Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

No description available.

Potato ranks fourth after wheat, rice and corn as a major food crop. It is an excellent source of nutrients and at the same time relatively inexpensive, therefore it is the mainstay in the diets of people in both developed and developing countries. Potato losses and quality degradation due to the effect of storage variables or processing conditions must be reduced to increase the world food supply. To accomplish these objectives, studies have been conducted to evaluate: (a) quality changes in potatoes during cooking and frying, (b) quality changes in raw potatoes as influenced by storage conditions, (c) changes in cooking quality of potatoes as influence by storage conditions, (d) changes in frying quality of potatoes as influenced by storage conditions, and finally (e) quality changes in potatoes as influenced by Erwinia carotovora ssp. carotovora infection (Ecc, casual agent of soft rot disease in potato). / Kinetics of quality changes during cooking and frying of potatoes were evaluated. Potatoes were cooked at 80--100°C or fried at 160--190°C for selected times and their texture and color were evaluated. Results showed that texture values of cooked potatoes decreased with the progress of cooking, and the rate of texture changes at each temperature was found to be consistent with two pseudo first-order kinetic mechanisms. Textural values of fried potatoes increased with frying time and followed a first order kinetic model. Cooked potatoes were less bright, more red and less yellow in color as compared to raw samples. A modified first order model was used to characterize the color changes kinetics of both cooked and fried potatoes based on the changes occurring between the initial and a maximum or minimum value. 10 min cooking at 100°C and 10 min frying at 180°C were considered to give the designed cooked and fried products, respectively. / The changes in quality characteristics of potatoes as a function of storage variables (temperature and time) were evaluated. Potatoes were stored at five temperatures (4, 8, 12, 16 and 20°C) for selected duration (at least 5 time intervals) and different physico-chemical quality parameters were evaluated. Potatoes remained healthier when they stored at lower temperatures due to absence of sprouts and visible spoilage. They became softer and darker by passage of time.

No description available.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2006. / Härtill 5 uppsatser.

Ingeniera Civil en Biotecnología / Chile: Potencia Alimentaria y Forestal es el nuevo slogan adoptado por el país y simboliza el buen escenario del sector silvoagropecuario. Sin embargo, la planta y los frutos de la vid son atacados por el hongo patógeno Botrytis cinerea, produciendo grandes pérdidas productivas y económicas. Nuevas oportunidades de negocio se abren con el cultivo de flores de exportación. Para cuidar que las flores permanezcan en óptimas condiciones se debe combatir el principal patógeno que enferma a estas plantas, la bacteria Erwinia carotovora. Recientemente se ha demostrado que extractos de plantas, algas y esponjas marinas que contienen geranilfenoles y geranilhidroquinonas, poseen propiedades antifúngicas y antibacterianas. Debido a esto y los bajos rendimientos con que se obtienen desde la fuente natural es que se ha decidido sintetizar 6 de estos compuestos en el Laboratorio de Síntesis Orgánica de la UTFSM. Se estudió el efecto de los compuestos H1, M1, I1, I5, L1 y L2 sobre el crecimiento de Botrytis cinerea y Erwinia carotovora. Además, se planteó aumentar la solubilidad de los compuestos y su efectividad contra los patógenos, mediante un sistema de encapsulamiento. Del estudio de actividad antifúngica se obtuvo resultados prometedores para los compuestos, en particular el compuesto H1, que incluso logró porcentajes de inhibición mayores que los del producto comercial Captan, utilizando las mismas concentraciones. H1 a 250 ppm provocó una inhibición del crecimiento de B. cinerea del 86%. También exhibieron altos porcentajes de inhibición del crecimiento del hongo, H1 a 150 ppm con 82% e I1 a 250 ppm con 81%. Al probar la actividad antibacteriana de los compuestos también se obtuvo un buen candidato de estudio, L1. Aunque demostró tener poder bactericida contra Erwinia carotovora a 100 ppm y contra Bacillus subtilis a 50 ppm, esta actividad antibacteriana no fue estable en el tiempo. Sólo fue estable contra Bacillus en el caso en que la infección se realiza al mismo tiempo que la adición del compuesto. El sistema de encapsulamiento fue efectivo en la solubilización de los compuestos pero inefectivo en su uso en pruebas biológicas. Los altos porcentajes de inhibición del crecimiento de Botrytis obtenidos por los compuestos sin encapsular se vieron disminuidos al utilizar los compuestos en su forma encapsulada, llegando a bajar, en el peor de los casos, desde 81% a 26% para I1 a 250 ppm. Al utilizarse el compuesto L1 encapsulado en los ensayos de actividad antibacteriana, en todos los casos, se revirtió el poder bactericida del compuesto, provocando gran proliferación de ambos patógenos, E. carotovora y B. subtilis. Se postula que estos compuestos son muy estables dentro de la micela de encapsulamiento y su liberación es muy lenta como para ser registrada durante la duración de los experimentos. Entre las recomendaciones realizadas para estudios futuros, se hace énfasis en la necesidad de un estudio de cinética de liberación. Se propone el compuesto H1 como componente principal de un potencial producto comercial para combatir el hongo Botrytis cinerea. Para el caso de la actividad antibacteriana, se debe seguir investigando para aumentar la estabilidad del compuesto L1.

