White clover (Trifolium repens L.) belongs to the Fabaceae family legume and is cultivated in China for its medicinal properties and ornamental value. White clover is grown around the world for ...forage, turf , green manure and soil conservation purposes (Zhang el al. 2016). In October 2021, an investigation of a 1,000 m2 plant nursery in Lanzhou, China (36°06'N, 103°83'E) found that 80% of White clover plants were infected, and powdery mildew covered 95% of the leaf area. The disease had seriously destroyed the forage quality and reduced the ornamental value. Initially, thin, radial, irregular white colonies appeared on leaves and gradually spread to stems. The white colonies then expanded and thickened to cover upper surface of the leaf, and microscopic hyphae appeared on the bottom of the leaf. In severe cases, the infection resulted in dieback of the leaf. A small area of sporulating fungus was stripped off from the leaf surface with tape and mounted in sterile water for microscopic examination (Mukhtar et al. 2017). Conidiophores were cylindrical, consisting of a foot cell followed by three to four short cells, measuring 75 to 160 × 7 to 10 μm. Conidiophores had straight, cylindric foot cells ranging from 25 to 40 µm long. Singly produced conidia were hyaline and ranged in shape from oblong to cylindrical. Conidia lacked distinct fibrotic bodies and measured 30 to 45 × 15 to 25 μm in length. Long, unbranched germ tubes formed from the ends of the conidia and nipple-shaped appressoria developed on epiphytic mycelia. Based on these morphological characteristics, the pathogen was initially identified morphologically as Erysiphe polygoni (Braun and Cook 2012). To validate the identity, the internal transcribed spacer (ITS) region of the pathogen (SY77) rDNA was amplified by PCR and sequenced using the ITS1/ITS4 primers (White et al. 1990). The resulting sequences were registered to GenBank (GenBank Accession No.OM280998). The ITS sequence of the SY77 was 100% (640/640) identical to E. polygoni (LC009892) on Polygonum aviculare in the United Kingdom and 99% (638/640) identical to E. polygoni (MK685172) on Antigonon leptopus in Taiwan. MEGA 7.0 was used to conduct the neighbor-joining phylogenetic analysis using the ITS sequences from GenBank. The data indicated that the strain SY77 and E. polygoni clustered together on the same branch. Pathogenicity tests were conducted by gently pressing the infected leaves onto five healthy potted White clover plants, while five non-inoculated plants were used as controls (Michael et al. 2021). The plants were maintained in a growth chamber (25 ℃, 14 h light, and 10 h dark period, RH > 80%). After 10 days, the inoculated plants developed powdery mildew symptoms, whereas the control plants remained symptom-free. The fungus on the inoculated plants was re-isolated, re-identified, and confirmed as E. polygoni based on morphological observations and molecular identification. There is no previous report on E. polygoni causing powdery mildew on White clover in China. The powdery mildew caused by E. polygoni on Red clover has been reported in China and Bulgaria, respectively (Yuan el al.1991; Galina el al. 2017). To our knowledge, this is the first report of powdery mildew caused by E. polygoni on White clover in China. References: 1. Zheng, L., et al. 2018. Plant Dis. 102:628. 2. Mukhtar, G., et al. 2017. Plant Dis.101:1, 246. 3. Braun, U., and Cook, R. T. A. 2012. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht. 4. Michael, R. F., et al. 2021.Plant Dis. First look.( doi.org/ 10.1094/PDIS-09-21-2060-PDN). 5. Yuan, Q. H., el al.1991. Pratacult Sci.05:59 (in Chinese). 6. Galina, N., et al, 2017. BIOTECHNOL Anim Husb.33.127.
Purpose
Listing popularity indicates the public’s interest in a listing on peer-to-peer (P2P) accommodation platforms. Although listing popularity is crucial to the survival and development of the ...P2P accommodation platform, this issue has received limited attention in the tourism management discipline. Drawing upon the heuristic-systematic model and uncertainty reduction theory, this study aims to examine the impacts of host and property attributes on listing popularity.
Design/methodology/approach
The model was empirically validated using a data set of 6,828 listings on a popular P2P accommodation platform called Airbnb. This study chooses a hierarchical regression analysis to perform the model validation.
Findings
The findings reveal that host self-disclosure, host reputation and host identity verification are key host attributes in promoting listing popularity. Meanwhile, property visual description, property photo verification and property visual appeal are important property attributes in facilitating listing popularity.
Research limitations/implications
The study adds useful insights on understanding on determinants of listing popularity. Future researchers are recommended to empirically verify the underlying psychological mechanism by which host attributes and property attributes influence listing popularity.
Practical implications
The P2P accommodation platform should promote the listing popularity by taking advantage of the host attributes and providing property attributes.
Originality/value
First, to the best of the authors’ knowledge, this study is one of the few studies to explore the formation of the listing popularity. Second, this study examines how the host and property attributes promote the listing popularity through the heuristic and systematic information processing modes.
