Waxflower (Chamelaucium spp. and hybrids) is the singlemost important Australian export cut-flower. The major problem in waxflower trading is flower abscission after harvest. While several factors are involved, ethylene production resulting from preharvest infection with the fungus Botrytis cinerea is the most important cause. The general objectives of this study were to investigate the biology of Botrytis infecting waxflower flowers and potential elicitation of host defence against this pathogen. Effects of anti-ethylene and S-carvone treatments on Botrytis-induced flower abscission were also evaluated. Infection of flowers by Botrytis was studied on two waxflower cvs. Mullering Brook and My Sweet Sixteen using light and electron microscopy. Conidial germination and protoappressorial formation occurred within 8 h post-inoculation (hpi). Infection of most floral organs, including petals, anthers and filaments, stigma, and hypanthium, was within 24 hpi. Infection cushions on stamen bases were formed at 36 hpi by saprophytic hyphae that originated from anthers. This infection route probably gives rise to the typical tan-coloured Botrytis symptoms that appear to radiate from this part of the flower. Subcuticular hyphae were present at very high density near stamen bases. They evidently resulted at multiple penetrations from single infection cushions. Flower abscission occurred at 72 hpi. At this time, floral tube tissues remained uninfected. This temporal pattern infers the possible transmission of a signal (e.g. ethylene) upon Botrytis infection (6–36 hpi) that intiates a defence response of shedding infected flowers (72 hpi). Susceptibility of waxflower before and after harvest to B. cinerea under various environmental conditions (laboratory, greenhouse, and field) was investigated. Flowers, either on plants or on cut stems showed similar susceptibility to B. cinerea and abscised under cool temperatures (~20 ºC) and high humidity (>95% RH) conditions following infection. Compared to cv. Mullering Brook, cv. My Sweet Sixteen was somewhat more resistant to B. cinerea infection under field conditions. Constitutive and inducible antifungal compounds in waxflower flower tissues were screened in cvs. CWA Pink, Stephan’s Delight, Mullering Brook and My Sweet Sixteen using thin layer chromatography bioassays with isolates of B. cinerea and Alternaria alternata (pathogenic) and Cladosporium cladosporioides (non-pathogenic). Common inhibition zone observed at Rf 0.28–0.38, 0.46–0.56 and 0.67–0.76 contained phenolic compounds. There were at least five (cv. Mullering Brook) and one (cv. My Sweet Sixteen) inducible antifungal phenolic compounds as judged by increases in inhibition area as a result of B. cinerea infection and methyl jasmonate treatment. The total areas of B. cinerea- and MeJA-induced inhibition zones were approximately 2.0- and 2.5-folds greater, respectively, than zones from control flowers. Preharvest sprays of three different known host plant defence elicitors, methyl jasmonate (MeJA), benzothiadiazole (BTH), and silicon (Si), were applied to waxflower cvs. Mullering Brook and My Sweet Sixteen plants. BTH or Si sprays generally had no significant effect on postharvest Botrytis severity on either cultivar. MeJA sprays did not reduce B. cinerea on cv. Mullering Brook. MeJA slightly suppressed B. cinerea on cv. My Sweet Sixteen at 500 and 750 µM. Overall, field applications of these host plant defence elicitor chemicals as spray treatments had little effect on vase life, water uptake and relative fresh weight of the cut sprigs. Moreover, they did not appreciably suppress B. cinerea or associated postharvest floral abscission. The efficacy of combined elicitor treatments and combined pre- and postharvest MeJA treatments were assessed. Preharvest foliar applications of MeJA (1000 µM; 2 or 4 times), MeJA (1000 µM) combined with BTH (150 mg/L), and MeJA combined with Si (1500 mg SiO2/L) generally did not suppress postharvest B. cinerea development and flower abscission from harvested sprigs. A pre- plus post-harvest 1000 µM MeJA spray treatment consistently but only slightly suppressed B. cinerea infection on flowers from both pot- and field-grown plants. Pre- and post-harvest MeJA treatments reduced B. cinerea development, but increased flower abscission. Combined MeJA and anti-ethylene treatments were then screened for potential to suppress B. cinerea while preventing flower abscission. However, the combined MeJA and 1-MCP treatment reduced neither Botrytis disease nor flower abscission on sprigs from pot- and field-grown plants. The combined MeJA and STS treatment reduced disease severity for up to 6 days on sprigs harvested from pot-grown plants but tended to increase Botrytis severity on sprigs from field-grown plants 6 days after inoculation. Antifungal effects of the essential oil S-carvone against B. cinerea germination and mycelial growth were demonstrated in vitro. Inhibition increased with increasing S-carvone concentrations from 0.64 mM to 5.08 mM. However, in planta, S-carvone concentrations in this range did not affect either Botrytis disease levels or flower abscission on cut waxflower flowers.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 23, 2010). Thesis advisor: Dr. Mengshi Lin. Includes bibliographical references.

