[ES] Las cucurbitáceas son la segunda familia de hortícolas más importante a nivel mundial, solo por detrás de las solanáceas. Tradicionalmente su cultivo se ha llevado a cabo en las zonas templadas del planeta. Sin embargo, las condiciones de cambio climático, el comercio internacional y los modelos de agricultura intensiva favorecen la aparición de nuevas virosis y enfermedades fúngicas en zonas donde antes no estaban presentes. En este sentido, resulta esencial el monitoreo periódico de las principales zonas productoras, para así poder detectar los virus y hongos emergentes en cada territorio y adaptar los programas de mejora a los objetivos específicos de cada zona. En el caso concreto del melón (Cucumis melo) existe una gran variabilidad intraespecífica que puede servir como fuente de alelos de resistencia frente a estos patógenos. Sin embargo, las fuentes de resistencia suelen encontrarse dentro del germoplasma silvestre, normalmente originario de África o Asia, y en el que el nivel de domesticación es reducido. Para un mejor aprovechamiento de las accesiones resistentes, resulta necesario un estudio del control genético de los caracteres de interés, que permita localizar las regiones asociadas a la resistencia y diseñar marcadores moleculares asociadas a las mismas. Esto facilita los programas de mejora orientados a la introgresión de las resistencias manteniendo el fondo genético de las variedades de interés En la presente tesis doctoral, durante las campañas de verano de 2019 y 2020, se ha llevado a cabo un estudio de la incidencia y diversidad genética de 9 especies virales potencialmente limitantes para el cultivo de cucurbitáceas en el sur este español. Se ha podido observar que los virus transmitidos por pulgones son prevalentes frente a los transmitidos por mosca blanca. Dentro del primer grupo destacó la presencia de watermelon mosaic virus (WMV), cucurbits aphid borne yellows virus (CABYV) y cucumber mosaic virus (CMV), ya que fueron detectados en todas las zonas y cultivos estudiados, apareciendo frecuentemente en infecciones mixtas. Moroccan watermelon mosaic virus (MWMV) y tomato leaf curl New Delhi virus (ToLCNDV) también fueron detectados en algunas zonas, pero con porcentajes de infección más bajos y normalmente en infecciones mixtas con WMV. Los análisis filogenéticos de los distintos aislados encontrados ha permitido la identificación de 7 nuevos perfiles moleculares de WMV y de aislados recombinantes de CMV, lo que es consistente con los resultados obtenidos en otros países y pone de manifiesto la gran variabilidad de estos patógenos. Las accesiones silvestres de melón recogidas en distintos bancos de germoplasma son un valioso recurso para los programas de mejora genética frente a estreses bióticos. La accesión africana TGR-1551 ha sido descrita previamente como resistente a WMV, CYSDV (cucurbit yellow stunting disorder virus), CABYV y el hongo Podosphaera xanthii (Px, razas 1, 2 y 5) agente causal del oídio en melón. Además, es tolerante a la mosca blanca (Bemisia tabaci) y portadora del gen Vat (virus aphid transmission), el cual limita la transmisión de virus por pulgón. Por lo tanto, esta accesión constituye una buena fuente de alelos de resistencia y, al poder utilizar un único parental donante, su uso acortaría los programas de mejora. En el marco de la presente tesis doctoral, mediante el desarrollo de poblaciones segregantes de mapeo y el aprovechamiento de las tecnologías de genotipado masivo se han podido cartografiar los QTLs asociados a la resistencia a CYSDV derivados de esta entrada. En el caso de la resistencia a CYSDV, se han detectado dos QTL en el cromosoma 5. El primero de ellos es de efecto mayor y herencia dominante, estando asociado al desarrollo de síntomas. El segundo QTL, de efecto menor y también de herencia dominante, no confiere resistencia por sí mismo y está asociado a la carga viral durante la infección. Siguiendo una estrategia similar se han podido cartografiar y estrecha / [CA] Les cucurbitàcies són la segona família d'hortícoles més important a nivell mundial, només per darrere de les solanàcies. Tradicionalment el seu cultiu s'ha dut a terme a les zones temperades del planeta. No obstant això, les condicions de canvi climàtic, el comerç internacional i els models d'agricultura intensiva afavoreixen l'aparició de noves virosis i malalties fúngiques en zones on abans no estaven presents. En aquest sentit, resulta essencial el monitoratge periòdic de les principals zones productores, per a d'aquesta manera, poder detectar els virus i fongs emergents en cada territori i adaptar els programes de millora als objectius específics de cada zona. En el cas concret del meló (Cucumis melo) existeix una gran variabilitat intraespecífica que pot servir com a font d'al·lels de resistència enfront d'aquests patògens. No obstant això, les fonts de resistència solen trobar-se dins del germoplasma silvestre, normalment originari d'Àfrica o Àsia, i en el qual el nivell de domesticació és reduït. Per a un millor aprofitament de les accessions resistents, resulta necessari un estudi del control genètic dels caràcters d'interés, que permeta localitzar les regions associades a la resistència i dissenyar marcadors moleculars associats a aquestes. Això facilita els programes de millora orientats a la introgressió de les resistències mantenint el fons genètic de les varietats d'interés. En la present tesi doctoral, durant les campanyes d'estiu de 2019 i 2020, s'ha dut a terme un estudi de la incidència i diversitat genètica de nou espècies virals potencialment limitants per al cultiu de