Abstract Dahlias, in addition to their use as ornamental flowers, are consumed in a wide variety of foods. However, once harvested their shelf life is less than three days. The aim of this study was ...to evaluate the antimicrobial effect of 0.25 % cinnamaldehyde on edible dahlias held in polyethylene terephthalate (PET) and low-density polyethylene (LDPE) packages stored at 8 and 25 °C. Also, the ripening and quality of treated flowers were evaluated. The total population of yeasts and molds, mesophilic aerobic bacteria and psychrophilic bacteria increased during storage. Both packaging materials and cinnamaldehyde influenced the microbial count; however, microbial development was not totally controlled. The lowest weight loss was observed with PET, regardless of storage temperature. The lowest respiration rate was obtained in dahlias stored at 8 °C, regardless of packaging material. Ethylene production was not influenced by packaging material or storage temperature. In general, phenolic compounds and antioxidant capacity remained unchanged during storage. However, further studies are needed to improve control of pathogenic microorganisms in this commodity.
Abstract Exporting avocado involves a number of postharvest problems because the fruit has a limited shelf life and marked sensitivity to development of chilling injury when using low temperatures to ...prolong its useful life. There are measures to alleviate the problem, such as infiltration of calcium ions; therefore, the aim of this study was to evaluate the effect of preharvest spraying of Ca(NO3)2, at 0.3 and 0.5 %, on the postharvest physiology of cv. Hass fruits stored at 5 °C and room temperature for five weeks. The sprayings were performed in the aerial part every six weeks until harvest, totaling six applications. The variables evaluated were: ethylene production, respiration rate, calcium concentration in the exocarp and mesocarp, firmness, polyphenol oxidase activity, weight loss and chilling injury. It was found that Ca(NO3)2, at 0.3 and 0.5 %, decreased the respiratory rate and ethylene production during storage at room temperature and under chilling conditions. An Increase in the calcium concentration in the exocarp (0.085 %) was observed when 0.5 % Ca(NO3)2 was sprayed, as compared to the control (0.08 %). In the mesocarp, concentrations of 0.081 % were reached by spraying Ca(NO3)2 at 0.3 % and 0.084 % with calcium at 0.5 %, values higher than those of the control (0.078 %). In general, the Ca(NO3)2 sprayings decreased weight loss, polyphenol oxidase activity and chilling injury.
Abstract The objectives of this research were: a) detect differences in leaf nutrient concentrations of various clonal avocado rootstocks prior to being grafted, and b) determine the effect of the ...rootstock on leaf nutrient concentrations in young and adult ‘Hass’ scions grown without irrigation. Rootstocks were planted in 2000 and grafted in 2001 in a rainfed orchard in the municipality of Tepic, Nayarit, Mexico. As control, ‘Hass’ on native rootstock grown from seed was used. Thirty six-month-old leaves from the winter vegetative flush were sampled from each tree and from them the concentration of macro- and micronutrients was determined. The ungrafted rootstocks and the young ‘Hass’ trees on the evaluated rootstocks showed no variations in leaf nutrient concentrations, and in adult trees there were only differences for P. Leaf concentrations of N, P, Ca, Mn and B were higher at the beginning of the productive stage of the trees, while nutrient concentrations of Fe and Zn were higher in trees in full production. The type of rootstock used did not affect fruit production. This research identified rootstocks that positively or negatively modify leaf nutrient concentrations in ‘Hass’ scions, which will help the commercial management of their nutrition.
Abstract The development of new postharvest technologies, which prolong useful fruit life and are also biodegradable, has promoted the use of edible coatings, prepared based on polysaccharides ...obtained from nonconventional sources, such as the starch and pectin in banana fruits. The objective of this study was to evaluate the effects of coatings based on starch and pectin from ‘Pear’ banana, as well as chitosan applied to ‘Ataulfo’ mango fruit. Coverings with 1 % starch and others with 1 % pectin were applied by immersion to mango fruits at physiological maturity; fruits were then stored for 12 days at 10 ± 2°C, plus another 9 days at 22 ± 2°C. The assessed variables were: weight loss (%), color (L*, a*, b*), firmness (kgf∙cm-2), total soluble solids (°Brix), and titratable acidity (%). ‘Ataulfo’ mango fruits covered with starch from ‘Pear’ banana (Musa ABB) showed greater firmness (3.34 kgf∙cm-2) and a high content of total soluble solids (16.96 °Brix), compared to the control fruits (2.26 kgf∙cm-2 and 15.8 °Brix, respectively); this coating extended the postharvest period to 21 days. The edible coatings did not affect the cuticle color of ‘Ataulfo’ mango fruits and retained their typical yellow color.
