Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Historically root diseases have been a production-limiting problem for the strawberry industry worldwide. In the Western Cape Province of South Africa the most serious root disease is black root rot, which causes losses of up to 30%, annually. The aims of this study were to investigate aspects of the etiology and epidemiology of this disease in the Western Cape, and to provide information that can be incorporated in an integrated disease management strategy. In Chapter I a summary of published information on this disease is presented. Disease symptoms include severe stunting of plants, which have black, rotted, reduced root systems. Even though this disease is of great economic importance, the etiology remains unresolved. However, soilborne fungal root pathogens, particularly Pythium and Rhizoctonia spp. have been implicated as major role players. Control of this disease, as well as the other root diseases affecting strawberries, has relied on soil fumigation with broad spectrum chemical fumigants, in particular methyl bromide. However, due to the ozone depleting action of methyl bromide it was decided at the signing of the Montreal Protocol to remove this chemical from the market. This action has caused great demand for alternative measures to control root diseases on many crops including strawberries. Development of integrated disease management strategies is dependent upon a more complete understanding of the etiology, biology and ecology of the disease complex. In Chapter 2 fungal pathogens associated with diseased plants were isolated and Koch's postulates were carried out. The most frequently isolated fungal pathogens were Pythium irregulare, Rhizoctonia spp. and Cylindrocarpon destructans. Two morphotypes of Rhizoctonia were isolated viz. a brown and a white type. Pythium irregulare was isolated more frequently in July than in September, and was not isolated at all in November. Rhizoctonia spp. were present at all sampling dates but were more frequently isolated in November than at the other times. All the fungi that were tested were pathogenic and caused root lesions. Cylindrocarpon destructans and Coniella fragariae did not have a stunting effect on the plants. These results confirm a major role for Pythium and Rhizoctonia in the black root rot complex and suggest that there is a complimentary seasonal variation in occurrence between these two pathogens. The Rhizoctonia species and anastomosis groups of isolates obtained from diseased strawberries in the Western Cape Province were determined, and their pathogenicity and relative virulence assessed. Both binucleate and multinucleate types were recovered from diseased roots and identified as R. fragariae and R. so/ani, respectively. All isolates of R. solani were members of anastomosis group (AG) 6, whereas three AG types were identified among isolates of R. fragariae, viz. AG-A, AG-G and AG-I at a relative occurrence of 69%, 25%, 6% respectively. All Rhizoctonia isolates were pathogenic to strawberry, but R. solani (AG 6) was the most virulent causing severe stunting of plants. This is the first species confirmation and AG type identification of Rhizoctonia taxa causing root rot of strawberries in South Africa. An assessment of the presence and quantity of black root rot pathogens associated with soils prior to fumigation and post fumigation with methyl bromide, was made in Chapter 4. Isolations were also made from nursery plants to determine whether any black root rot pathogens were in the plants before transplanting. Results demonstrated that after fumigation the soil was free of all pathogenic fungi associated with the disease. However, the main pathogens involved in black root rot, viz. Rhizoctonia fragariae, R. solani and Pythium spp. were isolated from nursery plants. The fact that the plants are already infected with these pathogens renders the prospects for control of this disease difficult. Further studies are urgently required to develop production practices that can be included in disease management programmes. In vitro studies were carried out to determine the ECso values of different fungicides for isolates of Pythium irregulare, Rhizoctonia fragariae AG-A, AG-G and AG-I and R. solani AG 6. Benomyl, fludioxonil and tolc1ofos-methyl were used in these tests. Field trials were also conducted using these fungicides. In Chapter 5 it is shown that in general application of fungicides improved the yield and did not