cucurbitàcies en el sud-est espanyol. S'ha pogut observar que els virus transmesos per pugons són prevalents enfront dels transmesos per mosca blanca. Dins del primer grup va destacar la presència de watermelon mosaic virus (WMV), cucurbits aphid born yellows virus (CABYV) i cucumber mosaic virus (CMV), ja que van ser detectats en totes les zones i cultius estudiats, apareixent sovint en infeccions mixtes. Moroccan watermelon mosaic virus (MWMV) i tomatoleaf curl New Delhi virus (ToLCNDV) també van ser detectats en algunes zones, però amb percentatges d'infecció més baixos i normalment en infeccions mixtes amb WMV. Les anàlisis filogenètiques dels diferents aïllats trobats ha permés la identificació de set nous perfils moleculars de WMV i d'aïllats recombinants de CMV, la qual cosa és consistent amb els resultats obtinguts en altres països i posa de manifest la gran variabilitat d'aquests patògens. Les accessions silvestres de meló recollides en diferents bancs de germoplasma són un valuós recurs per als programes de millora genètica enfront d'estressos biòtics. L'accessió africana *TGR-1551 ha sigut descrita prèviament com a resistent a WMV, CYSDV (cucurbit yellow stunting disorder virus), CABYV i el fong Podosphaera xanthii (Px, races 1, 2 i 5) agent causal de l'oïdi en meló. A més, és tolerant a la mosca blanca (Bemisia tabaci) i portadora del gen Vat (virus aphid transmission), el qual limita la transmissió de virus per pugó. Per tant, aquesta accessió constitueix una bona font d'al·lels de resistència i, en poder utilitzar un únic parental donant, el seu ús acurtaria els programes de millora. En el marc de la present tesi doctoral, mitjançant el desenvolupament de poblacions segregants de mapatge i l'aprofitament de les tecnologies de genotipat massiu s'ha pogut cartografiar els QTLs associats a la resistència a CYSDV derivats d'aquesta entrada. En el cas de la resistència a CYSDV, s'han detectat dues QTL en el cromosoma cinc. El primer d'ells és d'efecte major i herència dominant, estant associat al desenvolupament de símptomes. El segon QTL, d'efecte menor i també d'herència dominant, no confereix resistència per si mateix i està associat a la càrrega viral durant la infecció. Seguint una estratègia similar s'han pogut cartografiar i estrényer els *QTLs de resistència enfront de Px. En aquest cas es tracta d'una epistàsia dominant-re / [EN] Cucurbits represent the second most important horticultural family worldwide, second only the Solanaceae family. Traditionally, their cultivation has been concentrated in temperate regions across the globe. However, climate change conditions, international trade, and intensive agricultural practices are contributing to the emergence of new viral and fungal diseases in regions where they were previously absent. In this regard, it is crucial to regularly monitor major production areas to detect emerging viruses and fungi specific to each region. This monitoring allows for the adaptation of breeding programs to the unique goals of each area. In the case of melon (Cucumis melo), it exists significant intraspecific variability that can serve as a source of resistance alleles against these pathogens. However, sources of resistance are often found within wild germplasm, typically originating from Africa or Asia, and characterized by limited domestication. To better utilize these resistant accessions, a study of the genetic control of desirable traits is necessary. This study aims to locate regions associated with resistance and design molecular markers linked to these regions. Such an approach streamlines breeding programs focused on introgressing resistance traits while preserving the genetic background of the desired varieties. During the summer campaigns of 2019 and 2020, this doctoral thesis conducted a study on the incidence and genetic diversity of nine viral species potentially affecting cucurbit cultivation in southeastern Spain. It was observed that viruses transmitted by aphids were more prevalent than those transmitted by whiteflies. Within the first group, the presence of watermelon mosaic virus (WMV), cucurbits aphid borne yellows virus (CABYV), and cucumber mosaic virus (CMV) stood out, as they were detected in all the studied areas and crops, often in mixed infections. Moroccan watermelon mosaic virus (MWMV) and tomato leaf curl New Delhi virus (ToLCNDV) were also detected in some areas but with lower infection percentages, typically in mixed infections with WMV. Phylogenetic analyses of the found isolates have identified seven new molecular profiles of WMV and recombinant CMV isolates, which is consistent with results from other countries, highlighting the extensive variability of these pathogens. Wild melon accessions preserved in various germplasm banks represent a valuable resource for breeding programs against biotic stresses. The African accession TGR-1551 has been previously described as resistant to WMV, CYSDV (cucurbit yellow stunting disorder virus), CABYV, and the fungus Podosphaera xanthii (Px, races 1, 2, and 5), which causes powdery mildew in melons. Additionally, it is tolerant to whiteflies (Bemisia tabaci) and carries the Vat gene (Virus Aphid Transmission), limiting virus transmission by aphids. Therefore, this accession constitutes as an excellent source of resistance alleles, and its use, as a single donor parent, can expedite breeding programs. Within the scope of this doctoral thesis, through the development of segregating mapping populations and the utilization of high-throughput genotyping technologies, the QTLs associated with CYSDV resistance from this