O eucalipto participa de modo importante na silvicultura brasileira pela sua adaptabilidade, rápido crescimento e produtividade. Além disso, possui outras características como qualidade, diversidade e adequação de sua madeira para a indústria. A continuidade dos reflorestamentos com eucalipto demanda uma produção contínua de mudas. Entretanto, nos viveiros estas podem ser atacadas por doenças, como o mofo-cinzento e o oídio, causados por Botrytis cinerea e Oidium sp., respectivamente, principais doenças fúngicas que ocorrem na região Sul. O controle destas doenças é feito com fungicidas em outras culturas e em eucalipto o seu uso não é recomendado pela falta de produtos registrados. Além disso, podem surgir efeitos indesejáveis, como a poluição ambiental e a intoxicação do homem e de animais. O objetivo deste trabalho foi o estudo e a seleção de produtos eficientes para o controle alternativo dessas doenças. Para a execução dos experimentos foram utilizadas mudas de Eucalyptus dunnii nos experimentos com B. cinerea e mudas de E. benthamii com Oidium sp. Estas foram pulverizadas com fungicidas (parâmetro de controle), produtos químicos não fungicidas, óleos essenciais, extratos de plantas, leite e derivados e microrganismos. De cada um destes grupos foi selecionado o tratamento com menor valor de severidade, que foram testados entre si. A avaliação consistiu da medição da severidade das doenças, que foi determinada por meio de escalas descritivas de 0 (ausência de sintomas) a 4 (sintomas muito severos), específicas para cada patógeno. Verificou-se, em testes preliminares, os menores valores de severidade das doenças para o tanino e Mentha x villosa no controle do mofo -cinzento e para o leite de vaca e Lecanicillium sp. no controle do oídio. No experimento final, os produtos alternativos que apresentaram os menores valores de severidade foram: tanino controlando o mofo-cinzento e leite de vaca e Lecanicillium sp. controlando o oídio

Les vignerons du Val de Loire souhaitent faire évoluer les différents types de vins liquoreux produits actuellement dans leurs appellations en lien avec l’élaboration d’une qualité de raisin correspondant à ces types. Pour cela, il est nécessaire de caractériser objectivement les baies de raisin et leur qualité.Notre étude porte sur le développement d’une méthode multicritères combinant des mesures physiques et biochimiques des raisins, permettant d’identifier et de caractériser différents niveaux de développement de la pourriture noble sur raisins de Chenin blanc dans un objectif de production de vins liquoreux.Pour cela, des raisins correspondant à trois niveaux de pourriture noble ont été sélectionnés, lors de deux millésimes, 2012 et 2013. Des analyses classiques de qualité du raisin ont été réalisées et complétées par des analyses de couleur, de texture et de composés phénoliques.Outre la caractérisation phénolique du Chenin (sain et botrytisé), cette étude met en évidence la présence de myricétine, que l’on retrouve traditionnellement dans les variétés de raisin rouge, et qui semblerait être aussi synthétisée dans les baies de raisins blancs fortement atteintes par la pourriture noble.Nous avons également montré qu’une analyse multicritères permet une très bonne différenciation des baies plus ou moins botrytisées. Une combinaison des teneurs en myricétine, astilbine et glycérol permet notamment une très bonne discrimination des baies en fonction de leur niveau de botrytisation. Enfin, nous avons détectés de nouveaux composés dans les baies suite à l’attaque fongique, qui pourraient provenir de réactions d’oxydation. Ces résultats restent toutefois à confirmer. / Winemakers from the Loire valley are willing to improve the various types of sweet wines currently produced in their designation of origin altogether with the elaboration of grape quality that corresponds to these wines. For that purpose, it is necessary to objectively characterize the grapes and their quality. Our study implies the development of a multcriteria method that combines physical and biochemical measures on the grape, allowing the identification and characterization of the different levels of noble rot development on Chenin blanc grapes for the production of sweet wines. To do so, grapes corresponding to three noble rot levels were selected during two vintages, 2012 and 2013. Classical analysis of grape quality were carried out and complemented with color, texture and phenolic composition analysis. Besides the phenolic characterization of Chenin (healthy and botrytised), this study revealed the presence of myricetin, that is traditionally detected on red grape varieties, and that seems to be also synthetized on white grapes strongly affected by noble rot. We have also showed that a multicriteria analysis brings a very good differentiation of grapes more or less botrytised. A combination of myricetin, astilbin and glycerol concentrations showed a significantly good discrimination of grapes according to botrytisation level. Finally, we have detected new compounds on the grapes after the fungal attack that could be the result of oxidative reactions. These results are to be confirmed

