Control and TMV-infected leaf tissues of three varieties of tomatoes, Marglobe, Moscow and Delicious, were analyzed for Ribulose Diphosphate Carboxylase (RuDPCase). The specific activity of RuDPCase based on protein concentration determined by peak area obtained with the Model E Ultracentrifuge, specific activity of RuDPCase based on protein concentration determined by Lowry's method, total amount of RuDPCase per gram fresh weight, total protein of plant leaves, total chlorophyll, and ratio of Chlorophyll a to Chlorophyll b were determined. Tobacco Mosaic Virus (TMV) infection resulted in an increase in specific activity of RuDPCase and the amount of total protein (at 2 days after inoculation). During the same time period there was a decrease in the total amount and total activity of RuDPCase in TMV-infected plants. The TMV infection appeared to also impair the synthesis of chlorophylls. The abnormal growth of TMV-infected plants appeared to be associated with the utilization of energy and organic substances from host plants for TMV-particle multiplication. As shown by changes in RuDPCase, photosynthesis in TMV-infected plants was disturbed.

No description available.

A study was undertaken to investigate the morphological host-parasite interactions of selected resistant and susceptible lines of tomato to Meloidogyne incognita, M. incognita var. acrita, M. javanica, M. hapla and M. arenaria and to determine the mode of inheritance of nematode resistance and the number of genetic factors controlling resistance to the root-knot nematodes. Four resistant varieties of tomato were crossed with one susceptible variety. The F₁ populations showed hybrid vigor for height, yield, and fresh weight of roots, stems, and leaves. Resistance to M. javanica, M. incognita, M. incognita var. acrita was dominant and susceptibility was recessive. The F₂ populations segregated in a 3:1 ratio showing resistance is a monofactorial dominant character and controlled by the same gene. The resistant parents, and the F₁ and F₂ populations did not show resistance to M. hapla and M. arenaria. Anatomical studies showed that there were some slight differences between resistant and susceptible varieties. In resistant varieties a compact layer of cells was formed around the body of the nematode which may have caused the noticeable reduction in nematode development and egg-formation. Giant cells formed in resistant varieties were much smaller and fewer in number than in susceptible varieties. The contrast between these two reactions by the resistant and the susceptible hosts suggests that resistance is related to the cellular response of the host to the parasite. In the root penetration and attraction study it was observed that when 2000 larvae were used as inoculum, they freely penetrated the roots of susceptible seedlings whereas in resistant roots very few larvae entered and most remained half embedded in the roots even at the 96 hour interval after inoculation. When the concentration of the larvae inoculum was increased from 2000 to 8000 per seedling, the larvae entered the roots of resistant seedlings as freely and as rapidly as they entered the roots of susceptible ones, demonstrating that the concentration of inoculum is an important factor in penetration. / Ph. D.

