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Open access

Lushan Ghimire, Jude Grosser, and Tripti Vashisth

Huanglongbing {HLB [Candidatus Liberibacter asiaticus (C Las)]} has been one of the biggest challenges in citrus (Citrus sp.) production in Florida and wherever it is present. HLB-affected trees show significant shoot and root dieback, fruit drop, and reduction in yield. Currently, there is no cure for HLB, and there is no commercial HLB-resistant germplasm. Nonetheless, intensive nutrient management has been promising for citrus growers. The nutrient requirement of HLB-affected trees seems to be greater than that of healthy citrus trees. By understanding the nutrient uptake potential of rootstocks, fertilizer programs can be customized accordingly to enhance the performance of a rootstock in existing groves. Moreover, a reduction in the application of nutrients is possible by planting rootstocks with a high nutrient absorption capacity. Use of rootstocks with good nutrient uptake efficiency can take some burden off the growers who are intensively managing HLB-affected citrus groves. Therefore, the objective of this study was to evaluate and understand the nutrient uptake potential of the citrus rootstocks. To achieve this objective, a 100% hydroponic greenhouse study was conducted with six rootstocks with a range of tolerance to HLB. Several physiological and molecular tools were applied to evaluate the rootstocks for their nutrient uptake potential. A+Volk × O-19 (HLB-tolerant) rootstock had greater nutrient uptake efficiency, whereas US-896 (HLB-susceptible) had lesser nutrient uptake efficiency. Swingle, one of the most popular pre-HLB rootstocks, had poor zinc uptake and the least expression of ZINC TRANSPORTER, suggesting that zinc applications should be emphasized in Swingle plantings. US-896 rootstock expressed the least level of nutrient transporter genes, such as IRON TRANSPORTER. UFR-4 (a good performer under HLB conditions) had a large root biomass, but the uptake efficiency for nutrients was poor, suggesting that the nutrient uptake potential is a complex process that is not solely dependent on root biomass. This study is unique because it is one of the first citrus studies to report nutrient uptake efficiency and the potential of rootstocks. The information presented can be used to improve performance or select better-performing rootstocks under HLB conditions.

Open access

Zhong Wang, Xiaochun Shu, Ning Wang, Guanghao Cheng, and Fengjiao Zhang

Open access

Xiuxiu Sun, Marisa Wall, Peter Follett, Peishih Liang, Sai Xu, and Tian Zhong

Rambutan (Nephelium lappaceum L.) (Sapinadeae) fruit, a nutritional staple in Hawaii, exhibits desiccation and physiological browning soon after harvest, and methods to prolong shelf life may be commercially advantageous. In this study, freshly harvested fruit were treated with pectin coatings with or without trans-cinnamaldehyde (TCIN) and stored at 10 °C or 20 °C (room temperature) to evaluate postharvest quality attributes. Control fruit were treated with deionized water only. To find the best formulation of the coatings, three concentrations of TCIN were incorporated into a pectin solution to get 0.05% TCIN, 0.1% TCIN, and 0.2% TCIN coatings. At 0, 2, 4, and 6 days postharvest, fruit stored at 20 °C were evaluated for weight loss, firmness, pericarp browning, sugar, acid, and taste. The results showed that the 0.1% TCIN coating exhibited significantly lower weight loss than both control and the 0.2% TCIN coating through the entire storage time at 20 °C. The 0.1% TCIN coating–treated fruit were significantly firmer than control after 4 days of storage at 20 °C. The 0.1% TCIN coating also significantly reduced the pericarp browning over the control. Therefore, we selected 0.1% TCIN coating for fruit storage at 10 °C for up to 15 days. At 10 °C, the control fruit showed significantly higher pericarp browning than all TCIN-containing coated fruit. The 0.1% TCIN-treated fruit showed a significantly higher overall quality value than control fruit. The results indicate that the 0.1% TCIN coating may extend the commercial shelf life of rambutans and other perishable fruits. By extending shelf life, this coating can reduce postharvest losses and facilitate expanded fruit exports in Hawaii.

