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Alternative oxidase (AOX) is a non-energy conserving branch of the mitochondrial electron transport chain (ETC) which has been hypothesized to modulate the level of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in plant mitochondria. The aim of the research presented herein is to provide direct evidence in support of this hypothesis and to explore the implications of this during plant-pathogen interactions in Nicotiana tabacum. We observed leaf levels of ROS and RNS in wild-type (Wt) tobacco and transgenic tobacco with altered AOX levels and we found that plants lacking AOX have increased levels of both NO and mitochondrial O2 - compared Wt plants. Based on the results we suggest that AOX respiration acts to reduce the generation of ROS and RNS in plant mitochondria by dampening the leak of electrons from the ETC to O2 or nitrite. We characterized multiple responses of tobacco to different pathovars of the bacterial pathogen Pseudomonas syringae. These included a compatible response associated with necrosis (pv tabaci), an incompatible response that included the hypersensitive response (HR) (pv maculicola) and an incompatible response that induced defenses (pv phaseolicola). We show that the HR is accompanied by an early mitochondrial O2 - burst prior to cell death. Also, we found iii that the appearance of HR and the appearance of the mitochondrial O2 - burst are delayed in transgenic plants lacking AOX. A similar delay is seen in transgenic plants treated with the complex III inhibitor antimycin A. In Wt plants, expression of Aox1a is suppressed during the HR response to pv maculicola despite the accumulation of signaling molecules known to induce Aox1a transcription. Also, MnSOD activity declined during the HR. We suggest that the mitochondrial ROS burst controlled by AOX and MnSOD is an important component for the induction and coordination of the HR during plant-pathogen interactions.

Alternative oxidase (AOX) is a non-energy conserving branch of the mitochondrial electron transport chain (ETC) which has been hypothesized to modulate the level of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in plant mitochondria. The aim of the research presented herein is to provide direct evidence in support of this hypothesis and to explore the implications of this during plant-pathogen interactions in Nicotiana tabacum. We observed leaf levels of ROS and RNS in wild-type (Wt) tobacco and transgenic tobacco with altered AOX levels and we found that plants lacking AOX have increased levels of both NO and mitochondrial O2 - compared Wt plants. Based on the results we suggest that AOX respiration acts to reduce the generation of ROS and RNS in plant mitochondria by dampening the leak of electrons from the ETC to O2 or nitrite. We characterized multiple responses of tobacco to different pathovars of the bacterial pathogen Pseudomonas syringae. These included a compatible response associated with necrosis (pv tabaci), an incompatible response that included the hypersensitive response (HR) (pv maculicola) and an incompatible response that induced defenses (pv phaseolicola). We show that the HR is accompanied by an early mitochondrial O2 - burst prior to cell death. Also, we found iii that the appearance of HR and the appearance of the mitochondrial O2 - burst are delayed in transgenic plants lacking AOX. A similar delay is seen in transgenic plants treated with the complex III inhibitor antimycin A. In Wt plants, expression of Aox1a is suppressed during the HR response to pv maculicola despite the accumulation of signaling molecules known to induce Aox1a transcription. Also, MnSOD activity declined during the HR. We suggest that the mitochondrial ROS burst controlled by AOX and MnSOD is an important component for the induction and coordination of the HR during plant-pathogen interactions.

The aim of this thesis was to gain an understanding of the molecular and ecological basis for the biological control of Pythium by fluorescent pseudomonads. A fluorescent pseudomonad biocontrol agent (BCA), Pseudomonas fluorescens 54/96, identified as a potential candidate for commercial development, was analysed together with transposon induced mutants in a variety of assays for anti-fungal activity (Chapter 2). It was revealed that 54/96 had a fungistatic effect generated by a number of different mechanisms, which included nutrient competition and antibiosis. The synecology of this organism with Pythium was then compared to a similar organism (P. fluorescens SBW25) demonstrating a similar degree of anti-fungal activity (Chapter 3). The similarity of the population dynamics of these two strains prompted an examination of the genetic basis for the anti-fungal activity of the second strain, with the intention of comparing with 54/96 (Chapter 4). Again this revealed a multifactorial mode of action of SBW25 against Pythium. Whilst some mutants with reduced anti-fungal activity were deficient in growth on seed exudate others were unaffected, but the mechanisms appeared to be different to those utilized by 54/96. The comparison of strains was expanded to a larger collection of pseudomonad BCAs which were contrasted by a number of phenotypic and genotypic methods (Chapter 5). Various markers were identified which showed commonality within the different classes of BCA, the most useful of which was cyclopropanated fatty acids. These may prove to be a useful marker when screening for new pseudomonad BCAs. It was concluded that a greater understanding of the molecular, physiological and ecological basis of anti-fungal activity of bacterial will lead to the development of biocontrol strategies with improved efficacy.

