Certain naturally occurring compounds present in grapefruit have shown several health promoting properties such as anticancer, antioxidant, antimicrobial and cardioprotective. However, the levels of ...these naturally occurring compounds are influenced by several preharvest and postharvest factors. The primary objective of the current research is to determine the effects of different postharvest treatments on naturally occurring compounds present in grapefruit. In the first and second studies, effect of ethylene degreening on ‘Star Ruby’ and ‘Rio Red’ grapefruit natural compounds was investigated. Degreening helped to improve grapefruit color while maintaining the health promoting compounds. Significant influence of ethylene treatment was observed on flavonoids and furocoumarins. The third and fourth study examined the changes in ‘Star Ruby’ and ‘Rio Red’ grapefruit under cold storage and with low temperature conditioning treatment. Conditioning the fruits prior to cold storage reduced the incidence of chilling injury and conditioned fruits had similar or higher levels of health promoting compounds compared to fruits stored under cold storage without conditioning. However, results suggest that for short term storage of few weeks, storing fruits at 11?C was better for retention of most naturally occurring compounds. The fifth study focused on use of modified atmosphere packaging (MAP) to maintain grapefruit quality and nutritional properties. Two MAP films, micro-perforated (modified oxygen, carbon dioxide and humidity levels) and macro-perforated (modified humidity only), were investigated for their influence on naturally occurring compounds and fruit quality under a prolonged storage period. MAP treatments did not have significant effect on ascorbic acid, limonoids and fruit quality parameters such as total soluble solids, acidity, fruit taste, decay and disorders. Based on our research, use of MAP films is recommended to maintain fruit quality and health promoting compounds. The sixth and seventh studies focused on variation in health promoting compounds, specifically, flavonoid pathway gene expression and volatile compounds present in ‘Rio Red’ grapefruit during fruit development and maturity. Overall expression of flavonoid pathway genes and related flavonoid content decreased as the fruits developed and matured, with the levels being highest in immature fruits harvested in June. Levels of limonene decreased as the fruits developed from June to April; while, nootkatone levels increased with fruit development and maturity. The eighth study investigated the effect of different ethylene concentrations on flavonoid pathway gene expression and related flavonoids in grapefruit. Significant effect of ethylene concentration was observed on flavonoids and furocoumarins as well as the genes involved in the flavonoid biosynthesis. Overall, significant influence of different postharvest treatments was observed on grapefruit health promoting compounds. We believe that this research will be helpful to the citrus industry to optimize the postharvest treatments in order to maximize their benefits in regards to fruit quality and nutritional value.
Strip-tillage (ST) and cover crops can protect and improve soils in vegetable production systems but their effects on weed communities and weed management are often poorly understood. The objectives ...of this study were to 1) determine the effects of tillage and cover crops on weed seed persistence and emergence, 2) evaluate the extent to which these effects were mediated by fungal pathogens, changes in herbicide efficacy, and light or oxygen exposure, and 3) investigate potential relationships between seed persistence and indicators of microbial activity. Seed persistence and emergence of Powell amaranth and large crabgrass were evaluated in long-term field trials with tillage (ST vs. full-width tillage FWT) and cover crop (no cover, rye, and vetch) treatments. Persistence of both species was higher under ST compared to FWT and could largely be explained by lower light exposure in ST. Rye cover cropping resulted in greater persistence of crabgrass seeds, but this could not be explained by fungal pathogens. Soil enzyme indicators of microbial activity including β-glucosidase, leucine aminopeptidase, and acid phosphatase were often higher under ST and rye cover crops and positively correlated with seed persistence. Results suggest that tillage and cover crop effects on emergence are variable due to complex interactions between herbicides, soil moisture, and nitrogen dynamics, all of which impact germination.