affect the survival rate of strawberry plants. Fludioxonil showed potential for short-term use. Applications of fungicides that targeted specific fungal genera were not sufficient to control the disease. Seasonal fluctuation of Pythium and Rhizoctonia spp. became apparent with the occurrence of Pythium being relatively high early in the season but low late in the season. Conversely, the occurrence of Rhizoctonia was low at the beginning of the season but high late in the season. In the short-term there is potential for fungicide applications as part of an integrated disease management strategy, but the economic feasibility of this practice needs to be assessed. In this study the major pathogens causing black root rot were identified in the Western Cape Province of South Africa, and important information regarding the epidemiology of the disease was reported. These results can be incorporated in an integrated management strategy to reduce losses of strawberry production, attJibutable to black root rot. / AFRIKAANSE OPSOMMING: Wortelsiektes is wêreldwyd 'n produksie-beperkende probleem vir die aarbeibedryf. . Swartwortelvrot, wat jaarliks verliese van tot 30% veroorsaak, is die belangrikste wortelsiekte in die Wes-Kaap Provinsie van Suid-Afrika. Die doelwitte van hierdie studie was om aspekte van die etiologie en epidemiologie van die siekte in die Wes- Kaap te ondersoek en inligting wat in geïntegreerde siektebestuurstrategië ingesluit kan word, te voorsien. In Hoofstuk 1 word 'n opsomming van gepubliseerde inligting aangaande die siekte uiteengesit. Siektesimptome sluit ernstige verdwerging van plante met swart verotte en verkleinde wortelstelsels in. Alhoewel die siekte van groot ekonomiese belang is, is die etiologie grootliks onbekend. Grondgedraagde wortelpatogene swamme, spesifiek Pythium en Rhizoctonia spp., is egter as belangrike rolspelers geïdentifiseer. Tot dusver het die beheer van hierdie siekte sowel as ander wortelsiektes van aarbeie berus op grondberoking met breë spektrum chemiese berokingsmiddels, spesifiek metielbromied. As gevolg van die osoonafbrekende aksie van metielbromied is daar egter tydens die ondertekening van die Montreal Protocol besluit om dié middel van die mark te verwyder. Hierdie besluit het 'n groot aanvraag na alternatiewe beheermaatreëls vir wortelsiektes van verskeie gewasse, insluitende aarbeie, veroorsaak. Die ontwikkeling van geïntegreerd siektebestuurstrategieë is egter afhanklik van 'n meer volledige begrip van die etiologie, biologie en ekologie van die siektekompleks. In Hoofstuk 2 is die patogene swamme wat met die siekte geassosieer word, geïsoleer, en is Koch se postulate uitgevoer. Die mees algemeen geïsoleerde patogene swamme was Pythium irregulare, Rhizoctonia spp. en Cylindrocarpon destructans. Twee morfotipes van Rhizoctonia is geïsoleer, nl. 'n bruin tipe en 'n wit tipe. Pythium irregulare is meer dikwels in Julie as in September geïsoleer, maar glad nie in November nie. Rhizoetonia het tydens alle monstertye voorgekom, maar is meer dikwels in November geïsoleer. Al die swamme wat getoets is, was patogenies en het letsels op die wortels veroorsaak. Cylindroearpon des true tans en Coniella fragariae het nie'n verdwergingseffek op plante gehad nie. Hierdie resultate bevestig die dominante rol van Pythium en Rhizoctonia in die swartwortelvrot kompleks en dui op 'n komplementêre seisoenale variasie in die voorkoms van hierdie twee patogene. Die Rhizoctonia spesies en anastomose groepe (AG) van die isolate geisoleer vanaf siek aarbeiplante in die Wes-Kaap Provinsie is bepaal, en die patogenisiteit en relatiewe virulensie is beraam. Sowel tweekernige as multikernige tipes is vanaf siek wortels geïsoleer en respektiewelik as R. fragariae en R. so/ani geïdentifiseer. Alle isolate van R. so/ani was lede van anastomose groep 6, terwyl drie AG tipes, nl. AGA, AG-G en AG-I onder die R. fragariae isolate geïdentifiseer is met relatiewe voorkomste van 69%, 25%, 6% respektiewelik. Alle Rhizoctonia isolate was patogenies op aarbeie, maar R. so/ani (AG 6) was die mees virulente en het ernstige verdwerging van plante veroorsaak. Hierdie is die eerste bevestiging van spesies en identifisering van AG tipes van Rhizoctonia taksa wat wortelvrot van aarbeie in Suid Afrika veroorsaak. In Hoofstuk 4 is 'n beraming van die voorkoms en hoeveelheid swartwortelvrot patogene geassosieer met grond voor, en na beroking met metielbromied, gemaak. Isolasies is ook vanaf kwekeryplante gemaak om te bepaal of enige