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Purslane (Portulaca oleracea) is a succulent weedy annual in much of the United States. In other parts of the world, purslane is grown as a specialty crop, valued for its nutritional quality. As a leafy crop, purslane contributes carotenoid phytochemicals in the typical Mediterranean diet. Nitrogen (N) influences plant growth and alters pigment composition and accumulation. However, little is known about the impact N fertility may have on pigment concentrations in purslane shoot tissues. The objective of this study was to evaluate the influence of N fertility levels on biomass and concentrations of nutritionally important carotenoid and chlorophyll pigments in purslane. Green Leaf and Golden Leaf purslane cultivars were grown in nutrient solution culture under N concentrations of 13, 26, 52, or 105 mg·L−1. Plants were harvested at 45 days after planting (DAP), and measured for concentrations of shoot pigments using high-performance liquid chromatography (HPLC) methodology. There was no influence of N treatment concentration on purslane shoot tissue fresh weight (FW) accumulation. Nitrogen treatment significantly influenced shoot tissue β-carotene (BC), lutein (LUT), neoxanthin (NEO), total carotenoids, chlorophyll a, chlorophyll b, total chlorophyll, and the chlorophyll a to b ratio in purslane shoot tissues. Concentrations of LUT, NEO, violaxanthin (VIO), chlorophyll b, total xanthophyll cycle pigments, and the chlorophyll a to b ratio differed between the purslane cultivars. Increases in N concentrations acted to increase concentrations of nutritionally important shoot tissue carotenoid pigments in only the Green Leaf purslane cultivar. Therefore, N fertility management and cultivar selection should be considered when producing purslane as a nutritious specialty vegetable crop.

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Lettuce is one of the major crops of the United States and can provide a large portion of income for small to medium size growers. Growing lettuce in adverse environmental conditions can have negative effects on quality. Elevated levels of potassium (K) have been shown to positively influence quality in various fruits and vegetables, such as tomato, pepper, and strawberry. However, research is lacking on the effects of elevated levels of K on leafy vegetables such as lettuce. Therefore, seeds of ‘Cimmaron’ lettuce were sown into a soilless medium and grown in greenhouse conditions at 25/20 °C (day/night). At 27 days after seeding, the plantlets were transferred to 3.8-L plastic nursery pots. Plants were grown under increasing K treatments of 98 (control), 185 (2×), 370 (3×), and 740 (8×) kg·ha−1. Plants were harvested 56 days after seeding. Application of elevated levels of K fertilizer treatments in red romaine lettuce had a positive quadratic effect on plant height increasing 7.0% from the control. Fresh weight (FW) increased 13.0% from the control and dry weight (DW) increased 15.5%. There was linear increase of 30.0% in sucrose concentrations in lettuce leaf tissue. In addition, the increase in K treatments caused an increase of 43.3% in K concentrations in the leaf tissue. In other nutrients, such as Calcium (Ca), Magnesium (Mg), and Sulfur (S), there was a decrease in the leaf tissue of 61%, 52%, and 46% when compared with the control treatment, respectively. The results of the current study suggest that increasing K fertilizer to 185 kg·ha−1 has the best results for plant height, FW and DW, and mineral nutrient concentrations. This study may initiate research that could examine the effects of increasing K fertilizer levels in lettuce or other leafy green vegetables on antioxidant levels and postharvest storability.

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Glucosinolates are sulfur-containing secondary plant metabolites commonly found in the family Brassicaceae. The presence of selenium in soils increases the uptake of sulfur and inhibits the production of glucosinolates in brassicaceous plants. This study was undertaken to determine the extent of selenium's impact on sulfur uptake and glucosinolate production in Brassica oleracea L. Rapid-cycling B. oleracea plants were grown hydroponically in half-strength Hoagland's nutrient solution with selenium treatments delivered as sodium selenate concentrations of 0.0, 0.5, 0.75, 1.0, and 1.5 mg·L−1. Elevated sulfur treatments of 37 mg·L−1 sulfate and 37 mg·L−1 sulfate/0.75 mg·L−1 selenate were incorporated to compare with selenium treatments. Plants were harvested and freeze-dried 1 day before anthesis. Selenium and sulfur content of plant tissue was determined by flame atomic absorption spectrophotometry and a carbon–nitrogen–sulfur analyzer. Glucosinolate content of leaf tissue was determined by high-performance liquid chromatography. Selenium and sulfur uptake in plants positively correlated with selenium concentration in the nutrient solution. The sulfur concentration of plants exposed to selenium equaled or exceeded the sulfur concentration of plants exposed to elevated sulfur. Despite higher sulfur concentrations, there occurred a statistically significant decrease in production of five of the seven glucosinolates analyzed in selenium-enriched plants. Plants that underwent elevated sulfur treatments had higher glucosinolate production than selenium-treated plants. These results suggest that selenium either upregulates or prevents the downregulation of sulfur uptake in B. oleracea. In addition, the presence of selenium within the plant appears to have a negative impact on the production of certain glucosinolates despite adequate availability of sulfur.