Botrytis bunch rot, caused by Botrytis cinerea, is a fungal disease that primarily affects the fruit of wine grapes. Infection of fruit consequently results in reduced yields and wine quality. These factors lead to significant economic losses for growers which prompts the implementation of management practices to control the disease. One objective of this study was to evaluate the level of resistance that populations of B. cinerea in the Central Coast region showed to various chemicals. A fungicide assay was conducted to determine resistant phenotypes to six fungicide active ingredients (pyrimethanil, iprodione, fenhexamid, fludioxonil, trifloxystrobin, boscalid). Thirty-five (2020) and 88 (2021) B. cinerea isolates were collected from Santa Maria, Cambria, Paso Robles, and Edna Valley in California and screened for resistance. The frequencies of populations (2020, 2021) showing resistance to each active ingredient were: pyrimethanil (94.3%, 81.8%), trifloxystrobin (97.1%, 100%), boscalid (77.1%, 77.3%), fenhexamid (8.6%, 25%). The majority of isolates were sensitive to iprodione (100%, 100%), fludioxonil (100%, 100%), fenhexamid (88.6%, 75%), and boscalid (22.9%, 22.7%). These results documented the accumulation of resistance in B. cinerea to various fungicides commonly used for Botrytis bunch rot management in California’s Central Coast. Another objective of this study was to determine the effective concentration of the six fungicides that reduces mycelial growth of the fungus by 50% (EC50). Seven B. cinerea isolates in 2020 and ten isolates in 2021 were selected and subjected to a sensitivity screening with serial dilutions of the different fungicide active ingredients. The fungicides found to have the highest EC50 values indicating reduced efficacy for inhibiting B. cinerea growth were Scala® (FRAC 9), Flint® (FRAC 11), and Endura® (FRAC 7). The fungicides found to have the lowest EC50 values indicating higher efficacy for inhibiting B. cinerea growth were Scholar® (FRAC 12) and Rovral® (FRAC 2). The results from this study provided information regarding the accumulated resistance of B. cinerea populations to certain chemical groups and therefore the efficacy of different fungicide active ingredients. This information can be utilized by growers as a tool to enhance and develop fungicide spray programs that effectively manage Botrytis bunch rot in Central Coast vineyards.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Grey mould, caused by Botrytis cinerea, is the most important foliar disease of rooibos seedlings. Although the disease is primarily controlled with applications of fungicides, the improvement of cultural methods of disease management should lessen this dependence on chemical control. Such improvements would, however, not be possible without knowledge of the inoculum sources and dispersal of the pathogen. The aim of this study was to investigate the inoculum ecology of B. cinerea in rooibos nurseries in order to identify primary sources of inoculum and to improve the environmentally friendly management of the disease. The study was conducted in four nurseries over two production seasons (March to July 2003 and 2004). Levels of airborne inoculum of B. cinerea were monitored on a monthly basis inside and around the nurseries with spore traps. Samples of plant material and organic debris were taken in the corresponding areas to determine the incidence of plant material infected by the pathogen and the incidences of grey mould in the nurseries were recorded. Low numbers of B. cinerea colonies were observed on the spore traps. Similar levels of airborne inoculum were observed inside and around the nurseries. The incidence of plant material yielding B. cinerea was higher outside the nurseries than inside, indicating the importance of such materials as potential sources of inoculum. Since patterns of airborne inoculum observed in this study confirmed reports of the local dispersal of B. cinerea, the removal of possible hosts outside the nurseries could aid in the management of grey mould in rooibos nurseries. Resistance to dicarboximide fungicides is a genetically stable trait in B. cinerea, and therefore has the potential to be used as a phenotypic marker. This marker can be used to gain knowledge on the dispersal of B. cinerea inoculum inside and outside