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Yunmi Park, Seok-Woo Lee, Soon-ho Kwon and Hae Yun Kwon
Hanan M. El-Hoseiny, Mohamed N. Helaly, Nabil I. Elsheery and Shamel M. Alam-Eldein
Mango production faces several challenges, such as nutrient deficiency, physiological stress, and alternate bearing, which eventually affect tree productivity. This study was carried out during the 2017 and 2018 seasons to evaluate the effect of single and combined applications of humic acid (as potassium humate; 0.15%, 0.30%, 0.45%) and boron (as boric acid; 300, 600 mg·L−1) on ‘Zebda’ mango trees grown at Dir AlMalak region, Sharkeya Governorate, Egypt. Foliar spray was applied twice before flowering (first week of January and first week of February), and a third spray was applied by the beginning of flowering (first week of March) in both seasons. Humic acid and boron effectively enhanced tree growth, flowering, yield, and fruit quality. Humic acid was more effective than boron in this respect. Combined application of both materials surpassed the single application of each material on overall tree physiology and annual productivity. The observed results may be a consequence of the increase in tree photosynthetic pigments, nutrients, organic solutes, and phytohormones such as auxins, gibberellins, and cytokinins. The reduction in abscisic acid content may be related to the role of humic acid and boron protecting the plant against destructive oxidative reactions; improving the ability of the trees to withstand environmental stresses; thereby reduce floral malformation percentage, minimize the incidence of alternate bearing, and improve annual tree productivity and fruit quality. The most pronounced effect in this regard was noted with the application of 0.30% humic acid + 600 mg·L−1 boric acid.
Matthew A. Cutulle, H. Tyler Campbell, Monica Farfan and Phillip A. Wadl
Weed management is an important component of sweetpotato production. Currently, S-metolachlor is the only herbicide registered in sweetpotato that has some suppressive effect on nutsedge species (Cyperus spp.). It is integral that the release of any new germplasm from sweetpotato breeding programs be tolerant to S-metolachlor. Screening for thousands of experimental clones for S-metolachlor in a field trial would be cumbersome. Therefore, screening for tolerant lines might be streamlined in an hydroponics system. Research was conducted to determine whether a hydroponics assay could detect differences in S-metolachlor response between a known sensitive sweetpotato cultivar (Centennial) and a tolerant sweetpotato cultivar (Beauregard) in 10 days. Results of the study show that ‘Beauregard’ was ≈50 times more tolerant to S-metolachlor than ‘Centennial’ when accessing injury at the 25% threshold. No differences were detected in S-metolachlor response between cultivars in the soil-based assay. This assay could be used for screening for S-metolachlor tolerance in a sweetpotato breeding program.
Mary Ann D. Maquilan, Dominick C. Padilla, Donald W. Dickson and Bala Rathinasabapathi
Bell and chili peppers are important vegetable and spice commodities worldwide. Significant yield reductions have been attributed to damage caused by root-knot nematodes (RKNs; Meloidogyne spp.). This study addresses the need for developing pepper varieties that have high resistance to RKN, which is now of increasing importance due to restrictions on the use of fumigant nematicides. Our goal is to provide a nonchemical alternative to sustain commercial pepper production in Florida, which is a major producer of peppers in the United States. We evaluated ‘UFRJ107(6)A3’, an advanced inbred line developed from a cross between Capsicum annuum L. ‘Jalapeno’ and ‘Round of Hungary’, for resistance against the nematode in comparison with the parental and three other Capsicum cultivars, namely, C. annuum ‘Charleston Belle’, ‘California Wonder’, and C. chinense Jacq. ‘Datil’ in two separate growth chamber experiments. Based on egg mass indices and reproduction factors, ‘UFRJ107(6)A3’ was significantly more resistant to M. incognita compared with the other five cultivars. When tested with five RKN species, ‘UFRJ107(6)A3’ showed comparably high levels of resistance to M. arenaria and M. floridensis as ‘California Wonder’ based on the nematode reproduction factor. In ‘UFRJ107(6)A3’, however, there were no detectable M. arenaria egg masses, and M. incognita reproduction was minimal compared with that of ‘California Wonder’; both cultivars supported the reproduction of M. enterolobii and M. javanica, although the reproduction factors of M. enterolobii were ≈10-fold higher than M. javanica. To characterize the mechanism of high resistance to M. incognita in ‘UFRJ107(6)A3’, we examined the extent to which infective second-stage juveniles (J2s) were able to penetrate its roots in comparison with the susceptible ‘California Wonder’ and ‘Datil’ in two independent experiments; we conducted RKN root penetration assays with a single plant in a pot and two plants in a single-pot choice test using ‘Datil’ and ‘California Wonder’, respectively, as susceptible standards. In both assays, M. incognita J2s were absent in the roots of ‘UFRJ107(6)A3’ 7 days after inoculation but were present in the susceptible cultivars, indicating that resistance has an effect at the root invasion stage. In growth chamber experiments, at constant temperatures of 28 and 30 °C, ‘UFRJ107(6)A3’ exhibited M. incognita resistance superior to its parents and to the standard resistant bell pepper ‘Charleston Belle’, thus offering the potential to enhance specialty pepper production and for use as a nematode-resistant rootstock for commercial bell peppers.