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Biofumigation is a sustainable method of soil management in cash crop rotations that can increase soil organic matter (SOM), moderate soil pH, suppress weeds and soilborne pathogens through glucosinolates (GSL), and increase water infiltration. This 2-year (2011–13) field study evaluated four different Brassica crops for their biofumigant potential in a chile pepper rotation system in southern New Mexico. The four cultivars included: three mustards (Brassica juncea ‘Caliente 61’, ‘Caliente 199’, and ‘Pacific Gold’) and one broccoli (Brassica oleracea var. botrytis ‘Arcadia’). As a result of concerns that these mustards could be hosts for nematodes, a greenhouse study was conducted in the second year to evaluate the biofumigant crops for their southern root-knot nematode (Meloidogyne incognita, RKN) host suitability and their seedling establishment in the presence of RKN. In Year 1 (2011), conditions were ideal, which resulted in high mustard biomass production and, consequently, significantly higher SOM and lower pH than the bare soil control plots. However, there were no chile pepper yield differences among treatments. Conditions were much less favorable in Year 2 and the resultant poor biomass production did not cause an increase in SOM as seen in Year 1. In the RKN greenhouse study, broccoli was the least susceptible biofumigant crop. After one nematode generation (683 cumulative heat units), RKN populations were less than half of the original inoculum level on the broccoli. However, RKN populations increased in the presence of ‘Caliente 61’, ‘Caliente 199’, and ‘Pacific Gold’. Overall, broccoli produced lower biomass and lower GSL concentrations than the mustard treatments but may be a valuable crop for growers with nematode issues because RKN populations decreased in its presence. Based on high biomass production and high GSL concentration, ‘Caliente 199’ showed the most potential as a biofumigant crop for southern New Mexico.

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Plant spacing and production systems are important factors for maximizing production of greenhouse-grown tomatoes (Solanum lycopersicum). Two studies were conducted simultaneously and independently, each in a 33 × 96-ft greenhouse in Fall 2008 and Spring 2009 using perlite soilless bag culture. The purpose of the first study was to evaluate yield and fruit weight of ‘Trust’ tomatoes spaced 12, 16, 20, 24, or 28 inches in-row. The second study was conducted to determine the effect of pruning production systems on yield and fruit weight. The first system is pruning two plants per bag each to a single leader and the second is pruning one plant per bag to double leader. A plant spacing of 28 inches resulted in significantly more fruit per plant than the 12-inch plant spacing. However, yield per area decreased with wider plant spacings. Plants spaced 12 inches apart in-row produced 2.8 and 3.8 lb/ft2 total yield in the fall and spring, respectively, compared with plants spaced 28 inches apart that produced 1.7 and 2.2 lb/ft2 in the fall and spring. Using a production system with one plant per bag pruned to a double leader increased yield by 6.4 lb/plant in the fall and 15.7 lb/plant in the spring. On a per bag basis, pruning two tomato plants to one leader increased total yield by 2.6 lb/bag and was more economical in the fall; whereas, in the spring, the double leader production system did not affect yield but was more economical.

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Using soybean oil to control insect pests, delay bloom, and thin fruit in peach [Prunus persica (L.) Batsch] production could reduce yield losses and fruit thinning costs compared to the current practice of using petroleum oil spray to control insect pests alone. The higher annua cost of soybean oil spray compared to petroleum oil spray was more than offset by higher average annual revenue from increased peach yields and lower thinning costs. At one location, soybean oil to delay bloom and thin fruit unambiguously reduced production risk. At another location, both mean and variance of returns were higher, but a lower coefficient of variation suggested lower relative risk for the soybean oil spray alternative. Risk resulting from the unanticipated influence of weather and mismanagement on the effectiveness of soybean oil spray were not considered in this analysis. More research is needed to hone in on the optimum soybean oil spray rates under alternative environmental and management conditions.

