Made available in DSpace on 2014-07-29T14:42:44Z (GMT). No. of bitstreams: 1 claudia adriana.pdf: 420834 bytes, checksum: 841b3fc76b59f3d3b0619cb8de80fc1a (MD5) Previous issue date: 2009-08-10 / The objective of this study was to evaluate the association of cultural practices established with soil mulch with straw of Brachiaria ruziziensis, and biological control with sprayings of 2 x 109 viable spores / mL of Trichoderma harzianum strain 1306, to decrease the inoculum density of Sclerotinia sclerotiorum, causal agent of white mold on soybeans, and the incidence of white mold. The experiment was carried out in Jataí, GO, at the Brazilian Center-West Region, in a commercial soybean field naturally infested with the pathogen, in 2006/2007 and 2007/2008 seasons. Implemented in March 2006 on plots of 630 m² in a completely randomized design with three repetitions, the presence and absence of B. ruziziensis and applications of T. harzianum in dosages 0, 0.5, 1.0 and 1.5 L.ha-1 in one or two sprayings (March and October). The soil was sampled for quantification of sclerotia in March to assess the initial inoculum, in June, and September to evaluate the viability of sclerotia on PDA medium. Field and laboratory assessments were done for viability and parasitism of S. sclerotiorum sclerotia by Trichoderma spp. and other soil microorganisms, the number of apothecia, white mold incidence and yield components. In the presence of B. ruziziensis the viability of sclerotia was lower and at 0.5 and 1.0 L.ha-1 T. harzianum strain 1306 parasitism of sclerotia was higher than the control without T. harzianum strain 1306 . In the presence of straw in Brachiaria decreased the number of apotécios. The white mold incidence of residual effects was lower in the presence of straw in doses 0.5 and 1.0 L.ha-1 T. harzianum strain 1306 . The grain yield of soybean was higher dosage of 0.5 L ha-1 T. harzianum strain 1306 . / O objetivo desta pesquisa foi avaliar o efeito integrado dos métodos de controle cultural, pela semeadura de Brachiaria ruziziensis para formação de palha no Sistema Plantio Direto, e controle biológico com aplicação de Trichoderma harzianum 1306 , produto comercial Trichodermil®, na redução da densidade de inóculo e na incidência de Mofo branco. Realizado no município de Jataí, GO, em área comercial de soja naturalmente infestada por Sclerotinia sclerotiorum nas safras 2006/2007 e 2007/2008. Implantado em março de 2006 em faixas com parcelas de 630 m², na presença e ausência de B. ruziziensis e aplicações de T. harzianum 1306 nas dosagens 0, 0.5, 1.0 e 1.5 L.ha-1 em uma ou duas épocas (março e outubro). O solo foi amostrado para quantificação de escleródios, em março para avaliação inicial do inóculo, em junho, e em setembro para avaliação de viabilidade de escleródios em meio BDA. Foram avaliados o número de escleródios, a viabilidade e o parasitismo de escleródios por Trichoderma spp e por outros microorganismos, o número de apotécios, a incidência da doença e os componentes de produção. A palhada de braquiária reduziu a viabilidade de escleródios e o número de apotécios, e ainda, nas doses de 0,5 e 1,0 L.ha-1 de T. harzianum 1306 o parasitismo de escleródios foi superior. A incidência de Mofo Branco foi menor no efeito residual da presença de palhada de B. ruziziensis nas doses 0,5 e 1,0 L.ha-1 de T. harzianum 1306 . A produtividade de grãos de soja foi maior na dosagem de 0,5 L ha-1 de T. harzianum 1306 .

