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Simona Proietti, Stefano Moscatello, Fiorella Villani, Federica Mecucci, Robert P. Walker, Franco Famiani and Alberto Battistelli

Key nutritional characteristics of the fruit flesh of 41 sour cherries growing in the region of Umbria in central Italy have been determined. Fruit size, flesh dry matter content, nonstructural carbohydrates, organic acids, and anthocyanins were the analyzed parameters. Both the growing environment and genotype were statistically significant for most of the characteristics. Morello sour cherries were characterized by a large amount of sorbitol (up to 44.2 mg·g−1 FW), which contributed significantly to the dry matter content of the flesh, malic acid content that was higher (up to 48.4 mg·g−1 FW) than any published values for cherry flesh, and high anthocyanin content (up to 383.4 mg per 100 g FW). Cyanidin 3-glucosyl rutinoside was the most abundant compound. The analyzed germplasm could be the basis for breeding programs and new industrial products with high nutritional value.

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Ryan W. Dickson and Paul R. Fisher

Objectives were 1) to quantify acidic and basic effects on the root zone pH for eight vegetable and herb species grown in peat-based substrate and hydroponic nutrient solution and 2) to determine the applied NH4 +:NO3 ratio expected to have a neutral pH reaction for each species during its vegetative growth phase. In one experiment, plants were grown for 33 days in substrate (70% peat:30% perlite by volume), and were fertilized with a nutrient solution containing 7.14 milli-equivalents (mEq)·L–1 N and NH4 +:NO3 ratios ranging from 0:100 to 40:60. During the second experiment, the same species were grown in hydroponic nutrient solutions at 7.14 mEq·L–1 N with NH4 +:NO3 ratios ranging from 0:100 to 30:70, and data were collected over a 6-day period. In substrate, species increased root zone pH when supplied 0:100 solution, except for cucumber, which did not change substrate pH. Increasing the NH4 +:NO3 ratio to 40:60 increased acidity and decreased pH across species. Similar trends were observed in hydroponics, in which the most basic response occurred across species with 0:100, and the most acidic response occurred with 30:70. Arugula was the only species that increased root zone pH with all three NH4 +:NO3 ratios in substrate and hydroponics. In substrate and hydroponics, mEq of acidity (negative) or basicity (positive) produced per gram dry weight gain per plant (mEq·g−1) correlated positively with mEq·g−1 net cation minus anion uptake, respectively, in which greater cation uptake resulted in acidity and greater anion uptake resulted in basicity. In hydroponics, the greatest net anion uptake occurred with 0:100, and increasing the NH4 +:NO3 ratio increased total cation uptake across species. Cucumber had the most acidic effect and required less than 10% of N as NH4 +-N for a neutral pH over time, arugula was the most basic and required more than 20% NH4 +-N, and the remaining species had neutral percent NH4 +-N between 10% and 20% of N. Increasing the NH4 +:NO3 ratio decreased Ca2+ uptake across all species in hydroponics, which could potentially impact tip burn and postharvest quality negatively. Controlling root zone pH in substrate and hydroponic culture requires regular pH monitoring in combination with NH4 +:NO3 adjustments and other pH management strategies, such as injecting mineral acid to neutralize irrigation water alkalinity or adjusting the limestone incorporation rate for substrate.

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Yuxiang Wang, Liqin Li, Youping Sun and Xin Dai

Spirea (Spiraea sp.) plants are commonly used in landscapes in Utah and the intermountain western United States. The relative salt tolerance of seven japanese spirea (Spiraea japonica) cultivars (Galen, Minspi, NCSX1, NCSX2, SMNSJMFP, Tracy, and Yan) were evaluated in a greenhouse. Plants were irrigated with a nutrient solution with an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions with an EC of 3.0 or 6.0 dS·m−1 once per week for 8 weeks. At 8 weeks after the initiation of treatment, all japanese spirea cultivars irrigated with saline solution with an EC of 3.0 dS·m−1 still exhibited good or excellent visual quality, with all plants having visual scores of 4 or 5 (0 = dead, 1 = severe foliar salt damage, 2 = moderate foliar salt damage, 3 = slight foliar salt damage, 4 = minimal foliar salt damage, 5 = excellent), except for Tracy and Yan, with only 29% and 64%, respectively, of plants with visual scores less than 3. When irrigated with saline solution with an EC of 6.0 dS·m−1, both ‘Tracy’ and ‘Yan’ plants died, and 75% of ‘NCSX2’ plants died. ‘Minspi’ showed severe foliar salt damage, with 32% of plants having a visual score of 1; 25% of plants died. ‘Galen’ and ‘NCSX1’ had slight-to-moderate foliar salt damage, with 25% and 21%, respectively, of plants with visual scores of 2 or less. However, 64% of ‘SMNSJMFP’ plants had good or excellent visual quality, with visual scores more than 4. Saline irrigation water with an EC of 3.0 dS·m−1 decreased the shoot dry weight of ‘Galen’, ‘Minspi’, ‘SMNSJMFP’, and ‘Yan’ by 27%, 22%, 28%, and 35%, respectively, compared with that of the control. All japanese spirea cultivars had 35% to 56% lower shoot dry weight than the control when they were irrigated with saline irrigation water with an EC of 6.0 dS·m−1. The japanese spirea were moderately sensitive to the salinity levels in this experiment. ‘Galen’ and ‘SMNSJMFP’ japanese spirea exhibited less foliar salt damage and reductions in shoot dry weight and were relatively more tolerant to the increased salinity levels tested in this study than the remaining five cultivars (Minspi, NCSX1, NCSX2, Tracy, and Yan).