>Magister Scientiae - MSc / Fi1sarium verticillioides is a very important mycotoxin-produeing fungus associated with maize. Fverticillioides produces a group of mycotoxins known as fumonisins under suitable environmental conditions. A series of studies was designed to provide information regarding some of the factors associated with the production offumonisin B1 (FB1) in maize patties and MYRO liquid medium. Our investigation together with previous studies have detailed the important influence of several factors on the production of fumonisins by F verticillioides strains. To understand why these strains are able to produce these toxins, an investigation into the complex interaction that occurs between biotic and abiotic parameters and their impact on fumonisin production was necessary. The results reflect the interacting factors and the intraspecific differences between strains, which may also be present in field conditions. The parameters that were varied under a predetermined set of culture conditions, included initial moisture content of maize patty cultures, temperature, initial pH and the addition of the fumonisin precursors, L-alanine and L-methionineto the cultures. Investigations into the three-way interactions of initial maize patty moisture content (30 ml water to 30g of maize), L-methionine (0.3 %) and temperature (25°C), resulted in the highest yield ofFB1 (5777.26 μgig) produced by MRC 4316. In contrast, MRC 826 was negatively affected, producing lower levels ofFB1 (3492.24 μg/g), compared to MRC 4316 at an initial moisture content (20 ml water to 30 g maize), L-methionine (0.3 %) and 25 °C. An American strain of F verticillioides MRC 7424 (= NRRL 13616), produced the highest levels of FB, (116 μg/ml), while the South African isolates, MRC 4316 and MRC 826, produced lower FB1 levels (93 and 62 μg/ml, respectively) in MYRO liquid medium. In general, FB1 production in maize patty cultures far exceeded levels obtained in liquid shake cultures. It appears that not only the ability of a particular strain of F. verticillioides, but the interaction of a variety of physiological and nutritional factors and the culture medium, are important in the production of FB,. Thus, variation of a single factor such as temperature under field conditions due to seasonal change, may therefore have a major effect on fomonisin production. A chain reaction may occur when changes in moisture, pH, etc. take place, which may influence fumonisin production further. Lyophilisation of fungal cultures proves to be an excellent method to preserve a wide range of fungi over long periods of time. It is, however, necessary to determine the viability of conidia stored in lyophilised vials at 4 ° Con a regular basis. At present, plate count methods remain the most valid technique for the detection of the viability of lyophilised conidia. Membrane-permeant nucleic acid-binding dyes (FUN-I) are viability stains that are relatively new flourescent probes for assessing the viability of metabolically active yeast cells. The purpose of this study was to microscopically determine the viability oflyophilised conidia of Fusarium and A lternaria species, using the yeast, Saccharomyces cerevisiae, as a control. FUN-1 viability stain was compared to two other staining methods, i.e. ethidium bromide (EB) and methylene blue (MB) and the viability of the conidia was compared to colony-forming units (CFU) on solid media as a control. For the purpose of determining or screening for percentage viability in a specific inoculum, results indicate that EB can be used in the case of lyophilised conidia, and MB in the case of freshly harvested conidia. Although FUN-I are recommended as a good way to determine the cell viability of a fungus, it needs relatively complicated procedures and has a time limit in which the stain can be used. The result of this study emphasize that the use of dyes to determine viability of lyophilised conidia require a critical definition of protocols for a specific fungal species, and that a good correlation with CFU needs to be demonstrated. The findings of this study could find useful applications in various studies on living and dead conidial populations. The diverse toxicological effects of fumonisins m animals and plants raised the possibility that fumonisins may also inhibit the growth of filamentous fungi. This study investigated the antifungal activity of FB1 to some h1sariu111 and other fungal species. The sensitivity of these