The biological control agent Pseudomonas chlororaphis PA23 is effective at protecting Brassica napus (canola) from the necrotrophic fungus Sclerotinia sclerotiorum via direct antagonism. Despite the growing importance of biocontrol bacteria in protecting crop plants from fungal pathogens, little is known about how the host plant responds to bacterial priming on the leaf surface and certainly nothing about global changes in gene activity in the presence and absence of S. sclerotiorum. PA23 priming of mature canola plants reduced the number of lesion-forming petals by 90%. Global RNA sequencing of canola tissue at the host-pathogen interface showed a 16-fold reduction in the number of genes uniquely upregulated in response to S. sclerotiorum when pretreated with PA23. Upstream defense-related gene patterns suggest MAMP-triggered immunity via surface receptors detecting PA23 flagellin and peptidoglycans. Although systemic acquired resistance (SAR) was induced in all treatment groups, a response centered around a glycerol-3-phosphate (G3P)-mediated pathway was exclusively observed in canola plants treated with PA23 alone. Activation of these defense mechanisms by PA23 involved production of reactive oxygen species as well as pronounced thylakoid membrane structures and plastoglobule formation in leaf chloroplasts. PA23 therefore primes defense responses in the plant through the induction of unique local and systemic regulatory networks. / October 2016

Brassica napus ist eine der wichtigsten Pflanzen in der Landwirtschaft. Pathogene verursachen jährlich große Ertragsverluste. Im Rahmen dieser Arbeit wurden die Interaktionen zwischen der Nutzpflanze Brassica napus bzw. der Modellpflanze Arabidopsis thaliana und dem phytopathogenen Pilz Verticillium longisporum untersucht. Verticillium longisporum ist ein auf Brassica spezialisierter Pilz, der die sogenannte Verticillium-Welke verursacht. Er dringt in die Wurzeln der Pflanze ein und steigt durch die Leitgefäße in den Spross auf. Die Pflanze zeigt in Folge der Infektion vor allem einen stark verkürzten Spross, Chlorosen und eine Notreife. Für die Experimente wurde Brassica napus und Arabidopsis thaliana mit Verticillium longisporum infiziert. Die Emissionen von Volatilen (volatile organic compounds (VOC)) der Pflanzen wurden sowohl ober- als auch unterirdisch bezüglich sich ändernder VOCs analysiert. Bei der Probennahme wurde darauf geachtet, die Pflanzen nicht zu verletzen und durch Messungen bedingten Stress zu minimieren. Auch während der Messungen der Wurzel-emissionen wurden die Pflanzen nicht aus ihrem Substrat entfernt, sondern innerhalb dessen gemessen. Während sich das Duftspektrum der Wurzeln von Brassica napus nicht änderte, emittierten die Sprosse infizierter Brassica Pflanzen signifikant mehr Dimethyldisulfid, ß-Ionon und ß-Cyclocitral. Bei der Infektion von Arabidopsis thaliana mit Verticillium longisporum hingegen spielten diese VOCs keine Rolle. Im zweiten Teil der Arbeit wurde die Vermutung überprüft, dass sich im Infektionsverlauf ändernde VOCs als Abwehrmoleküle dienen könnten. Hierfür wurde ein Bioassay entwickelt und zwei weitere pathogene Pilze, Gaeumannomyces graminis var. triciti und Sclerotinia sclerotiorum, unterschiedlicher Spezialisierung einbezogen. Wir setzten sie Dimethyldisulfid und ß-Ionon in unterschiedlichen Konzentrationen aus. Sowohl Dimethyldisulfid als auch ß-Ionon zeigten nur eine geringe fungizide Wirkung, gemessen am Myzelwachstum, gegen den Brassica-Spezialisten Verticillium longisporum. Gaeumannomyces graminis var. triciti wurde bereits bei geringeren Konzentrationen gehemmt. Sclerotinia sclerotiorum reagierte nicht oder sogar positiv auf die VOCs. Die (Mikro-) Sklerotienbildung wurde nur bei Verticillium longisporum beeinflusst. ß-Ionon unterstützte diese Entwicklung signifikant.