swartwortelvrot patogene voor oorplanting in die plante teenwoordig was. Die resultate het getoon dat grond na beroking vry was van alle patogeniese swamme geassosieër met die siekte. Die hoof patogene betrokke in die swartwortelvrot kompleks, nl. Rhizoctonia fragariae, R. so/ani en Pythium spp. was egter in die kwekery plante teenwoordig. Die feit dat plante reeds met hierdie patogene geïnfekteer is, maak die vooruitsigte vir die beheer van hierdie siekte moeilik. Verdere studies word dringend benodig vir die ontwikkeling van produksiepraktyke wat by siektebestuursprogramme ingesluit kan word. In vitro studies om die ECso waardes van die isolate van Pythium irregulare, Rhizoctonia fragariae AG-A, AG-G en AG-I en R. so/ani AG 6 vir die fungisiedes benomyl, fludioxonil en tolclofos-metiel te bepaal, is uitgevoer. Hierdie fungisiedes is ook in veldproewe getoets. In Hoofstuk 5 is getoon dat aanwending van fungisiedes die opbrengs verbeter het en nie die oorlewing van aarbeiplante beïnvloed het nie. Fludioxonil het potensiaal vir korttermyn gebruik getoon. Die aanwending van fungisiedes wat spesifieke swamgenera teiken, was nie voldoende om die siekte te beheer nie. Seisoenale fluktuasies van Pythium en Rhizoctonia spp. het duidelik geword met die relatief hoë voorkoms van Pythium vroeg in die seisoen, maar lae voorkoms laat in die seisoen, terwyl die voorkoms van Rhizoctonia laag was aan die begin van die seisoen, maar hoog later in die seisoen. In die korttermyn is daar potensiaal vir fungisiedtoedienings as deel van 'n geïntegreerde siektebestuurstrategie, maar die ekonomiese haalbaarheid van hierdie praktyk moet bepaal word. In hierdie studie is die hoof patogene wat swartwortelvrot van aarbeie in die Wes-Kaap Provinsie van Suid-Afrika veroorsaak geïdentifiseer, en belangrike inligting rakende die epidemiologie van die siekte is aangeteken. Hierdie resultate kan in 'n geïntegreerde bestuurstrategie geïnkorporeer word om verliese van aarbeiproduksie, toeskryfbaar aan swartwortelvrot te, verminder.

Bibliography: leaves 307-329. This study concludes that in soils in South Australia where root-rotting fungi and P. neglectus exist together, root disease of wheat is caused by their combined effect. Evidence suggests that P. neglectus not only contributes to this interaction through mechanical wounding of roots, but also causes biochemical and physiological changes in plants, making them more prone to fungal infection.

Bibliography: leaves 307-329. / xvi, 329 leaves, [21] leaves of plates : ill. (chiefly col.), map ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This study concludes that in soils in South Australia where root-rotting fungi and P. neglectus exist together, root disease of wheat is caused by their combined effect. Evidence suggests that P. neglectus not only contributes to this interaction through mechanical wounding of roots, but also causes biochemical and physiological changes in plants, making them more prone to fungal infection. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1996

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Orientador: José Fernando Durigan / Banca: Ben-Hur Mattiuz / Banca: Mário Sérgio Carvalho Dias / Resumo: Este trabalho objetivou testar o uso de tratamento químico combinado ou não com tratamento hidrotérmico, na conservação e qualidade pós-colheita de mangas 'Tommy Atkins' e 'Palmer', bem como avaliar o efeito da modificação da atmosfera de armazenamento por filmes plásticos e cera de carnaúba no prolongamento da vida útil pós-colheita de mangas 'Palmer'. Utilizou-se mangas provenientes de pomar comercial de Taquaritinga-SP, safra 2006/2007, que foram colhidas no estádio de maturação "de vez" e imediatamente transportados para o laboratório de Tecnologia dos Produtos Agrícolas da FCAV, Jaboticabal, onde foram selecionadas, visando padronizá-las quanto a coloração, tamanho e ausência de injúrias. Na primeira fase os frutos foram submetidos a tratamento com os fungicidas Sporekill® (cloreto de dodecil dimetil amônio a 12%) e Magnate 500 EC® (imazalil a 50%), associados ou não com tratamento hidrotérmico a 53°C/5 min ('Tommy Atkins') e 53°C/10 min ('Palmer'). Após secagem, eles foram armazenados sob condição de ambiente (23°C, 65% UR), e eram analisados a cada três ('Palmer') ou quatro dias ('Tommy Atkins'), quanto a ocorrência de podridões, aparência, perda de massa e firmeza, assim como quanto ao pH e teores de sólidos solúveis, acidez titulável e ácido ascórbico da polpa. Na segunda