<i>Trichoderma harzianum </i>and <i>Aneurinobacillus migulanus </i>were tested separately and in combination as potential biological control agents against <i>F. oxysporum </i>f. sp. <i>gladioli </i>on gladiolus in soil-less culture.  The major secondary metabolites produced by <i>Trichoderma harzianum </i>against <i>F. oxysporum </i>f. sp. <i>gladioli </i>in the treated gladiolus corms as well as in the potato dextrose broth were studied.  The impact of re-application times on the effectiveness of <i>Trichoderma harzianum </i>and <i>Aneurinobacillus migulanus </i>against gladiolus corm rot and Gladiolus production in soil-less culture was examined. Results showed that <i>T. harzianum </i>proved to use different mechanisms against <i>F. oxysporum </i>f. sp. <i>gladioli </i>depending on  the inoculation method. <i>T. harzianum </i>and <i>A. migulanus </i>reduced host defence enzymes.  Also, they increased GA ₃ and IAA content in the corms.  SEM showed that the suppressive mechanisms of <i>T. harzianum </i>and <i>A. migulanus </i>differed <i>T. harzianum </i>appeared to operate through a combination of antibiosis and substrate competition, 6-n-pentyl-6H-pyran-2-one (6PP) and harzianic acid (HA) were found as the main metabolites secreted by <i>T. harzianum.  </i>A significant positive correlation was revealed between qPCR and CFU for both <i>T. harzianum </i>and <i>F. oxysporum </i>f. sp. <i>gladioli.  </i>Multiple applications of <i>T. harzianum </i>and <i>A. migulanus </i>re- application was a successful strategy for suppression of <i>F. oxysporum </i>f. sp. <i>gladioli.  </i>Briefly, <i>T. harzianum </i>was more effective than <i>A. migulanus </i>in <i>F. oxysporum </i>f. sp. <i>gladioli </i>suppression and Gladiolus growth enhancement in soil-less culture. The mixing strategy between <i>T. harzianum </i>and <i>A. migulanus </i>failed.

Para prevenir que el consumidor rechace las bebidas deterioradas por mohos, es importante evaluar la probabilidad de que una determinada bebida sea deteriorada microbiológicamente antes que alcance su vida útil. Los modelos matemáticos, que son capaces de predecir el efecto de diferentes factores sobre el crecimiento fúngico, mejoran la toma de decisiones de la vida útil y optimizan las medidas de control durante la producción, siendo de gran utilidad como herramientas efectivas en el control de calidad de la industria de bebidas. Por esta razón, el objetivo principal de esta investigación fue usar el modelo logístico de la microbiología predictiva para determinar la probabilidad de crecimiento de Fusarium oxysporum en la bebida isotónica sabor mandarina, frente a dos condiciones de temperaturas de almacenamiento: 20 y 30 °C y a dos cargas de inóculo: 100 y 101 esporas/100 mL de bebida isotónica. Los resultados mostraron que el deterioro ocurrió más rápido a 30 °C con una carga de 101 esporas/100 mL de bebida isotónica (con un RMSE “Raíz del Error Cuadrático Medio” = 5.9196) que a 20 °C con 100 esporas/100 mL de bebida isotónica (RMSE = 5.4397) y el tiempo al crecimiento de Fusarium oxysporum decrece en función del incremento tanto de la temperatura de almacenamiento como del tamaño del inóculo. El menor valor de t10% (67.04 horas), que representa el tiempo que da la alerta a la industria de bebidas para recuperar los productos del mercado por un caso de contaminación, se obtuvo con un tratamiento de 101 esporas/100 mL de bebida isotónica a 30 °C. Este estudio logró demostrar que incluso a muy bajas concentraciones de inóculo, la bebida isotónica es deteriorada fácilmente por Fusarium oxysporum y el modelo logístico proporciona a la industria de bebidas un método rápido y de bajo costo para estimar el efecto de la temperatura de almacenamiento y tamaño del inóculo en la bebida isotónica. / Tesis

Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Kirk J. Cymmek, Dept. of Biological Sciences. Includes bibliographical references.

3 pp. / This publication provides information on the development and management of Fusarium wilt of lettuce. Topics covered include the characteristics of the plant pathogen, disease development, and disease management considerations.