accession have been mapped. In the case of CYSDV resistance, two QTLs have been detected on chromosome 5. The first of these, with major effects and dominant inheritance, is associated with symptom development. The second QTL, with minor effects and also dominant inheritance, does not confer resistance by itself and is linked to viral load during infection. A similar strategy was employed to map and narrow down the QTLs for resistance against Px. In this case, it involves a dominant-recessive epistasis, with the recessive gene located on chromosome 12 and the dominant gene on chromosome 5, specifically in the same region where the major CYSDV resistance QTL is located. Regarding resistance against WMV, previous studies conducted by the research / This research was funded by the Spanish Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033), grant number PID2020-116055RB (C21 and C22), and by the Conselleria d’Educació, Investigació, Cultura i Esports de la Generalitat Valenciana, grant number PROMETEO/2021/072 (to promote excellence groups, cofinanced with FEDER funds). M.L. is a recipient of a predoctoral fellowship (PRE2018-083466) of the Spanish Ministerio de Ciencia, Innovación y Universidades co-financed with FSE funds. / López Martín, M. (2023). Breeding Melons for Resistance to Viral and Fungal Diseases. Exploiting the Multi-Resistant Accession TGR-1551 [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/202060

Biotische und abiotische Stressfaktoren mindern die Quantität und die Qualität landwirtschaftlicher Erzeugnisse. Sogar die kontrollierten Wachstumsbedingungen eines Gewächshauses tragen nur bedingt zur Minderung der schädlichen Auswirkungen von suboptimalen Wachstumsfaktoren bei. Die negativen Effekte, die durch die Entstehung suboptimaler Wachstumsbedingungen auftreten können, manifestieren sich oft erst nach geraumer Zeit. Aus diesem Grund ist es wichtig, Maßnahmen zu treffen, die diesen negativen Auswirkungen entgegenwirken und eine nachhaltige Produktion von Obst und Gemüse sichern. Um die Widerstandsfähigkeit der Pflanzen gegenüber den zahlreichen Stressfaktoren zu erhöhen, werden sogenannte Pflanzenstärkungsmittel verwendet. Die zahlreichen gärtnerischen Substrate, die bei der Kultivierung von Obst und Gemüse heutzutage unentbehrlich geworden sind, besitzen verschiedene chemische und physikalische Eigenschaften. Diese Eigenschaften unterliegen dem ständigen Einfluss von verschiedenen Faktoren, insbesondere dem Pflanzenwachstum. Anderseits beeinflussen gärtnerische Substrate die Entwicklung der Pflanzen. Die Fähigkeit eines Substrates zur Wasserhaltung, sowie zur Gewährleistung einer optimalen Versorgung mit pflanzlichen Nährstoffen während der kritischen Wachstumsperioden der Pflanzen kann die Produktivität der gärtnerischen Kulturen stark beeinflussen. Dynamische Veränderungen der Substrateigenschaften während des Pflanzenwachstums und Änderungen in physiologischen Reaktionen der gärtnerischen Pflanzen können als System betrachtet werden, und als System können sie, zwecks Optimierung der pflanzlichen Systeme, beeinflusst werden. Diese Einflussnahme kann durch Verwendung von Pflanzenstärkungsmitteln verschiedener Herkunft erreicht werden. In der Fachliteratur wird häufig über Pflanzenstärkungsmittel diskutiert. Dabei wird sehr oft außer Acht gelassen, dass jedes Pflanzenstärkungsmittel ein eigenes Wirkungsspektrum besitzt. Die Breite des Wirkungsspektrums eines Pflanzenstärkungsmittels ist begrenzt, weshalb die positiven Effekte des verwendeten Mittels häufig geringer ausfallen können als erwartet. Die Arbeitshypothese dieser Arbeit belegt, dass durch die Kombination verschiedener bioaktiver Stoffe mit Pflanzenstärkungsmitteln dieses Wirkungsspektrum erweitert werden kann. Aus diesen Zusammenhängen leitet sich das Interesse an Kombinationen verschiedener Pflanzenstärkungsmittel sowie anderer bioaktiver Stoffe ab. Diese Arbeit untersucht die biologischen Effekte verschiedener Kombinationen von bioaktiven Stoffen und Pflanzenstärkungsmitteln zur Stabilisierung pflanzlicher Systeme. Als bioaktive Stoffe werden in dieser Arbeit Laktate und Humate bezeichnet, wobei Mikroorganismen als Pflanzenstärkungsmittel eingesetzt wurden. Die Ergebnisse dieser Arbeit zeigen, dass ein kombinierter Einsatz von Mikroorganismen, Humaten und Laktaten zum Einen zum Erhalt der chemischen und physikalischen Eigenschaften gärtnerischer Substrate, zum Anderen zur Stabilisierung der Pflanzen gegenüber suboptimalen Wachstumsfaktoren beiträgt. Die Anwendung der Kombination von allen drei Komponenten auf Versuchsvarianten mit Gewächshausgurken als Modellpflanze zeigte, dass die Pflanzenproduktivität bei diesen Varianten am höchsten war. Die physiologischen Reaktionen der Gurkenpflanzen im Versuch mit modellierten Stressfaktoren wurden durch Chlorophyllfluoreszenz ermittelt. Die Ergebnisse zeigten, dass die Pflanzen, die mit allen drei Komponenten behandelt wurden, gegenüber suboptimalen Wachstumsbedingungen resistent sind. Die Resultate dieser Arbeit wurden in einem gärtnerischen Unternehmen approbiert. / Biotic and abiotic stress factors reduce the quality and quantity of the horticultural produce. Even controlled growing conditions of a greenhouse can not reduce all the negative influences of the suboptimal growing factors. The negative effects caused by the suboptimal growing factors manifest themselves only after substantial period of time. That is why it is important to take steps that counter these negative effects and enable sustainable production of fruits and vegetables. To improve the resistance of the plants against