Abstract In the development of tomato hybrids, a large number of parental lines involves an excessively high number of possible hybrids, making their formation and evaluation problematic. The ...magnitude of this can be reduced to manageable levels with the use of hybrid performance prediction methods. In this study we compared two methods based on genomic fingerprints, mixed model theory and the experimental evaluation of a sample of hybrids: 1) best linear unbiased prediction or BLUP and 2) ridge regression BLUP. Thirty-six single crosses were performed with the objective of determining the number, firmness and total and commercial yield of fruits. With 1,000 size-independent random samples, n = 6, 12, 18, 24 and 30, the behavior of the remaining 36-n hybrids was predicted. The correlation coefficients between predicted and observed values ranged between 0.25 and 0.83. BLUP consistently recorded the highest values. In both prediction methods when n increased the magnitude of the correlations also increased.
Abstract The sweet potato (Ipomoea batatas (L.) Lam.) is an important agroenergy source for producing ethanol, which is mainly made from renewable sources through the conversion of mono- and ...disaccharides (sugarcane, beet, corn, wheat, sweet potato, cassava, etc.). The aim of this research was to obtain new sweet potato genotypes with high potential for ethanol production from simple crosses to be used as commercial varieties. For this, crosses were made from selected parents with high root yield and dry matter content. A hundred single crosses were evaluated in two environments using an experimental lattice design with three replicates. It was observed that the use of single crosses is an effective strategy for exploiting sweet potato variability. Of the 73 hybrids evaluated, eight exceeded the best cultivars used as controls. The crosses BDI#57, BDI#73, BDI#52 and the cultivar Duda, with ethanol yields of 9.45, 10.37, 10.85 and 11.24 m3∙h-1, respectively, were the best in root production; in addition, they had a low incidence of soil insect attack, so they represent a good alternative for the cultivation of sweet potato intended for the ethanol-producing industry.
Electrical weeding is an emerging practice for late-season weed control that is being adopted in numerous cropping systems and agricultural industries, including Michigan vegetable production. ...However, little scientific research has been conducted directly evaluating the performance of electrical weeding and its effects on the agroecosystem. The objectives of the research program were to investigate electrical weeding in terms of 1) weed control, 2) crop injury, 3) economic viability, as well as its effects on 4) weed seed germinability and 5) rhizosphere microbial communities. Field trials at Hart, MI in 2021 and 2022 investigated these research objectives in conventional carrot and organic green bean production systems. Late-season weed control methods including one hand-weeding event (HW), one electrical weeder pass (1P), two electrical weeder passes performed consecutively 2P(ST), one pass followed by one pass after a 14-day interval 2P(14d), two passes followed by one pass after a 14-day interval (3P), and no late-season control (NLC) were evaluated in both carrot and green beans. Early-season weed control methods low, medium, and intensive herbicide programs, weed-free, and no early-season control (NEC) were also included in the carrot trials in order to produce different weed densities within which to assess the performance of the late-season weed control methods. In carrot, use of the intensive herbicide program typically led to lower densities of above-canopy redroot pigweed compared to NEC or the low herbicide program. There was no difference reported in redroot pigweed control with respect to early-season weed control methods after performing the various late-season weed control methods in 2021. However, in 2022, redroot pigweed control tended to be higher for treatments that caused initially lower weed densities (weed-free and intensive herbicide program). Increasing passes above 2P(ST) did not provide any higher control of redroot pigweed in carrot, while 3P did have higher weed control in green beans. Foliar injury did not exceed 10% in carrot and 20% for green beans. Electrical weeding did not cause any internal damage to carrot root tissue or have any effect on carrot root length. Hand weeding was correlated with a yield increase in 2022, whereas none of the electrical treatments led to any difference in yield in either year that was not related to natural variation in weed pressure. For green beans, neither electrical weeding nor hand weeding led to a yield difference in both years. Hand weeding had a significantly higher cost acre-1 than all electrical treatments in both years (19.6 and 28.4 times higher than 1P in carrot and green bean, respectively) due to the greater amount of time required. The range of time and cost acre-1 observed relates to the differences in weed pressure, where fields with higher weed competition requiring longer hand and electrical weeding times. Electrical weed control was found to significantly reduce redroot pigweed seed germination in 2021 (10 to 14%) but not in 2022. However, germination did not differ between early—or late season weed control methods in either year. Electrical weeding did not generally lead to differences in NH4+ or NO3– that would indicate changes in N mineralization in the rhizosphere. Microbial biomass C was higher after 1P than NLC in 2021. Apart from this, there were no differences in microbial biomass C or N reported with respect to early-season or late-season weed control methods in either year. Informed by the experimental results, growers can make more pragmatic decisions around investing in electrical weeding equipment based on its weed control performance, risk of crop injury, and economic feasibility compared with alternative late-season control practices. As well, electrical weeding has the potential to be an effective integrated weed management solution in vegetable production for control of the weed seedbank with little to no significant impacts on rhizosphere microbial communities.