fase, o melhor tratamento para a manga 'Palmer' foi combinado com diferentes proteções e armazenamento sob condição ambiente (23°C, 65% UR) ou refrigerada (12°C, 65% UR). Os frutos armazenados sob refrigeração, após 28 dias foram levados ao ambiente, para avaliação da evolução do amadurecimento, aos 3 e 6 dias. Utilizou-se os seguintes tratamentos: Testemunha (sem tratamento); Testemunha com tratamento fitossanitário; Filme de polietileno de baixa densidade (PEBD), com espessura de 0,050mm; Polifilme multicamada; ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work was undertaken to test the use of chemical control in combination or not with hydrothermal treatment on the preservation and post harvest quality of 'Tommy Atkins' and 'Palmer' mangoes. Also, we evaluated the effect of modifying the storage atmosphere by the use of plastic film and carnauba wax on the shelf life of 'Palmer' fruits. Mangoes from a commercial orchard in Taquaritinga-SP were harvested in the season 2006/2007 at the breaker ripening stage, immediately transported to the laboratory of Technology of Agricultural Products, FCAV, Jaboticabal, and selected by color, size and absence of injuries. In the first stage, fruit were treated with the fungicides Sporekill® (12% dodecyl dimethyl ammonium) and Magnate 500 EC® (50% imazalil), associated or not with hydrothermal treatment at 53°C for 5 min ('Tommy Atkins') and 53°C for 10 min ('Palmer'). After drying, fruits were stored at room temperature (23°C, 65% RH), and analyzed every three ('Palmer') or four days ('Tommy Atkins') for the occurrence of rots, appearance, weight loss and firmness, as well as pH and the levels of soluble solids, titable acidity and ascorbic acid in the pulp. In the second phase, the best treatment for 'Palmer' mangoes was combined with different protections and storage at room conditions (23°C, 65% RH) or refrigerated (12°C, 65% RH). Fruits stored with refrigeration were transferred to room conditions after 28 days for ripening evaluations 3 and 6 days later. The following treatments were used: untreated control, fungicide-treated control, low-density polyethylene film (0.050mm), multilayer polyfilm, polyvinyl chloride (PVC) film (0.017mm), and 18% carnauba wax. In the first stage, fruits from the cultivars Palmer and Tommy Atkins submitted to different treatments showed no wilting symptoms until the sixth and eighth day, respectively ...(Complete abstract / Mestre

Phytophthora lateralis is the causal agent of cedar root rot, a fatal forest pathogen whose principal host is Chamaecyparis lawsoniana (Port-Orford-cedar), a predominantly riparian-restricted endemic tree species of ecological, economical, and cultural importance to coastal Oregon and California. Local scale distribution of P. lateralis is thought to be associated with timber harvest and road-building disturbances. However, knowledge of the landscape-scale factors that contribute to successful invasions of P. lateralis is also important for effective land management of Port-Orford-cedar. P. lateralis is able to infest in wet conditions via stream networks (zoospore) and dry conditions via road networks (resting spore). This study tested the hypothesis that vehicles spread P. lateralis by relating its distribution to traffic intensive, anthropogenic disturbances (i.e. a road network, timber harvest) over a 31-yr period in a 3,910-km² portion of the Rogue River-Siskiyou National Forest in the Siskiyou Mountains of Oregon. Indices of road disturbance (presence/absence, configuration, length, density, road-stream network connectivity) and timber harvest (presence/absence, area, density, frequency) were related to locations of infested cedar populations from a USFS survey dataset using a geographic information system (GIS). About 40% of 934 7th-field catchments were infested with the pathogen. Total road length of the study site was 5,070 km; maximum road density was 8.2 km/km2 and averaged 1.6 km/km² in roaded catchments (n = 766). Timber activities extracted 17,370 ha (2,338 cutting units) of forest across 509 catchments; 345 catchments were cut ≥ twice. Maximum harvest density was 0.92 km²/km² ([mean] = 0.04). Both road networks and timber harvest patchworks were significantly related to cedar root rot heterogeneity. Chi-squared contingency tables showed that infestation rates were 2.2 times higher in catchments with roads compared to roadless catchments and 1.4 times higher in catchments with road-stream intersections compared