different stress factors, the plant strengtheners are applied. The horticultural substrates, which are used for cultivation of the fruits and vegetables, have become unalienable and possess the range of different physical and chemical properties. These properties are subjected to constant influence of different biotic and abiotic factors; especially those resulted from the plant growth itself. On the other hand, the substrates influence the growth of the horticultural plants. The water holding capacity of the substrate and its capacity to provide plants with nutrient elements during the critical vegetation periods can influence the productivity of the plant system. Dynamic changes of the substrate properties during the plant growth and changes in physiological reactions of horticultural plants can be viewed as a system, and as the system it can be influenced for the purposes of its optimization. This influence can be achieved by application of different plant strengtheners of different origin. The role of the plant strengthening agents is being discussed in the literature. The missing point in the discussion however is the fact that the plant strengtheners have their own activity spectrum. The activity spectrum of the bioactive substance is limited and expected positive effects of its application can be lesser that expected. The hypothesis of the thesis is based on the premise that combination of the different bioactive substances and plant strengthening agents can increase the activity spectrum. These interrelations cause an interest on combinations of different plant strengtheners and others bioactive substances. This thesis investigates biological effects different combinations of bioactive substances and plant strengtheners with an aim to stabilize plant systems. In this work, lactates and humates are described as bioactive compounds, whereas microorganisms are perceived as plant strengtheners. The results of this work show that the combined application of microorganisms, humates and lactates sustain chemical and physical properties of the horticultural substrates and at the same time stabilize plant systems under the suboptimal growing factors. The experiment variants with greenhouse cucumbers as a model plant treated with all three components showed the highest productivity. Physiological reactions of the cucumber plants were investigated through measurement of the chlorophyll fluorescence of the cucumber leaves in the experiments with modeled suboptimal growing factors. The results showed that the plants treated with a combination of humates lactates and microorganism were more resistant to suboptimal growing conditions than the plants on variants without treatment. The results of this work were approbated at a horticultural enterprise.

The response of cucumber (Cucumis sativus L.) plants to various root and shoot environments (solution depth, temperature, ionic strength, nitrogen and calcium level and light intensity) were studied. Cucumber plants were grown in continuously circulating-solution in a heated-glasshouse. Dry weights of leaves, stems and roots, leaf area, leaf number, root length and root number were measured as well as uptake of potassium, calcium and nitrogen. The relationship between shoot and root in terms of functional equilibrium equations was also examined. The results presented show that: 1. Shoot growth of cucumber plants was reduced if grown in solutions of less than 50mm in depth; 2. When roots were grown in shallow solution depths at 1 or 5mm the dry weight allocated to the root increased. The ratio of root number/root length(no./cm) also increased. Lowering solution temperature to 12.5±2.5°C enhanced the production of root number relctive to root length, and 5 and 2% of full strength and 5% of full strength nitrogen level solution stimulated the growth of root length relative to root number; 3. Under low solution temperature treatment leaf number was maintained at the expense of leaf area. Under low total ionic strength and low nitrogen solution, enhanced root length growth was at the expense of leaf area growth; 4. Low solution temperature enhanced the dry weight allocated to the stem relative to the leaf. Low total ionic strength and low nitrogen solution increased the dry weight allocated to the leaf relative to the stem; 5. The specific activity of root, represented by specific absorption rate, increased when the shoot was under light stress and, the specific activity of shoot, represented by unit shoot rate, increased when the root was under nitrogen-stress; 6. The form of equation developed by Thornley (∆M = fm∆W, where ∆M is the increment in weight of element M and ∆W the increment in total plant dry weight during a time period ∆t with fm a constant) showed a better relationship than the equation developed by Davidson [root mass x rate(absorption) ∝ leaf mass x rate(photosynthesis)] and subsequently used by Hunt in the form of mass ratio(root/shoot) ∝ l/activity ratio; 7. The equation developed by Chung et al, total plant weight/(leaf number/leaf area) ∝ total "k"/(root number/root length), where k represents the total contents of elements or compounds, showed a good approximation of the relationship between shoot and root under all the environmental stresses imposed with the exception of calcium uptake. The results support the concept that the activity of the root or shoot in carrying out its function is influenced by the demand created by the opposite organ and appears to be a better assumption than that which proposes that the activity of an organ is solely dependent on its own size.