rooibos nurseries. Isolates of B. cinerea collected from the air and from plant material in and around four rooibos nurseries were assessed for resistance to iprodione at 1 and 3 μg/ml a.i. Some of the isolates showed resistance to iprodione at 1 μg/ml a.i. However, none of the isolates showed resistance at 3 μg/ml a.i. iprodione. The initial incidence of dicarboximide-resistance at the nurseries was slightly higher than expected. As the season progressed, the incidence of iprodione-resistant isolates decreased towards May, after which an increase was observed towards July. A relatively high percentage of isolates collected outside the nurseries was found to be dicarboximide-resistant. Two of the nurseries had a significant higher incidence of resistant isolates on plant material collected inside, than on plant material collected outside the nursery. However, when looking at resistance levels of airborne isolates, no significant differences were found in the incidence of resistant isolates sampled inside and outside the four nurseries. The data indicated the importance of organic debris and seed-borne infections in the survival and dispersal of dicarboximide-resistant isolates of the pathogen. With the current emphasis on organic agriculture the knowledge gained in this study presents valuable possibilities of improving the cultural management of grey mould in rooibos nurseries. / AFRIKAANSE OPSOMMING: Vaalvrot, veroorsaak deur Botrytis cinerea, is die belangrikste bo-grondse siekte van rooibossaailinge. Alhoewel die beheer van die siekte hoofsaaklik op die gebruik van fungisiede berus, behoort die verbetering van verbouingspraktyke hierdie afhanklikheid van chemiese beheer te verminder. Sulke verbeteringe sal egter slegs moontlik wees indien voldoende kennis van die inokulumbronne en verspreiding van die patogeen beskikbaar is. Die doel van hierdie ondersoek was om die inokulum ekologie van B. cinerea in rooibos kwekerye te ondersoek sodat primêre inokulumbronne opgespoor en omgewingsvriendelike siektebestuurspraktyke verbeter kan word. Die ondersoek is in vier kwekerye oor twee produksie seisoene (Maart tot Julie 2003 en 2004) uitgevoer. Vlakke van luggedraagde inokulum van B. cinerea is op ’n maandelikse basis met behulp van spoorvangers binne en buite die kwekerye gemonitor. Monsters van plantmateriaal en organiese materiaal is in ooreenstemmende areas geneem om die voorkoms van B. cinerea geïnfekteerde plantmateriaal vas te stel en die voorkoms van vaalvrot in die kwekerye is aangeteken. Min B. cinerea kolonies is op die spoorvangers waargeneem. Soortgelyke vlakke van luggedraagde inokulum is binne en buite die kwekerye waargeneem. Die hoër voorkoms van B. cinerea geïnfekteerde plantmateriaal buite die kwekerye as binne, dui op die belang van sulke materiaal as potensiële inokulumbronne. Aangesien die patrone van luggedraagde inokulum, soos waargeneem in hierdie ondersoek, ander berigte van B. cinerea se beperkte verspreidingsvermoë bevestig, kan die verwydering van moontlike alternatiewe gashere buite die kwekerye die bestuur van die siekte binne die kwekerye verbeter. Weerstand teen dikarboksimied fungisiede is ’n geneties-stabiele kenmerk in B. cinerea en het daarom potensiaal om as ’n fenotipiese merker gebruik te word. Hierdie merker kan gebruik word om kennis aangaande die verspreiding van B. cinerea in en om rooibos kwekerye in te samel. Botrytis cinerea isolate in lug en op plantmateriaal in en om vier rooibos kwekerye is gedurende 2003 en 2004 versamel. Die isolate is vir weerstandbiedendheid teen iprodioon by konsentrasies van 1 en 3 μg/ml aktiewe bestandeel (a.b.) getoets. Isolate met weerstand teen 1 μg/ml a.b. iprodioon is waargeneem, maar nie teen 3 μg/ml nie. Die aanvanklike voorkoms van dikarboksimiedweerstand by die kwekerye was hoër as verwag. Hierdie vlak het egter gedaal met die verloop van die seisoen tot in Mei, waarna ’n toename tot in Julie waargeneem is. Die persentasie dikarboksimied-weerstandbiedende isolate buite die kwekerye was relatief hoog. In twee van die kwekerye was die voorkoms van weerstandbiedende isolate op plantmateriaal in die kwekerye betekenisvol hoër as op plantmateriaal buite die kwekerye. Daar was egter geen betekenisvolle verskille in die voorkoms van luggedraagde weerstandbiedende isolate nie, ongeag van die kwekery of posisie. Die data dui op die belang van organiese materiaal en saadgedraagde infeksies in die oorlewing en verspreiding van dikarboksimied-weerstandbiedende isolate van die patogeen. Met die huidige klem op organiese landbou bied die inligting wat in hierdie ondersoek versamel is moontlike praktyke wat geïmplementeer kan word om die beheer van vaalvrot in kwekerye met behulp van verbouingspraktyke te verbeter.

