The effect of fruit removal from cantaloupe was studied under field conditions in a soil naturally infested with Monosporascus cannonballus. Fruit removal resulted in greater sugar accumulation in the cantaloupe roots compared to the roots from plants on which the fruits were allowed to develop normally. Individual, total, and combined root carbohydrate levels were greater in plants without fruit than in plants with fruit. Five major sugars (stachyose, raffinose, sucrose, glucose, and fructose) were found in the cantaloupe roots. Stachyose concentrations were higher than all the other sugars in the cantaloupe roots. Disease severity on the cantaloupe roots with fruit removed was less severe than on roots of plants with fruit, and dry weights were higher in the fruit removal treatment than those of the fruit non-removal treatment. Fruit removal results in increased root growth and carbohydrate accumulation in the cantaloupe roots. Root sugar concentrations affected infection efficiency and disease progress of Monosporascus root rot and vine decline. Therefore, the retarded development of Monosporascus root rot and vine decline is associated with a greater carbohydrate accumulation in the cantaloupe root.

Thesis (M.S.)--Oregon State University, 2004. / Printout. Includes bibliographical references (leaves 148-159). Also available online.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 204-228). Also available on the Internet.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 204-228). Also available on the Internet.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 159-167). Also available on the World Wide Web.

Lettuce (Lactuca sativa L.) seedlings diseases caused by soilborne pathogens are characterised by root rot, stem rot and damping-off of the seedlings that can occur at any time during growth. Fusarium solani, Pythium ultimum and Rhizoctonia solani are known to be the important destructive pathogens of lettuce, causing severe yield losses in South Africa. The aim of this research was to evaluate the effects of three selected fungicides to control these pathogens on lettuce seedlings. In this study the fungicides metalaxyl (Apron®), fludioxonil (Celest®) and mefenoxam (Subdue®) were applied at two concentrations as single and double doses on lettuce seedlings to determine their efficacy to control the pathogens Fusarium solani, Pythium ultimum and Rhizoctonia solani after significant reduction of mycelia growth was observed in vitro. Cultures of P. ultimum (UPGH024), R. solani (UPGH122) and F. solani (UPGH122) were obtained from the culture collection of the Department of Microbiology and Plant Pathology, University of Pretoria and cultivated on PDA for 2 days at 25ºC. Pasteurised soil was artificially inoculated with these pathogens. For the first experiment lettuce seeds were planted in polystyrene seedling trays at a depth of 1.0 cm. There were four replications of 50 seeds per treatment. In Experiment 2 pots (12 cm x 7 cm) were filled with pasteurised growing medium and 3-week old seedlings were transplanted. There were three replications of six pots containing three plants each. Seedling trays and pots were drenched with fungicides and placed in a randomised block design in a controlled environment room at 20- 26°C with a 12h-light/dark regime. The seedling trays and pots were rotated daily in the room. Seedling trays and pots were watered daily to maintain field capacity. The seedlings were able to grow larger in the pots than in seedling trays. It was confirmed that the treatment with fludioxonil (Celest®) at double and single dose inhibited the growth of the three fungi F. solani, P. ultimum and R. solani on lettuce seedlings without causing phytotoxicity. All three fungicides significantly reduced the diseases caused by the three pathogens. These findings are consistent with previous reports that fludioxonil, metalaxyl and mefenoxam can control oomycete fungi. There are few registered fungicides for the control of Fusarium solani, Pythium ultimum and Rhizoctonia solani on lettuce, therefore further work will aim to confirm these results in the field. / Dissertation (MInstAgrar)--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted

Phymatotrichum root rot is a fungal disease with a host range that includes many economically important crops in the southwestern United States and Mexico. While it has been studied since the late nineteenth century, ecological relationships of the disease, particularly those related to its distribution and dispersal, are not understood. Combined ground radiance sampling and aerial photographic interpretation was employed to study the distribution of Phymatotrichum root rot in cotton. Radiometric ground sampling showed that diseased cotton has a characteristic spectral signature that is significantly different from healthy cotton at visible wavelengths. Micro-scale examination of distribution within fields utilized multitemporal photography, both within season (1983) and for four seasons (1979-1982), revealed that the disease spreads during a season, but is not recurrent in many cases between years. Meso-scale mapping employed multitemporal photography to map distribution during a four-year period. When compared to mapped soil units, these data revealed a significantly non-random relationship between the diseased areas of fields and fine-textured soil units that may be based on moisture-holding potential. A yield analysis was also preformed using Thematic Mapper Simulator data and computer analysis.

