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  • Author or Editor: T.J. Radovich x
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Glucosinolates are secondary plant products of the Brassicaceae that may influence vegetable flavor and human health. Soil moisture levels and plant water status are thought to influence cabbage head glucosinolate levels. However, no information is available on the effect of irrigation timing relative to plant developmental stage on glucosinolate concentrations in cabbage. To address these gaps in the literature, cabbage (cv. Bravo) was grown in 2002 and 2003 at The Ohio State Univ., Ohio Agricultural Research and development Center in Wooster, Ohio. The four irrigation treatments, arranged in a RCB design, were: 1) irrigation throughout development [no stress (NS)], 2) irrigation only during head development [frame stress (FS)], 3) irrigation only during frame development [head stress (HS)], and 4) no irrigation [frame and head stress (FHS)]. Irrigation was supplied via drip tape and scheduled by the hand-feel method. Differential soil moisture levels among treatments were confirmed with gypsum block, time domain reflectometry (TDR) and gravimetric measurements. Analyzed across years, irrigation timing significantly affected total glucosinolate concentrations, with levels 36% greater in cabbage not irrigated during head development (HS, FHS) relative to cabbage receiving irrigation during head development (NS, FS). Concentrations were highest (29.4 mmol·kg-1) and lowest (19.4 mmol·kg-1) in FHS and FS cabbage, respectively. Irrigation effects were greater in 2002, when air temperatures were higher and rainfall and relative humidity lower than in 2003. We conclude from the data that head development is the critical stage at which irrigation should be applied in order to influence cabbage glucosinolate levels at maturity.

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The sensory quality of fresh basil (cv. Sweet Italian) was evaluated to determine if compost or mineral fertilizer applications affected flavor and aroma intensity. The four treatments, arranged in a randomized complete-block design with three replications, were: compost applied at 50 t·ha–1; compost applied at 200 t·ha–1; mineral N applied at 110 kg·ha–1; and a control receiving no amendment. Leaves from the first four nodes of young shoots were used in the evaluation. Twelve trained panel members scored samples of three leaves from each treatment for aroma and flavor intensity using a linear scale, converted to a scale of 1–10 where 1 = much less intense than a reference sample (control), and 10 = much more intense than the reference. No significant difference between treatments was found in flavor intensity. Significant difference between treatments in aroma intensity was found. Aroma scores were highest in samples from the compost and synthetic fertilizer treatments, and lowest in those from the control. Scores for aroma from the compost and synthetic fertilizer treatments were similar to each other. Aroma intensity increased with increased rate of compost application. No significant correlation was found between aroma intensity and plant tissue N content, sap NO3 levels, or yield.

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Clarifying the influence of abiotic environmental factors on the glucosinolate-myrosinase complex in vegetables of the Brassicaceae is an important step in understanding physiological processes that affect crop quality. Previous related work in this lab has shown that irrigation timing in the field may influence physical-, chemical- and sensory-based indicators of cabbage quality. The objective of this study was to record glucosinolate concentrations and myrosinase activity in crop tissues from plants subjected to varying soil moisture levels, employing radish as a model. Plants of cv. Belle Glade were grown in a controlled environment system designed at the Ohio Agricultural Research and Development Center in Wooster, Ohio for maintenance of target soil moisture levels. Pots were maintained at three soil moisture ranges, 40% to 60% (A), 20% to 30% (B) and 10% to 20% (C) volumetric soil moisture content at 30 °C. Preliminary observations revealed that treatments A, B and C corresponded to soil tensions which were not stressful, moderately stressful, and severely stressful to plants, respectively. Pot evapotranspiration, leaf stomatal conductance and plant size followed the order A>B>C, while canopy temperatures followed the order C>B>A. In leaves, glucosinolate concentrations and myrosinase activity were about 15% greater in treatments B and C than in A, while glucosinolate levels and myrosinase activity were 28 and 50% lower in hypocotyls and roots, respectively, in C than in A. It is hypothesized that changes in enzyme and substrate synthesis and translocation within the plant in response to sub-optimal soil moisture levels may explain the differential response of tissue glucosinolate concentrations and myrosinase activity to soil moisture treatments.