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`Golden Delicious' apples (Malus domestics Borkh.) were treated with heat or CaCl2 solutions or a combination thereof to determine the effects of these treatments on decay and quality of fruit in storage. Heat treatment at 38C for 4 days, pressure infiltration with 2% or 4% solutions of CaCl2, or a combination of both, with heat following CaCl2 treatment affected decay and firmness during 6 months of storage at 0C. The heat treatment alone reduced decay caused by Botrytis cinerea (Pers.:Fr.) by ≈30%, while heat in combination with a 2% CaC12 solution reduced decay by ≈60 %. Calcium chloride solutions of 2% or 4% alone reduced decay by 40 % and 60 %, respectively. Heat treatments, either alone or in combination with CaC12 treatments, maintained firmness (80 N) best, followed by fruit infiltrated with 2% or 4% solutions of CaCl2 alone (70 N) and the nontreated controls (66 N). Instron Magness-Taylor and Instron compression test curves show that heat-treated fruit differed qualitatively and quantitatively from nonheated fruit. Heat treatment did not increase the amount of infiltrated Ca bound to the cell wall significantly, and a combination of heat treatment after CaCl2 infiltration increased surface injury over those fruit heated or infiltrated with CaCl2 solutions alone.

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The effects of 36 organosilicone and conventional carbon-based surfactants on postharvest infiltration of radiolabeled and unlabeled Ca solutions into `Golden Delicious' apples (Malus domestica Borkh) were examined to devise a more efficient pressure infiltration technique to increase fruit Ca concentration. Radiolabeled Ca infiltration and the proportional increase in fruit Ca estimated by fruit weight gain from Ca solutions of known concentration were significantly enhanced by a range of surfactants having different chemical structures. Tween 60 and 80; Triton X-45, X-100, X-114, X-305, and X-405; and Silwet L-77 and L-7604 enhanced Ca infiltration. The two organosilicone surfactants, Silwet L-77 and Silwet L-7604, known for their greater capacity to lower the surface tension of solutions than conventional carbon-based surfactants, were the most effective at augmenting Ca infiltration. Applications of surfactants to fruit were as or more effective when used as a pretreatment rather than mixing the surfactant with the Ca solutions. The pressure necessary to increase Ca to levels considered sufficient to maintain fruit firmness and resist decay during storage could be lowered in fruit treated with organosilicone surfactants. Sequential postharvest surfactant and Ca treatments may be a practical means of increasing the Ca concentration in apples.

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`Golden Delicious' apples (Malus domestica Borkh.) were treated after harvest with heat (air at 38 °C for 4 days or 42 °C for 1 day) or 2% CaCl2 (w/v; applied as a dip or pressure-infiltrated) or a combination of the two and stored at 0 °C for ≤6 months. Decay caused by Botrytis cinerea Pers.:Fr. after inoculation to a depth of 2 mm with a conidial suspension virtually was eliminated in stored fruit heated at 38 °C, regardless of Ca treatment. Apples punctured to a depth of 0.5 mm (but not 2 mm) and inoculated with B. cinerea on removal from storage were almost completely protected from poststorage decay if they had previously been pressure-infiltrated with 2% CaCl2, regardless of the heat regime. Heating fruit at 42 °C and dipping in 2% CaCl2 were only partially effective in preventing decay from either pre- or poststorage inoculations. Fruit firmness was not related to resistance to decay.

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Glucosinolates (GSs) and carotenoids are important plant secondary metabolites present in several plant species, including arabidopsis (Arabidopsis thaliana). Although genotypic and environmental regulation of GSs and carotenoid compounds has been reported, few studies present data on their regulation at the molecular level. Therefore, the objective of this study was to explore differential expression of genes associated with GSs and carotenoids in arabidopsis in response to selenium fertilization, shown previously to impact accumulations of both classes of metabolites in Brassica species. Arabidopsis was grown under 0.0 or 10.0 μM Na2SeO4 in hydroponic culture. Shoot and root tissue samples were collected before anthesis to measure GSs and carotenoid compounds and conduct gene expression analysis. Gene expression was determined using arabidopsis oligonucleotide chips containing more than 31,000 genes. There were 1274 differentially expressed genes in response to selenium (Se), of which 516 genes were upregulated. Ontology analysis partitioned differentially expressed genes into 20 classes. Biosynthesis pathway analysis using AraCyc revealed that four GSs, one carotenoid, and one chlorophyll biosynthesis pathways were invoked by the differentially expressed genes. Involvement of the same gene in more than one biosynthesis pathway indicated that the same enzyme may be involved in multiple GS biosynthesis pathways. The decrease in carotenoid biosynthesis under Se treatment occurred through the downregulation of phytoene synthase at the beginning of the carotenoid biosynthesis pathway. These findings may be useful to modify the GS and carotenoid levels in arabidopsis and may lead to modification in agriculturally important plant species.

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