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Open access

Eduardo D. Munaiz, Russell L. Groves and Michael J. Havey

Onion thrips (Thrips tabaci) is the main insect pest of onion (Allium cepa), and feeding damage routinely causes serious yield losses. Lower amounts of epicuticular waxes on onion leaves have been associated with fewer onion thrips and less feeding damage, and research is needed to assess the relationships between amounts and composition of epicuticular waxes and feeding damage by onion thrips. This study used gas chromatography mass spectroscopy to determine amounts and types of epicuticular waxes on the foliage of onion accessions that had been field-selected for lower damage from onion thrips. Hentriacontanone-16 (H16), octaconasol-1, and triacontanol-1 were the most prevalent waxes on the foliage of these selections. Amounts of H16 were significantly lower on selections visually classified as having glossy or semiglossy foliage. Semiglossy selections were identified with similar amounts of total epicuticular wax as waxy phenotypes, due primarily to lower amounts of H16 and higher amounts of other waxes. These semiglossy selections suffered significantly less feeding damage from onion thrips in a field evaluation, supporting the identification of unique wax profiles toward the development of thrips-resistant onion.

Open access

Natalie Bumgarner, Sheri Dorn, Esther McGinnis, Pam Bennett, Ellen Bauske, Sarada Krishnan and Lucy Bradley

Many fields of research converge to assess the impact of plants on human health, well-being, and nutrition. However, even with a recent history of horticulturists contributing to human–plant interaction work, much of the current research is conducted outside the context of horticulture and specifically outside of consumer horticulture (CH). To connect CH to research being conducted by other disciplines that explore the role of plants in improving human quality of life, a workshop was held on 1 Aug. 2018 in Washington, DC, at the American Society for Horticultural Science (ASHS) annual conference. The workshop focused on current food science, nutrition, and crop-breeding efforts to enhance nutrition and flavor, and human health and well-being research related to nature and plant interactions in an increasingly urban population. Following these presentations regarding potential research linkages and collaboration opportunities, a facilitated discussion identified ways to improve future CH research and foster collaborative work. Action items identified included connecting research and vocabulary to help cultivate an interest in plants in younger generations; supporting awareness of collaborative opportunities with health, nutrition, urban planning, and public health practitioners; ensuring CH is known to administrators; and taking responsibility for initiating communication with colleagues in these areas.

Open access

Christopher D. Ryan, J. Bryan Unruh, Kevin E. Kenworthy, Alexa J. Lamm, John E. Erickson and Laurie E. Trenholm

Every county and municipality in Florida can adopt its own unique ordinance regulating the fertilization of lawns and landscapes. With increased concern for eutrophication to state waterbodies, many have chosen to implement seasonal fertilizer restrictive periods prohibiting the application of nitrogen and phosphorus fertilizers, typically during the rainy summer months. These fertilizer “blackout” policies have been the subject of controversy among environmental activists, university scientists, and policy decision makers, with their efficacy being called into question. A Foucauldian discourse analysis was undertaken to trace the dynamics of the controversy, and survey research was conducted with Florida residents and with Florida decision makers to compare their lawncare maintenance practices, sentiments surrounding turfgrass, their trust in landscape science, as well as their awareness of policy in the city or county in which they reside. Differences were found between the two populations in terms of how many respondents fertilized, used automated irrigation systems and hand-pulled weeds. Although both populations had very neutral sentiments around turfgrass with no significant differences, Florida decision-maker respondents had a higher mean response for trust in landscape science. Only 32% of Florida resident respondents were able to accurately identify if their city or county had a blackout ordinance, compared with 81% of decision-maker respondents. Increasing civic science may be the best way for reducing this discrepancy, while also giving power to citizens in environmental policy adoption.

Open access

Kayla R. Sanders and Jeffrey S. Beasley

Controlled-release fertilizers (CRFs) provide an extended period of nutrient availability for turfgrass growth and may limit offsite nutrient losses compared with water-soluble fertilizers (WSFs). However, increasing temperatures and soil moisture accelerate nutrient release from many CRFs. As a result, turfgrass managers growing turfgrass in warm, humid climates with high rainfall question how effective CRFs are in reducing nutrient runoff losses while maintaining aesthetic quality. A study was conducted to examine the effect of three fertilizer treatments—an unfertilized control, a CRF applied at 87 lb/acre nitrogen (N), and a WSF applied at 87 lb/acre N as a split application (43.5 lb/acre N) at 0 and 45 d after initial fertilization (DAIF)—on nutrient losses from ‘Tifway’ hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) during surface runoff events. Rainfall simulations were conducted 3, 28, 56, and 84 DAIF at an intensity of 3 inches per hour to induce 30 minutes of runoff. Water samples were analyzed for inorganic N and dissolved total phosphorus (DTP). Hybrid bermudagrass quality was similar among fertilizer treatments with CRF application, resulting in slightly higher quality. Across all fertilizer treatments, hybrid bermudagrass exhibited similar runoff initiation time and volumes within each rainfall simulation event. Nutrient losses from fertilized hybrid bermudagrass were greatest at the first runoff event at 3 DAIF, with WSF having the greatest losses. The subsequent application of WSF 45 DAIF did not result in greater N and DTP losses compared with CRF application, most likely a result of water incorporation applied to prevent wilting. Hybrid bermudagrass fertilized with a single application of CRF resulted in 23.6% and 55.6% reductions in cumulative inorganic N and DTP losses, respectively, compared with hybrid bermudagrass fertilized with the a split application of WSF.