Ürünlerin yetişme süreleri boyunca istedikleri iklim koşullarını en iyi şekilde sağlayan kontrollü üretim ortamlarına sera denir. Sıcaklığın düşük olduğu zamanlarda, sera içerisindeki ürünlerin ...gelişmesi için gerekli olan sıcaklık değerlerinin korunmasında mutlaka seraların ısıtılması gereklidir. Çevre, Şehircilik ve İklim Değişikliği Bakanlığı Meteoroloji Genel Müdürlüğü yayınlarından ulaşılan veriler çerçevesinde, ülkemizde Balıkesir ve çevresi, günlük ortalama güneşlenme süresi ile güneş ışınımının yoğunluğu açısından ilk sıralarda yer alan ilimizdir. Bu bakımdan Balıkesir ve ilçelerinde örtü altı ziraatının ekonomik olarak yapılabileceği düşünülebilir. Bu tez çalışmasında, Susurluk ilçesindeki çalışma yapılan seranın ve bölgeye uyumlu olan sera örneklerinin ısı gereksinimleri hesaplanarak, sera modelleri için öneriler sunulmuştur. Bu amaç doğrultusunda seralarda çoğunlukla kullanılan 3 farklı örtü malzemesi ele alınmış ve sera içi sıcaklığın 10°C ve 20°C olması halindeki ısı gereksinimleri ile yakıt giderleri belirlenmiştir. Hesaplamalar neticesinde, seralarda çift katlı Polietilen plastik örtülerin kullanılması durumunda seralardaki ısı ihtiyacının en az olduğu görülmüştür. Bununla birlikte, bölgenin iklim şartlarının örtü altı ziraatına uygunluğu tespit edilmiştir. İthal Sibirya Kömürü ile Linyit Kömürünün seraların ısıtılması için kullanılması durumunda örtü altı yetiştiriciliğin ekonomik olarak yapılabileceğini göstermişti
Freestanding high tunnels are cost-effective, plastic film-covered growing structures that use very little to no modern environmental control technology. Natural ventilation is used to control ...temperature and humidity. This dissertation investigates design and management decisions that impact the high tunnel environment and ventilation, including vent design, high tunnel orientation, plant canopy height, shoulder-season management, and high tunnel row spacing. The main tool used for this investigation was computational fluid dynamics (CFD) simulations because they can accurately and quickly describe the airflow within a complex system, while allowing for an iterative design process. Field experiments were conducted at the Pennsylvania State University High Tunnel Research and Education Facility (Rock Springs, PA) in order to collect environmental data within and immediately outside of a reference high tunnel. This data was used to validate a CFD model made using commercially available software (ANSYS Fluent), which incorporated the physical processes of energy transfer (convection, conduction, and radiation), turbulence, plant canopy induced drag, plant evapotranspiration, and water vapor transport. The model had a root mean squared error of 1.17 °C (n = 144), showing good agreement between experimental and simulated results since this error is close to the measurement error of the temperature sensors used. Permutations to this base model were made to investigate the research questions posed. These included separate simulations of five roof vent designs, three tunnel orientations, three plant canopy heights, four distinct sets of weather conditions representing the colder periods of the year, and five row spacings for two differently sized tunnels (research size and commercial size). Finally, practical recommendations are presented related to how the findings of this dissertation can be implemented by growers.
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