CpG repression in RNA viruses has been known for decades, but a reasonable explanation has not yet been proposed to explain this phenomenon. In this study, we calculated the CpG odds ratio of all RNA ...viruses that have available genome sequences and analyzed the correlation with their genome polarity, base composition, synonymous codon usage, phylogenetic relationship, and host. The results indicated that the viral base composition, synonymous codon usage and host selection were the dominant factors that determined the CpG bias in RNA viruses. CpG usage variation between the different viral groups was caused by different combinations of these pressures, which also differed from each other in strength. The consistent under-representation of CpG usage in -ssRNA viruses is determined predominantly by base composition, which may be a consequence of the U/A preferred mutation bias of -ssRNA viruses, whereas the CpG usage of +ssRNA viruses is affected greatly by their hosts. As a result, most +ssRNA viruses mimic their hosts' CpG usage. Unbiased CpG usage in dsRNA viruses is most likely a result of their dsRNA genome, which allows the viruses to escape from the host-driven CpG elimination pressure. CpG was under-represented in all reverse-transcribing viruses (RT viruses), suggesting that DNA methylation is an important factor affecting the CpG usage of retroviruses. However, vertebrate-infecting RT viruses may also suffer host' CpG elimination pressure that also acts on +ssRNA viruses, which results in further under-representation of CpG in the vertebrate-infecting RT viruses.
Sweet cherry is an important fruit crop in China with a high economic value. From 2019 to 2020, a leaf spot disease was reported, with purplish-brown circular lesions in three cultivating regions in ...China. Twenty-four Fusarium isolates were obtained from diseased samples and were identified based on morphological characteristics and multi-locus phylogenetic analyses. Seven species, including F. luffae (7 isolates), F. lateritium (6 isolates), F. compactum (5 isolates), F. nygamai (2 isolates), F. citri (2 isolates), F. ipomoeae (1 isolate) and F. curvatum (1 isolate) were identified. The pathogenicity test showed that analyzed strains of all species could produce lesions on detached cherry leaves. Therefore, Fusarium was proved to be a pathogen of cherry leaf spots in China. This is the first report of F. luffae, F. compactum, F. nygamai, F. citri, F. ipomoeae and F. curvatum on sweet cherry in China.
This study aimed to identify fungal species associated with trunk diseases of sweet cherries (Prunus avium) in several commercial cherry orchards in Beijing, Guizhou and Shandong provinces, China. In ...total, eighteen fungal strains that fitted well into the species concept of Diaporthe were isolated. Based on both morphological and multi-locus phylogenetic analyses of internal transcribed spacer region (ITS), beta-tubulin (tub-2), calmodulin (Cal) and translation elongation factor 1-α (tef1–α) sequencing data, fourteen isolates were identified as Diaporthe eres, while four isolates were classified as D. hongkongensis. Here, we report D. hongkongensis causing sweet cherry branch dieback disease and, further, we confirmed the host association of D. eres with sweet cherries in China. A pathogenicity assay revealed the ability of both D. eres and D. hongkongensis to cause shoot necrosis and stem lesions on Prunus avium cv. ‘Brooks’ (mean lesion lengths of 1.86 cm and 1.56 cm, respectively). The optimal temperature for the growth of both Diaporthe species was tested. The optimal growth temperature for D. hongkongensis was 30 °C, and the 25–28 °C temperatures were the most favorable for the growth of D. eres strains. This research advances the understanding of fungal trunk diseases in fruit crops, particularly gummosis and branch dieback disease in Chinese cherry orchards, and will aid growers in making decisions about cultural practices and disease management.
This study aimed to identify fungal species associated with trunk diseases of sweet cherries (Prunus avium) in several commercial cherry orchards in Beijing, Guizhou and Shandong provinces, China. In ...total, eighteen fungal strains that fitted well into the species concept of Diaporthe were isolated. Based on both morphological and multi-locus phylogenetic analyses of internal transcribed spacer region (ITS), beta-tubulin (tub-2), calmodulin (Cal) and translation elongation factor 1-α (tef1–α) sequencing data, fourteen isolates were identified as Diaporthe eres, while four isolates were classified as D. hongkongensis. Here, we report D. hongkongensis causing sweet cherry branch dieback disease and, further, we confirmed the host association of D. eres with sweet cherries in China. A pathogenicity assay revealed the ability of both D. eres and D. hongkongensis to cause shoot necrosis and stem lesions on Prunus avium cv. ‘Brooks’ (mean lesion lengths of 1.86 cm and 1.56 cm, respectively). The optimal temperature for the growth of both Diaporthe species was tested. The optimal growth temperature for D. hongkongensis was 30 °C, and the 25–28 °C temperatures were the most favorable for the growth of D. eres strains. This research advances the understanding of fungal trunk diseases in fruit crops, particularly gummosis and branch dieback disease in Chinese cherry orchards, and will aid growers in making decisions about cultural practices and disease management.