Erwinia soft rot is a widespread disease destructive to numerous important crop plants. Damage to plants is primarily due to celldegrading enzymes (CDEs) secreted by the bacteria. I am interested in potato (Solanum tuberosum) soft rot because it is of agricultural importance and it represents an ideal model system for understanding molecular events in plant-pathogen interactions. Much has been learned in vitro about the molecular genetics of CDEs in the past decade; however, little is known about their expression in plantae To study expression of genes for these enzymes during pathogenesis and plant responses to erwinias or their enzymes, I developed a membrane-separated system for simultaneous studies of potato and bacterial gene expression. This system facilitates the isolation of plant tissue-free bacterial cells and bacteria-free plant tissue for subsequent analysis of gene expression by RNA blot hybridization. Using this system, I demonstrated that in compatible interactions, rnRNAs for three Erwinia carotovora subsp. carotovora (Ecc) CDE genes were induced to high levels and were induced sequentially: exo-pectate lyase (PL), endo-PL, and then endopolygalacturonase (PG) with maximal mRNA accumulations at 6, 9, and 12 hr, respectively. Induction of these mRNAs was well correlated with tissue maceration. In the incompatible interaction, however, induction of all three Ecc genes was reduced several-fold compared to the compatible interaction. The kinetics of mRNA accumulation during pathogenesis were distinct from those of in vitro accumulation induced by polygalacturonic acid. My results confirm that in planta expression of these genes was induced by exo-PL reaction products as suggested by other researchers. In studies of plant genes correlated with plant responses to pathogens and environmental stresses [plant defenseresponse (PDR) genes], I also showed Ecc triggered active responses distinct from wound responses. I used gene probes for phenylalanine ammonia- lyase (PAL) and 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), key genes in the biosynthesis of phenylpropanoid- and terpenoidderived compounds believed to be important in plant defenses. Ecc inoculation caused much more rapid and greater increases in PAL mRNA and enzyme activity levels in potato tuber than wounding alone. Escherichia coli, a non-plant pathogen, carrying a plasmid which encodes Ecc endo-PL, also induced PAL mRNA accumulation. Ecc induced a specific HMGR isogene (HMGR1) not activated by wounding. My results support the existence of an HMGR mul-ci-gene family. Wounding resulted in a rapid and transient accumulation of HMGR2 mRNA followed by a slower accumulation of HMGR3 mRNA. These isogenes are distinct from the Ecc-induced HMGRI gene. / Ph. D.

Environmental use of genetically-engineered microorganisms (GEMs) has raised concerns over potential ecological impact. Development of microcosm systems useful in preliminary testing for risk assessment will provide useful information for predicting potential structural, functional, and genetic effects of GEM release. This study was executed to develop techniques that may be useful in risk assessment and microbial ecology, to ascertain which parameters are useful in determining risk and to predict risk from releasing an engineered strain of Erwinia carotovora. A terrestrial microcosm system for use in GEM risk assessment studies was developed for use in assessing alterations of microbial structure and function that may be caused by introducing the engineered strain of E. carotovora. This strain is being developed for use as a biological control agent for plant soft rot. Parameters that were monitored included survival and intraspecific competition of E. carotovora, structural effects upon both total bacterial populations and numbers of selected bacterial genera, effects upon activities of dehydrogenase and alkaline phosphatase, effects upon soil nutrients, and potential for gene transfer into or out of the engineered strain. No significant difference was found in survival of the engineered strain as compared to its wildtype parent. Both strains survived for over two months in microcosms. The effects of both strains upon populations of total bacteria and selected bacterial genera were determined; while some effects upon community structure were observed, they were not significant. The engineered strain was not found to be a superior competitor compared to its parent; three different doses of engineered and wildtype strains were used. ln addition, neither strain affected activities of dehydrogenase or alkaline phosphatase in soil. Likewise, no effects were observed upon the nutrients monitored. However, transfer of the kanamycin resistance gene that had been inserted into the engineered E. carotovora strain may have occurred. Five species of indigenous bacteria displayed kanamycin resistance 15 days after being exposed to the engineered Erwinia. DNA from these strains was isolated, purified, and hybridization experiments executed to determine if any homology existed between these DNAs and the kanamycin resistance gene that had been inserted into E. carotovora. Using biotin-Iabeled probes and Iow-stringency washing conditions, homology was observed. However, before gene transfer can be proven, additional studies, including amplification and sequencing, may be required. Although a simple microcosm design was employed, it yielded sufficient information to conclude that release of the engineered Erwinia carotovora will not affect any of the microbial measures of integrity that were studied in a manner different from that of the wildtype. Effects upon plant material and other higher taxa will be the focus of future studies. / Ph. D.