fungi was tested by an agar-diffusion method on PDA plates. FB1 inhibited the myceliaJ growth of five of the nine fungi tested. The FB1-producing Fusarium species isolated from maize, i.e. F verticil/ioides, F glohosum and F proliferatum were resistant to FB1 even though a small inhibition zone at the highest FB1 concentration of 40mM was noted in the case of F. proliferatum. However, amongst two non-producing Fusarium spp. also isolated from maize, one (F subglutinans) was resistant and one (F graminearum) was sensitive. The most sensitive fungi tested were non-producing species not isolated from maize, i.e. A lternaria alternata, Botrytis cinerea and Penicillium expansum. The minimum inhibitory concentration ofFB1 ranged between 0.25-0.SmM for A. alternata, 1-SmM for P. expansum and B. cinerea and 5-1 OmM for F. graminearum, while the other fungi tested showed no sensitivity to FB1. This is the first report on the antifungal activity ofFB1 to filamentous fungi. Another study investigated the effect of FB1 on the germination of freshly harvested conidia of Fusarium and some other fungal species. The FB1 -producing F'usarium species isolated from maize, i. e. F vertici llioides, F. globosum and F. prolifer alum showed a decrease in germ tube length with an increase in FB1 concentrations. This indicated that these fungi can tolerate their own toxic metabolite to a ce11ain extent. However, amongst the two non-fumonisin producing Fi1sarium spp. examined, i.e. F. subglutinans and F. graminearum, isolated from maize, F. subglutinans was induced to genninate faster in the presence ofFB1 but soon developed stunted germ tubes, while F graminearum developed shorter germ tubes compared to the control cultures. The most sensitive fungi tested were species not isolated from maize, i.e. A. alternata, B. cinerea and P. expansum, which did not germinate at higher FB1 concentrations at all. Statistical analyses showed that the inhibiting effect of FB1 was highly significant (P <0.001). The conidial germination bioassay was more sensitive in the detection of the antifungal activity ofFB1 than the petri dish bioassay. The minimum inhibitory concentrations of FB1 for visible mycelial growth were closely comparable to those obtained from conidial germination. Results of these studies provide considerable information on the parameters affecting the production of FB1 and will be of great benefit in further studies focussing on fumonisin prodnction.

Philosophiae Doctor - PhD / Plants are continuously exposed to varying conditions in their environment, to which they have to adapt by manipulating various cellular processes. Environmental (abiotic) and pathogen (biotic) stress are challenges against which plants have to defend themselves. Many plant responses to stress stimuli are a result of cellular processes that can be divided into three sequential steps; namely signal perception, signal transduction m1d execution of a response. Stress signal perception is, in most of these cases, facilitated by cell surface or intracellular receptors that act to recognize molecules presented to the cell. In several cases, hormones are synthesized in response to stress signals and in turn these hormones are perceived by cellular receptors that trigger signal transduction cascades. Propagation of signal transduction cascades is a complex process that results from activation of various signaling molecules within the cell. Second messengers like calcium (Ca2+) and guanosine 3', 5'-cyclic monophosphate (cGMP) play a vital role in mediating many signal transduction processes. The result of these signal transduction cascades is, in most instances, expression of genes that contribute to the plant's ability to cope with the challenges presented to it. Plant natriuretic peptides (PNPs) are novel plant hormones that regulate water and salt homeostasis via cGMP-dependent signaling pathways that involve deployment of Ca2+. The aim of this study is to partially characterize a PNP and a guanylyl cyclase, both from Arabidopsis thaliana. Guanylyl cyclases synthesize cGMP from the hydrolysis of guanosine 5' -triphosphate (GTP) in the cell. The study also aims to investigate the effect of drought and salinity on cGMP levels in plants, using sorbitol to mimic the osmolarity/dehydration effect of drought and NaCl as a source of salinity stress and thus link NaCl and sorbitol responses to both AtPNP-A and cGMP up-regulation.

Thesis(Ph.D.)--University of Western Australia, 2006.