Leaf spot is a common and serious disease of sweet cherry worldwide and has become a major concern in China. From 2018 to 2020, disease investigations were carried out in Beijing City, Sichuan, ...Shandong, and Liaoning Provinces in China, and 105
isolates were obtained from diseased samples. Isolates were identified by morphological characterization coupled with multigene phylogenetic analyses based on six loci (internal transcribed spacer region, glyceraldehyde 3-phosphate dehydrogenase, calmodulin, actin, chitin synthase, and β-tubulin). A total of 13
species were identified, namely
,
,
,
,
,
,
,
,
,
,
,
, and
Among these,
(25.7%) was the most prominent species isolated from diseased leaves, followed by
(19.0%) and
(12.4%). Pathogenicity was tested on detached leaves of cv. 'Tieton' and 'Summit' and young seedlings of cv. 'Brooks' under greenhouse conditions. All 13 species were pathogenic to cherry leaves, and
,
, and
showed high levels of virulence. Seedlings inoculated with the isolates developed similar symptoms to those seen in the orchards. This study provides the first reports for 11 of the 13
species on sweet cherry in the world, excluding
and
. This is the first comprehensive study of
species associated with cherry leaf spot in China, and the results will provide basic knowledge to develop sustainable control measures for cherry leaf spot.
Sweet cherry is an important fruit crop in China with a high economic value. From 2019 to 2020, a leaf spot disease was reported, with purplish-brown circular lesions in three cultivating regions in ...China. Twenty-four Fusarium isolates were obtained from diseased samples and were identified based on morphological characteristics and multi-locus phylogenetic analyses. Seven species, including F. luffae (7 isolates), F. lateritium (6 isolates), F. compactum (5 isolates), F. nygamai (2 isolates), F. citri (2 isolates), F. ipomoeae (1 isolate) and F. curvatum (1 isolate) were identified. The pathogenicity test showed that analyzed strains of all species could produce lesions on detached cherry leaves. Therefore, Fusarium was proved to be a pathogen of cherry leaf spots in China. This is the first report of F. luffae, F. compactum, F. nygamai, F. citri, F. ipomoeae and F. curvatum on sweet cherry in China.
CpG repression in RNA viruses has been known for decades, but a reasonable explanation has not yet been proposed to explain this phenomenon. In this study, we calculated the CpG odds ratio of all RNA ...viruses that have available genome sequences and analyzed the correlation with their genome polarity, base composition, synonymous codon usage, phylogenetic relationship, and host. The results indicated that the viral base composition, synonymous codon usage and host selection were the dominant factors that determined the CpG bias in RNA viruses. CpG usage variation between the different viral groups was caused by different combinations of these pressures, which also differed from each other in strength. The consistent under-representation of CpG usage in -ssRNA viruses is determined predominantly by base composition, which may be a consequence of the U/A preferred mutation bias of -ssRNA viruses, whereas the CpG usage of +ssRNA viruses is affected greatly by their hosts. As a result, most +ssRNA viruses mimic their hosts' CpG usage. Unbiased CpG usage in dsRNA viruses is most likely a result of their dsRNA genome, which allows the viruses to escape from the host-driven CpG elimination pressure. CpG was under-represented in all reverse-transcribing viruses (RT viruses), suggesting that DNA methylation is an important factor affecting the CpG usage of retroviruses. However, vertebrate-infecting RT viruses may also suffer host' CpG elimination pressure that also acts on +ssRNA viruses, which results in further under-representation of CpG in the vertebrate-infecting RT viruses.
What determines whether one purchases products online shopping or through another channel? A flow experience model is proposed and tested with the structural equation modeling method. The results ...show that in the context of human-computer interactions while browsing a website, flow experience is characterized by time distortion, enjoyment and telepresence. The entertainment, website services' quality, the customers' web close and the perception of novelty have negative effect on flow experience. Otherwise, the website can enhance the consumers' intention through improving its interaction and entertainment.
In this paper, a new split iterative compact difference scheme for a class of system is constructed. Then, the conservation properties of the scheme are discussed, and the convergence of the split ...iterative difference scheme is analyzed by using the discrete energy method on the basis of the prior estimation. Finally, numerical experiments verify these properties of the new scheme. In addition, the numerical results also show the influence of fractional derivative on the variation of the transport equation.
As a mature and reliable method, this study is based on the flow function method for mathematical modeling and establishes a class of mathematical models that are approximately realistic, flexible, ...and easy to calculate. According to the characteristics of fractional order calculus, the initial boundary conditions are modified and optimized to reduce the model error of this class of equations. According to the minimum energy principle and linearized integral calculation method, the multi-field multi-parameter non-linear coupling problem in the calculation process is solved, and the rapid calculation of the initial boundary model is realized. The accuracy of the model is tested by numerical simulation and simulation validation of different processes. A reliable theoretical and technical support is provided for the calculation of this type of equations.
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