Solanaceous crops such as peppers and more commonly tomatoes have been linked to Salmonella outbreaks that have occurred in the United States. The source of contamination for some of these outbreaks was traced back to the preharvest environment. Sources of contamination at the preharvest level of production often include irrigation water, soil, and the use of biological soil amendments of animal origin (BSAAO). This dissertation aims to (i) determine how factors such as the use of BSAAO's, Salmonella strain, soil type, and irrigation influence the survival of Salmonella in agricultural soils and (ii) determine the risk of Salmonella internalization in to transplanted solanaceous crops (tomatoes and bell peppers) and identify factors that influence internalization through the roots such as mode of contamination, soil contamination level, and root damage. Sandy loam (SL) and clay loam (CL) soils both unamended and amended with poultry litter (PL), irrigated either daily or weekly were inoculated with one of twelve strains of Salmonella enterica and monitored for growth and survival until no longer detected. Tomato plants were transplanted into one of three contamination treatments: contaminated soil (A) or irrigation water administered either once (B, single exposure event) or for 7 d following transplantation (C, repeated exposure event). Plants were sampled 1, 2, 3, 7 and 90 d post-transplantation for Salmonella internalization. Pepper plant roots were left intact, damaged, or removed and placed in inoculated water (6.2 log CFU/ml). Pepper plants in the soil contamination study, were transplanted into soil inoculated with Salmonella at different contamination levels (High, Mid, and Low). Samples were collected 1, 2, 3, and 7d post-transplant. Plants were surface sanitized and enumerated for Salmonella internalization by plant section. Strains in soils treated with PL survived significantly (P<0.05) longer (56 and 112 days for SL and CL respectively), than Salmonella strains in unamended soils. In PL amended SL and CL soils, most strains grew significantly (P<0.05) within the first week following inoculation and ranged from 84 to 210 days in the point it was last detected. Strains survival increased significantly (P<0.05) in soil irrigated weekly compared to soils irrigated daily, weekly irrigation increased survival by 140 to 224 and 42 to 168 days in SL and CL soils respectively depending on the strain. Root sections in the tomato plants of treatment A had significantly (P<0.05) higher recovery of Salmonella internalization compared to the other treatments. No tomato fruit sampled were positive for Salmonella internalization. Pepper plants with damaged roots had significantly higher (P<0.05) Salmonella internalization in the stem than plants with intact roots, while plants with no root stalk had significantly higher (P<0.05) Salmonella internalization in the stem and leaves of plants with intact and damaged roots. Pepper plants exposed to high concentrations of Salmonella had significantly more internalization occur in the roots than plants exposed to mid and low concentrations of Salmonella. Due to the results of these studies assessing the risk of using PL and irrigation regime should be considered in the Salmonella growth and survival in agricultural soils. Though it is unlikely, steps should be considered to limit Salmonella contamination of soil and irrigation water and root damage to prevent the internalization of Salmonella in tomato and bell pepper plants through intervention measures such as composting, water treatment, and effective transplanting techniques. / Doctor of Philosophy / Produce such as tomatoes and peppers has commonly been associated with Salmonella outbreaks in the United States. Fresh produce may be contaminated during the growing period by irrigation water, soil, or manure contaminated with Salmonella. This dissertation aims to (i) determine how factors such as poultry litter, Salmonella strain, soil type, and irrigation affects the survival of Salmonella in agricultural soils and (ii) identify the capability of Salmonella uptake through the roots of tomato and bell pepper plants, and identify factors that facilitate the uptake of Salmonella such as how the plant is contaminated, the Salmonella population level in the soil, and root damage. Sandy loam and clay loam soils untreated and treated with poultry litter, irrigated daily or weekly, were contaminated with one of twelve strains of Salmonella and tested for Salmonella levels until it was no longer detected in the soils. Tomato plants were planted into one of three treatments: Salmonella contaminated soil (A) or irrigated with Salmonella contaminated water once after planting (B, single exposure event) or for 7 days following planting (C, repeated exposure event). Tomato plants were tested for Salmonella uptake within the first week or 90 days following planting. The roots of pepper plants were either left intact, damaged, or removed and placed into Salmonella contaminated water. Pepper plants in the Salmonella contaminated soil study were planted into soil containing one of three different Salmonella contamination levels (high, mid and low). Plants were tested for Salmonella uptake within the first week following planting. Factors such as the use of poultry litter and irrigation influenced the growth and presence of Salmonella in both soil types. The uptake of Salmonella of tomato plants in contaminated soil was observed in the roots more than the roots of plants irrigated with contaminated irrigation water. No tomatoes tested were found positive for Salmonella internalizing. The uptake of Salmonella in the stems and leaves of pepper plants was highly dependent on root damage and the presence of the roots. Pepper plants that were exposed to high levels of Salmonella in the soil had more instances of Salmonella uptake than plants with lower levels of Salmonella in the soil. Based on these results, the use of poultry litter and irrigation should be considered in the potential risk of Salmonella contamination during the growing stage of produce. Though the uptake of Salmonella in tomato and pepper plants is unlikely, precautions should be taken to limit the potential contamination of soil and irrigation water with Salmonella and prevent root damage from occurring to prevent possible uptake of Salmonella.

