Rising water costs and concern for groundwater contamination are driving growers to improve irrigation and fertilization efficiency. A tentative Best Management Practice (BMP) for nitrogen fertilization of watermelon, a high water and nitrogen fertilizer use crop, has been developed, but needs further field verification. Information from tensiometers is used to schedule irrigations and watermelon petiole nitrate levels at critical growth stages are used to recommend rates of nitrogen fertilizer to apply with the objective of producing economic yields while limiting conditions which favor nitrate leaching to groundwater. In 1991, a field experiment consisting of a complete 3x4 factorial arrangement of soil moisture tensions, -12, -7 and -4 kPa, and 60, 214 315 and 500 kg N/ha, respectively, applied through a subsurface trickle irrigation system to watermelon was conducted on a Casa Grande sandy loam at the Maricopa Agricultural Center. Petioles were sampled from the youngest mature leaf beginning at the 3-4 leaf stage and then at major growth stages until first harvest. Harvested melons were weighed and soluble solids, dry matter and N uptake were determined on two representative melons from each experimental unit. An estimate of vine dry matter and N uptake was also determined. Soil samples were taken at 30 cm depth intervals to 1.2 m and analyzed for extractable N. A trench profile method was used to determine root distribution patterns for the three soil moisture treatments receiving optimum N. Petiole nitrate levels were highly responsive to N fertilizer treatments and accurately quantified visual observations of crop N status. Petiole nitrate results also indicated that the preliminary tissue nitrate test was adequate in assisting with a nitrogen management program though minor modifications were necessary. Marketable yield showed a tension x N interaction with a ridge of maximum yield occurring from high soil water tension and low N to low soil water tension and high N with yield reductions on either side of the ridge. Yield estimates along the ridge ranged from 101 Mg/ha (45.4 ton /ac) at -8 kPa tension and 280 kg N/ha to 105 Mg/ha (47.3 ton /ac) at -4.4 kPa tension and 376 kg N/ha. A cost return analysis determined that maximum economic returns were $12,059/ha when 311 kg N/ha were applied in conjunction with -6 kPa soil tension (145 cm water). Unaccounted for N, as determined by an N balance method indicated large amounts of N were unaccounted for when high rates of N were applied under wet soil conditions. N loss was concluded to be due to either leaching and/or denitrification under these conditions.

A commercial product called Beescent® containing a mixture of chemicals including chemicals used by honey bees as pheromones, was applied to watermelons in early bloom on Aug. 15, 1991. Honey bee visitation to treated, 18-row plots, were significantly higher than to untreated for only 2 days, the day of treatment and the next day. Watermelon yields were not effected. The daily high temperatures reached 86-88 °F, so that most of the chemical had volatilized away by the end of the first day.

Tailored wild watermelon (Citrullus lanatus) juice clarification process is a fundamental step in improving its appearance and consumer acceptability. The purpose of this research was to investigate the mineral and proximate composition of wild watermelon juice (Citrullus lanatus) and to design an optimum processing condition for the enzymatic clarification of the juice. This investigation will help identify the sustainable processing parameters (incubation time, incubation temperature, and enzyme concentration) for ultimate clarification. Wild watermelon juice was treated with pectinase enzyme at different concentrations (0.05 to 0.15 w/w%), incubation temperatures (30 - 50 ͦ C), and incubation times (60 - 180 min). The different process parameters were utilised with each sample treated individually to determine their effect on selected responses: turbidity, clarity, viscosity, L* value, and brix. It was determined that the incubation temperature was the most crucial factor affecting the physiochemical properties of the juice as it exerted a significant influence on most (turbidity, absorbance, and viscosity) of the clarity attributes of the juice. Incubation time significantly affected turbidity and percent brix, whereas enzyme concentration only significantly affected percent brix of the juice. The optimum conditions for juice clarification were established by the Response Surface Methodology at the following parameters: enzyme concentration 0.15 w/w%, incubation time 60 min, and incubation temperature 60 ͦ C. The optimum output parameters at the following: turbidity: 14.18 NTU; clarity: 0.04 Abs; colour: 52.30 L value; viscosity: 1.96 cps; brix: 3.08 %. It may be useful to investigate the optimum parameters for other juices. / Life and Consumer Sciences / M. Sc. (Consumer Science)

Distribution of Fusarium wilt of muskmelon and watermelon in southwestern Ontario was studied. Particular attention was paid to morphological and physiological variations of the isolates obtained. Morphological variations were based on comparison in culture with a selected standard. Physiological variations were detected by pathogenicity experiments, and a study of assimilation of various carbon and nitrogen compounds. Some further aspects of the biology of the organisms were investigated. An experiment was carried out, employing several muskmelons and watermelon varieties, to compare their resistance under field conditions. / Thesis / Master of Science (MS)

No description available.

