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

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

An important disease of Vitis vinifera production in Oregon and all other commercial growing regions is powdery mildew of grape, caused by the obligate fungal pathogen Uncinula necator (Schwein.) Burril. Grape production can be characterized as a long-term investment in the establishment and maintenance of the vineyard. Establishment times have been reduced with the use of plastic vine shelters, but powdery mildew disease pressure within vine shelters had been an unaddressed issue. Control of the pathogen requires frequent spray applications and costly cultural management of the grape canopy. Industry interest in forecasting programs have shown promise in regulating spray applications to times when they are most effective, or needed. The timing of when to begin spray programs is believed to be a point of weakness in the forecasting programs currently available for grape powdery mildew. The influence of vine shelter use on the development of powdery mildew was investigated in the field during the 1998 and 1999 growing season. Industry standard installations of various brands of vine shelters were tested against modified installations for both incidence and severity of Uncinula necator infection. The industry standard installation of 76 cm high tubes hilled with 8 cm of soil at the bottom to prevent airflow, were effective in reducing the incidence of powdery mildew in both field seasons. Disease reduction was associated with prolonged temperatures above 36��C and the exclusion of infective spores by the artificial barrier created by the vine shelters. The effectiveness of three forecasting programs for predicting the initial spray application was investigated for three seasons. Actual disease onset dates were determined by using trap leaves or plants. The forecasting programs consistently predicted initial spray dates between 31 and 44 days prior to the detection of powdery mildew with the trapping system. Modifications to the existing forecasting programs were attempted to adjust the forecasting programs to more closely predict the actual detected disease onset dates. The UC-Davis program performed the best over the three years of the study, but improvements will be necessary for an adequate forecasting program in the region. Flag shoots were reported for the first time in Oregon. / Graduation date: 2000

Barley powdery mildew disease is caused by the highly specialised phytopathogenic fungus, Blumeria graminis f.sp. hordei. Disease is spread prolifically by the production of asexual conidia. Following contact with the barley leaf surface, a short, primary germ tube (PGT) emerges, followed by elaboration of a second-formed germ tube, the appressorial germ tube (AGT). This second-formed germ tube elongates, swells and hooks to form an appressorium, which allows direct penetration of the barley cuticle and infection of the host. Infection structure differentiation in B. graminis is a highly regulated and complex process. It demands the coordinated perception of multiple external signals, but little is known about how these signals are integrated and transduced within the fungus. Protein kinase A (PKA) and cAMP signalling are known to play important, but complex, roles during infection structure development. However, signalling via cAMP alone is not sufficient to promote progression through infection structure differentiation. This study describes the characterization of two B. graminis protein kinase C genes, pkc1 and pkc-like. PKC activity was identified in B. graminis protein extracts. Efforts to find an inhibitor specific for B. graminis PKC were unsuccessful. However, phorbol ester, a PKC agonist, invoked both appressorium formation when applied to spores in vivo and PKC activity in protein extracts. In addition, real-time PCR confirmed the differentially regulated transcript profiles of both pkc1 and pkc-like, revealing a peak in transcript levels just prior to PGT emergence for pkc1, and during PGT differentiation for the pkc-like gene. Two mitogen-activated protein (MAP) kinases, mpk1 and mpk2, were characterized. MAP kinase activity was detected in conidial protein extracts. The MAP kinase kinase (MEK) inhibitor, PD98059, inhibited B. graminis germling morphogenesis. However, a MAP kinase agonist failed to show any effect on germling differentiation. In addition, real-time PCR confirmed the differentially regulated transcript profiles of both mpk1 and mpk2, and revealed a peak in transcript levels during appressorial germ tube elongation and swelling for both genes. The "model" phytopathogenic fungus, Magnaporthe grisea, was employed as a "surrogate host" for the functional analysis of the B. graminis MAP kinase gene, mpk1. Firstly, the mpk1 promoter was sequenced and a plasmid construct made comprising the mpk1 gene under the control of the mpk1 promoter. This, and the control construct, that is the M. grisea PMK1 gene under the control of the PMK1 promoter, were transformed into M. grisea Δpmk1. Southern analysis identified transformants for phenotypic studies. These showed that whereas Δpmk1 was complemented by M. grisea PMK1 in the control experiments, B. graminis mpk1 failed to complement Δpmk1. Expression studies showed that there was no expression of mpk1 in an mpk1 transformant.