Fusarium root rot is one of the most important diseases of pulse crops, with numerous Fusarium spp. comprising the disease complex. Fusarium solani and F. avenaceum have been reported to be major pathogens in the pea root rot complex, and all commonly grown varieties are susceptible. Greenhouse methods to evaluate peas for resistance to Fusarium root rot resulted in inconsistent disease severity across varieties. In 2015, F. avenaceum infested field plots were more heavily damaged based on emergence and yield than F. solani infested plots, and opposite trends were observed in 2016. Differences in root rot severity between years could be due to F. solani infestation causing more damage under warmer temperatures, while plots infested with F. avenaceum caused more damage under cooler temperatures. These results highlight the difficulties observed when screening for soil-borne pathogens, and the increased difficulties when a pathogen complex and changing environmental conditions are involved.

Tesis por compendio / [ES] Phytophthora es uno de los géneros fitopatógenos más relevantes y agresivos en la agricultura y silvicultura. Muestreos realizados en la última década han revelado una gran cantidad de interacciones entre especies de Phytophthora y plantas, desconocidas con anterioridad. La introducción de nuevos patógenos de suelo, como Phytophthora en los bosques de Fagaceae, modifica la comunidad microbiana presente en la rizosfera, con importantes consecuencias ambientales y económicas. El género Quercus es uno de los géneros de Fagaceae más extendidos en Europa, y Quercus ilex es la especie dominante en España. El vínculo entre la dispersión de Phytophthora en los ecosistemas naturales y las actividades del ser humano, ha sido previamente estudiado. Numerosos muestreos en viveros y espacios públicos, mostraron la presencia de gran diversidad de especies de Phytophthora que podían suponer una amenaza para la producción y los ecosistemas naturales. En este contexto, se realizó un muestreo de viveros ornamentales y forestales en cuatro comunidades autónomas españolas, centrándose en los posibles síntomas asociados a Phytophthora en diferentes hospedantes e incluyendo muestras de agua de los viveros. Los resultados mostraron 17 filotipos de Phytophthora que afectan a 22 especies vegetales incluidas en 19 géneros. Algunas de estas interacciones se citaron por primera vez en España. Entre los patógenos de suelo aislados en los viveros, se identificó una gran cantidad de formas asexuales tipo Cylindrocarpon en las raíces de hospedantes leñosos. Se caracterizó una colección de aislados mediante estudios morfológicos y moleculares. Se identificaron 12 especies pertenecientes a los géneros Cylindrodendrum, Dactylonectria e Ilyonectria en hospedantes pertenecientes a 15 géneros y otras cuatro nuevas especies se describieron. El estudio demostró la prevalencia de este grupo fúngico asociado con plántulas de diversos hospedantes que muestran síntomas de decaimiento en viveros forestales. Se evaluó la susceptibilidad de Q. ilex a la inoculación con ocho especies de Phytophthora obtenidas de muestreos en viveros. Las especies más agresivas fueron Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora gonapodyides, Phytophthora plurivora y Phytophthora psychrophila, seguidas de Phytophthora megasperma, mientras que Phytophthora quercina y Phytophthora nicotianae fueron las especies menos agresivas. Los resultados obtenidos en el ensayo de patogenicidad confirmaron que todas las especies de Phytophthora evaluadas podrían representar una amenaza para los encinares. En este contexto, se realizó un estudio para verificar la presencia y / o detección de especies de Phytophthora en dos áreas de España (dehesas del sudoeste y bosque del noreste) utilizando diferentes métodos de aislamiento y detección. El aislamiento directo y el método de trampeo vegetal en muestras obtenidas a partir de encinas con y sin decaimiento, identificaron Phytophthora cambivora, P. cinnamomi, P. gonapodyides, P. megasperma y Phytophthora pseudocryptogea en las dehesas, mientras que, en el bosque del noreste, no se aisló Phytophthora spp. Los análisis estadísticos indicaron que no había una relación significativa entre la frecuencia de aislamiento de las especies de Phytophthora y la expresión de los síntomas de la enfermedad en las encinas de las dehesas. Además, P. quercina se detectó con mayor frecuencia que P. cinnamomi en las dos áreas estudiadas utilizando sondas TaqMan de PCR a tiempo real. Se evaluaron seis masas de Q. ilex ubicadas en tres comunidades autónomas de España mediante “Next