The use of biological control agents (BCAs) in the past has shown limited success as its application has often been done incorrectly, and in addition, management practices are rarely altered to incorporate BCAs. Criteria for the correct application of BCAs have been devised as part of the research, and companies selling these products may use the said criteria. Such application will ensure the correct BCAs are used and, more specifically, used under the correct conditions. The powdery mildew (PM) fungus is often seen to develop resistance to synthetic fungicides and, therefore, alternative control measures are required. BCAs as an alternative pose less risk to the environment, workers and the consumer. A pre-trial has been conducted with a range of BCAs to see if they can control powdery mildew (PM) in a greenhouse environment on hydroponically grown cucumber (Cucumis sativus L.) plants using the variety Baccara that has only a moderate tolerance to PM. The BCAs have been compared to the control (synthetic fungicide: Bravo). Comparative work includes Coyier's model, which has been modified and adapted for these trials to determine the percentage of leaf area covered by the PM infection. Furthermore, the number of fruit harvested per treatment, kilogram yield, total mass of yield and average fruit mass is also used to determine the efficacy of the BCAs as these factors have economic significance to commercial growers. The pre-trial showed promise until the fertigation computer failed, resulting in a nutrient shortage and imbalance, confirming that BCAs alone cannot control PM. Synthetic fungicides were applied until control of PM and plant nutrition was regained. BCAs were re-introduced and used until the end of crop production. The confirmation from the pre-trial has led to the inclusion of silicon in conjunction with the BCAs in the two subsequent trials (Trials 1 & 2). Silicon was applied with the BCAs as a foliar spray on a weekly basis. In trials 1 and 2, the cucumber variety, Palladium, with a high genetic tolerance to PM is used, as this variety is suited to form part of the holistic approach used for trials 1 and 2. Trial 1 showed that treatment A, containing Streptomyces griseovirdis and Streptomyces aureofaciens, had the highest yield. Both of these are bacterial BCAs and demonstrated their adaptability to varied climatic conditions, notably when low humidity was experienced. In treatment B, Trichoderma harzianum strains, Rifai and Uppington, show the slowest rate of PM development. In trials 1 and 2, the best actual PM control was obtained by two fungal based BCAs (Trial 1, treatment C was Ampelomyces quisqualis) and (Trial 2, treatment B was Trichoderma harzianum strains, Rifai and Uppington), showing that fungal BCAs have a place for this application, but the growth-enhancing properties of bacterial based BCAs make economic sense and would make them attractive to growers. Treatment A (Streptomyces spp.) had the most number of fruit for the entire growing period and the best overall yield (kg yield) again. Two of the BCA / silicon treatments have marginally better PM control compared to that of the control (E) treatment, although not statistically significant. Treatment E (control) has the highest average fruit mass in this instance but does not have the highest yield (kg yield) when compared to treatments A and B, possibly due to the growth-enhancing properties of most of these BCAs. Therefore, most of these BCA treatments give fairly inconsistent results that vary possibly according to season, humidity and temperature, making it difficult to predict their efficacy. Using combinations or weekly alternations of these BCAs with extremes of climatic adaptation will probably be the most reliable method of obtaining consistent results. Bacterial BCAs are shown to have lower humidity requirements and produce the most consistent results in terms of fruit number, yield and fruit mass and a combination of bacterial and fungal based BCAs would possibly be the best as this would control PM and yet still have the growth enhancing properties from the bacterial based BCAs. From the research, it can be said that some BCAs in trials 1 and 2 produce results similar to that of the control in terms of percentage leaf area covered by PM and some are shown to have improved yields. Results produced from certain BCA treatments are thus equal to the control; yet provide an environmentally friendly alternative to synthetic fungicides. Silicon is listed as a beneficial element rather than an essential element; however, literature claims it to be highly effective in treating PM in cucurbits. Results from trials 1 and 2 show that control of PM is possible in most cases, when a holistic approach is used. This approach includes a cucumber variety with a high PM tolerance, optimum nutrition, cultural practices and silicon in combination with the BCAs. A complete change of management practices is necessary to implement such a BCA program. / Agriculture, Animal Health & Human Ecology / M. Tech. (Nature Conservation)