To evaluate the impact of top-pruning time on fertilizer N use efficiency (NUE) of flue-cured tobacco, we adopted
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N tracing technique and conducted a 2-year experiment from 2014 to 2015 in eastern ...China. The experiment included three top-pruning points of time: 5th, 25th and 45th day after flowering (DAF), abbreviated, respectively, as TP5, TP25 and TP45. The amounts of plant N derived from fertilizer (Ndff) and soil (Ndfs) were observed during 0-55th DAF. Results showed that top-pruning slowed down the increase of Ndff in tobacco organs, particularly in the leaf, but accelerated the increase of Ndfs dramatically. The proportion of Ndff (%) accounted for the total N reduced dramatically after top-pruning. This reduction might attribute to the selectivity of plant to different N sources as influenced by top-pruning while had little relationship with soil N supply, according to the analysis on the soil total mineral N and mineral
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N. The average NUE for the 2 years was 32%, 41% and 47%, respectively, for TP5, TP25 and TP45, showing significant (p < 0.05) differences. We concluded that the tobacco preferred to uptake soil N rather than fertilizer N after top-pruning; thus, optimizing the top-pruning time might be one of the approaches to improve the in-season NUE of flue-cured tobacco.
The experiment was conducted in a solar greenhouse to determine the optimum irrigation frequency and quantity for cucumber under subsurface drip irrigation based on evaporation from a 20cm diameter ...pan (E p) placed above the crop canopy. Two irrigation intervals (I1: 4-day and I2: 8-day) and three plant-pan coefficients (K cp1: 0.6; K cp2: 0.8 and K cp3: 1.0) were compared. Crop evapotranspiration (ET) and fruits yield increased with the increasing of irrigation water. The K cp3 treatments had the highest yield, while K cp2 had the highest irrigation water use efficiency (IWUE) and water use efficiency (WUE) values in both irrigation intervals. The yields of K cp2 treatments decreased only 4.87% and 5.93% in both intervals though total irrigation water decreased 14.3% compared to K cp3 treatment. Irrigation water amount significantly (P <0.01) and positively affected the fruit number and fruit water content, whereas significantly and negatively affected the soluble sugar (SS), Vitamin C (Vc) and free amino acid (FAA) content in fruits. In conclusion, I2K cp2 (0.8E p with 8-day interval) was the optimum irrigation schedule for cumber plants grown in solar greenhouse under subsurface drip irrigation in arid and semi-arid areas that are in lack of water resources.
In this paper, the grounding line selection technology is applied to the field. Under a substation model, the SL-0l grounding line selection device is used for small current system, and multiple ...tests are carried out in the field, and the corresponding waveform analysis is carried out. In this paper, the principle of small current system single-phase ground fault line selection based on transient traveling wave is studied, and the influence of neutral grounding method on traveling wave line selection method is analyzed. The corresponding device hardware and software algorithm is designed to solve the high frequency problem. Field test results and waveform analysis show that under the existing technical conditions, it is feasible to use high-speed sampling technology and wavelet algorithm for traveling wave selection. SL-0l traveling wave line selection device can meet the needs of the site.
Aiming at the problem that the mechanical structure of the ordinary pendulum spherical robot is improperly designed to cause a certain degree of freedom to swing the range, this paper proposes a ...two-degree-of-freedom spherical robot XK-I with a swing around the X and Y axes. The design concept, mechanical principle and rolling and rotating motion characteristics of the XK-I robot are introduced. According to the characteristics of XK-I robot motion, the dynamic model of linear motion is established by Lagrangian equation and simulated. According to the kinetic model, the XK-I robot steering is implemented by controlling the number of steps of the stepping motor by the pulse signal, so that the XK-I robot can move in any direction. The linear and steering tests of the XK-I robot were carried out through real experiments to verify the feasibility of the design.
Permineralized osmundaceous rhizome with anatomical and phylogenetic information plays a significant role in understanding the origin, evolution, and diversity variation of the fern family ...Osmundaceae in geological history. The northern Hebei and western Liaoning region is one of the most important fossil localities for the Jurassic osmundaceous rhizome fossils in the Northern Hemisphere; however, the diversity character of osmundaceous rhizome fossil remains poorly known. A new struc- turally preserved fern rhizome species, Ashicaulis wangii sp. nov., is described from the Middle Jurassic Tiaojishan Formation in Beipiao City, Liaoning Province, northeastern China. The rhizome is composed of heterogeneous pith, an ecto- phloic-dictyoxylic siphonostele, a two-layered cortex, and a mantle of adventitious roots and petiole bases. The xylem cylin- der, with complete leaf gaps, consists of 15-17 xylem strands. The petiole base is characterized by a heterogeneous sclerotic ring and numerous sclerenchyma masses in the petiolar cortex. Among five known Ashicaulis species with heterogeneous sclerotic ring, four of them are documented from China. Therefore, osmundaceous rhizome fossils from China show endemic anatomical characteristics and significances for palaeobiogeography. Comparisons of anatomical features suggest that A. wangii sp. nov. bears close similarities to Osmunda pluma Miller from the Paleocene of Dakota, USA. Fossil species of A. wangii provides new evidence for further understanding the species diversity of osmundaceous rhizome fossil in China and in the Northern Hemisphere, and contributes to exploring the macroevolution process of the Mesozoic osmundaceous plants.
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