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Grapevine powdery mildew, caused by the fungus Uncinula necator Schweinitz Burrill, is a major disease affecting grape yield and quality worldwide. In conventional vineyards, the disease is controlled mainly by regular applications of sulphur and synthetic fungicides, such as demethylation inhibiting fungicides (DMIs), and in organic agriculture by sulphur and canola-based oils. The impending restrictions on the use of sulphur in organic viticulture, the development of resistance to DMls in Australia and elsewhere, and the demand for residue-free grapes create a need for effective alternatives to sulphur and synthetic chemicals. This research has identified potential replacements for synthetic fungicides and sulphur in the control of powdery mildew, such as milk, whey, bicarbonates and canola oil-based sprays. A series of greenhouse experiments was conducted to evaluate 34 potential novel materials and biological agents for efficacy in controlling powdery mildew. The most effective treatments applied were Bacillus subtilis (which reduced disease by 94% compared to the untreated control), Synertrol Horti-Oil® (a canola oil-based product, 92%), milk (70%), whey (64%) and Ecocarb® (potassium bicarbonate, 58%). Milk and whey provided increased control of powdery mildew as the concentration increased. The efficacy of milk tended to decrease as the fat content of the milk was reduced. The materials that were most promising in the greenhouse were then assessed in field trials in commercial vineyards. Applications of milk, whey and mixtures of a canola oil-based product and potassium bicarbonate, applied at rates of 300 L/ha to 1000 L/ha depending on canopy development, reduced the severity of powdery mildew. The severity of powdery mildew on vines sprayed with a 1:10 dilution of milk, 45 g/L whey powder and mixed programs was not significantly different from that on vines sprayed with sulphur (wettable powder, 3 g/L). However, the relative control of powdery mildew by the test materials in field trials was highly dependent on the degree of coverage of the plant surface achieved. In vineyards where coverage was compromised, the degree of control of powdery mildew was reduced, often to commercially unacceptable levels. Electron spin resonance (ESR) and scanning electron microscopy (SEM) were used to investigate the possible mode or modes of action of milk and whey in the control of powdery mildew. The ESR experiments showed that production of oxygen radicals by various components of milk in natural light was associated with reduced severity of powdery mildew. SEM images showed that milk and whey caused the hyphae of U necator to collapse and damaged conidia within 24 h of treatment. Hydrogen peroxide, applied as a source of free radicals, also caused collapse of the hyphae of U necator within 24 h but did not damage conidia, and appeared to stimulate germination. Lactoferrin (an antimicrobial component of milk) ruptured conidia, but damage to hyphae was not evident in lactoferrin-treated samples until 48 h after treatment. The results suggested that fats, free radical production along with the action of lactoferrin, and possibly other proteins, are associated with the control of powdery mildew by milk. Novel soft fungicides, such as milk and oil plus bicarbonate mixtures, were effective alternatives to sulphur and synthetic fungicides in certain South Australian conditions. Biological agents (including B. subtilis, which was highly effective in greenhouse experiments) did not provide acceptable control of powdery mildew in the vineyard. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1116612 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2004

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / Grapevine powdery mildew, caused by the fungus Uncinula necator Schweinitz Burrill, is a major disease affecting grape yield and quality worldwide. In conventional vineyards, the disease is controlled mainly by regular applications of sulphur and synthetic fungicides, such as demethylation inhibiting fungicides (DMIs), and in organic agriculture by sulphur and canola-based oils. The impending restrictions on the use of sulphur in organic viticulture, the development of resistance to DMls in Australia and elsewhere, and the demand for residue-free grapes create a need for effective alternatives to sulphur and synthetic chemicals. This research has identified potential replacements for synthetic fungicides and sulphur in the control of powdery mildew, such as milk, whey, bicarbonates and canola oil-based sprays. A series of greenhouse experiments was conducted to evaluate 34 potential novel materials and biological agents for efficacy in controlling powdery mildew. The most effective treatments applied were Bacillus subtilis (which reduced disease by 94% compared to the untreated control), Synertrol Horti-Oil® (a canola oil-based product, 92%), milk (70%), whey (64%) and Ecocarb® (potassium bicarbonate, 58%). Milk and whey provided increased control of powdery mildew as the concentration increased. The efficacy of milk tended to decrease as the fat content of the milk was reduced. The materials that were most promising in the greenhouse were then assessed in field trials in commercial vineyards. Applications of milk, whey and mixtures of a canola oil-based product and potassium bicarbonate, applied at rates of 300 L/ha to 1000 L/ha depending on canopy development, reduced the severity of powdery mildew. The severity of powdery mildew on vines sprayed with a 1:10 dilution of milk, 45 g/L whey powder and mixed programs was not significantly different from that on vines sprayed with sulphur (wettable powder, 3 g/L). However, the relative control of powdery mildew by the test materials in field trials was highly dependent on the degree of coverage of the plant surface achieved. In vineyards where coverage was compromised, the degree of control of powdery mildew was reduced, often to commercially unacceptable levels. Electron spin resonance (ESR) and scanning electron microscopy (SEM) were used to investigate the possible mode or modes of action of milk and whey in the control of powdery mildew. The ESR experiments showed that production of oxygen radicals by various components of milk in natural light was associated with reduced severity of powdery mildew. SEM images showed that milk and whey caused the hyphae of U necator to collapse and damaged conidia within 24 h of treatment. Hydrogen peroxide, applied as a source of free radicals, also caused collapse of the hyphae of U necator within 24 h but did not damage conidia, and appeared to stimulate germination. Lactoferrin (an antimicrobial component of milk) ruptured conidia, but damage to hyphae was not evident in lactoferrin-treated samples until 48 h after treatment. The results suggested that fats, free radical production along with the action of lactoferrin, and possibly other proteins, are associated with the control of powdery mildew by milk. Novel soft fungicides, such as milk and oil plus bicarbonate mixtures, were effective alternatives to sulphur and synthetic fungicides in certain South Australian conditions. Biological agents (including B. subtilis, which was highly effective in greenhouse experiments) did not provide acceptable control of powdery mildew in the vineyard. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1116612 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2004