Thesis (PhD)--Stellenbosch University, 2002 / ENGLISH ABSTRACT: Prototypes of a new polymer S02 gas-generating sheet for the control of Botrytis cinerea during the post-harvest storage of table grapes, were developed and manufactured for evaluation using a pilot scale production plant. Attention was paid to the appearance of the sheet, in order to make it technologically efficient as well as aesthetically acceptable to both industry and consumers. The storage quality of semi-commercial export consignments of various cultivars table grapes packed with the monolithic thin-film polymer S02 slow release sheet, was evaluated and compared to results obtained using the locally manufactured Uvasys S02 sheet. The following were investigated: the efficacy of the new polymer sheets in controlling storage decay, the stage at which S02 damage is manifested on table grapes, the level of S02 damage associated with different S02 concentrations, whether S02 damage is manifested more readily at a particular position on the bunch, and the possible effect of an increase in storage temperature, from an initial storage at -O.5°C to 10°C, on the levels of S02 bleaching. Results showed that the new polymer S02 sheet compared favourably with the existing, commercially available Uvasys S02 sheets. The exact S02 concentration required for effective decay control varied for different cultivars, as well as for the different types of grape packages. The S02 concentration incorporated within the sheet was shown to be lower for grapes packed in non-perforated bags, and slightly higher for those in perforated bags. Differences between cultivars occurred with regard to the level of control and the levels of S02 damage. Levels of S02 damage were also significantly affected by the storage period and temperature fluctuations. No significant differences in the levels of decay development and S02 damage were observed in relation to the orientation of the bunches in the carton. The extent of damage incurred to grape tissue by the absorption of S02 gas was determined by low-temperature scanning (LTSEM) and transmission electron microscopy (TEM) techniques. LTSEM and TEM micrographs of areas damaged by S02 gas revealed that exposure to S02 gas may lead to plasmolysis and the loss of cellular fluids. Although damage to the cell walls, cell wall structures and cell membranes, caused by S02 gas, was more prominent in the tissue layers nearer to the fruit surface, damage also occurred to a lesser extent in deeper tissue layers. S02 gas release-rate studies of polymer S02 sheets containing various concentrations Na2S205 revealed that levels of S02 gas emitted depended largely on the levels of Na2S205 incorporated into the sheets. Higher levels of S02 gas were released with the polymer sheets of higher concentrations Na2S205. The release curve for the commercial Uvasys S02 sheet was very different to that of the polymer sheets, with much higher levels of S02 gas emitted initially by the Uvasys S02 sheet compared to the polymer sheets, while the polymer sheets emitted low levels of S02 gas for longer periods compared to the Uvasys S02 sheet. The manufacturing process and the pilot scale production plant that was developed and constructed was successfully used to manufacture polymer S02 generating sheets that are technically sound and efficient, and aesthetically acceptable to industry. The efficacy of such sheets, regarding levels of decay control and S02 damage, was similar to that obtained with the presently available, commercially used Uvasys S02 sheet. / AFRIKAANSE OPSOMMING: 'n Nuwe polimeriese S02-gasvrystellingsvel vir die beheer van Botritis cinerea gedurende die na-oes opberging van tafeldruiwe is ontwikkel en vervaardig. 