De novo shoots, roots, and flower buds were regenerated on thin cell layer explants excised from pedicel tissue of tomato. Direct shoot organogenesis was greatest when media contained 10µM kinetin and 0.001µM indole-3-acetic acid (IAA); however, shoot regeneration was increased in subsequent experiments by substituting 10 µM zeatin or 10 µM benzyladenine for kinetin. Root formation occurred when media contained higher (0.1 and 10µM) auxin concentrations. Flowers were formed on elongated shoots with several leaves when media contained 10µM IAA and 0.1µM kinetin. Competence for de novo shoot morphogenesis was tested on thin cell layers of eleven tomato cultivars. All tomato cultivars formed shoots directly on thin cell layer explants at varying frequencies (29%-63%). The mean number of shoots per explant was greatest for 'Large Red Cherry', 'Ohio 7814' and 'BL 6807', and poorest for 'Campbell 1327' and 'Red Alert'. Active cell divisions were observed in subepidermal cells during the first week of culture, and meristematic centers of dividing cells were evident after 2 weeks. Well developed shoot apices were observed on 50% of the explants 4 weeks after culture initiation. Shoot morphogenesis was compared among tomato plants placed into micropropagation, callus, and thin cell layer tissue culture systems. More shoots were produced on thin cell layer explants than on cotyledon calli, or micropropagated shoot tips. Genetic recombination rates and map distances were compared among hybrid plants grown in the greenhouse and regenerated from the aforementioned tissue culture systems. Increased recombination rates and map distances were detected between the sunny (sy) and baby leaf syndrome (bls) genes on chromosome 3, and between the white virescence (wv) and anthocyanin reduced (are) genes on chromosome 2. The percent change in the former ranged from 4.5%-5.9% for micropropagated shoot tips, 3.7%-8.5% for plants from cotyledon calli and 2.8%-5.9% for plants from thin cell layers. The percent change between the wv and are loci ranged from 4.5%-6.1% for micropropagated shoot tips, and 3.2%-5.0% and 3.9%-5.7% for plants from cotyledon calli and thin cell layers, respectively. Conversely, a decreased map distance was observed between bls and the solanifolia (sf) locus which is more distal to the centromere on the same arm of chromosome 3 as bls. Changes in recombination rates among plants regenerated from tissue culture may result from an influence of the tissue culture process on meiosis of regenerated plants. / Ph. D.

The effects of hormonal chemicals and different genotypes on fruit growth of greenhouse-grown tomatoes (Lycopersicon esculentum Mill.) were examined. Continuous root application of 10nM N⁶-benzylaminopurine in Hoagland's nutrient solution to tomato seedlings of 'Fireball' and 'Red Cherry' significantly delayed anthesis of 'Fireball', but not 'Red Cherry'. Ovary diameter at anthesis, final fruit diameter, and fruit weight of both cultivars were unaffected. Irrespective of treatments, a significant positive correlation was obtained between ovary diameter at anthesis and final fruit diameter. A single foliar application of 0.25mM or 0.37mM β-na-phthoxyaceticacid (βNOA) at the appearance of the first in florescence of ‘Fireball' significantly increased ovary diameter at anthesis, but had no effect on final fruit diameter. Flowers on the second inflorescence of tomato plants treated with 0.37mM βNOA had smaller ovary sizes at anthesis than those of untreated plants. Application of 0.125mM βNOA, and 1µM, 10µM, and 100µM gibberellin A₃ had no significant effect on ovary diameter at anthesis or final fruit diameter. A significant positive correlation was also shown between ovary diameter at anthesis and final fruit diameter of βNOA treated plants. Among the twelve genotypes tested, significant correlations between ovary diameter at anthesis and final fruit diameter were found for 'Fireball', 'Michigan/Ohio Hybrid', and 'New Yorker'. The remaining genotypes showed no significant correlations between ovary diameter at anthesis and final fruit diameter. The average ovary diameter at anthesis (of all the genotypes) was significantly correlated with final fruit diameter, fruit weight, and locule number. / Master of Science

Anthracnose of tomato was first described by Chester in 1891. It has been of economic importance to the growers of canning tomatoes nearly ever since. Anthracnose is cause by Colletptrochum phomoides (sacc.) Chester which appears to have different physiologic and morphologic forms. There is evidence that it is a soil organism but this remains to be definitively proved. The organism has a broad pH range and different isolates show different temperatures opimums but about the same temperature range for growth. The organism does not show the “dual phenomenon” but does sector frequently. Sectors are morphologically different from the parent mycelium and offers an explanation as to the origin of different strains of the organism. / Master of Science