Use of light emitting diodes (LED) technology is beginning to replace traditional lighting in greenhouses. This research focused on the effects of LED lighting and GA3 supplementation on growth and ...flowering of cut flowers. Dahlia spp. (Cav.) 'Karma Serena' and 'Karma Maarten Zwaan', Liatris spicata (Gaertn. ex Schreb) 'Kobold', and Lilium asiatic (L.) 'Yellow Cocotte' and 'Montreux' were subjected to varying light treatments including LED flowering lamps and halogen lamps. The flowering lamps emitted a combination of red + far-red + white and red + white. Photoperiod was extended by operating all lamps for 7 hours in the night and the experiment ran from late fall to early spring. Results varied within species and cultivars in response to light and GA3. Light was the most effective on growth and flowering characteristics especially in liatris and both cultivars of dahlia. In liatris, flowering occurred 2 weeks earlier under sole LED lighting than under other light treatments and no supplemental light. Although flowering occurred earliest in both cultivars of dahlias under no light, plants under light treatments had greater height, width, and shoot weight. There were significant effects of GA3 on growth and flowering characteristics in dahlia cultivars and lily cultivars such as greater height, width, and flower number. A significant interaction of light with GA3 influenced height, width, mean flower number, flower diameter, days to anthesis, and flowering percentage in several crops. The role of silicon (Si) as a needed supplement in soilless media is gaining interest. This research studied the effects of diatomaceous earth (DE) as a supplemental Si source on growth and flower characteristics, physiology, and nutrient uptake of cut flowers such as Dahlia spp. (Cav) 'Dahlinova Montana', Rudbeckia hirta (L.) 'Denver Daisy', and Gerbera jamesonii (L.) 'Festival Light Eye White Shades'. Nine Si treatments were established, and plants were considered well-watered at 10 centibars or water-stressed at 20 centibars. Silicon treatments included application of DE across the top of the pots (top-dressed) incorporation, and Metro-Mix 360 media with and without Si. For each species, there were six pots per Si rate per irrigation treatment. Significant effects were seen from Si supplementation, irrigation, and interaction in all plants. Growth and flower characteristics, leaf nutrient content, and tolerance to stress were improved by application of DE.
This research was conducted to develop nitrogen management plans and nutrient budgets for prune production in California. The major objectives of this study were to determine how nitrogen management ...affects yield, fruit nutrient accumulation and nutrient removal. In addition, preliminary data was collected for the development of an early season leaf-sampling model in prunes. Prune fruit samples were collected in 2015 and 2016 throughout the growing season to determine nitrogen (N) accumulation in the fruit as the season progresses and to determine total N removal from the orchard at harvest. N accumulation throughout the season increased to a peak of 5.78 and 5.37 kg N per dry ton of fruit exported from 2015 and 2016 respectively. Between the two years, 76% of N was accumulated within the fruit by the first week of July. In addition, N applications (Low Nitrogen 0 kg N ha-1, Medium Nitrogen 104 kg N ha-1 and High Nitrogen 204 kg N ha-1) were applied to an organic orchard in Yuba City, California to determine the effects of applied N on N removal in the harvested fruit and yield. This information is vital when determining how much N is exported from farmers’ orchards each year. The small sized fruit endocarp and seed N concentration was lower under High N treatment with a p value of 0.002. The medium sized fruit endocarp and seed N concentration was higher under low N treatment with a p value of 0.0226. After accounting for fruit size distribution and tree yield, there was not a significant difference in the total amount of N accumulated within each fruit size in the seed and endocarp. Within the Low N treatment, there was a significantly higher Amber Nicole Bullard March 2017 Horticulture and Agronomy concentration of N within the small sized fruit mesocarp relative to medium and large sized fruits. Overall, there was no effect of the N application on total N removal from any treatment (Low, Medium, or High), which was likely a result of residual N in the soil and tree biomass that prevented an N response in the 2-year experiment. There was a significantly higher concentration of N accumulated in small sized fruits compared to medium and large. The same also applies to the mesocarp in small sized fruits in the Low N treatment. Preliminary data was collected in six different orchards to start the development of a model for early season leaf sampling. Samples were collected from 2014 to 2016 and captured yearly variation in addition to tree-to-tree variation. -2-