Das Pflanzenwachstum fördernde Bakterien (PGPB) kommen ubiquitär sowohl an der Wurzel als auch am Spross der Pflanzen vor und sie können über direkte oder indirekte Mechanismen einen bedeutenden Beitrag zur Stickstoffernährung der Pflanzen leisten. Die vorliegende Arbeit umfasst a) die Isolierung von PGPB, welche das Wachstum verschiedener Pflanzenarten fördern und durch Fusarien verursachte Pflanzenkrankheiten bekämpfen, b) die Analyse der Möglichkeiten Probleme der Pflanzenernährung durch den Einsatz von PGPB zu lösen, c) die Entwicklung neuer molekularbiologischer Methoden zur Messung der Diversität und Aktivität der PGPB. Im Rahmen dieser Arbeit wurden Methoden zur Beschreibung der Diversität von rhizosphären PGPB entwickelt und verbessert um Verbindungen zwischen applizierten PGPB und deren Aktivitäten zu prüfen. Die sensitive quantitative real-time-PCR Methode wurde zur Quantifizierung bzw. zum Nachweis der inokulierten PGPB und zum Nachweis des nitrogenase-reduktase-Gens (nifH), des Markergens für potentiell diazotrophe Bakterien. Bakterienartspezifische Primer wurden aus dem Sequenzvergleich der 16S-23S ISR ausgewählter Bakterienstämme selektiert und Protokolle zur Quantifizierung dieser Bakterienarten erarbeitet. Die nifH Gen Quantifizierung an Pflanzen eröffnet die Möglichkeit Schlüsselorganismen in der assoziativen biologischen Luftstickstoffbindung zu identifizieren und kurzfristige Reaktionen der Bakteriengesellschaften auf Umweltveränderungen und Regulationsmechanismen in situ zu analysieren. / Plant growth promoting bacteria (PGPB) are ubiquitous in both plant root and shoot, and are important contributors to the nitrogen-input of plants exerting their positive effects on plant growth directly or indirectly through different mechanisms. The present work focuses on a) the isolation of PGPB, which promotes the growth of different plant cultures and controls plant diseases caused by Fusarium species, b) the prospects of PGPB to solve plant nutritional problems, c) developing new molecular methods for the assessment of their diversity and activity. In the frame of this thesis, the methods for the description of the diversity of root colonizing PGPB have been developed and improved to provide links between introduced PGPB abundance and activities. The approach used was based on the sensitive real – time PCR detection/quantification of introduced PGBP and the nitrogenase reductase gene (nifH), which served as a marker gene for potential diazotrophs. The amplified 16S-23S ISR sequences of studied bacteria were subjected to strain – specific primer design and a highly specific bacteria quantification protocol were developed. The bacteria quantification protocol was based on real – time PCR using strain specific primers in order to evaluate the colonization ability of studied bacteria, which were inoculated to plant roots. The results presented in this thesis have shown that monitoring of nifH amount in plant root is a suitable and promising approach to link inoculated diazotrophic bacteria abundance and its potential activity. The study of nifH gene abundance in plant offers the opportunity to identify key players in asymbiotic nitrogen fixation, to study short-term community responses in changing environments, or to analyze the effect of regulation in situ.

The use of biological control agents (BCAs) in the past has shown limited success as its application has often been done incorrectly, and in addition, management practices are rarely altered to incorporate BCAs. Criteria for the correct application of BCAs have been devised as part of the research, and companies selling these products may use the said criteria. Such application will ensure the correct BCAs are used and, more specifically, used under the correct conditions. The powdery mildew (PM) fungus is often seen to develop resistance to synthetic fungicides and, therefore, alternative control measures are required. BCAs as an alternative pose less risk to the environment, workers and the consumer. A pre-trial has been conducted with a range of BCAs to see if they can control powdery mildew (PM) in a greenhouse environment on hydroponically grown cucumber (Cucumis sativus L.) plants using the variety Baccara that has only a moderate tolerance to PM. The BCAs have been compared to the control (synthetic fungicide: Bravo). Comparative work includes Coyier's model, which has been modified and adapted for these trials to determine the percentage of leaf area covered by the PM infection. Furthermore, the number of fruit harvested per treatment, kilogram yield, total mass of yield and average fruit mass is also used to determine the efficacy of the BCAs as these factors have economic significance to commercial growers. The pre-trial showed promise until the fertigation computer failed, resulting in a nutrient shortage and imbalance, confirming that BCAs alone cannot control PM. Synthetic fungicides were applied until control of PM and plant nutrition was regained. BCAs were re-introduced and used until the end of crop production. The confirmation from the pre-trial has led to the inclusion of silicon in conjunction with the BCAs in the two subsequent trials (Trials 1 & 2). Silicon was applied with the BCAs as a foliar spray on a weekly basis. In trials 1 and 2, the cucumber variety, Palladium, with a high genetic tolerance to PM is used, as this variety is suited to form part of the holistic approach used for trials 1 and 2. Trial 1 showed that treatment A, containing Streptomyces griseovirdis and Streptomyces aureofaciens, had the highest yield. Both of these are bacterial BCAs and demonstrated their adaptability to varied climatic conditions, notably when low humidity was experienced. In treatment B, Trichoderma harzianum strains, Rifai and Uppington, show the slowest rate of PM development. In trials 1 and 2, the best actual