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Richard P. Marini, James R. Schupp, Tara Auxt Baugher and Robert Crassweller

Canopies of ‘Gala’ and ‘Fuji’ trees, trained to the vertical axis, were divided into eight vertical sections, each representing 12.5% of the tree canopy. The diameter of all ‘Gala’ fruit and fruit weight for all ‘Fuji’ fruit were recorded for each canopy section. Fruit size from most canopy sections was normally distributed and distributions were similar for most sections. Therefore, fruit size distribution for a tree can be estimated by harvesting fruit from two sections of a tree, representing 25% of the canopy. For small trees in intensive plantings, with canopy diameters less than 2.0 m, average fruit diameter or fruit weight estimated from all fruit collected from 25% of the canopy may provide estimates within 7% of the true value.

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Alex J. Lindsey, Joseph DeFrank and Zhiqiang Cheng

The use of nonpotable water for irrigation on various sport venues has led to an increased use of seashore paspalum (Paspalum vaginatum) turf in Hawaii. An ongoing challenge many seashore paspalum turf managers struggle with is bermudagrass (Cynodon dactylon) infestations. Herbicide efficacy studies were conducted at the Hoakalei Country Club [‘SeaDwarf’ seashore paspalum (fairway cut)] and the Magoon Research Station [‘SeaStar’ seashore paspalum (grown in container)] on the island of Oahu in Hawaii. Spray applications of the herbicides mesotrione, topramezone, metribuzin, and ethofumesate were evaluated alone and in tank mixtures for bermudagrass suppression and seashore paspalum injury. At the Hoakalei Country Club, maximum bermudagrass injury with minimal seashore paspalum discoloration was obtained with tank mixes of mesotrione (0.06 lb/acre) + metribuzin (0.19 lb/acre) + ethofumesate (1.00 lb/acre) and topramezone (0.02 lb/acre) + metribuzin (0.19 lb/acre) + ethofumesate (1.00 lb/acre). Unacceptable seashore paspalum turf injury was obtained in all treatments that did not include metribuzin. At the Magoon Research Station, maximum selective bermudagrass suppression was achieved with tank mixes of topramezone (0.01 lb/acre) + ethofumesate (1.00 lb/acre) and topramezone (0.01 lb/acre) + metribuzin (0.09 lb/acre) + ethofumesate (1.00 lb/acre). The addition of metribuzin and/or ethofumesate to the tank mix safened (reduced turf discoloration) seashore paspalum to topramezone or mesotrione foliar bleaching. Tank mixes of mesotrione, topramezone, metribuzin, and ethofumesate have the potential for bermudagrass suppression and control of other grassy weeds in seashore paspalum turf.

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M. Lenny Wells, Eric P. Prostko and O. Wendell Carter

A large number of agronomic and horticultural crops are susceptible to injury and yield loss from drift-level exposures to synthetic auxin herbicides. A new generation of genetically modified crops including cotton (Gossypium hirsutum), field corn (Zea mays), soybean (Glycine max), and canola (Brassica napus) with resistance to dicamba and 2,4-D herbicides has been developed to address the problem of glyphosate-resistant weeds. In the few years since their commercial introduction, these technologies have been rapidly adopted. The objective of this study was to determine the potential effects of simulated, single drift events of 2,4-D and dicamba on pecan (Carya illinoinensis) trees. 2,4-D amine [3.8 lb/gal acid equivalent (a.e.)] or dicamba-Diglycolamine salt (4.0 lb/gal a.e.) were applied in 1.0%, 0.1%, and 0.01% by volume spray solutions to pecan trees in June 2013. In 2016 and 2017, 2,4-D choline (3.8 lb/gal a.e.) or dicamba-N,N-Bis-(3-aminopropyl) methylamine (5.0 lb/gal a.e.) were applied in 1.0%, 0.1%, and 0.01% by volume spray solutions to pecan trees in May. These results suggest that serious injury can occur to pecan trees receiving a drift application of 1.0% by volume dicamba or 2,4-D. This injury includes deformed foliage, dead foliage, dead limbs, and/or branches, and arrested nut development. There were no major differences in the response of pecan to either dicamba or 2,4-D at similar rates in this study. Pecan damage resulting from off-target movement of 2,4-D and dicamba at rates ≥1% by volume has the potential to cause significant injury. Yield was not negatively affected by any of the treatments, suggesting that pecan trees can compensate for the observed injury to some extent. The effect of treatments on percent kernel was variable.