Open access

Saad B. Javed, Abdulrahman A. Alatar, Mohammad Anis and Mohamed A. El-Sheikh

The coral tree (Erythrina variegata) is a multipurpose horticultural plant with a plethora of medicinally important alkaloids. Regeneration via tissue culture can provide an efficient alternative to seed-grown plantlets and reduce the cost of the plant significantly. Thidiazuron (TDZ) is an efficient plant growth regulator and is effective in numerous species. However, the response to it varies with the type and position of the tissue on the plantlet treated. This study was carried out to ascertain the best tissue types for micropropagation of the coral tree using TDZ. Three tissue types (shoot tip, nodal, and hypocotyl), originating from different strata of the plantlet were evaluated. Adventitious shoots were observed in all three explants at the tested concentrations. However the quality and the shoot number varied significantly with the type of explant. Explants with a meristematic zone (shoot tip and nodal) were more responsive to the treatment compared with hypocotyl tissue lacking preexisting meristem. Nodal explants produced the maximum number of shoots (about eight) per explant after 4 weeks of culture, whereas shoot tips produced about only five shoots per explant at an equimolar concentration (1.5 µm). Approximately three shoots were observed in hypocotyl explants. Moreover, growth and rooting of the regenerated shoots was influenced by the origin of the explants. The molecular characterization of the regenerants using intersimple sequence repeat (ISSR) markers revealed genetic homogeneity among regenerants. An efficient micropropagation method for the coral tree is described.

Open access

Ricardo Goenaga, Brian Irish and Angel Marrero

Plantain (Musa balbisiana AAB) is a tropical rhizomatous perennial plant in the genus Musa spp., closely related to banana (Musa acuminata AAA). It is an important cash crop and staple for inhabitants in many parts of the world, including various ethnic groups in the United States. Black leaf streak disease (BLSD) or black sigatoka, caused by Pseudocercospora fijiensis (formerly Mycosphaerella fijiensis), is responsible for significant losses of this crop due to the high susceptibility of the most economically important cultivars. BLSD does not immediately kill plantain plants, but it causes severe leaf necrosis, which results in reduced photosynthetic area, thereby adversely impacting bunch weight and fruit production. Without cultural and chemical control, yields can be reduced by 20% to 80%, depending on severity. This study evaluated a BLSD-resistant cultivar, FHIA-21, against Maricongo, a standard commercial cultivar with no BLSD tolerance, at two locations in Puerto Rico on Ultisol (Corozal site) and Oxisol (Isabela site) soils. Total number of fruit and bunch yield were significantly higher at Isabela, with BLSD severity being significantly lower at this location. Average fruit production of ‘FHIA-21’ was significantly higher than that of ‘Maricongo’ at both locations, with fruit yields of 122,522 and 99,948 fruit/ha at Isabela and Corozal, respectively. Overall, fruit of ‘FHIA-21’ were significantly longer and had greater diameters than those of ‘Maricongo’. At Isabela, the mean bunch fruit weight was significantly higher for ‘FHIA-21’, but both cultivars exceeded the minimum local marketable fruit weight criterion of 270 g. At both locations, the numbers of functional leaves present at flowering and at harvest were significantly higher for ‘FHIA-21’ than for ‘Maricongo’, indicating more availability of photosynthetic area for ‘FHIA-21’ during the fruit-filling period. There were no significant differences between cultivars regarding the concentration of starch and soluble sugars for green fruit. Regarding ripe fruit, ‘FHIA-21’ had a significantly higher concentration of soluble sugars and less starch. In this study, ‘FHIA-21’ had good resistance against BLSD and, if accepted by consumers, is a viable alternative to current commercial cultivars. We also conclude from this study that the expression of the Banana streak virus (BSV) in planting material of this cultivar remains an unknown threat in yield decline of ‘FHIA-21’.

Restricted access

Wei Zhou, Xiaoming Wang, Jianhua Chen, Liangming Chen, Zhongquan Qiao and Huijie Zeng

Lagerstroemia indica (crape myrtle) is a popular Chinese landscape plant with a long flowering period that contributes to its gorgeous flowers and high ornamental value, which motivate L. indica breeding. We found a wild acarpous individual of L. indica that did not bear seeds after flowering and had a significantly longer flowering period than fructiferous L. indica. This study identified differences in floral organ morphology, and stamen and pistil structure between fructiferous and acarpous L. indica through observation, paraffin sectioning, and scanning electron microscopy (SEM). The flowering time of each acarpous L. indica inflorescence lasts as long as 18 to 25 days. When a single flower withers, it falls from the pedicel without any fruit. The abortion in the floral organ of acarpous L. indica is characterized by sterile and undehisced anthers, pollen abortion, and deformed and irregularly arranged filament cells. Acarpous L. indica features short and loosely arranged papilla cells in the stigma, a flat style and narrow stylar canal, loosely arranged epidermal cells, and no obvious nuclei. No embryo sac cavity is found in acarpous L. indica ovules. In some nucelli, the egg apparatus structure can be observed indistinctly but without cell contour. In others, the egg apparatus structure is completely absent, and only flocculent tissue is observed. This study may provide a theoretical foundation for future studies on the molecular mechanisms of the mutations in acarpous L. indica.