Open access

Gökhan Baktemur

Garlic (Allium sativum L.) is an important plant species because of its nutritional and medical value. One of the important advantages of plant tissue culture is in vitro selection. The tolerance of garlic to some heavy metals under in vitro conditions was studied. In vitro experiments were carried out in Murashige and Skoog (MS) nutrient medium supplemented with different doses of cadmium (Cd), cobalt (Co), nickel (Ni), aluminum (Al), copper (Cu), chromium (Cr), and lead (Pb) at 100 µm, 200 µm, 300 µm, 400 µm, and 500 µm. During experiments, plant length, number of leaves, leaf length, root number, and root length parameters were considered. In the findings, there was a decrease in both leaf and root development as doses of heavy metals increased. In addition, it has been found that the decrease in plant development at doses of 400 µm and 500 µm was higher compared with other doses. There was no root formation at high doses of Cd, Co, Ni, and Cu (400 µm and 500 µm). As a recommendation, further research should be conducted under in vivo conditions to evaluate the level of tolerance to heavy metals in garlic.

Open access

Vance M. Whitaker, Cheryl Dalid, Luis F. Osorio, Natalia A. Peres, Sujeet Verma, Seonghee Lee, and Anne Plotto

Open access

Xiaoyan Liu, Xiao Xu, Mingxia Ji, Erick Amombo, and Jinmin Fu

Soil salinization is an environmental problem globally. Bermudagrass (Cynodon dactylon) has long been used for soil restoration in saline-alkali land. Urbanization and the compound planting pattern combining trees, bushes, and grasses induced shading are becoming one of the most significant environmental constraints on the management of bermudagrass, which directly affects photosynthetic characteristics. Salinity and shade have become the most important environmental constraints on lawn development and implementation. Previous studies have shown that the plant physiological response under combined stress was different from that under single stress. The purpose of this research was to investigate the effects of salinity stress, shade stress, and the combined stress on bermudagrass. Shade nets were used to simulate shade stress to 85% shade. The NaCl concentration gradient for salinity stress was 1.0% for 7 days, 1.5% for 7 days, and 2.0% for 13 days, respectively. The combined stress combines the two approaches mentioned previously. The results showed that the salinity stress significantly inhibited the plant height, leaf relative water content, chlorophyll content, the chlorophyll a fluorescence induction (OJIP) curve and other photosynthetic parameters of bermudagrass while increasing electrolyte leakage when compared with control. Shade stress significantly enhanced the plant height, chlorophyll content, electrolyte leakage, the OJIP curve, and other photosynthetic parameters. Under the combined stress, the plant height and relative water content did not change significantly, but the photosynthetic parameters such as chlorophyll content and the OJIP curve increased. Furthermore, under the combined stress, the photosynthesis-related genes were regulated. Salinity stress inhibited the photosynthetic ability of bermudagrass more than shade stress, while the combined stress exhibited a considerably better photosynthetic ability. These findings provide information for the usage of bermudagrass in salinized shade conditions.

Open access

Pei-Hsuan Lai, Chia-Wei Li, Shih-Han Hung, A-Young Lee, Chun-Yen Chang, and Hsing-Feng Tang

Research has confirmed that there are physical and mental benefits associated with performing horticultural activities, such as being in contact with soil and viewing plants. In addition, due to the rapidly increasing volume of affective neuroscience research, it is now possible to understand emotional processing in the brain through neuroimaging. The present study was conducted to explore subjects’ emotional responses after participating in horticultural activities, with functional magnetic resonance imaging (fMRI) and the Profile of Mood States used for physiological and psychological measurements, respectively. First, the subjects’ baseline brain activation levels were determined before any engagement in horticultural activities. A week later, the subjects participated in a 5-week horticultural activity. fMRI was used to detect physiological changes during the different stages of the activity—namely, preparation and sowing, fertilizing and weeding, and harvesting. The findings show that the functional connectivity of the brain regions was activated, including the emotional prosody network. Hence, this study provides evidence that gardening can stimulate functional connectivity, activation of positive emotions, and mindfulness in the brain. The findings provide a neuroscientific understanding of the types of horticultural activities that increase positive emotions, meditation, creativity, attention, and relaxation and reduce depression.

