The current study used a probabilistic Quantitative Microbial Risk Assessment (QMRA) framework to describe the change of E. coli O157:H7 concentration in lettuce through a foodborne pathway, to develop a predictive model for risk estimation for E. coli O157:H7 infection associated with lettuce. The model consisted of a series of pathogen-associated events including initial contamination, growth during cooling, cold storage and distribution, disinfection (chlorine, gaseous chlorine dioxide and gamma irradiation), and dose response after consumption. A modified Baranyi growth model was proposed which described the initial physiological state of E. coli O157:H7 as a function of the initial temperature. The modified Baranyi growth model was used to predict E. coli O157:H7 growth under realistic time-temperature profiles, accounting for the time dynamics of temperature fluctuation. The risk assessment model was constructed in an Excel spreadsheet and Monte Carlo uncertainty analysis was simulated using Crystal Ball. The results in the current study showed that temperature control was the key measure for minimizing the risk of E. coli O157:H7 infection associated with lettuce. Disinfecting contaminated lettuce using the hypothetical methods examined in the study had limited effectiveness in risk reduction. Temperature abuse occurring before or after the hypothetical disinfections significantly diminished the disinfection effect and contributed to increased risk. Of all simulated scenarios, the lowest risk was associated with adequate temperature control and irradiation (44 infections per 1000 consumptions [95%: 94 infection per 1,000 consumption; 5%: 5 infections per 1,000 consumption]). The model can be used to explore the public health impact of other potential strategies that can be adopted to minimize the risk of E. coli O157:H7, while taking into account the possible amplification of pathogen through the food chain.

The current study used a probabilistic Quantitative Microbial Risk Assessment (QMRA) framework to describe the change of E. coli O157:H7 concentration in lettuce through a foodborne pathway, to develop a predictive model for risk estimation for E. coli O157:H7 infection associated with lettuce. The model consisted of a series of pathogen-associated events including initial contamination, growth during cooling, cold storage and distribution, disinfection (chlorine, gaseous chlorine dioxide and gamma irradiation), and dose response after consumption. A modified Baranyi growth model was proposed which described the initial physiological state of E. coli O157:H7 as a function of the initial temperature. The modified Baranyi growth model was used to predict E. coli O157:H7 growth under realistic time-temperature profiles, accounting for the time dynamics of temperature fluctuation. The risk assessment model was constructed in an Excel spreadsheet and Monte Carlo uncertainty analysis was simulated using Crystal Ball. The results in the current study showed that temperature control was the key measure for minimizing the risk of E. coli O157:H7 infection associated with lettuce. Disinfecting contaminated lettuce using the hypothetical methods examined in the study had limited effectiveness in risk reduction. Temperature abuse occurring before or after the hypothetical disinfections significantly diminished the disinfection effect and contributed to increased risk. Of all simulated scenarios, the lowest risk was associated with adequate temperature control and irradiation (44 infections per 1000 consumptions [95%: 94 infection per 1,000 consumption; 5%: 5 infections per 1,000 consumption]). The model can be used to explore the public health impact of other potential strategies that can be adopted to minimize the risk of E. coli O157:H7, while taking into account the possible amplification of pathogen through the food chain.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