A study was made of the response of six kinds of melons to different nitrogen fertilizer rates when grown with drip irrigation. Results indicated a general response of petiole nitrate and yields to increasing N rates, depending on the kind of melon. The study will be continued in 1990 and include water and N rates with three kinds of melons.

Rural change and the ability of farming communities to respond and withstand change is a topic of ongoing concern in the current research agenda. ‘Rural community resilience’ is a concept that has become a core theme of academic, policy and lay discourses discussing dynamics of rural change, widely associated with community studies and allied to notions of social capital. This work reviews approaches to community relations developed within community studies and social capital scholarship, and suggests that the relational agency of the network ties might also be explored through the application of an assemblage approach. However, and unlike many previous approaches to community resilience that use the concept in a normative way and which understandably highlight agency of social relations, this research has been constructed in such a way that network ties established through day-to-day community practices are characterized both vital and far from passive. Developing this current line of thinking in rural studies, this project argues that more-than-social agency evoked by relations between human and non-human components of the rural assemblage is an important factor affecting community resilience. The empirical research feeds from two case studies and gathers evidence from two distinctive agricultural communities of Hungary and Wales, whilst also recognizing similarities in the context of globalization. It argues that rural community resilience lies in relations between the humans, the land and the agricultural commodities.

Thesis (Ph.D. (Plant Protection)) --University of Limpopo, 2012 / Global withdrawal of synthetic fumigant nematicides like methyl bromide due to their eco-unfriendliness resulted in serious consequences in production of crops which do not have genotypes that are resistant to plant-parasitic nematodes. Watermelon (Citrullus lanatus) is one such crop, where infection by highly aggressive root-knot nematodes (Meloidogyne species) invariably results into as high as 50% yield loss, with occasional total crop failures. Initial screening for nematode resistance in Cucumis species indigenous to South Africa suggested the possibility of the existence of nematode resistance, with the probability of these species being compatible with Citrullus species in inter-generic grafting technology. Uses of indigenous genera in Cucurbitaceae family as nematode-resistant seedling rootstocks in watermelon production could promote the South African watermelon industry as outlined in ISO 9001 certification guidelines to have competitive advantage in lucrative watermelon export markets. The objectives of this study were to determine the: (1) host-status and host-sensitivity of C. africanus and C. myriocarpus seedlings using a series of inoculation levels of M. incognita race 2 under various conditions, (2) host-status and host-sensitivity of C. africanus and C. myriocarpus seedlings using a series of inoculation levels of M. incognita race 4 and M. javanica, including the resistance form in these plant species, at least, under selected environmental conditions, (3) host-status and host-sensitivity of C. africanus and C. myriocarpus seedlings using a series of inoculation levels of M. incognita race 2 with multi-nematode xxviii infestations in order to establish whether the observed nematode resistance was sustainable when the plant was attacked by various pests at the root system level, (4) compatibility of inter-generic grafting of Citrullus and Cucumis seedlings in order to establish the potential uses of Cucumis species in olericulture, and (5) influence of the greenhouse whitefly (Trialeurode vaporariorum) infection on resistance of C. africanus to Meloidogyne species in order to establish whether the observed nematode resistance was sustainable when the plant was attacked by pests on complimentary organs. Reliability of measured variables was ensured by using statistical levels of significance (P ≤ 0.05) and coefficient of determination (R2), with validity being ensured by conducting experiments at the same location over two seasons or conducting one experiment during one season at two different locations, viz. the University of Limpopo and the Agricultural Research Council – Institute for Industrial Crops, and/or by setting up factorial treatments. Results consistently demonstrated that C. africanus and C. myriocarpus were non-hosts to M. incognita races 2 and 4 and M. javanica, without the test nematodes inflicting any damage to plants, which in plant-parasitic nematodes is described as nematode resistance. Quadratic relationships between RF values and log10(Pi + 1) transformations, in addition to confirming the density-dependent growth patterns of plant-parasitic nematodes, also suggested that chemical compounds responsible for suppression of nematodes in the two Cucumis species were different. The two Cucumis species were