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2016-04-18T16:16:44Z No. of bitstreams: 1 texto completo.pdf: 350102 bytes, checksum: f63374577f4c51e4a93a1ed9f2503a88 (MD5) / Made available in DSpace on 2016-04-18T16:16:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 350102 bytes, checksum: f63374577f4c51e4a93a1ed9f2503a88 (MD5) Previous issue date: 2015-07-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Trichoderma spp., antagonistas a vários fitopatógenos, são comumente isoladas do solo, da rizosfera, e como endofíticos. Nosso objetivo foi selecionar isolados de Trichoderma spp. nas culturas do feijão e da soja em Minas Gerais e avaliar o antagonismo a S. sclerotiorum, agente causal do mofo-branco de ambas as culturas. Obtiveram-se 48 isolados, sendo 30 da rizosfera, 11 epifíticos, quatro endofíticos e três de restos culturais. Com base no sequenciamento das regiões ITS, TEF1-α e RPB2, incluíram-se os isolados em oito espécies de Trichoderma: 29 como T. harzianum; 5 como T. koningiopsis; 4 como T. hamatum; 4 como T. atroviride; 2 como T. asperelloides; 2 como T. longibrachiatum; 1 como T. asperellum e 1 como T. neokoningii. Oito isolados inibiram completamente o crescimento do patógeno em teste de pareamento. Oito isolados foram os mais eficientes no crescimento em meio de cultura. Vinte e quatro isolados foram os mais eficientes em parasitar escleródios no solo, com 79-99% de eficiência. Em ágar-água, 31 isolados inibiram a germinação miceliogênica entre 78-100%, e sete isolados inibiram a germinação carpogênica em mais de 85%. Sete isolados inibiram 100% a infecção em folíolos destacados e um isolado inibiu em 79% a infecção em hastes destacadas. Dois isolados de T. harzianum, UN34 e IM2, foram os mais promissores: UN34 por reduzir a sobrevivência e as germinações miceliogênica e carpogênica de escleródios; e IM2 por reduzir a infecção em folíolos e hastes destacados. De acordo com os resultados, existe um potencial dos isolados de Trichoderma spp. no controle biológico de S. sclerotiorum. / Trichoderma spp., antagonists to plant pathogens, are commonly isolated from soil, rhizosphere, and as endophytic. We aimed to select Trichoderma spp. isolates from bean and soybean crops in Minas Gerais and to evaluate their antagonism to S. sclerotiorum, the causal agent of white mold on both crops. We got 48 isolates: 30 rhizospheric, 11 epiphytic, four endophytic, and three isolates from crop debris. Based on the sequencing of ITS, TEF1-α, and RPB2 regions, the isolates were classified in eight Trichoderma species: 29 as T. harzianum, 5 as T. koningiopsis, 4 as T. hamatum, 4 as T. atroviride, 2 as T. asperelloides; 2 as T. longibrachiatum, 1 as T. asperellum, and 1 as T. neokoningii. Eight isolates completely inhibited pathogen growth in dual culture test. Eight isolates were the most efficient in growing in culture medium. Twenty-four isolates were the best in parasitizing sclerotia in soil, with 79-99% of efficiency. In water-agar, 31 isolates inhibited miceliogenic germination from 78-100%, and seven isolates inhibited the carpogenic germination by more than 85%. Seven isolates inhibited 100% infection on detached leaflets and one isolate inhibited 79% infection on detached stems. Two isolates of T. harzianum, UN34 and IM2, were the most promising: UN34 for reducing the survival and both miceliogenic and carpogenic germination of sclerotia; and IM2 for reducing infection in both leaflets and stems. According to the results, there is a potential of the isolates of Trichoderma spp. in the biocontrol of S. sclerotiorum.

Made available in DSpace on 2014-06-11T19:32:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-04Bitstream added on 2014-06-13T20:23:55Z : No. of bitstreams: 1 venegas_f_dr_botfca.pdf: 1153063 bytes, checksum: 9f832b2c549da2249defccb8d2f58d82 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Universidade Estadual Paulista (UNESP) / O presente estudo objetivou determinar a severidade da doença mofo branco (Sclerotinia sclerotiorum (Lib.) de Bary) e os componentes de produção do feijoeiro (Phaseolus vulgaris L.), var. Pérola, submetido a aplicação do fungicida procimidone, via fungigação (pivô central) e pulverizador automotriz (Uniport). O estudo foi realizado sob condições de produção comercial em campo, no Município de Primavera do Leste - MT. O experimento foi conduzido