In Lactuca sativa, the dominant gene Tu confers resistance to infection by turnip mosaic virus (TuMV). Tu and Dm5/8, a gene for resistance to Bremia lactucae, are linked in L. sativa. The area surrounding Dm5/8 on the genetic map of L. sativa contains restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers. The orientation of Tu relative to Dm5/8 was not known. Locating Tu would indicate which markers are on the map of lettuce close to Tu. To locate Tu on the L. sativa genetic map, F$ sb3$ families from recombinant F$ sb2$ in the Dm5/8 area of a cross between TuMV-resistant (Cobbham Green) and susceptible (Calmar) cultivars were inoculated with TuMV and phenotyped for Tu by indirect enzyme-linked immunosorbent assay. Polyclonal antibodies for immunodetection were produced using turnip mosaic virus coat protein expressed in E. coli. Phenotypic ratios within F$ sb3$ families were used to determine individual F$ sb2$ genotypes for Tu. With these genotypes, Tu was located on the genetic map of L. sativa relative to data present for Dm5/8 and surrounding markers, between OPM18 and OPY13. Using bulked segregant analysis, bulks created for the Dm5/8 locus were screened for genetic polymorphisms by the RAPD technique. Five new RAPD markers, UBC346, UBC517, UBC563, UBC599, and UBC675 were found linked to Tu after mapping relative to F$ sb2$ genotypes for Tu and other RAPD markers. The resulting three-point mapping information indicates that Tu is flanked by two markers, OPM18/OPL08 and UBC346, at respective genetic distances of 0.4 and 0.7 cM.

In lettuce (Lactuca sativa), the dominant gene Tu confers resistance to turnip mosaic virus (TuMV) infection. In order to eventually clone and characterize the Tu gene using a map-based cloning strategy, the chromosome region in which Tu is located needs to be saturated with molecular markers. Random polymorphic DNA (RAPD) markers were screened using bulked segregant analysis. Nine new RAPD markers, UBC431$ rm sb{420}, UBC431 sb{940}, UBC434 sb{360}, UBC434 sb{1000}, UBC439 sb{520}, UBC448 sb{685:750}, UBC135 sb{240}, OP108 sb{410} and OP108 sb{1305},$ were identified as linked to Tu. Each marker was mapped relative to Tu using F$ sb2$ individuals previously known to be recombinant in the area surrounding the Tu locus. Three new markers, UBC431$ rm sb{420}, UBC439 sb{520} and UBC135 sb{240}$ are within a 5 cM area of Tu. As the number of DNA markers on the map increased map expansion and difficulties in determining a unique order were encountered. To increase the confidence in the estimate of genetic distances, a population of 500 F$ sb2$ plants was screened in order to identify more recombinant individuals around the Tu locus. The population was screened using markers UBC431$ sb{420}$ and UBC135$ sb{240}.$ Thirty-three recombinants were identified in an interval of 6.6 cM. Two markers, UBC346$ sb{1067}$ and OP108$ sb{634},$ tightly flanking Tu were converted to sequence characterized amplified regions (SCAR 346 and SCAR L08). No polymorphism was detected among the SCARs generated. The area surrounding Tu now includes 24 RAPD markers in an interval of 44 cM.

Thesis (Doctoral)--Wageningen University, The Netherlands, 2007. / Vita. "Prepositions (stellingen)" ([1] leaf) inserted. Includes bibliographical references. Also available via the Internet on the university's web site.

Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Universiẗat, Diss., 2001--Mainz. / Auch als gedr. Diss.

Urban agriculture serves a growing and valuable market in today's food industry yet is challenged by the lack of available space in urban settings. Green roofs are proving not to only offer environmental benefits to buildings, but to also function as sites to grow produce. Adding fertilizer is important for plant health though fertilizer runoff and over application is a concern. Therefore, an evaluation of four Romaine lettuce cultivars (Lactuca sativa L.) comparing the use of three different fertilizers was conducted on the green roof of the Agriculture Building on the Southern Illinois University Carbondale campus in the fall of 2012 and 2013. The fertilizer treatments were OsmocoteTM (190,000 mg/kg N), Miracle GroTM (16,100 mg/kg N), and a control (no fertilizer). Supplemental water was applied though a drip tape irrigation system as needed. The lettuce cultivars evaluated were: ‘Parris Island Cos’, ‘Rouge d'Hiver’, ‘Rubens Baby’, and ‘Outredgeous’ Romaine lettuce. Results indicated that plant growth measurements of height and width, chlorophyll index, leaf mass and wet/dry weight were greater (P < 0.05) when OsmocoteTM and Miracle GroTM were used as a fertilizer source compared to the no fertilizer treatment. This study indicates that with supplemental nutrients, acceptable lettuce yields can be achieved in a three-inch extensive medium on a green roof. Results of this evaluation will contribute to the emerging interest in urban agriculture, specifically regarding lettuce production on extensive green roofs.