Generation Sequencing” (NGS) para tener un mayor conocimiento sobre la diversidad de Phytophthora spp. en los bosques de encinas. Se detectaron 37 filotipos de Phytophthora pertenecientes a los clados 1 al 12, excepto los clados 4, 5 y 11, lo que demuestra una gran diversidad de Phytophthora en los encinares estudiados. Los filotipos más abundantes fueron P. quercina, P. psychrophila, P. cinnamomi y P. plurivora. / [EN] Phytophthora is one of the most relevant and aggressive plant pathogenic genus in agriculture and forestry. Due to the increasing environmental threat of invasive plant pathogens, monitoring new areas in the last decade has revealed a large number of new Phytophthora species-plant host interactions. The introduction of soilborne pathogens, such as Phytophthora in Fagaceae forests modifies the microbial community present in the rhizosphere with relevant environmental and economic consequences. The genus Quercus is one of the most extended Fagaceae genera in Europe, and Q. ilex is the dominant tree in Spain. The link between Phytophthora dispersion in natural ecosystems and human derived activities has been previously studied. Numerous sampling in nurseries and public spaces revealed a great diversity of Phytophthora species that compromised production and threated natural ecosystems. In this context, sampling ornamental and forest nurseries in four Spanish regions was carried out focusing on possible symptoms associated to Phytophthora on different hosts and including water samples from the nurseries. The results showed 17 Phytophthora phylotypes affecting 22 plant species included in 19 plant genera and some of them reported for the first time in Spain. Among the soilborne pathogens isolated in the nurseries, a large number of Cylindrocarpon-like asexual morphs were identified from the roots of woody hosts. A collection of Cylindrocarpon-like isolates recovered from Spanish nurseries was characterised by morphological and molecular studies. Twelve species belonging to the genera Cylindrodendrum, Dactylonectria and Ilyonectria were identified from damaged roots of 15 different host genera and other four species were newly described. The study demonstrated the prevalence of this fungal group associated with seedlings of diverse hosts showing decline symptoms in forest nurseries in Spain. The susceptibility of Quercus ilex to the inoculation with eight Phytophthora species obtained from nurseries was evaluated. The most aggressive species were Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora gonapodyides, Phytophthora plurivora and Phytophthora psychrophila followed by Phytophthora megasperma, while Phytophthora quercina and Phytophthora nicotianae were the least aggressive species. Results obtained in the pathogenicity test confirmed that all Phytophthora species tested could represent a threat to holm oak ecosystems. In this context, a study to verify the presence and/or detection of Phytophthora species was conducted in two holm oak areas of Spain (southwestern dehesas and northeastern woodland) using different isolation and detection methods. Direct isolation and baiting methods in declining and non-declining holm oak trees revealed Phytophthora cambivora, P. cinnamomi, P. gonapodyides, P. megasperma, and Phytophthora pseudocryptogea in the dehesas, while in the northeastern woodland, no Phytophthora spp. were recovered. Statistical analyses indicated that there was not a significant relationship between the Phytophthora spp. isolation frequency and the disease expression of the holm oak stands in the dehesas. Phytophthora quercina and P. cinnamomi TaqMan real-time PCR probes showed that P. quercina was detected in a higher frequency than P. cinnamomi in both studied areas. A better understanding of the Phytophthora spp. diversity in holm oak forests was assessed using Next Generation Sequencing (NGS) in six Q. ilex stands located in three regions in Spain. Thirty-seven Phytophthora phylotypes belonging to clades 1 to 12, except for clades 4, 5 and 11, were detected in this study, demonstrating a high diversity of Phytophthora species in holm oak Spanish forests. The most abundant phylotypes were P. quercina, P. psychrophila, P. cinnamomi and P. plurivora. In summary, this Thesis demonstrated a high diversity of Phytophthora and Cylindrocarpon-like species in Spanish nurseries, reporting new pathogen-plant host in / [CA] Phytophthora és un dels gèneres fitopatògens més rellevants i agressius en l'agricultura i la silvicultura. Mostrejos realitzats en l'última dècada han revelat una gran quantitat d'interaccions desconegudes fins ara