no delineamento de blocos casualizados com 5 tratamentos: volumes de calda de 55.000 e 110.000 L ha1 via fungigação, e 120 e 200 L ha1 no pulverizador automotriz, com 4 repetições de 4 ha cada, sendo 4 deles envolvendo duas aplicações de procimidone (1,2 kg ha -1 cada aplicação), aos 42 dias e aos 52 dias após a semeadura (DAS), e um deles sem aplicação deste produto. O critério adotado em todas as avaliações da severidade da doença foi o da porcentagem das plantas lesionadas utilizando escala diagramática de severidade da doença mofo branco. Os valores foram usados para calcular a área abaixo da curva de progresso de doença (AACPD). Foram analisados também, o número dos apotécios do fungo durante o ciclo da cultura e o peso dos escleródios residuais do patógeno na colheita. Nesta ocasião foram avaliados os seguintes componentes da produção da cultura: número de plantas por metro linear, número de vagens por planta, número de grãos por vagem, peso médio de 200 grãos e produtividade. Os valores da AACPD, apotécios aos 42, 49 e 56 DAS, escleródios em 2 kg de solo e os parâmetros de produtividade da cultura foram submetidos à análise de variância e ao teste de comparação de médias de Tukey no nível de 5 % de significância, utilizando o programa computacional STAT. Não foram constatadas diferenças significativas entre as diferentes técnicas de aplicação estudadas em relação ao 2 parâmetros de... / The aim of this research was to evaluate the white mold severity (Sclerotinia sclerotiorum (Lib.) of Bary), bean crop production components and yield (Phaseolus vulgaris L.), variety Perola, according to the application of procimidone fungicide, through fungigation (center pivot) and automotive sprayer (Uniport). The study was carried under field production commercial conditions, in Primavera do Leste MT - Brazil. The experiment consisted of 5 treatments (with 4 repetitions of 4 ha each), all with two procimidone applications (1.2 kg ha-1 each application, same as, 0.6 kg a.i. per hectare) to the 42 and 52 days after seeding. The water depths of 5.5 and 11.0 mm were tested in the application through central pivot, providing volumes of 55.000 and 110.000 L ha-1, respectively, and the volumes of 120 and 200 L ha-1 in the automotive sprayer. The severity of disease was evaluated by the percentage of the area affected by plant damage using diagramatic grade scale of white mold severity, as described by Azevedo (1998). The values were used to calculate the area under the disease progress curve (AUDPC). They were also analyzed, the number of the fungus apothecia during the crop cycle and the residual sclerotias weight in harvest. On this occasion, it was also evaluated the crop yield parameters: number of plants per plot (final estande), pods per plant, grains per pod, medium weight of 200 grains and productivity of grains. The AUDPC values, apothecia to 42, 49 and 56 days after seeding, sclerotias in 2 soil kg and the crop productivity parameters were submitted to the variance analysis and Tukey Test at 0.05 of probability. This test was also applied in the comparison among the different fungicide application methods, independent of spray volumes in each one. The statistical processing was accomplished by STAT program. The results showed that weren't differences among 4 application techniques... (Complete abstract, click electronic address below).

La sclérotiniose, causée par le champignon Sclerotinia sclerotiorum, est une des maladies les plus importantes de la culture du soya dans l’est du Canada. L’utilisation de cultivars résistants est la manière la plus efficace et économique pour lutter contre l’agent pathogène. Or, la pression de maladie au champ varie considérablement d’une année à l’autre selon les conditions climatiques, ce qui complique l’identification de matériel résistant. Nous avons donc développé une méthode d’inoculation artificielle fiable et reproductible pour évaluer la résistance à la sclérotiniose du soya en serre et au champ. Appelée méthode «du coton», elle consiste à appliquer des morceaux de tampon à démaquiller, trempés