Bernadine C. Strik, Amanda J. Davis, David R. Bryla and Scott T. Orr
A 2-year trial was established in Oct. 2016 in western Oregon to evaluate the effects of various in-row mulch treatments on the establishment of northern highbush blueberry (Vaccinium corymbosum L. ‘Duke’). The treatments included douglas fir [Pseudotsuga menziesii (Mirb.) Franco] sawdust, black weed mat (woven polypropylene groundcover), green weed mat, and sawdust covered with black or green weed mat. Soil temperature was unaffected by the color of the weed mat, but it was often higher during the day in beds with weed mat mulch than in those with sawdust alone or sawdust covered with weed mat. Black or green weed mat also resulted in higher canopy temperatures, particularly when sawdust was underneath the weed mat. Plant growth was mainly unaffected by the color of the weed mat, and the maximum depth of the root system was similar among the mulch treatments. However, plants grown with sawdust mulch, with or without weed mat, had a greater canopy width and volume in year 2, a wider root system in both years, and more dry weight (DW) in the crown in year 1 and in the whips in year 2 than those with weed mat alone. Furthermore, plants with weed mat over sawdust were taller in year 1 and had greater canopy cover and more DW in new wood in year 2 than those with sawdust alone, and they had a larger canopy, more root development, and greater DW in the crown, new and old wood, fruit, and pruning wood in one or both years than those with weed mat alone. Over the course of the 2 years of the study, the net gain in total plant DW was lowest when the plants were grown with black weed mat and highest when they were grown with black weed mat over sawdust. Although it was more expensive initially, the use of weed mat over sawdust resulted in more plant growth than weed mat alone due to the insulating properties of the sawdust, and it was more effective for weed control than using sawdust alone.
Xiaohui Lin, Hongbo Li, Shenggen He, Zhenpei Pang, Shuqin Lin and Hongmei Li
Leaf stomata are the main channels for water loss of plants including cut flowers. In this study, we investigated the organographic distribution, morphological characteristics, light–dark response, and water loss contribution of stomata in cut carnations (Dianthus caryophyllus L. ‘Master’), which are prone to typical water deficits despite a few and small leaves. Stomata were observed in the upper and lower leaf epidermis, stem surface, abaxial bract epidermis, and abaxial sepal epidermis. Stomatal density (SD) on the stem surface was the highest and significantly greater than that on the upper and lower leaf and abaxial bract epidermis. The sepal epidermis had the lowest SD and the smallest stomata whereas the upper leaf epidermis had the largest stomata. Changes in the water loss rate increased in the light and decreased in the dark in both intact and leaves-removed cut carnations. The water loss rate of the former was greater than that of the latter. However, the water loss rate for the stem-only cut carnations had weak change rhythms and was much lower than that for the intact and leaves-removed cut carnations. These findings demonstrate the differential contributions of stomata in leaves, stems, and floral organs to water loss, and help to elucidate further the mechanism underlying postharvest water deficit in cut carnations.
Lulu Zhang, Yunfei Mao, Yunyun Wang, Lu Yang, Yijun Yin, Xiang Shen, Canhong Zhang and Duojiao Zhang
Ravneet K. Sandhu, Nathan S. Boyd, Shaun Sharpe, Zhengfei Guan, Qi Qiu, Tianyuan Luo and Shinsuke Agehara
Strawberry growers face rising production costs combined with competition from foreign imports. Relay cropping vegetables with strawberries is a unique approach that can diversify income and reduce the risk associated with strawberry production. Planting vegetable transplants on the same bed before strawberry crop termination enables continued berry harvesting while the new vegetable transplants become established. Relay cropping techniques of strawberry with eggplants were evaluated during the 2016–17 and 2017–18 seasons in Balm, FL. The strawberry crop was planted in September, and eggplant was transplanted into the beds either as a sole crop or with strawberry plants. Two experiments were conducted to optimize the planting date of strawberries and the termination date of strawberries. The objective of the research was to examine the competitive relationship between strawberry and eggplant crops and to define the optimal planting date for the eggplant and termination date of strawberries to minimize the competitive interaction and maximize the yield of both crops. Strawberry yields were unaffected (P = 0.938) by relay cropping or by the planting date of the eggplant. Eggplants grown without strawberries had 27% to 32% higher yields (P = 0.004) compared with relay-cropped eggplants, and eggplant yield decreased with later planting dates (P < 0.001). A partial budget analysis showed that transplant dates of 4 and 18 Jan. for eggplants with strawberries resulted in increased profits of $7320 and $3461 per ha, respectively, over the baseline treatment of strawberries alone, but later planting dates resulted in an overall economic loss ($7800–$16,000/ha). Strawberry termination dates did not affect eggplant yields. In conclusion, relay cropping eggplants with strawberries resulted in no effect on strawberry yields, reduced eggplant yields, but increased overall profits when eggplant were transplanted in early to mid-January. Relay cropping of strawberries with eggplants in early February to early March is less profitable than a monocrop of strawberries.