'n Nuwe loodsaanleg is spesiaal vir hierdie doel ontwerp en gebou. Aandag is geskenk aan die voorkoms van die velle aangesien dit belangrik is dat die nuwe velle beide tegnologies effektief en esteties aanvaarbaar moet wees vir die sagtevrugtebedryf en verbruikers. Die opbergingskwaliteit van semi-kommersiële uitvoerbesendings van verskeie kultivars tafeldruiwe, verpak met die nuwe monolitiese S02- gasvrystellingsvelle, is bepaal. Die volgende is ook bepaal: die effektiwiteit van die nuwe polimeriese velle, die stadium waarby S02-skade op die druiwe duidelik word, die vlak van S02-skade wat met verskillende konsentasies S02-gas geassosieer is, die moontlike invloed wat 'n toename in temperatuur (vanaf -0.5° tot 1DOC) op die verbleiking deur S02 sal hê, en of die S02-skade by voorkeur in 'n sekere posisie op die druiwe sal plaasvind. Die nuwe S02-vel het baie goed vergelyk met die kommersieël beskikbare Uvasys S02-vel. Die S02-konsentrasie benodig vir die effektiewe beheer van Botritis cinerea beskadiging het egter van kultivar tot kultivar verskil. Die keuse van die tipe verpakking, geperforeerd of ongeperforeerd, het ook 'n rol gespeel. Die konsentrasie S02-gas benodig vir effektiewe beheer was laer wanneer die druiwe in die nie-geperforeerde sakke verpak was. Vlakke van S02-skade is ook noemenswaardig beïnvloed deur die opbergingsperiode en variasies in temperatuur. Daar was geen duidelike verskil in die ontwikkeling van bederf en S02-skade ten opsigte van die posisie van die trosse in die karton nie. Die mate van S02-skade aan vrugweefsel is deur middel van laetemperatuurskandeerelektronmikroskopie (LTSEM) en transmissieelektronmikroskopie (TEM) bepaal. Daar is bevind dat die blootstelling aan S02 moontlik tot plasmolise en die uitlek van sellulêre vloeistof kon lei. Alhoewel S02-skade aan die selwande en membrane meer prominent in die weefsel naby die oppervlak van die vrug was, het skade ook in die onderliggende lae plaasgevind. Die vlakke van vrygestelde S02-gas het grootendeels afgehang van die konsentrasie natriummetabisulfiet in die velle. Die S02-vrystellingskurwe van die nuut ontwikkelde polimeriese S02-velle het baie verskil van dié van die Uvasys vel. Laasgenoemde lewer aanvanklik 'n hoë konsentrasie vrygestelde S02-gas vir 'n kort periode, gevolg deur baie lae S02 vlakke daarna, terwyl eersgenoemde 'n laer aanvanklike S02 vrystelling het, gevolg deur vergelykederwys hoër S02 konsentrasies daarna. Die ontwikkelde vervaardigingsproses en die loodsaanleg wat daaruit voortgevloei het is dus suksesvol aangewend om goeie polimeriese S02- vrystellingsvelle te vervaardig. Hierdie velle is tegnies effektief vir die beheer van Bofrifis cinerea gedurende die na-oes verpakking van tafeldruiwe en is esteties aanvaarbaar vir die Suid Afrikaanse sagtevrugtebedryf.