dans une suspension de mycélium broyé, sur un bourgeon floral, et à mesurer la longueur de la lésion qui se développe sur la tige après une semaine. Cette méthode simple et rapide donne des résultats comparables à la méthode de référence utilisée au Québec tout en départageant la résistance vraie des mécanismes d’évitement. Nous avons ensuite utilisé la méthode du coton pour caractériser le degré de résistance au sein d’une collection de 130 lignées de soya représentative de l’étendue de la diversité génétique présente chez cette espèce au Québec. En parallèle, nous avons mis au point une méthode de génotypage par séquençage à haut débit pour le soya et l’avons utilisée pour génotyper la collection. Le séquençage a produit 266,7 millions de séquences distinctes qui, après différents filtres, ont révélé 7 864 marqueurs SNP répartis sur les 20 chromosomes du soya. Des analyses d’association entre le degré de résistance et le génotype des lignées de la collection ont révélé la présence de quatre locus de caractère quantitatif (QTL) conférant une résistance accrue à l’agent pathogène. L’association la plus forte a été validée chez une population issue d’un croisement entre deux parents contrastés à ce locus. De plus, aucun des génotypes les plus résistants ne porte tous les allèles de résistance, ce qui indique qu’on peut développer du matériel présentant une résistance accrue à la sclérotiniose. Ces résultats ouvrent des perspectives prometteuses pour la sélection assistée de marqueurs ou la sélection génomique. / Sclerotinia stem rot (SSR), caused by the fungus Sclerotinia sclerotiorum, is one of the most important soybean diseases in Eastern Canada. Using resistant varieties is the most efficient and economic way to repress this disease. However disease pressure in the field fluctuates considerably from year to year according to climatic conditions, thus impeding the identification of resistant material. We developed a reliable and reproducible artificial inoculation method to assess resistance in the greenhouse and in the field. Named the «cotton pad method», it relies upon applying a piece of cotton pad soaked in a mycelial suspension on a floral bud and to measure the ensuing lesion length one week after inoculation. This quick and easy method provides disease ratings similar to the reference method used in Québec and is able to distinguish true resistance from disease avoidance mechanisms. We then used the cotton pad method to evaluate the degree of resistance in a panel of 130 soybean lines representing the genetic diversity present in this species in Quebec. In parallel, we developed a high-throughput genotyping by sequencing method for soybean and used it to genotype the collection. Sequencing provided 266.7 million distinct sequences, which yielded 7,864 SNPs on the 20 soybean chromosomes after several filtering steps. Association mapping performed between the genotype of the lines and their resistance level revealed the presence of four quantitative trait loci (QTLs) associated with SSR resistance. The strongest association was validated in a biparental population generated from a cross between two parents contrasted at this locus. Furthermore, none of the most resistant lines developed so far carries all of the resistance alleles, which suggests that it is possible to develop lines presenting increased SSR resistance. These results are promising for marker assisted or genomic selection.

Ph.d.-afhandling. Den Kongelige Veterinær- og Landbohøjskole, 2002. / Haves også i trykt udg.