PM control was obtained by two fungal based BCAs (Trial 1, treatment C was Ampelomyces quisqualis) and (Trial 2, treatment B was Trichoderma harzianum strains, Rifai and Uppington), showing that fungal BCAs have a place for this application, but the growth-enhancing properties of bacterial based BCAs make economic sense and would make them attractive to growers. Treatment A (Streptomyces spp.) had the most number of fruit for the entire growing period and the best overall yield (kg yield) again. Two of the BCA / silicon treatments have marginally better PM control compared to that of the control (E) treatment, although not statistically significant. Treatment E (control) has the highest average fruit mass in this instance but does not have the highest yield (kg yield) when compared to treatments A and B, possibly due to the growth-enhancing properties of most of these BCAs. Therefore, most of these BCA treatments give fairly inconsistent results that vary possibly according to season, humidity and temperature, making it difficult to predict their efficacy. Using combinations or weekly alternations of these BCAs with extremes of climatic adaptation will probably be the most reliable method of obtaining consistent results. Bacterial BCAs are shown to have lower humidity requirements and produce the most consistent results in terms of fruit number, yield and fruit mass and a combination of bacterial and fungal based BCAs would possibly be the best as this would control PM and yet still have the growth enhancing properties from the bacterial based BCAs. From the research, it can be said that some BCAs in trials 1 and 2 produce results similar to that of the control in terms of percentage leaf area covered by PM and some are shown to have improved yields. Results produced from certain BCA treatments are thus equal to the control; yet provide an environmentally friendly alternative to synthetic fungicides. Silicon is listed as a beneficial element rather than an essential element; however, literature claims it to be highly effective in treating PM in cucurbits. Results from trials 1 and 2 show that control of PM is possible in most cases, when a holistic approach is used. This approach includes a cucumber variety with a high PM tolerance, optimum nutrition, cultural practices and silicon in combination with the BCAs. A complete change of management practices is necessary to implement such a BCA program. / Agriculture, Animal Health and Human Ecology / M. Tech. (Nature Conservation)

Some microorganisms are known to form mutualistic symbiosis with plant roots and by their impact they can improve some plant parameters. These symbiotic microorganisms, which are able to improve some plant parameters, include especially mycorrhizal fungi, plant growth promoting bacteria and some saprotrophic mycoparasitical fungi. Mechanisms of changes of these parameters, as influenced by symbiotic microorganisms, are known only in part and nowadays are being actively researched. Aims of this work were to find out if selected microbial treatments influence selected growth, physiological and yield parameters of plants and contents of selected substances in fruits. Within this work were made three pot greenhouse experiments (experiments 1, 2 and 3) and three pilot greenhouse experiments (experiments 4, 5 and 6), performed on tomato (Solanum lycopersicum) and cucumber (Cucumis sativus) plants. Plants were grown in hydroponics using a carrier of rockwool and they were watered by nutrient solution. As microbial treatments for plants in experiments have been used a mixture of arbuscular mycorrhizal fungi (AM), mixture of plant growth promoting bacteria (PGPB), saprotrophic mycoparasitical fungus Trichoderma harzianum (Th) and various mutual combinations of these treatments. There have been observed...

Les nématodes à galles demeurent l'un des problèmes les plus graves des ‎agriculteurs de serres du Liban et du Moyen-Orient. Dans le passé, la fumigation du sol au ‎bromure de méthyle a été considérée comme la meilleure mesure de contrôle contre ces ‎nématodes. Toutefois, à la lumière de l'élimination globale du bromure de méthyle, l'accès ‎aux alternatives efficaces et durables est devenu une nécessité essentielle.‎L'objectif de cette étude est d'évaluer l'efficacité des deux engrais verts, le radis ‎huileux (Raphanus sativus oleifera) et à la roquette (Eruca vesicaria sativa) appliquées ‎avec ou sans bâche en plastique, séparément et en combinaison avec Oxamyl, dans la ‎gestion des nématodes à galles en cultures de concombres de serre. En outre, cette étude ‎vise à évaluer la faisabilité financière de la technique de biofumigation avec les deux ‎cultures utilisées et de la rentabilité finale de ces engrais verts en termes de taux coût-profit ‎par rapport au bromure de méthyle.‎A cette fin, trois expériences sur le terrain ont été menées dans des serres ‎commerciales, situées sur la zone côtière du Liban.‎Dans les deux expériences A et B, des résultats cohérents ont été enregistrés en ‎termes de production de rendements significativement plus élevés et de la réduction des ‎populations de nématodes avec les engrais verts‎ utilisés avec ou sans bâche en plastique, ‎par rapport au témoin non traité.