Soil and water salinity is an issue in many areas worldwide because of drought, human activities, and using poorer quality water for irrigation. High levels of salinity severely affect plant growth ...as well as soil qualities. Some plants are naturally salt tolerant; however, most others are sensitive to salinity. Many areas are forced to use effluent water for turf and landscape irrigation due to the increase of the World’s population and the fresh water shortage. However, the long-term use can change soil quality. In this dissertation, the effects of using effluent water on soil chemical qualities as well as the interactive effects of salinity and/or waterlogging on perennial ryegrass (Lolium perenne L.) and switchgrass (Panicum virgatum L.) growth were examined. In the first and second chapters, the use of effluent water for golf course irrigation are reported. The reason for the study is that landscape irrigation with effluent water has become a common practice to alleviate fresh water shortage in many arid and semiarid areas, especially for golf courses. The objectives of the first study were to assess changes in soil chemical properties of sand-based greens following conversion from fresh water irrigation to effluent water irrigation, and to identify potential concerns related to long-term use of effluent water on sand-based greens. Putting greens were studied because of their unique nature and construction. Soil samples were collected and analyzed from greens of Heritage Golf Course in Westminster, Colorado. The course started to use effluent water for irrigation in 2000. Nine out of 18 (1, 3, 5, 7, 9, 11, 13, 15, 17) greens were selected for soil sample collection. Soil samples (0–10 cm below the soil surface) were collected in September of 1999, 2003 and 2009. Soil test data showed that the soil’s chemical characteristics changed over time. Soil organic matter increased from 0.12% to 1.5% and cation exchange capacity increased by as much as double over nine years. Extracted phosphates increased by 388% after nine years of effluent water use. Exchangeable calcium, magnesium, potassium, and sodium also increased, by 198%, 116%, 148%, and 452%, respectively, over nine years of effluent water irrigation. In addition, increase over time was shown for extractable iron, manganese, copper, zinc, and aluminum. The second study was conducted at two golf courses in the Cheyenne, Wyoming area: Prairie View Golf Course and Airport Golf Course. Soil data for both golf course putting greens and fairways were available from 2003 to 2013. The Prairie View Golf Course started to use effluent water for irrigation in 2007, while Airport Golf course has always used fresh water. Comparison between effluent and fresh water irrigation on soil chemical properties suggested that both benefits and risks exist when effluent water is used for irrigation. Increased soil EC by 200% after three years of using effluent water and increased sodium levels by 176% after a year of using effluent water. However, our results showed that salinity and sodium accumulation levels were below the critical threshold levels. In addition, our results showed that phosphorus and potassium levels increased by 35% in 2013 and 43% in 2010, respectively, in the soil after using effluent water. These inputs could benefit the grass and lower fertilizer costs. In conclusion, using effluent water for irrigation has both benefits and risks. Increased salinity (EC) and sodium levels are the greatest risks when using effluent water; however, to a certain degree, these can be managed by appropriate cultural practices such as leaching and adding gypsum. Supplemental nutrients and decreased fertilizer costs are the greatest benefits of using effluent water for irrigation. Our results showed that soil phosphorus, magnesium, and potassium levels increased after using effluent water, which could be beneficial for the grass and lower the fertilizer cost. In the third chapter, the interactive effects of salinity and oxygen availability on nine perennial ryegrass lines (Lolium perenne L.) and one alkaligrass (Puccinellia tenuiflora) was studied. Many salt-affected soils in the world are also affected by compaction and waterlogging due to shallow water tables or decreased infiltration of water in soil. In a controlled greenhouse, grasses were exposed to four salinity levels (3, 6, 9, 12 dS m–1) with and without hypoxia condition for four weeks each. All entries exhibited decreased clipping yield with increasing salinity in both salinity and hypoxia + salinity treatments except Fults alkaligrass. Turf quality declined over time to unacceptable quality ratings with high salinity (12 dS m–1) treatment. In general, all entries had better turf quality in control and hypoxia treatments than in salinity and salinity with hypoxia treatments. (Abstract shortened by ProQuest.)
Fruit size is one of the important quality parameters that controls the fruit value. There have been many studies conducted to determine factors that affect apple fruit size. The apple fruit pedicel ...is not only responsible for the attachment of fruit to the tree, but also it provides a connection between the fruit and the source of water and nutrients. The pedicel can be such a factor that affects the apple fruit size. Therefore, we conducted a study to determine the correlation between fruit size and both pedicel size and anatomy among 10 different apple genotypes differing in fruit size. Our results suggested that among the genotypes, there was a positive correlation between pedicel diameter and final fruit weight at harvest. In contrast, there was a significant negative relationship between pedicel length and fruit weight. Additionally, there was a positive correlation between number of tracheary elements in the pedicel and fruit size among the genotypes. Likewise, a significant positive correlation between fruit weight and pedicel vascular bundle area was found among the genotypes. Further, among the genotypes, tracheary elements lumen area had a significant positive correlation with fruit weight. In conclusion, pedicel with larger diameter and shorter length, and both larger and more tracheary elements tended to bear larger fruit size.