Open access

Nana Millicent Duduzile Buthelezi, Joshua Oluwole Olowoyo, and Tieho Paulus Mafeo

The production of cherry tomato (Solanum lycopersicum var. cerasiforme) is negatively affected by harsh environmental conditions such as extremely high and low temperatures, wind and hail damage, and pest and disease infestation. These factors delay maturity and cause uneven ripening, fruit abrasion, and blemishes, which consequently result in poor fruit quality and reduced shelf life. Preharvest bagging is an environmentally friendly alternative technique for enhancement of fruit quality and hence alleviates the stated problems. The study evaluated the physico-chemical quality of ‘Tinker’ and ‘Roma VF’ cherry tomato as influenced by preharvest bagging (transparent and blue plastics) during 8 days of shelf life at ambient conditions. Five clusters of fruit per plant per cultivar with a diameter of 1.5 to 2.0 cm were bagged after 16 days of fruit set and harvested at the green maturity stage, 12 days after preharvest bagging for the assessment of postharvest quality. Preharvest bagging effectively accelerated fruit maturity and ripening as indicated by enhanced fruit size, uniform color development, high pH, dry matter (DM) content, soluble solid content (SSC), and low titratable acidity (TA) during shelf life. Bagged fruit had higher loss of firmness and weight mainly due to ripening and showed very slight incidence of diseases during shelf life of 8 days. Unbagged cherry tomato had delayed maturity and ripening; small-sized fruit; uneven color development; low pH, SSC, and DM; and high TA. Although unbagged cherry tomato had lower firmness and weight loss due to delayed ripening, fruit showed moderate to severe incidence of tomato bacterial canker disease (Clavibacter michiganensis subsp. michiganensis) during shelf life. These results indicated that preharvest bagging accelerated fruit maturity and ripening, improved physico-chemical quality, and reduced disease infestation on cherry tomato during shelf life.

Open access

Barbara J. Smith, Eric T. Stafne, Hamidou F. Sakhanokho, and Blair J. Sampson

The effect of supplemental lighting on strawberry growth and anthracnose disease response of three strawberry (Fragaria ×ananassa) cultivars was evaluated in two greenhouse trials, and the effect on strawberry anthracnose pathogens (Colletotrichum sp.) was evaluated in the laboratory. The objective of the greenhouse trials was to determine the effect of various intensities of the red and blue light emitting diode (LED) light treatment on strawberry plant vigor, injury, and disease development. In these trials, the duration of supplemental light treatments was split into two 4-hour periods: dawn and dusk. The intensity of the red and blue LED bulbs was set using an adjustable dial at 1 or 3 in trial 1 and at 1, 5, or 10 in trial 2. Illuminance and photosynthetic photon flux densities of the light treatments ranged from lows of 402 lx and 5 μmol⋅m–2⋅s–1 (blue LED 1) to highs of 575 lx and 25 μmol⋅m–2⋅s–1 (red LED 1 + blue LED 3) in trial 1, and from lows of 4213 lx and 81 μmol⋅m–2⋅s–1 (red LED 1) to highs of 7051 lx (red LED 5) and 194 μmol⋅m–2⋅s–1 (red LED 10) in trial 2. Lower light intensities in trial 1 resulted in no significant differences as a result of light treatments in relative chlorophyll content, plant vigor ratings, or disease severity ratings (DSRs). However, plant injury ratings were significantly greater in plants in the wide-spectrum fluorescent (WSF) plus ultraviolet B (UVB) light treatment compared with the other treatments. Under the higher light intensities in trial 2, there were more significant effects among light treatments. Relative chlorophyll content of plants in the WSF + UVB, WSF, and red LED 1 treatments was significantly greater than that of plants in the red LED 10 treatment; however, plants in the red LED 10 treatment had the greatest injury ratings. Detached leaves from plants in the red 5 LED and red 10 LED treatments inoculated with Colletotrichum gloeosporioides received the greatest DSRs, and leaves from plants in the red LED 1 and WSF treatments received the lowest DSRs. In the laboratory, five days of exposure to supplemental lights did not prevent the growth of isolates of three species of Colletotrichum pathogens even though the intensity of the LED lights was set at their highest intensity. However, growth of isolates exposed to the WSF + UVB light treatment was slowed.