For a successful and economical integrated control program aimed at a particular disease, pertinent information, regarding the environmental conditions prevailing in the growing area, the crop itself and the pathogen, must be available. Recently, the control of powdery mildew disease on cashew has moved from the use of non-systemic fungicides with a wide range of action, to highly specific systemic ones. Such a shift requires a more effective integrated control system, whereby tolerant varieties in combination with fungicide unaffected biocontrol agents are timely used to ensure disease control and reduce the hazards associated with excessive fungicide applications. The purpose of this study was to understand the relationship between the disease epidemic and some climatic factors over time. Appropriate periods for management interventions were determined. The cellular host reaction to infection by Oidium anacardii Noack was studied with a view to rapidly identify disease tolerant host types. Potential antagonists were isolated, screened and compared with commercial biocontrol products using in vivo techniques and chemical control programs were finally evaluated. Electron microscopy elucidated that the powdery mildew tolerant cashew variety (H1) had a relatively higher consistency of cytoplasmic aggregates upon infection by O. anacardii when compared to the susceptible clone. Based on conidia and conidiophore morphology, conidial germination and conidiogenesis processes observed indicated that O. anacardii belongs to the subgenus Pseudoidium (Y.S. Paul&J.N. Kapoor) comb.Et. Stat. Nov. (Holomorph Erysiphe Sect. Erysiphe U. Braun). There was no direct relationship between the progress of the cashew powdery mildew epidemic and temperature, relative humidity or dew point over time. However, the epidemic did not start until conditions of average temperatures under the tree canopy were below 30°C, relative humidity was 80% and dew point was above 15. In vivo screening of 72 isolates, amongst them bacteria and fungi, from cashew leaves and florets showed that none were effective against O. anacardii, the causal agent of cashew powdery mildew. However, commercial antagonists, Candida saitoana, Bacillus subtilis and B. licheniformis, significantly reduced the growth and branching of primary hyphae. One antagonist, B. licheniformis, was as effective as the commercial fungicide triadimenol 25% EC (Bayfidan). Chemical fungicides were found to be effective against powdery mildew; however, the currently prevailing economic environment in Mozambique was found inappropriate for the use of expensive organic fungicides. Additional gain from the use of fungicides was found to be solely qualitative and thus did not represent a fair investment return ratio in terms of cashew nut prices and production costs. The use of integrated cashew management was finally recommended. Further studies should focus on development of integrated and cost effective disease management strategies. / Dissertation (MSc(Plant Pathology))--University of Pretoria, 2003. / Microbiology and Plant Pathology / unrestricted

No description available.

An experiment was instituted to incorporate resistance to the powdery mildew fungus <i>Erysiphe cichoracearum</i> DC into the Ambrosia muskmelon, a melon of the Casaba or winter type. First generation hybrid (F1), first generation backcross (B1) and second generation inbred (F2) plants were grown to maturity at Blacksburg and Warsaw, Virginia. On the basis of the data obtained the following conclusions are drawn: • The muskmelon material acquired from the Plant Exploration and Introduction Service is a good source of powdery mildew resistance and of the material tested, PI3 showed the most promise as a source of commercial resistance. • The general technique of hybridizing a susceptible with a resistant plant can be used to advantage in incorporating disease resistance into the Ambrosia melon. • Further work is needed to obtain a commercially acceptable Ambrosia melon which is essentially homozygous for resistance to powdery mildew, and to determine the exact mechanism of inheritance of powdery mildew resistance. / Master of Science

Bibliography: leaves 173-200 / iv, 200 leaves, 7 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. / Thesis (Ph.D.)--University of Adelaide, 1986