resistant to M. incognita races 2 and 4 and M. javanica, regardless of the environment under which the experiments were conducted. In field studies, the xxix two Cucumis species supported the ring nematodes (Criconema mutabile) and the spiral nematodes (Helicotylenchus dihystera), without these exo-parasitic nematodes inflicting any damage to plants, which in plant-parasitic nematodes is described as tolerance. Interactions among Meloidogyne species, C. mutabile and H. dihystera were either stimulatory or inhibitory, depending on whether Meloidogyne species were in the soil or inside the roots. Mechanisms of nematode resistance in the two Cucumis species were different, with C. africanus and C. myriocarpus depicting pre-infectional and post-infectional forms of resistance, respectively, without any sign of hypersensitivity in roots. When, seeds of Citrullus species were primed in water to hasten germination. Using the developed technology, survival of grafts improved from 36% to 100%, translating to relative improvement of 178%, with nematode-resistant rootstocks retaining their nematode resistant capabilities, while watermelon scions flowered earlier, with relatively higher fruit yield, without any deleterious effect on accumulation abilities of essential nutrient elements in leaves. Resistance of C. africanus to M. javanica was invariably broken by the greenhouse whitefly infection at high population levels, possibly through loss of non-structural carbohydrates, which are essential in synthetic pathways of secondary metabolites. Cucumis africanus and C. myriocarpus contain cucurbitacin B (C32H48O8) and cucurbitacin A [cucumin (C27H40O9), leptodermin (C27H38O8)], respectively, which have high demand for carbon and energy. Consequently, the efficacy of indigenous Cucumis species as nematode-resistant rootstocks in suppression of Meloidogyne species would be dependent upon the management of the xxx greenhouse whitefly population densities. In conclusion, C. africanus and C. myriocarpus have the potential for use as nematode-resistant rootstocks in the production of watermelon cultivars ‘Congo’ and ‘Charleston Gray’ in South Africa, where nematode population densities of M. incognita races 2 and 4 and M. javanica are widely distributed and are highly injurious to watermelons. Although nematode resistance in the two Cucumis species had attributes of sustainability, populations of the greenhouse whitefly broke the resistance. Proposed future research areas included influence of cucurbitacins in fruit quality of watermelons and protocols for mass culturing the nematode-resistant Cucumis rootstocks using tissue culture technology. / the National Research Foundation,the Agricultural Research Council (ARC) and the Landbank Chair of Agriculture-University of Limpopo

The evaluation of environmental and genotypic effects on fruit physical and chemical characteristics enables assessment of the feasibility of selecting diploid and/or triploid cultivars for either specific or more diverse locations. Isolation and characterization of genes encoding enzymes in the carotenoid biosynthetic pathway provides fundamental genetic information which can facilitate breeding of watermelon cultivars having desirable flesh colors and enhanced beneficial carotenoids. For the environmental studies, the effects of deficit irrigation on lycopene content, total soluble solids, firmness, and yield of diploid and triploid watermelon were evaluated in different locations and growing seasons. Irrigation regimes were 1.0 evapotranspiration (ET), 0.75 ET, and 0.5 ET. To investigate if there is a consistent response in cultivars across diverse locations, studies were conducted in three distinct Texas regions. Deficit irrigation reduced total marketable yield, and increased the yield of small fruits. Location and irrigation regimes had major influences on yield. Soluble solids content increased with deficit irrigation at 0.5 ET in triploids, but not in diploids. Flesh firmness also increased in triploids compared to diploids. Lycopene content increased with maturity at all irrigation regimes and cultivars. This work confirms that deficit irrigation directly reduces yield, but does not reduce lycopene and fruit quality of the triploids used in this study. From the genetic studies, a total of eight genes encoding enzymes in the carotenoid biosynthetic pathway were isolated and characterized. Two members of the phytoene synthase (PSY) gene family were identified; PSY-A was expressed in all type of tissues, but PSY-B transcript was detected only in ovary, leaf, and root tissues. Gene expression of carotenoid isomerase (CRTISO) was not detected in salmon yellow. A color inheritance study of watermelon flesh indicated that a single gene might determine color difference between canary yellow and red without an inhibitory effect. A cleaved amplified polymorphic sequence (CAPS) marker developed from the SNP marker tagging two different lycopene β-cyclase (LCYB) alleles cosegregated perfectly with color phenotypes. It was concluded that color determination may be due to a reduced activity of LCYB enzyme in red, whereby a phenylalanine is conserved among canary yellow and valine is conserved among red watermelon.