INTRODUCTION In the summer of 1918, at Blacksburg, Virginia, there developed a considerable amount of a soft rot of tomatoes. This occurred in experimental plots which were designated to study the control of septoria leaf blight, and the soft rot of the fruit developed into an important factor. In describing these experiments Fromme (2) states: "Practically all of the unsoundness of the fruit was caused by bacterial soft rot, a disease which is exceedingly common and often very destructive in tomato fields in Virginia." Isolations from diseased fruits made by S. A. Wingard proved a bacterium to be the causative agent. Its growth in pure culture resembled that of the group of bacteria which causes soft rots of plants but it could not be readily assigned to any of the described species of this group. There has been only casual mention of a bacterial soft rot of tomato in literature, and the distinguishing features of the organisms which might be responsible have not been as sharply defined as is desirable. It was decided, therefore, to undertake comparative studies of the organism in question together with some of the non-chromogenic soft rot forms. / Master of Science

Tuta absoluta, a member of the moth family, causes devastating yield loss to tomato farmers around the world. Its recent migration into the tomato fields of Nepal puts tomato farmers at a high risk of yield loss. In response, chemical pesticide use by Nepali farmers is increasing. Integrated pest management (IPM) practices have been implemented in hopes of reducing the frequency of chemical pesticide use while controlling yield risks. This study examines the extent and determinants of Tuta absoluta IPM adoption and its effect on the frequency of pesticide use for Nepali tomato farmers. Primary data was collected from four-hundred and one households in four districts throughout Nepal. Two levels of IPM practices were assessed, simple and complex, based on the need for additional knowledge and tools. An instrumental variable probit analysis was used to analyze the determinants of IPM adoption. Household distance to nearest agricultural extension office was a significant factor decreasing the likelihood of the adoption of complex practices. Amount of land dedicated to tomato production, membership status of the primary decision maker, IPM training regarding Tuta absoluta practices and severity of Tuta absoluta were found to increase the likelihood of the adoption of complex practices. In order to analyze pesticide use, a simple linear regression was used. Primary decision maker's age, gender, and education level were significant determinates to decrease the amount of expenditures spent on chemical pesticides to control for Tuta absoluta. IPM adoption level, amount of land dedicated to tomato production and severity of Tuta absoluta damage were significant determinates to increase the amount of expenditures spent on chemical pesticides to control for Tuta absoluta. / Master of Science / Tuta absoluta, a member of the moth family, causes devastating yield loss to tomato farmers around the world. Its recent migration into the tomato fields of Nepal puts tomato farmers at a high risk of yield loss. In response, chemical pesticide use by Nepali farmers is increasing. Integrated pest management (IPM) practices have been implemented in hopes of reducing the frequency of chemical pesticide use while controlling yield risks. This study examines the extent and determinants of Tuta absoluta IPM adoption and its effect on the frequency of pesticide use for Nepali tomato farmers. Data was collected from four-hundred and one households in four districts throughout Nepal. Different economic tools were used to conduct the analyses. Results show the farther a household is to the near agricultural extension office, the less likely a household is to adopt complex practices. An increased amount of land dedicated to tomato production, the primary decision maker being a member of a marketing or community organization, the primary decision maker having attended IPM training regarding Tuta absoluta practices and the greater the severity of Tuta absoluta in the household tomato fields, the more likely a household is to adopt complex practices. Contrary to one of the goals of IPM practices, this study shows complex adopters use more chemical pesticides than simple adopters. Results this study shows a need for further education of the relationship between IPM practices and the use of chemical pesticides.

MSCAGR (Agricultural Economics) / Department of Agricultural Economics and Agribusiness / study aimed to determine factors that influenced the price of tomatoes sold by hawkers on the roadside market. The study also aimed at determining whether any socio-economic characteristics of hawkers who sold tomatoes had significant impact on the price paid my consumers. The study was conducted in the Thulamela local municipality under Vhembe District of Limpopo, South Africa. A stratified random sampling technique was used to select participants for this study. A sample size of 198 hawkers were drawn randomly. Structured questionnaires were administered through face-to-face interview. Descriptive statistics, correlation matrix, multiple linear hedonic regression and stepwise linear regression were used to analyse collected data. With regards socio-economic characteristics, only age was found to have significant impact on the market price received by hawkers. Smooth appearance, rough appearance, round shape, oval shape, and red and yellow colour tomatoes had a significant impact on the average market price. It is therefore recommended that attribute such appearances, colour, shapes and sizes of tomatoes should be considered when selling tomatoes at both retail and farm level. This will result in more purchase of tomatoes that will eventually contribute to increase in household income and reduction in poverty.