the foundation for investigating the population biology of U. necator, by identifying two distinct genetic groups, A and B, and micro-geographical variation among 35 clonal lines from various Australian viticultural regions. / Thesis (Ph.D.)--University of Adelaide, Dept. of Crop Protection, 1996