Restricted access

Yun Kong, Devdutt Kamath and Youbin Zheng

An elongated stem has beneficial effects on microgreen production. Previous studies indicate that under 24-hour light-emitting diode (LED) lighting, monochromatic blue light, compared with red light, can promote plant elongation for some species. The objective of this study was to investigate whether shortened photoperiod can change blue vs. red light effects on elongation growth. The growth and morphology traits of arugula (Brassica eruca, ‘Rocket’), cabbage (Brassica oleracea, unknown variety name), mustard (Brassica juncea, ‘Ruby Streaks’), and kale (Brassica napus, ‘Red Russian’) seedlings were compared during the stage from seeding to cotyledon unfolding under two light quality × two photoperiod treatments: 1) R, monochromatic red light (665 nm) and 2) B, monochromatic blue light (440 nm) using continuous (24-hour light/0-hour dark) or periodic (16-hour light/8-hour dark) LED lighting. A photosynthetic photon flux density of ≈100 μmol·m−2·s−1 and an air temperature of ≈22 °C was used for the preceding treatments. After 7 to 8 days of lighting treatment, regardless of photoperiod, B promoted elongation growth compared with R, as demonstrated by a greater stem extension rate, hypocotyl length, or petiole length in the tested microgreen species, except for mustard. The promotion effects on elongation were greater under 24- vs. 16-hour lighting in many cases. Among the tested species, mustard showed the lowest sensitivity in elongation response to B vs. R, which was independent of photoperiod. This suggests that the blue-light-promoted elongation is not specifically from 24-hour lighting, despite the varying promotion degree under different photoperiods or for different species. The elongation growth promoted by blue LED light under a photoperiod of either 24 hours or 16 hours can potentially benefit indoor production of microgreens.

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Phu-Long Pham, Ying-Xue Li, He-Rong Guo, Rui-Zhen Zeng, Li Xie, Zhi-Sheng Zhang, Jianjun Chen, Qing-Lian Su and Qing Xia

Dendrobium officinale Kimura et Migo is a famous traditional Chinese medicinal plant. It produces various phytochemicals, particularly polysaccharides, which have nutraceutical and pharmaceutical values. To increase its biomass production and polysaccharide content, our breeding program has generated a series of polyploid cultivars through colchicine treatment of protocorm-like bodies (PLBs). The present study compared two tetraploid cultivars, 201-1-T1 and 201-1-T2, with their diploid parental cultivar, 201-1, in an established in vitro culture system. Tetraploid ‘201-1-T1’ and ‘201-1-T2’ had shorter leaves and shorter and thicker stems and roots, and they produced higher biomass compared with the diploid cultivar. The length and width of stomata significantly increased, but stomatal density decreased in tetraploid cultivars. The PLB induction rates from the stem node explants of the tetraploid cultivars were significantly higher than those of diploid. However, the PLB proliferation of tetraploids was lower than that of the diploid. The mean number of plantlets regenerated from tetraploid PLBs was also lower than that of the diploid after 4 months of culture. Polysaccharide contents in stems, leaves, and roots of 6-month-old tetraploid plantlets were significantly higher than those of diploids. The polysaccharide content in the stem of ‘201-1-T1’ was 12.70%, which was a 2-fold increase compared with the diploid cultivar. Our results showed that chromosome doubling could be a viable way of improving D. officinale in biomass and polysaccharide production.

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Yusuke Kubo, Shinobu Satoh, Haruka Suzuki, Toshinori Kinoshita and Nobuyoshi Nakajima

During the transport of vegetables, it is important to maintain quality. The cotyledons of Japanese radish (Raphanus sativus var. longipinnatus) sprouts curl during transport, lowering quality. It is known that ethylene causes the leaf curling of some true leaves by promoting cell growth on the adaxial side (epinasty); however, the mechanism of cotyledon curling is unknown. We investigated the effect of ethylene on cotyledon curling of Japanese radish sprouts. Curling was promoted by exogenous treatment with ethylene and repressed by treatment with 1-methylcyclopropene, an inhibitor of ethylene perception. Microscopic observation of ethylene-exposed curled cotyledons and normal cotyledons indicates that ethylene did not affect cell number but did inhibit transverse (lateral) cell growth on the abaxial side of the cotyledons, causing cotyledon curling through differential growth. Ethylene inhibition of cell growth on the abaxial side of leaves has not been reported before. We show a new mechanism responsible for curling.