Renewal of fruiting wood to maintain young reproductive meristems with optimal canopy light interception and distribution is key for high productivity and fruit quality throughout the life of a sweet ...cherry (Prunus avium L.) orchard. Typical renewal involves replacement of 10 to 20% of the tree canopy annually by removing one to several of the largest branches. In a mature orchard, this renewal process is subject to competition between sun-exposed fruiting sites and interior canopy renewal sites that intercept less light and compete poorly for translocated photoassimilates, often resulting in poor renewal growth. This is particularly problematic for high density orchards that utilize rootstocks selected for reduced vigor and high productivity. Renewal of canopy fruiting sites on a whole tree basis is an alternative renewal method that eliminates the competitive inhibition of shoot regrowth. This study explores the initial response of sweet cherry trees on various training systems and size-controlling rootstocks to whole tree renewal. Four training systems were studied: Tall Spindle Axe, Super Slender Axe, Upright Fruiting Offshoots, and Kym Green Bush. In 2016, whole tree renewal of the four systems was studied with ‘Benton’ cultivar on three rootstocks of varying vigor: Gisela 3, Gisela 5, and Gisela 6. During bloom, all fruit-bearing components of the canopy were pruned back to stubs close to the permanent structure. TSA resulted in the higher number of shoots, while KGB and UFO had the longest average shoot length. The results indicate that each canopy system-rootstock combination refilled canopy space, except for KGB on each rootstock, to quickly regenerate fruiting sites.
Root phenes play a primary role in plant adaptation to edaphic stress. The identification and understanding of the functional implications of root phenes may enable breeding and the development of ...crop varieties with improved soil resource acquisition. Root cortical senescence (RCS) is a type of programmed cell death in cortical cells of several Triticeae species. Until recently there has been very little attention as to the functional implications of RCS for water and nutrient capture. My research used physiology studies in the laboratory, greenhouse, and field and in silico experiments to characterize the development of RCS and understand its adaptive value and genetic control. This dissertation explores the functional implications of RCS for water and nutrient capture including its effects on root respiration and radial water and nutrient transport. Simulation results suggest that RCS improves plant growth in edaphic stress conditions. Empirical experiments demonstrated its development of RCS is modulated by ethylene. RCS may be a useful trait for water and nutrient acquisition, particularly in edaphic stress conditions. RCS may be an adaptive trait for nutrient acquisition by reallocating nutrients from senescing tissue and secondarily by reducing root respiration. As RCS progresses, less metabolic resources need to be invested in cortical maintenance, which could permit greater resource allocation to the growth of shoots, other roots, and reproduction. These results suggest that RCS merits investigation as a breeding target for enhanced soil resource acquisition and edaphic stress tolerance. The development of crops with enhanced soil resource acquisition would impact global agriculture, since merits of RCS may be analogous to other species which also form RCS including wheat, oats, and triticale.
Most muskmelon (Cucumis melo L.) production in the upper Midwest relies on intensive tillage and plasticulture. An alternative system starts with the use of a roller-crimper to terminate winter cover ...crops, thus forming a thick organic mulch. Then, all tillage performed is restricted to a narrow strip in which muskmelons are transplanted. Cover crops and strip-tillage can increase soil health, suppress weeds, and improve net profitability. Muskmelons are an important crop for vegetable growers and are among the top consumed produce items in the U.S. Foodborne illness outbreaks of Salmonella and Listeria monocytogenes associated with muskmelon consumption have resulted in consumer fatalities, and negatively impacted the livelihood of producers. A study was carried out over two seasons (2014-15 and 2015-16) to assess the effect of cover crops and tillage on the performance of muskmelon production. Data was collected on cover crop growth, soil temperature, soil moisture, weed biomass, the concentration of nitrate-nitrogen