Made available in DSpace on 2014-06-11T19:26:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2000-04Bitstream added on 2014-06-13T19:14:05Z : No. of bitstreams: 1 leitejunior_jb_me_botfca.pdf: 548112 bytes, checksum: 3c54996aed140271001523e8eeadb99f (MD5) / Com o objetivo de encontrar uma solução para a salinização dos solos sob cultivo protegido que possibilite reduzir sua salinidade com a contínua utilização das estufas, foi realizado um experimento na Fazenda Experimental São Manuel, em São Manuel, pertencente a Faculdade de Ciências Agronômicas - UNESP/ Campus de Botucatu.O experimento foi conduzido nos meses de outubro e novembro de 1999, num solo denominado Latossolo Vermelho Amarelo textura média, e consistiu na simulação de adubação excessiva, através da adição de 645 g.m-2 de cloreto de potássio (KCl) e 51 g.m-2 de fosfato monoâmonico (MAP). A cultura utilizada foi a alface americana cultivar Tainá, transplantada no espaçamento de 35 x 35 cm e irrigada através de gotejamento. O experimento consistiu num fatorial 23, cujos fatores foram (nos níveis presença e ausência): pré-lavagem do solo antes do transplantio com uma lâmina de 101,89 mm; cobertura plástica preta do solo (mulching) e lixiviação a cada irrigação (com fração de 50% e irrigação diária, até 20 dias após o transplantio (DAT), e 30% até o final com irrigação a cada 2 dias.Com base nos resultados, pode-se concluir que a pré-lavagem não foi eficiente na redução de íons do solo, somente reduziu o pH havendo uma interação significativa entre a presença deste com a presença do mulching para os íons H++Al3+ no aumento da concentração desse, mas teve efeito na redução da condutividade elétrica na profundidade de 20cm aos 2 DAT e aos 14 DAT interagindo com a lixiviação.O mulching de cor preta foi eficiente na redução dos níveis dos elementos K, Ca e Mg a 20 cm de profundidade refletindo nas características químicas soma de bases, capacidade de troca catiônica e saturação de bases, mas reduziu o diâmetro das cabeças da alface americana. Apesar da condutividade elétrica não ter diferido significativamente, ele reduziu os sais na superfície dos canteiros...(Resumo co / With the objective of finding a solution for the salinization of the soils under protected cultivation and that it facilitates to reduce its salinity with the continuous use of the stoves, an experiment was accomplished in Experimental Farm São Manuel, in São Manuel, belonging the Faculdade de Ciências Agronômicas - UNESP/ Campus of Botucatu. The experiment was driven the months of October and November of 1999, in a soil denominated latosoil red yellow medium texture, and it consisted of the simulation of excessive fertilization through the addition of 645 g.m-2 of potassium chloride (KCl) and 51 g.m-2 of phosphate monoammmonic (MAP). THE used culture went to American lettuce to cultivate Tainá , transplanted in the spacing of 35 x 35 cm and irrigated through leak. The experiment consisted of the combination of 3 factors in 2 levels, whose factors were: pré-wash with a sheet of 101,89 mm; black plastic covering of the soil (mulching) and leaching to each irrigation (with fraction of 50% and daily irrigation, until 20 days after the transplant DAT , and 30% until the end with irrigation to every 2 days), in the levels with and without presence of the factor. With base in the results, it can be concluded that the pré-wash was not efficient in the reduction of ion of the soil, it only reduced the pH having a significant interaction among the presence of this with the presence of the mulching for the ion H++Al3+ in the increase of the concentration of that, but it had effect in the reduction of the electric conductivity in the depth of 20cm to 2 DAT and to 14 DAT combining the effects with the leaching...(Complete abstract, access undermentioned electronic address).