‎Quant aux résultats obtenus par les engrais verts‎ par rapport ‎ au bromure de ‎méthyle, dans l'expérience A, le rendement produit par le bromure de méthyle était ‎significativement plus élevé que celui du radis huileux avec bâche en plastique. ‎Cependant, la différence n'était pas significative entre la réduction de la population de ‎nématodes résultant du bromure de méthyle et celle du radis huileux avec bâche en ‎plastique. Les différences du rendement ainsi que la réduction des nématodes étaient ‎significatives entre le bromure de méthyle et le radis huileux sans bâche en plastique.‎Dans l'expérience B, aucune différence significative n'a été observée dans le ‎rendement ni la réduction de la population de nématodes entre aucun des deux engrais ‎verts‎ utilisés avec bâche en plastique et le bromure de méthyle. Ces différences étaient ‎significativement en faveur du bromure de méthyle uniquement lorsque le radis huileux a ‎été utilisé sans bâche en plastique.‎Dans l'expérience C, où Vydate (Oxamyl) a été appliqué à la dose de 1 litre par 1,000 ‎m2 à tous les traitements, il n'y avait pas de différence significative dans le rendement ni la ‎réduction de la population de nématodes entre chacun des deux engrais verts utilisés avec ‎ou sans bâche en plastique et le bromure de méthyle.‎L'analyse coût-profit menée sur tous les traitements appliqués dans les 3 ‎expériences a montré que dans tous les cas, tous les traitements appliqués, qu'ils soient ‎chimiques, non-chimique (avec ou sans bâche en plastique) ou en association ont produit ‎des bénéfices nets supérieurs au bromure de méthyle, même lorsque le rendement produit ‎par le bromure de méthyle était significativement plus élevée.‎L'utilisation du plastique pour couvrir les radis huileux a généralement produit de ‎meilleurs résultats en termes de production de rendements plus élevés, une meilleure ‎réduction des populations de nématodes à galles dans le sol, ainsi conduisant à des ‎augmentations raisonnables des profits nets.‎A la base de ces résultats et à la lumière de l'élimination globale du bromure de ‎méthyle, on peut conclure que l'utilisation du radis huileux et la roquette comme engrais ‎verts avec bâche en plastique peut être considéré comme un outil alternatif pour la gestion ‎des nématodes à galles dans la production de concombres de serre dans les conditions ‎libanaises.‎ / Root-knot nematodes remain one of the most serious problems faced ‎by ‎greenhouse farmers of Lebanon and the Middle East region. In the past, soil fumigation ‎with methyl bromide has been considered as ‎the best control measure against root-knot ‎nematodes. However, in the light of the global phase out of methyl bromide, finding ‎efficient and viable alternatives is an essential necessity.‎The objective of this study is to evaluate the efficacy of the two biofumigation ‎crops ‎Oil Radish (Raphanus sativus oleifera) and Arugula (Eruca vesicaria sativa) applied ‎with ‎and without plastic tarp, separately and in combination with Oxamyl in the ‎management of ‎the root-knot nematodes in greenhouse cucumber crops. Additionally, this ‎study aimed at ‎assessing the financial feasibility of the biofumigation technique with the ‎two cops used ‎and the final profitability of these green manure crops in terms of cost to ‎benefit ratio as ‎compared to methyl bromide.‎For this purpose, three field experiments were carried out in ‎commercial ‎greenhouses situated on the coastal zone of Lebanon.‎In both experiments A & B consistent results were recorded in terms of production ‎of ‎significantly higher yields and reduction of nematode population with the ‎biofumigation ‎crops used whether with or without plastic cover, as compared to untreated ‎fallow.‎As to the results achieved by the biofumigation crops with respect to methyl ‎bromide, ‎in experiment A yield produced by methyl bromide was significantly higher than ‎oil radish ‎with plastic cover. However, no significant difference was found between ‎reduction of ‎nematode population resulting from methyl bromide and oil radish with plastic ‎cover. ‎Difference was significant between methyl bromide and oil radish without plastic ‎cover in ‎both yield and reduction of nematodes.‎In experiment B no significant difference was observed in neither yield nor ‎reduction ‎of nematode population between any of the two biofumigation crops used with ‎plastic ‎cover and methyl bromide. These differences were significantly in favor of methyl ‎bromide ‎only when oil radish was used without plastic cover.‎In experiment C where Vydate (Oxamyl) was incorporated at the rate of 1 liter ‎per ‎‎1,000 m2 to all treatments, there was no significant difference in neither yield nor ‎reduction ‎of nematode population between any of the two biofumigation crops used with or ‎without ‎plastic cover.‎Cost-benefit analysis made on all treatments applied in the 3 experiments ‎showed ‎that in all cases, all treatments applied, whether chemical, non-chemical (with or ‎without ‎plastic cover) or in combination have produced higher net profits than methyl ‎bromide, ‎even when yield produced by methyl bromide was significantly higher.‎Use of plastic for covering oil radish has generally produced ‎better results in terms ‎of ‎production of higher yields, better reduction of soil ‎populations of root-knot nematodes‏‎ ‎and ‎‏leading to ‎‏reasonable increases of net profits.‎Based on these findings and in the light of global phase out of methyl bromide, ‎it ‎can be concluded that the use of oil radish and arugula as biofumigation crops with ‎plastic ‎cover can be considered as ‎an alternative management tool for the root-knot ‎nematode in ‎greenhouse cucumber ‎production under Lebanese conditions.‎