in leachate, soil nutrient concentrations, muskmelon plant growth, soil microbial biomass carbon, soil microbial functional diversity, muskmelon yield, net profitability, and fruit quality. Our goal was to take a comprehensive view of the differences between the use of cover crops no cover, cereal rye (Secale cereale L.), and cereal rye-hairy vetch (Vicia villosa Roth) with conventional tillage and strip-tillage. We also assessed how treatments would affect the survival of soilborne Listeria innocua, a non-pathogenic surrogate for the human pathogen L. monocytogenes, either applied near the time of cover crop planting or near cover crop termination. We hypothesized that cover crop based ST would increase soil moisture, reduce weed biomass, reduce nitrate-nitrogen leaching, increase soil microbial biomass carbon, increase microbial functional diversity, and fruit quality, without sacrificing yield or net profitability. We also tested the hypothesis that cover crop mulch would prevent the contamination of muskmelon fruits by soilborne L. innocua. In one year, the earlier termination of cover crops in conventional tillage plots and also the use of a rye-vetch biculture lowered the C:N ratio of cover crop biomass. Cover crops and strip-tillage did reduce weed biomass, though not consistently over both years. In-row soil moisture was higher in strip-tillage, and in-row soil temperature was higher in conventional tillage. Strip-tillage occasionally reduced the concentration of NO3--N in leachate, this effect was inconsistent and only observed at a few sampling dates for only one year of the study. Rye-CT increased microbial biomass carbon over no cover-CT. During one year of the study, microbial functional diversity increased in rye and rye-vetch plots. The proportion of fruits that were marketable was increased under strip-tillage, as were several measures of fruit quality, but only in 2016. Populations of L. innocua introduced to the field in Oct. were able to overwinter and were detected the following May. The survival of May-applied L. innocua was measured in the first year of the study and showed that populations were reduced under both rye and rye-vetch cover crops. Treatments had no effect on the contamination of fruits at harvest. An economic analysis had mixed results, no cover strip-till plots had the lowest profit in both years, and rye strip-tillage and rye-vetch strip-tillage out performed their respective conventional tillage treatments in one year.
Çalışma 2013-2015 yılları arasında 300 nL L-1 konsantrasyonda 1-metilsiklopropen (1-MCP) uygulamasının ve kontrollü atmosferli (KA) depolamanın 'Ankara' armut (Pyrus communis L.) çeşidi meyvelerinde ...soğukta muhafaza ve raf ömrü sırasında kalite korunumuna etkisini belirlemek amacı ile yürütülmüştür. Ticari derim zamanında derilen meyvelerin yarısına oda sıcaklığında 24 saat süreyle 1-MCP uygulaması yapıldıktan sonra meyveler 0±1 °C sıcaklık ve %85-90 oransal nem koşullarında normal atmosferli (NA) depolarda ve kontrollü atmosferli (KA) (%3 O2 + %1.5 CO2) kabinlerde, uygulama yapılmayanlar ise doğrudan NA ve KA'lı koşullarda yıllara göre sırasıyla 210 ve 240 gün süreyle depolanmıştır. Depolama süresince meyvelerde solunum hızı, etilen üretimi, asetaldehit, etanol ve metanol konsantrasyonları, antioksidan aktivitesi, şeker bileşimi, askorbik asit miktarı, meyve kabuğundaki vaks miktarı, meyve kabuk ve et rengi, meyve eti sertliği, suda çözünür kuru madde ve titre edilebilir asitlik içeriği, ağırlık kaybı ve duyusal değerlendirmede oluşan değişimler izlenmiştir. Aynı parametrelerde raf ömrü süreçlerinde oluşan değişimler, her analiz tarihinde alınıp 20±1 °C sıcaklıkta 14 gün tutulan meyvelerde birer haftalık aralıklar ile saptanmıştır.Soğukta muhafaza periyodu ve raf ömrü süresince 1-MCP, KA ve 1-MCP+KA grubu meyvelerinin solunum hızı ve etilen üretim değerleri, kontrol meyvelerine göre daha düşük olmuştur. 1-MCP uygulaması hem NA hem de KA'lı koşullarda depolanan meyvelerde gerek soğukta muhafaza gerekse raf ömrü süreçlerinde kalite parametrelerinin korunumuna olumlu etkide bulunmuştur. Çalışma sonunda, 210 günlük depolama süresi için en yüksek kalite korunumu KA'lı depolama ve 1-MCP uygulamasının ayrı ayrı ve kombine olarak kullanılması ile sağlanmıştır. Bununla birlikte 1-MCP+KA uygulaması, daha uzun depolama süresi (240 gün) ve 14 günlük raf ömrü sürecinde, meyve kabuk ve et rengi ile meyve eti sertliğinin korunumu, tüketici tercihini olumsuz etkileyen aromatik bileşiklerin azaltılmasında, ümitvar depolama tekniği olarak bulunmuştur.