This work encompasses studies on the phylogeny of F. oxysporum f. sp. lactucae, the development of a PCR-based seed assay for the detection of this fungus in seed, the potential of seed transmission of the fungus that may result in seed dissemination, and the genetic variation existing within pathogen populations. In phylogenetic analysis, the mtSSU and EF-1&amp;#945; sequences provided limited phylogenetic resolution and did not differentiate the lactucae isolates from other F. oxysporum isolates, while the IGS region resolved lactucae race 1 isolates as a monophyletic group with three other f. spp. of F. oxysporum. In all analyses, lactucae race 2 isolates comprised a separate lineage that was phylogenetically distinct. Based the IGS, PCR primers were designed for detection of the fungus, and a PCR-based seed assay was developed for detection of the fungus in seed. This assay allowed for detection of the pathogen from artificially infested seed lots with infestation rates as low as 0.5%. To investigate seedborne transmission, the moderately resistant cultivars Sharpshooter, Vulcan, and King Henry were inoculated and grown to maturity in the greenhouse. The pathogen was recovered from sections of surface disinfested inflorescence stalks at rates of 14.3 - 62.7% but not from the floral parts. The incidence of recovery from nondisinfested seeds was between 0.02% and 0.08%. The pathogen was not isolated from surface disinfested seeds suggesting that it was externally seedborne. The pathogen was recovered from pathogen-free seeds mixed with infested debris suggesting infested seed may contribute to recently documented dissemination of this pathogen worldwide. Isolates of Fusarium oxsyporum f. sp. lactucae were analyzed for genetic diversity using inter-simple sequence repeat molecular markers. Results revealed 2 main groups within the Arizona isolates corresponding to eight haplotypes in 2005, which evolved from 2 haplotypes in 2001. Haplotype 1-05 was widespread, occurring in two of the four countries where F. o. f. sp. lactucae has been reported. 23 haplotypes were identified among the California isolates that clustered into two subgroups. The clustering of isolates from Arizona suggests that there has been more than one introduction of the pathogen into Arizona.

Growth chamber trials were performed to investigate optimal conditions for the small scale production of isolate M12-4A of Fusarium oxysporum on substrate materials that are locally available to subsistence farmers in West Africa. Field trials were conducted in Mali to evaluate the effectiveness of F. oxysporum for the control of Striga hermonthica and to determine the host range of F. oxysporum. F. oxysporum grew and colonized substrates over a range of temperatures (24, 28 and 32 C). Chopped sorghum straw pieces, straw fibres, and glumes supported abundant mycelial growth. Full colonization of the substrates was observed within 10 days. Production of infective propagules (microconidia and macroconidia) was optimum at 28 C. Optimum wetness of the substrates was obtained by soaking straw or glumes overnight. In field studies, the incorporation of 2.6 g of dried ground straw inoculum per sorghum seed pocket (120 cm$ sp2$), at a depth of 5 or 10 cm, resulted in a 60% reduction of emerged S. hermonthica 82 days after sowing. At harvest, biomass of Striga was also reduced by 70% and sorghum grain yield was almost doubled compared with the control. Sorghum, millet, maize, rice, fonio, cotton, cowpea, groundnut, okra and sorrel were immune to isolate M12-4A.

Fusarium oxysporum M12-4A fungus is being evaluated for the biocontrol of Striga hermonthica, a parasitic weed of African cereal crops. The production of M12-4A inoculum was assessed in four Malian villages using local technology and substrates. A delivery system using arabic gum to temporarily glue inoculum powder onto the crop seed was tested. In controlled conditions, coating of sorghum seeds with arabic gum and inoculum powder did not affect seed germination or inoculum viability. However, one week at 40°C significantly decreased the viability of the inoculum by 31%. Fungus growth and chlamydospore germination were also reduced by temperatures of 34 and 36°C. M12-4A was susceptible to the fungicide thiram (ED50 = 38.5mug). Field trials were conducted in Mali to evaluate the large-scale efficacy of the seed coating technology. F. oxysporum M12-4A was detected from some S. hermonthica tissue and soil samples using specific primers and Real Time PCR.

Thesis (M. Ag. Sci.) -- University of Adelaide, 1959. / [Typewritten]. Includes bibliography.

Thesis (M.Sc.). / Written for the Dept. of Plant Science. Title from title page of PDF (viewed 2008/12/10). Includes bibliographical references.

Zugl.: Hohenheim, Univ., Diss., 2009