Organic mulches and cover crops mulched in situ were assessed for their effects on B. cinerea primary inoculum and disease levels in inflorescences at flowering and/or bunches at harvest. Organic mulches were used to enhance biological degradation of vine debris to reduce levels of B. cinerea primary inoculum the following season. Four mulch types (anaerobically and aerobically fermented marc (grape pressings), inter-row grass clippings and shredded office paper) were applied under ten-year-old Riesling vines in a ten-replicate randomized block design in New Zealand over two consecutive years. Plastic mesh bags, each containing naturally infected vine debris, were placed under vines on bare ground (control) and at the soil-mulch interface, in winter (July) 2003 and 2004. In each year, half the bags were recovered at flowering (December) and the remainder at leaf plucking (February), for assessment of B. cinerea sporulation from the vine debris and debris degradation rate. Bait lamina probes, which measure soil biological activity, were placed in the soil-mulch interface three weeks before each of the two bag-recovery dates in both years and were then removed and assessed at the same times as were the bags. All mulches led to a reduction in B. cinerea sporulation. This reduction was significantly correlated with elevated rates of vine debris decomposition and increased soil biological activity. Over both years, compared with the controls, all treatments gave a 3-20-fold reduction in B. cinerea sporulation, a 1.6-2.6-fold increase in vine debris degradation and in the two marc and the paper treatments, a 1.8-4-fold increase in activity of soil organisms. The mulches also altered vine characteristics and elevated their resistance to B. cinerea through changes to the soil environment. Functional soil biological activity, as measured by Biolog Ecoplates and bait lamina probes, was increased 2-4 times in the two marc and paper treatments, compared with the control, an effect relating to the elevated soil moisture and reduced temperature fluctuations under these mulches. Soil nutrient levels and the C:N ratios were also affected in these treatments. The mulched paper lowered vine canopy density by up to 1.4 times that of the other treatments, an effect which probably led to elevated light penetration into the canopy and consequent increased canopy temperature, photosynthesis and lowered canopy humidity. These changes to soil and vine characteristics increased grape skin strength by up to 10% in the paper treatment and sugar concentrations by 1.2-1.4 °Brix in the two marc and paper treatments. The severity of B. cinerea infections in the anaerobic marc, aerobic marc and paper treatments were reduced to 12%, 3% and 2.2% of the control, respectively, in field assessments averaged over two consecutive harvests. Cover crops mulched in situ had similar effects to those of the organic mulches, increasing soil biological activity and reducing B. cinerea primary inoculum and the severity of B. cinerea infection in grapes at harvest (2006). Inter-row phacelia and ryegrass were mulched in winter 2005 and compared with a bare ground control, under 10-year-old Chardonnay vines in a ten-replicate randomized block design. Functional soil biological activity increased by 1.5-4.5 times in the two cover crop treatments compared with the control, an effect possibly related to elevated soil moisture in these treatments. This increase in soil moisture and soil biological activity increased vine debris degradation, reduced B. cinerea primary inoculum on the debris and decreased B. cinerea severity at flowering (December 2005) and harvest (April 2006). These results show the potential of organic mulches and cover crops mulched in situ to enhance soil ecosystem services and improve the sustainability of viticultural practices.

La pourriture grise, causée par le champignon Botrytis cinerea, est l'une des principales maladies aériennes fongiques sur diverses cultures d'importance agronomique. La diversité génétique de B. cinerea est très forte et la capacité rapide d'adaptation de ce champignon à une pression sélective est également avérée. Ce champignon est ainsi capable de développer des résistances à une grande variété de composés fongicides de synthèse ou d'origine naturelle. Des méthodes alternatives de lutte ont de ce fait été développées ces dernières années : divers agents de lutte biologique (ALB) présentant différents modes d'actions ont été identifiés et pour certains d'entre eux commercialisés pour contrôler B. cinerea. Cependant la durabilité de la lutte biologique est un domaine encore très peu étudié. La perte d'efficacité d'un ALB pourrait résulter de la préexistence d'isolats moins sensibles de pathogènes dans les populations naturelles et/ou de la capacité de l'agent pathogène à produire, sous une pression de sélection continue exercée par l'ALB, des mutants ayant une sensibilité réduite. L'objectif global de la présente étude est d'évaluer le risque potentiel de perte d'efficacité de la lutte biologique vis-à-vis de B. cinerea. Dans cette étude, les efforts ont été concentrés sur la pyrrolnitrine, un antibiotique produit par divers ALBs, dont certains