Rhuanito Soranz Ferrarezi, Thomas C. Geiger, Jayar Greenidge, Shamali Dennery, Stuart A. Weiss and Gustavo H.S. Vieira
Drip irrigation presents higher distribution efficiency than sprinkler irrigation. Proper system design and the use of pressure-compensating emitters have important roles in irrigation uniformity and efficiency, which directly affect plant growth. This study evaluated the performance of four pressure-compensating and noncompensating emitters and the effects of these irrigation equipment on the yield of three okra [Abelmoschus esculentus] varieties cultivated in the U.S. Virgin Islands. Trials were performed in two seasons (Spring and Fall 2016), and tested four types of irrigation equipment (flow control drip tape, thin wall drip line, thin wall drip tape, and heavy wall drip line) and three varieties of okra (‘Clemson Spineless 80’, ‘Clemson Spineless’, and ‘Chant’), arranged on a complete randomized block design with three replications. Irrigation was performed based on reference evapotranspiration and measured daily using an automated weather station. Soil moisture, electrical conductivity (EC), and soil temperature were monitored using capacitance sensors. The ability of the irrigation equipment to increase pressure was evaluated in the laboratory, in experimental modules using clean water, and while simulating three different slopes (leveled, uphill, and downhill). In the field trial, yield and leaf physiological parameters were influenced by season (P < 0.05) and the percentage of the marketable yield was influenced by variety (P < 0.05); however, fruit morphological parameters and soluble solids content were variety-dependent (P < 0.01). The pressure-compensating emitters maintained water flow within the range indicated by the manufacturers when used within the recommended pressure range. Distribution uniformity decreased over time for all equipment except the heavy wall drip line in Fall 2016. Irrigation equipment did not impact okra morphological attributes and yield, indicating that the same productivity can be successfully maintained while improving irrigation efficiency. Equipment should be selected based on price and irrigation efficiency to reduce the amount of water used.
Haijie Dou, Genhua Niu, Mengmeng Gu and Joseph Masabni
Understanding the responses of plant growth and secondary metabolite synthesis to different light wavelengths is important for optimizing lighting conditions for vegetable production in indoor vertical farms. Basil (Ocimum basilicum) ‘Improved Genovese Compact’ (green leaf) and ‘Red Rubin’ (purple leaf), green mustard ‘Amara’ (Brassica carinata), red mustard ‘Red Giant’ (Brassica juncea), green kale ‘Siberian’ (Brassica napus var. pabularia), and red kale ‘Scarlet’ (Brassica oleracea), which are high-value and multifunctional culinary herbs and leafy greens, were used to characterize the effects of red (R), blue (B), and green (G) wavelengths on plant photosynthesis, morphology, biomass production, and secondary metabolites accumulation. Light quality treatments consisted of three R and B light combinations, R88B12 (the proportions of R and B wavelengths were 88% and 12%, respectively), R76B24, and R51B49, and two white light combinations, R44B12G44 (the proportions of R, B, and G wavelengths were 44%, 12%, and 44%, respectively) and R35B24G41. Experiments were conducted in a walk-in growth room with a photosynthetic photon flux density set at 224 μmol·m−2·s−1 and a 16-hour photoperiod. Results indicated that the net photosynthesis in purple basil and green kale were positively correlated with B proportions (BP), and that higher BP increased the relative chlorophyll concentration in purple basil and red kale. In contrast, higher BP suppressed stem elongation and leaf expansion and reduced shoot biomass in all tested species except red mustard. Higher BP increased phytochemical concentrations but decreased the total amounts of phytochemicals per plant. For all basil and brassica (Brassica sp.) cultivars, the inclusion of G wavelengths decreased shoot biomass compared with that of plants grown under R and B light combinations with similar BP. Inclusion of G wavelengths stimulated stem elongation in green basil and green mustard under 12% BP; whereas it suppressed stem elongation in purple basil, green kale, red kale, and green mustard under 24% BP. The effects on phytochemical accumulation were species-specific for the inclusion of G wavelengths. Considering biomass production, nutritional values, and working environment for growers, a white light with lower BP and G proportions is recommended for culinary herbs and Brassica leafy greens production at vertical farms.