to those that were unconnected. Infestation was twice as likely in catchments with both harvest and road presence than road presence alone. Single-variable logistic regression showed that a one percent increase in harvest density increased infestation odds 25% and a one-unit (km/km²) increase in road density increased infestation odds 80%. Road and stream network configuration was also important to pathogen distribution: 1) uninfested catchments are most likely to be spatially removed from infested, roaded catchments, 2) only 11% of 287 roaded catchments downstream of infested, roaded catchments were uninfested, and 3) only 12% of 319 catchments downstream of infested catchments were uninfested. Road networks and timber harvest patchworks appear to reduce landscape heterogeneity by providing up-catchment and down-catchment access to host populations by linking pathogenic materials to the stream network. Timber harvest data suggest that while infestation risk to Port-Orford-cedar populations remains high, management policies may have curbed infestation risk in timber-harvested catchments; if this is a result of specific P. lateralis mitigation policies adopted in the late 1980's or broader, region-wide conservation policies (i.e. the Northwest Forest Plan) is yet unclear. / Graduation date: 2012

Root rot diseases of bean (Phaseolus vulgaris L.) are a problem wherever they are grown, and are a major constraint to dry edible and snap bean production. Root rot is a primary yield limitation of snap bean production in the US, especially within the top three snap bean producing states of Wisconsin, Oregon and New York. Bean root rot pathogens will be present by the end of the first season even when starting with clean ground. The decline in yield can be relatively slow, so growers might not notice or appreciate the hidden yield cost associated with root rot disease. Traditional methods for disease control such as fungicides, crop rotations, cover crops, seedbed preparations have been proven ineffective (either physically ineffective or economically unviable) against root rot. Therefore, genetic resistance is needed. In order to address the need for genetic resistance to root rot in snap beans, the highly root rot resistant line RR6950, a small seeded black indeterminate type IIIA accession of unknown origin, was crossed with OSU5446, a highly root rot susceptible determinate type I blue lake four-sieve breeding line to produce the RR138 recombinant inbred mapping population. In this study we evaluated the RR138 RI population in the F₆ generation for resistance to Fusarium solani root rot in Oregon and Aphanomyces euteiches root rot in Wisconsin. We also evaluated this population for morphological traits and root structural traits including pod height, pod width, pod length, pod wall thickness, strings, seed color, flower color, tap and basal root diameter, and root angle measurements. The RR138 population was also genotyped on the 10K BeanCAP Illumina Beadchip. The Single Nucleotide Polymorphism (SNP) data was used to assemble a high-density linkage map and Quantitative Trait Loci (QTL) for phenotypic data were evaluated. The linkage map produced from this study contained 1,689 SNPs across 1,196cM. The map was populated with 1 SNP for every 1.4cM, spanning across 11 linkage groups. Three QTL associated with A. euteiches root rot resistance were consistently expressed in 2011 and 2012 trials. A. euteiches QTL were found on Pv02, Pv04, and Pv06 and accounted for 7-17% of total genetic variation. Two QTL associated with F. solani were found in 2011 trial on Pv03 and Pv07, account for 9 and 22% of total genetic variation, respectively. We also found several QTL for morphological traits and root structural traits including QTL for pod fiber and pod height on Pv04, pod length on Pv01, strings on Pv01, taproot diameter on Pv05, and shallow basal root angle on Pv05, accounting for 21, 26, 12, 20, 11, and 19% of total genetic variation, respectively. QTL discovered from Oregon data for F. solani resistance did not cluster with QTL for A. euteiches root rot resistance. "SNP0928_7", was highly associated with F. solani resistance on Pv07 and "SNP0508_2", was highly associated with A. euteiches on Pv02. QTL and markers associated with QTL from this study will be of value to snap bean breeders developing root rot resistant lines with processing traits, and provide more information about targeting the mechanism of resistance. / Graduation date: 2013