sont efficaces contre B. cinerea. Les objectifs spécifiques de l'étude étaient (i) d'évaluer la diversité de la sensibilité à la pyrrolnitrine au sein de la population naturelle de B. cinerea, (ii) d'estimer le risque de perte d'efficacité des ALBs produisant la pyrrolnitrine due à la pression de sélection exercée par la pyrrolnitrine et (iii) d'étudier le mécanisme de résistance à la pyrrolnitrine chez B. cinerea. Parmi 204 isolats de B. cinerea, une gamme importante de sensibilité à la pyrrolnitrine a été observée, avec un facteur de résistance de 8,4 entre l'isolat le plus sensible et l'isolat le moins sensible. La production de 20 générations successives pour 4 isolats de B. cinerea, sur des doses croissantes de pyrrolnitrine, a abouti au développement de mutants avec des niveaux élevés de résistance à l'antibiotique, et à une réduction in vitro de la sensibilité à la bactérie productrice de pyrrolnitrine Pseudomonas chlororaphis PhZ24. La comparaison entre les mutants résistants à la pyrrolnitrine et leurs parents sensibles pour la croissance mycélienne, la sporulation et l'agressivité sur plantes a révélé que la résistance à la pyrrolnitrine est associée à un fort coût adaptatif. Des observations cytohistologiques sur tomates ont confirmé que l'isolat sensible à la pyrrolnitrine attaque le pétiole rapidement et envahit la tige, alors que le mutant résistant à la pyrrolnitrine ne s'étend pas au-delà du pétiole. De plus, ce dernier mutant forme un mycélium anormal et des cellules ressemblant à des chlamydospores. Les résultats ont d'autre part révélé que les mutants de B. cinerea résistants à la pyrrolnitrine sont résistants au fongicide iprodione, suggérant ainsi qu'une pression exercée par la pyrrolnitrine sur le champignon conduit à une résistance au fongicide. Réciproquement, la production de générations successives sur iprodione conduit à une résistance à l'antibiotique. Afin d'étudier les déterminants moléculaires de la résistance de B. cinerea à la pyrrolnitrine, le gène histidine kinase Bos1, impliqué entre autres dans la résistance aux fongicides chez B. cinerea a été séquencé chez les souches sensibles et les mutants résistants. La comparaison des séquences a mis en évidence des mutations ponctuelles différentes chez les mutants de B. cinerea obtenus sur la pyrrolnitrine et ceux obtenus sur l'iprodione. De plus, les résistances à la pyrrolnitrine et à l'iprodione ne sont pas systématiquement associées à une mutation ponctuelle dans le gène Bos1. Enfin, aucune modification n'a été détectée dans la taille des allèles de neuf locus microsatellites quelle que soit la pression sélective exercée et quelle que soit le phénotype du mutant produit. Cette étude montre qu'un champignon pathogène des plantes est capable de développer progressivement une moindre sensibilité à un agent de lutte biologique mais que cette moindre sensibilité est associée à une forte perte de fitness

Eight phylloplane yeasts were isolated from backyard apple trees in Corvallis, OR. Yeast isolates were classified to genus or species level. All isolates were tested in vitro for antagonistic activity against the postharvest pathogens Botrytis cinerea and Penicillium expansum. Of these isolates, Aureobasidium pullulans, Sporobolomyces roseus Rhodotorula sp., consistently reduced mycelial growth of B. cinerea and P. expansum in nutrient yeast dextrose agar (pH 4.5 or 7.0) incubated for 8 or 30 days at 24 or 1 C, respectively. These three yeasts also were evaluated for their ability to suppress spore germination of B. cinerea and P. expansum in a gradient of apple juice concentrations and to suppress development of gray and blue mold lesions in inoculated fruits of Golden Delicious apple. Germination of B. cinerea and P. expansum was reduced significantly (P���0.05) when incubated with the yeast isolates in 100 or 50% apple juice, but not in 0, 1 or 10% apple juice. S. roseus and A. pullulans reduced significantly (P���0.05) the size of gray mold lesions in wounded fruit stored at 5 C and 24 C by 63 to 72 and 81 to 90%, respectively, when compared to the nontreated control. Size of blue mold lesions in fruit stored at 5 and 24 C also were reduced significantly (P���0.05) by 66 to 38 and 74 to 63%, respectively, when pre-treated with S. roseus and A. pullulans. In general, fruit rot suppression by some yeasts isolated in this study was similar in magnitude to suppression obtained by Cryptococcus laurentii isolate 87-108, a yeast with commercial potential to suppress postharvest rots of pome fruits. Pretreatment of apple wounds with washed cells of A. pullulans, S. roseus, Rhodotorula sp., resulted in disease suppression, but treatment of wounds with cell-free culture supernatant of these isolates did not affect lesion development. Population size of A. pullulans, S. roseus, and C. laurentii increased in apple wounds incubated at 5 or 24 C for up to 25 days, indicating that they colonized the wound site. Data collected in this study support the hypothesis that yeast isolates antagonize fruit pathogens by competing for nutrients in wounds on fruit surfaces. The isolates of A. pullulans and S. roseus show promise for commercial development. / Graduation date: 1997