Made available in DSpace on 2014-06-11T19:32:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-01Bitstream added on 2014-06-13T20:23:52Z : No. of bitstreams: 1 figueiredo_vb_dr_botfca.pdf: 780253 bytes, checksum: d090ae928a19da93dc481db7bc90a6ab (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / planejamento mais eficaz do aproveitamento da água na agricultura, e o desenvolvimento de tecnologias que permitam estimar volumes cada vez mais exatos para a melhor eficiência da irrigação, têm papel fundamental para se alcançar ótimas produções agrícolas, aliada a melhor qualidade. Nesse caso a exata determinação da evapotranspiração da cultura (ETc) é um ponto crucial para o uso eficiente da água, bem como pelo fato da atual escassez dos recursos hídricos, principalmente em regiões áridas e semi-áridas, fazendo com que se utilize da água salina para irrigação. Diante disso, o presente trabalho teve como objetivo determinar a evapotranspiração da melancia e melão, em diferentes níveis de salinidade da água de irrigação e verificar seus efeitos no crescimento e na produção destas culturas. Para tanto foram realizados dois experimentos em campo, na Fazenda Experimental da Alagoinha pertencente a Universidade Federal Rural do SemiÁrido situada em Mossoró-RN, com melancia e posteriormente com melão, na mesma área, medindo 0,24 ha. Os níveis de salinidade da água de irrigação foram de S1=0,55, S2=1,65, S3=2,35, S4=3,5 e S5=4,5 dS m-1 para a melancia e S1=0,57, S2=1,65, S3=2,65, S4=3,45 e S5=4,5 dS m-1 para o melão. Os experimentos constaram de quatro blocos ao acaso com quatro repetições, cada um dividido nos cinco níveis de salinidade e no caso do melão em mais três níveis de nitrogênio subdivididas em cada parcela de salinidade. Os níveis de nitrogênio aplicados no melão foram de 67,5%, 90% e... / The water agricultural used effective design and the developments of technologies to estimated irrigation water exact are important irrigation management. Once evapotranspiration culture determinations (ETc) is crucial for use efficient irrigation water and irrigation water salinity. The objectives this work were determined evapotranspiration of watermelon and melon, in different levels of irrigation water salinity and verify effects in growth and production of these cultures. Were conducted two experiments in field, watermelon and melon, in same area with 0,24 ha. The levels of irrigation water salinity were of S1=0.55, S2=1.65, S3=2.35, S4=3.5 and S5=4.5 dS m-1 for watermelon and S1=0.57, S2=1.65, S3=2.65, S4=3.45 and S5=4.5 dS m-1 for melon. The experiments was four randomized blocks with four replications, divided in five salinity levels and in the case of melon in more three levels of nitrogen subdivided. The levels of nitrogen applied were of 67.5%, 90% and 135% of the applied dose (92.5 kg ha-1). The determination of evapotranspiration reference (ETo) was realized by method Penmam-Monteith-FAO through from formulations by Allen et al. (2006), and the ETc readings from two weight lysimeters installed in S1 and S5. The results showed that ETc of watermelon decreases between S1 and S5 where the total evapotranspiration was 245 and 214 mm, respectively. In melon the ETc also decreased between the two salinities, but was observed reduction 0.56 for S1, and 0.22, 0.64, 0.98 and 0.40values for the S5 in the watermelon. In melon observed medium Kc of 0.14, 0.57, 1.13, 0.66 for S1, and 0.11, 0.34, 0.91 0.54 for the S5 respectively. These values of Kc are verified for S1 was larger than Kc recommended by FAO (Allen et al., 2006), excepting for stage initial and final of each culture, and smaller for the S5, so much for melon as watermelon. There wasn’t significant ...(Complete abstract click electronic access below)