entre espècies de Phytophthora i plantes. La introducció de nous patògens del sòl, com Phytophthora en els boscos de Fagaceae, modifica la comunitat microbiana present en la rizosfera, amb importants conseqüències ambientals i econòmiques. El gènere Quercus és un dels gèneres de Fagaceae més estesos a Europa, i Quercus ilex és l'espècie dominant a Espanya. El vincle entre la dispersió de Phytophthora en els ecosistemes naturals i les activitats de l'ésser humà, ja ha sigut estudiat prèviament. Nombrosos mostrejos en vivers i espais públics, van mostrar la presència d'una gran diversitat d'espècies de Phytophthora que podien suposar una amenaça per a la producció i els ecosistemes naturals. En aquest context, es va realitzar un mostreig de vivers ornamentals i forestals en quatre comunitats autònomes espanyoles, centrant-se en els possibles símptomes associats a Phytophthora en diferents hostes i incloent mostres d'aigua dels vivers. Els resultats van mostrar 17 filotipus de Phytophthora que afecten 22 espècies vegetals incloses en 19 gèneres. Algunes d'aquestes 'interaccions es van citar per primera vegada a Espanya. Entre els patògens del sòl aïllats en els vivers, es va identificar una gran quantitat de formes asexuals tipus Cylindrocarpon en les arrels de plantes llenyoses. Es va caracteritzar una col·lecció d'aïllats mitjançant estudis morfològics i moleculars. Es van identificar 12 espècies pertanyents als gèneres Cylindrodendrum, Dactylonectria i Ilyonectria en hostes pertanyents a 15 gèneres i altres quatre noves espècies es van descriure. L'estudi va demostrar la prevalença d'aquest grup fúngic associat amb plàntules de diversos hostes que mostren símptomes de decaïment en vivers forestals espanyols. Es va avaluar la susceptibilitat de Q. ilex a la inoculació amb huit espècies de Phytophthora obtingudes de mostrejos en vivers. Les espècies més agressives van ser Phytophthora cinnamomi, Phytophthora cryptogea, Phytophthora gonapodyides, Phytophthora plurivora i Phytophthora psychrophila, seguides de Phytophthora megasperma, mentre que Phytophthora quercina i Phytophthora nicotianae van ser les espècies menys agressives. Els resultats obtinguts en l'assaig de patogenicitat van confirmar que totes les espècies de Phytophthora avaluades podrien representar una amenaça per als ecosistemes d'alzines. En aquest context, es va realitzar un estudi per a verificar la presència i / o detecció d'espècies de Phytophthora en dues àrees d'Espanya (deveses del sud-oest i bosc del nord-est) utilitzant diferents mètodes d'aïllament i detecció. L'aïllament directe i el mètode de parany vegetal en mostres obtingudes a partir d'alzines, amb i sense decaïment, van identificar Phytophthora cambivora, P. cinnamomi, P. gonapodyides, P. megasperma i Phytophthora pseudocryptogea en les deveses, mentre que, en el bosc del nord-est, no es va aïllar Phytophthora spp. Les anàlisis estadístiques van indicar que no hi havia una relació significativa entre la freqüència d'aïllament de les espècies de Phytophthora i l'expressió dels símptomes de la malaltia en les alzines en les deveses. A més, P. quercina es va detectar amb major freqüència que P. cinnamomi en les dues àrees estudiades utilitzant sondes TaqMan de PCR a temps real. Es van avaluar sis masses de Q. ilex situades en tres comunitats autònomes d'Espanya mitjançant "Next Generation Sequencing" (NGS) per a tindre un major coneixement sobre la diversitat de Phytophthora spp. en els boscos d'alzines. Es van detectar 37 filotipus de Phytophthora pertanyents als clades 1 al 12, excepte els clades 4, 5 i 11, la qual cosa demostra una gran diversitat d'espècies de Phytophthora en els alzinars estudiats. Els filotipus més abundants van ser P. quercina, P. psychrophila, P. cinnamomi i P. plurivora. / Mora Sala, B. (2020). Detection and identification of Phytophthora spp. in woody plant nurseries and holm oak forests [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153808 / TESIS / Compendio

Thesis (MScAgric (Plant Pathology))--University of Stellenbosch, 2005. / The genus Rhizoctonia includes important soilborne plant pathogens that can cause severe economic losses on a wide range of crops including cereal, canola, pasture and grain legume crops. Limited information is available on specific anastomosis groups (AGs), nuclear status, pathogenicity and cross-pathogenicity of Rhizoctonia isolates associated with each of these crops in the Western Cape province. Therefore, these aspects were investigated in this study, since information in this regard is crucial for the development of Rhizoctonia disease management practices.