Open access
Open access

Mohsen Hatami, Siamak Kalantari, Forouzandeh Soltani and John C. Beaulieu

Dudaim melon (Cucumis melo Group Dudaim) is a unique edible melon for which few postharvest physiology studies have been conducted. To investigate the postharvest behavior of dudaim melon, two cultivars (Zangi-Abad and Kermanshah) were planted, tagged at anthesis, and harvested at two maturity stages: 21 and 28 d after anthesis (DAA). Harvested fruit were stored at 5 or 13 °C for up to 3 weeks and various quality parameters including color, firmness, titratable acidity (TA), total soluble solids (TSS), weight loss, chilling injury (CI), ethylene production, protein content, glucose content, fructose content, sucrose content, and maltose content were assessed during storage. After 3 weeks of storage at 13 °C, early-harvested fruit (21 DAA) had relatively similar color values (L*, lightness; a*, green–red tones; b*, blue–yellow tones) and TA compared with late-harvested fruit (28 DAA); however, some quality traits, such as TSS, were not similar. Ethylene content decreased initially after harvest and then started to increase during storage at 13 °C. For most treatments, glucose and fructose contents decreased whereas sucrose and maltose contents increased with advancing maturity. Increased ethylene production, in concert with color development at 13 °C, similar to ripe fruit, and the changing balance of measured mono- and disaccharide sugars in harvested fruit likely indicates ‘Kermanshah’ is climacteric. Results for ‘Zangi-Abad’ were not as definitive. Dudaim melon fruit can be harvested at an optimum stage of maturity, similar to known climacteric melon fruit, and then allowed to ripen at proper storage temperatures before consumption. Based on the results of this study, we recommend that harvest at 21 DAA and storage at a nonchilling temperature such as 13 °C are the optimal stage and temperature for long storage purposes.

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Russell Galanti, Alyssa Cho, Amjad Ahmad and Javier Mollinedo

Nitrogen (N) management in macadamia (Macadamia integrifolia) orchards is an important concern for growers. Leaf tissue analysis is the accepted method for determining N status in macadamia; however, this process is expensive and time-consuming. The chlorophyll meter has been used in other crops to estimate N status in plants through estimation of the amount of chlorophyll in leaf tissue. The use of the chlorophyll meter in two macadamia cultivars (Kakea and Kau) at two locations in Hawai’i (Kapa’au and Pahala) and five time periods (12 Apr. 2017, 13 June 2017, 15 June 2017, 18 Dec. 2017, and 20 Feb. 2018) was assessed. Leaf samples were collected based on a tissue-sampling protocol, chlorophyll meter (SPAD) values were collected, and leaves were analyzed for total N concentration. Data were analyzed statistically using linear regression. Leaf tissue N concentration had a positive monotonic relationship to SPAD values for both macadamia cultivars, both locations, and all sampling periods. The sampling period of Apr. 2017 for ‘Kakea’ macadamia had the greatest R 2 value for the linear regression at 0.85. The Feb. 2018 sampling period had an R 2 value for the linear regression of 0.74. ‘Kau’ macadamia had the greatest R 2 value for the linear regression of 0.24 in the Dec. 2017 sampling period. The slopes of the two macadamia cultivars for June 2017 were different from each other, suggesting that N recommendations need to be customized for specific macadamia cultivars if sampled in summer. The chlorophyll meter can be used for general estimation of tissue N in macadamia. Additional methods need to be considered and researched to refine procedures for direct estimation of total N concentration when using the chlorophyll meter.

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Jenny C. Moore and Annette L. Wszelaki

Plasticulture systems with polyethylene (PE) mulch and drip tape are common for production of peppers (Capsicum annuum L.) in the United States because of their soil warming, moisture conservation, and other advantageous effects. However, disadvantages include disposal costs and plastic pollution of the environment and temperature stress in warm climates with black mulch. Use of biodegradable plastic mulches (BDMs) is becoming more common, as they provide the same benefits of PE mulch without the disposal problems. In 2017 and 2018, we conducted experiments in Knoxville, TN, comparing production of pepper fruit with five different BDM [one white-on-black (WOB) and four black], one black PE mulch, one brown creped, paper mulch, and bare ground control treatments. We also measured the durability and effectiveness of weed suppression of the different mulches over the growing season compared with a hand-weeded bare ground control. Most mulches were degraded, with 40% to 60% of the soil exposed by the end of the season, with the exception of the paper mulch, which was completely degraded at the end of both seasons. Yields were similar among treatments in 2017, with the exception of Naturecycle, which had the lowest yield. Weed pressure was severe, especially in 2018, largely due to early penetration of all mulches except paper by nutsedge. Due to the early and season-long weed pressure and heat stress in black mulches, there were fewer healthy plants in all black-colored mulch treatments in 2018, leading to reduced yields in these treatments. Paper mulch was the only treatment that prevented nutsedge growth; therefore, this treatment and the hand-weeded bare ground treatment had the greatest yields in 2018. WOB also had yields comparable with paper and bare ground plots in 2018, likely due to the cooling effect of the white mulch. The results suggest that in hot climates and in fields infested with nutsedge, paper mulches perform best for midseason pepper cultivation due to the cooling effects and superior weed control.