Με στόχο την απομόνωση και χαρακτηρισμό εγγενών μυκοπαράσιτων του φυτοπαθογόνου μύκητα Sclerotinia sclerotiorum, απομονώθηκαν 199 υποψήφια μυκοπαράσιτα από χώματα καλλιεργουμένων εδαφών ή κήπων της δυτικής Ελλάδας. Από την προκαταρκτική αξιολόγηση των μυκοπαράσιτων αυτών επιλέχθηκαν τα πλέον αποτελεσματικά δεκαοκτώ, τα οποία αξιολογήθηκαν σε άγαρ ύδατος, σε αποστειρωμένο χώμα και σε μη-αποστειρωμένο (φυσικό χώμα). Σε γενικές γραμμές τα 18 μυκοπαράσιτα έδωσαν υψηλά επίπεδα παρασιτισμού του φυτοπαθογόνου απουσία ενδογενών ανταγωνιστών ενώ ένα από τα απομονωθέντα στελέχη του γένους Gliocladium παρουσίασε άριστα αποτελέσματα και παρουσία ενδογενών ανταγωνιστών. Ειδικότερα η απομόνωση Α-9 εκδήλωσε άριστη ανταγωνιστική δράση. Η μορφή του μολύσματος (υφές, σπόρια) αλλά και το περιβάλλον (άγαρ ύδατος, αποστειρωμένο και μη αποστειρωμένο χώμα) επηρεάζουν αποφασιστικά την συμπεριφορά και ικανότητα μυκοπαρασιτισμού των μυκοπαράσιτων με αποτέλεσμα στα πειράματα αξιολόγησης να παρατηρούνται σημαντικές διαφορές. Τα πλέον σταθερά στην συμπεριφορά τους ήταν τρία στελέχη που ανήκουν στο γένος Gliocladium. Ο ανταγωνισμός που υφίστανται τα προστιθέμενα μυκοπαράσιτα από τα ιθαγενή μικρόβια είναι σημαντικός και είναι ένας παράγοντας που θα πρέπει να λαμβάνεται σοβαρά υπόψη. Η ιστοπαθολογική μελέτη του παρασιτισμού των σκληρωτίων έδειξε ότι ένα από τα απομονωθέντα στελέχη του γένους Gliocladium ήταν το ταχύτερο και καταστρεπτικότερο μυκοπαράσιτο των σκληρωτίων του φυτοπαθογόνου μύκητα. Αρχικά διαπιστώθηκαν οι υφές του μυκοπαράσιτου κάτω από τον φλοιό του σκληρωτίου και λίγο αργότερα στην εντεριώνη. Παράλληλα σχηματίσθηκαν τα πρώτα χλαμυδοσπόρια κοντά στον φλοιό ακολουθούμενα από την εμφάνιση μεγάλα διάκενων. Τελικά οι υφές του μυκοπαράσιτου αποίκισαν ολόκληρο το σκληρώτιο και ακολούθησε αποδιοργάνωση του σκληρωτίου. Η μελέτη στο ηλεκτρονικό μικροσκόπιο σάρωσης έδειξε ότι η βλάστηση των σπορίων γενικεύεται στις 15 ώρες επώασης. Στις περισσότερες περιπτώσεις διαπιστώθηκε περιπλάνηση των βλαστικών σωλήνων πριν τη διείσδυσή τους εντός του σκληρωτίου, ενώ δεν διαπιστώθηκε σχηματισμός απρεσσορίων και διακλαδώσεων του βλαστικού σωλήνα. Τα πειράματα θερμοκηπίου έδειξαν ότι το πλέον καταστρεπτικό μυκοπαράσιτο του γένους Gliocladium συνέβαλε στη μέγιστη προστασία των σποριόφυτων λάχανου έναντι του φυτοπαθογόνου μύκητα S. sclerotiorum, γεγονός που υποδηλώνει ότι το μυκοπαράσιτο αυτό μπορεί να χρησιμοποιηθεί για την αποτελεσματική καταπολέμηση του φυτοπαθογόνου μύκητα στον αγρό. / In order to isolate and characterize endogenous mycoparasites against the phytopathogenic fungi, Sclerotinia sclerotiorum, we isolated 199 candidate mycoparasites from soils of western Greece. Preliminary evaluation resulted in the isolation of 18 isolates with significant mycoparasitic efficiency. Evaluation of these isolates in water agar, sterilized soil and natural soil gave good results upon the parasitism of sclerotia of S. sclerotiorum and revealed that one of them belonging to genus Gliocladium was the most efficient under all tried conditions. This isolate showed high efficiency at both presence and absence of endogenous antagonist. Particularly, isolation A-9 revealed excellent antagonistic action. Histopathology studies demonstrated that the isolated A-9 (Gliocladium spp) was the most fast in parasitizing and destroying the sclerotia of S. sclerotiorum. At the beginning of the infection, there were observed mycoparasite hyphae under the rind and little later into the medulla of the sclerotia. At the same time the first chlamydospores were formed near the rind followed by the appearance of gaps. Finally, the mycoparasite hyphae colonize the whole sclerotium leading to there disorganization. The added mycoparasites face out strong antagonism from the indigenous microorganism and this (antagonism) is an agent that must be seriously taken account. The scanning electron microscopy study showed spore germination initiation about 12 hours after the beginning of incubation and (the spore germination) is generalised after 15 hours of incubation. In most cases it was observed wandering of the germination tubes before sclerotic penetration. Formation of appressoria was difficult to be observed because of the shape of the surface and the crust that exists due to deflation of exudates. Evaluation of plant-protection capability in pot-trials showed that the isolated A-9 (Gliocladium spp) with the faster and highest parasitic exhibited presented the highest plant-protection capability a fact that indicates that this mycoparasite could be used for large-scale biocontrol applications against the phytopathogenic fungi, Sclerotinia sclerotiorum.