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Cabbage (cv. Bravo) was grown in 2002 and 2003 at The Ohio State Univ., Ohio Agricultural Research and development Center in Wooster, Ohio. The four irrigation treatments, arranged in a RCB design, were: 1) irrigation throughout development [no stress (NS)], 2) irrigation only during head development [frame stress (FS)], 3) irrigation only during frame development [head stress (HS)], and 4) no irrigation [frame and head stress (FHS)]. Irrigation timing relative to crop stage significantly affected all head characteristics except density, with the greatest differences between cabbage receiving irrigation during head development (NS, FS) and cabbage not irrigated during head development (FHS, HS). On average, heads from NS and FS plots were heavier (38%), larger (15%), less pointed and had less volume occupied by the core than heads from HS and FHS plots. Combined head fructose and glucose concentrations were significantly greater in cabbage receiving irrigation during head development than in cabbage not irrigated during head development (47% vs. 41% dwt, respectively). Sucrose concentrations were significantly greater in cabbage not irrigated during head development than cabbage receiving irrigation during head development (8% vs. 6% dwt, respectively). The higher ratio of sucrose: fructose+glucose observed in HS and FHS relative to NS and FS treatments was interpreted as an osmo-regulatory response with potential implications for cabbage flavor. Overall, it was concluded that physiological responses elicited in cabbage by differential irrigation can affect important head traits, and that targeted applications of water during specific stages of crop development may be utilized to maximize water use efficiency and crop quality.

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Cucurbita maxima and C. pepo are difficult to hybridize, and it was our objective to generate F1 hybrids between ornamental cultivars of the two species. C. maxima `Lakota' and C. pepo `Jack O'Lantern'; and `OZ'; were selected as parents. `Lakota' (L) is an heirloom, hubbard-type cultivar producing pear-shaped, red-orange fruit with dark green mottling, `Jack O'Lantern'; (J) is an open-pollinated Halloween-type pumpkin cultivar and `OZ' is a Halloween-type hybrid. Sixteen plants of each cultivar were greenhouse-grown in a CRB design during the period July-Sept. 2003. Interspecific crosses were made in both directions, with intraspecific crosses (J × O) and selfs (L) serving as controls. Fruits were harvested about 20 d after pollination. Embryos were excised under aseptic conditions and grown on either full strength Murashige and Skoog (MS) media with 6% sucrose (S6), full strength MS media with 6% maltose (M6), or half strength MS media with 3% sucrose (S3). Fruit set was generally greater in the intraspecific crosses (33%) and selfs (67%) than in the interspecific crosses (15 %), with the notable exception of the interspecific combination L × J (85% fruit set). Embryos of interspecific and control crosses were about 1.5mm and >1cm long, respectively. Hypocotyl and root growth 10 d after plating was better on S3 (3.2 and 1.7 cm) than on S6 (1.6 and 0.25 cm) or M6 (0.35 and 0 cm), and a greater number of functional hybrids were obtained from embryos grown on S3 (6 plants) than on S6 (2 plants) or M6 (2 plants). The interspecific plants were backcrossed to one of the parents and novel combinations of shape, color and variegation in hybrid fruit were observed.

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To help develop fertilizer recommendations for organic vegetable production in Hawaii, the effects of organic amendments on basil yield were studied in two experiments. The treatments were synthetic nitrogen applied at 100 kg·ha–1 per crop, organic amendments applied at a rate of 8–160 MT·ha–1, and an unammended control. Each treatment was replicated four times in a RCB design. In the first experiment, chicken manure was the organic amendment at 8 MT·ha–1 with a single basil variety grown. In the second experiment, conducted at the same location immediately following the first experiment, the organic amendment was locally produced compost (0.3% N) applied at 40 and 160 MT·ha–1 with three basil varieties grown. Data taken included soil fertility levels before and after experimental completion, marketable yields recorded weekly over 5–10 weeks, and tissue N and nitrate sap analysis measured at two to three different plant growth stages. In the first experiment, treatments receiving chicken manure or synthetic N showed similar yields (256–289 g/plant), which were significantly greater than the control (197 g/plant). Tissue N levels were greatest in the synthetic fertilizer treatment (4.9%) and lowest in the control (4.5%). In the second experiment, there was a differential response by varieties to treatments with respect to yields. Yields from the compost treatments (292–700 g/plant) were equal to or greater than those receiving synthetic fertilizer (320–651 g/plant) and were generally greater than the control (324–532 g/plant). Tissue N levels were greatest in plants receiving synthetic fertilizer (4.6% to 4.7%) and lowest in the control (4.3% to 4.4%). A positive correlation was found between lab tissue N levels and nitrate sap analysis determination.

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