Made available in DSpace on 2017-07-10T17:37:23Z (GMT). No. of bitstreams: 1 Luciano_Stefanello.pdf: 1381556 bytes, checksum: 6bd57829a5462b5319b07e3a1fb7ba7a (MD5) Previous issue date: 2016-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Cassava culture has great importance for agriculture and for populations mainly those in development, for being a culture with high rusticity and productivity, but diseases have been reducing the productivity and invalidating croplands, as in the case of root rot. Therefore the aim of this study was to investigate the potential of Trichoderma to control root rot in cassava caused by Fusarium and Phytophthora, and to investigate the ability of Trichoderma to promote the development of culture and the use of Trichoderma combined with different varieties in both systems. Initially in vitro tests were performed with 23 isolates of Trichoderma spp., the pair of test cultures, production of volatile and non-volatile antimicrobial compounds, against Phytophthora drechsleri development and Fusarium solani, under field conditions cassava planting was realized using the range Fécula Branca in conventional system where at planting was performed spraying spore suspension six of Trichoderma isolates on cuttings in the planting furrow. A second experiment was performed in two culture systems with two varieties with and without Trichoderma harzianum application. For nonvolatiles antimicrobial compounds the isolate studied presented a high ability to reduce mycelial growth of P. drechsleri and F. solani with inibiting up to 100%, to evaluate nonvolatiles antimicrobial compounds produced by Trichoderma the results were less expressive with the maximum inhibition value of 23,87%. for the first experiment under field conditions,the isolated TLB 14 promoted a better root development, consequently providing more productivity, for the incidence of disease the isolates TOD2A, TLB14 and TI2 presented lower incidence. for the second experiment under field conditions, about the plant stand it was lower in range Baianinha and using T. harzianum, the incidence of brown streak was lower in conventional tillage and the productivity was higher in convencional tillage and using T. harzianum / A cultura da mandioca possui grande importância para as populações principalmente aquelas em desenvolvimento, por ser uma cultura com alta rusticidade e produtividade. No entanto doenças vem reduzindo a produtividade e inviabilizando áreas de cultivo como é o caso das podridões radiculares. Portanto o objetivo deste trabalho foi verificar o potencial de Trichoderma em controlar podridão radicular na mandioca causada por Fusarium e Phytophthora, além de investigar a capacidade do Trichoderma em promover o desenvolvimento da cultura e o uso de Trichoderma combinado com diferentes variedades em dois sistemas de cultivo. Inicialmente testes in vitro foram realizados com 23 isolados de Trichoderma spp., pelos testes de pareamento de culturas, produção de compostos antimicrobianos voláteis e não voláteis, frente ao desenvolvimento de Phytophthora drechsleri e Fusarium solani. Em condições de campo o plantio de mandioca foi realizado utilizando a variedade Fécula Branca em sistema convencional efetuando-se pulverização de suspenção de esporos de seis isolados de Trichoderma sobre as manivas dentro do sulco de plantio. Um segundo experimento foi realizado em condições de campo em dois sistemas de cultivo com duas variedades (IAC 90 e Baianinha) com e sem a aplicação de Trichoderma harzianum. Para compostos antimicrobianos não voláteis os isolados estudados apresentaram uma alta capacidade em reduzir o crescimento micelial de P. drechsleri e F. solani com inibição de até 100 %. Para a avaliação de compostos antimicrobianos voláteis produzidos por Trichoderma os resultados foram menos expressivos com valor de inibição máximo de 23,87 %. Para o primeiro experimento em condição de campo o isolado TLB 14 promoveu um melhor desenvolvimento radicular, consequentemente proporcionando maior produtividade, para a incidência de doença os isolados TOD2A, TLB14 e TI2 foram os que reduziram a incidência em raízes de mandioca. Para o segundo experimento em condições de campo, quanto ao estande de plantas ele foi menor na variedade Baianinha e com o uso de T. harzianum. A incidência de podridão radicular foi menor em sistema de plantio convencional e a produtividade foi maior em sistema de plantio convencional e com o uso de T. harzianum

The overall goal of this research is to develop ground-based technologies for disease detection and mapping which can maximize the effectiveness and efficiency of cotton root rot (CRR) treatments. Accurately mapping CRR could facilitate a much more economical solution than treating entire fields. Three cotton fields around CRR-prone areas of Texas have been the sites for three years of data collection. A complete soil apparent electrical conductivity (ECa) survey was conducted for each field with an EM38DD sensor. Multiple linear regression was used to relate physical and chemical soil properties to the ECa values obtained from the EM38DD. The variability in soil ECa measurements can be best accounted for using calcium carbonate levels as well as clay and sand contents in the soil. T-tests were used to determine that soil pH, clay, sand, and inorganic carbon content were significantly related to CRR incidence as determined by aerial images of each location. Spectral data were obtained for freshly picked cotton leaves from healthy, disease-stressed, and dying or dead plants using an ASD VisNIR spectroradiometer. The leaf spectra were evaluated using linear discriminant analysis (LDA), the receiver operator characteristic, and wavelet analysis to relate them to classifications of infection level. It was determined that healthy and infected leaves can be correctly classified 85% of the time based on the spectral data. The results from this study suggest that differences in soil characteristics may not be pronounced enough to accurately map CRR in the soil; however, the precision treatment of CRR may possible using an optoelectronic sensor to diagnose infected plants based on leaf reflectance.