The soil-borne fungi Rhizoctonia solani Kuhn and Sclerotinia sclerotiorum De Bary are ubiquitous plant pathogens with a wide host range. They are among the most widespread and destructive diseases of many crops, including sunflowers. Although in many cases, the use of chemicals appears to be the most economical and efficient means of controlling plant pathogens, their environmental concerns and the development of tolerance in pathogen populations have led to drastic reduction in their usage and increased the need to find alternative means of disease control. The potential benefits of applying Trichoderma harzianum Rifai and silicon (Si) nutrition to plants have been extensively reviewed. In this study, the ability of T. harzianum (Eco-T®), soluble silicon, and their combination was evaluated on sunflower (Helianthus annuus L.), for their potential to suppress pathogenic strains of R. solani and S. sclerotiorum. The ability of this crop to take up and accumulate Si in different plant parts was also investigated. In vitro assessment of fungal responses to Si in PDA showed that both R. solani and S. sclerotiorum were inhibited in the presence of Si. More inhibition was observed as the Si concentration increased with a relative increase in pH. Maximum growth inhibition was observed at 3000 mg ;-1 – 6000 mg ;-1 of PDA. No difference in inhibition between the two pathogens was observed, thus confirming the fungitoxic/suppressive ability of high Si concentrations to fungal growth. In addition, in vivo trials showed that the Si concentration of 200 mg ;-1 applied weekly significantly increased the dry weight of plants inoculated with R. solani and S. sclerotiorum and was therefore considered the optimum concentration. Assessments on in vitro antifungal activities of Eco-T® on R. solani and S. sclerotiorum, showed that Eco-T® significantly inhibited mycelial growth, in both dual culture methods and volatile and non-volatile compounds produced by Eco-T®. In addition, the combination of Eco-T® and Si was most effective in suppressing damping-off and increasing plant dry weight of sunflower seedlings in the greenhouse. The combination of Si and Eco-T® significantly increased percentage germination, number of leaves and head dry weight of the sunflower cultivars tested. Silicon alone increased growth but was unable to control R. solani and S. sclerotiorum effectively. Rhizotron studies showed that S. sclerotiorum infected the host through the roots and the stem, whereas R. solani only infected the host through the roots. A study on Si uptake and distribution showed that sunflower accumulates Si in various plant tissues. Analysis of plant tissues revealed that more Si was accumulated in leaves > stems > roots, with the Si levels in leaves being significantly higher than in stems and roots. In conclusion, Si alone could be used to increase growth but was unable to control R. solani and S. sclerotiorum. However, Si together with Eco-T® provides an environmentally friendly alternative for the control of R. solani and S. sclerotiorum, and enhanced plant growth and yield. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

This thesis is an investigation of detecting and quantifying airborne inoculum of Sclerotinia sclerotiorum (Lib.) de Bary to improve the Sclerotinia rot of carrot (SRC) forecast model. A quantitative polymerase chain reaction (qPCR) assay was developed to specifically detect and quantify DNA from airborne ascospores of S. sclerotiorum. The qPCR assay was evaluated on air samples collected using a Burkard Sampler, and showed that ascospores of S. sclerotiorum were specifically detected among a pool of foreign DNA. The concentration of detected ascospores was related to the observed incidence of SRC to suggest a preliminary threshold of 2 to 4 ascospores m-3 of air for SRC development. Evaluation of an Andersen Sampler, the blue plate test (BPT) and the qPCR assay showed that the latter two methods were equally effective in detecting and quantifying ascospores of S. sclerotiorum and consistently detected greater numbers of ascospores than an Andersen Sampler. Three days are required to confirm the presence of S. sclerotiorum using the BPT, while results from the qPCR assay can potentially provide results within five hours of air sampling. The choice of detection method depends on the available resources and need for a quick result. Analysis of data from nine years of air sampling using the BPT indicated that a single air sampling site is sufficient to detect ascospores when counts are low, increasing to two sites during periods when ascospores are detected near threshold levels and crop and environmental conditions are conducive to disease. Chitosan and canopy trimming were evaluated to manage SRC under field conditions. Chitosan reduced area under the disease progress curve (AUDPC) by 55 and 42% in 2009 and 2011, respectively, which was comparable to a standard fungicide. Trimming enhanced chitosan efficacy, reducing AUDPC by 88 and 82% in 2009 and 2011, respectively. Trimming as a stand-alone treatment reduced AUDPC by 66% in 2011. Under controlled environmental conditions, chitosan inconsistently enhanced defense responses against S. sclerotinia. The results show that chitosan has potential to be integrated into SRC management systems, particularly when combined with foliar trimming in years with moderate to high disease risk. / National Research Council of Canada; University of Guelph; Department of Plant Agriculture; Ontario Ministry of Agriculture, Food and Rural Affairs