First Report of Fusarium solani Causing Leaf Sheath Rot of Bush lily in China

Bush lily (Clivia miniata) is an important indoor flower. It is the city flower of Changchun City and has important ornamental and medicinal value in China where it is culitvated on an area of 125 hectare. During the summer of 2018, symptoms of a leaf sheath rot disease were observed on bush lily in 103 greenhouses in Changchun city, Jilin Province. The disease incidence ranged from 25 to 60% in 11 surveyed greenhouses. At the early stage, the diseased plants displayed symptoms as initial leaf sheath lesions. Progressively, the whole leaves wilted, and even the plant ultimately died. Once a leaf exhibits leaf sheath lesions, the whole plant’s ornamental value significantly drops. To identify the pathogen, symptomatic leaves were cut into pieces, surface sterilized, placed on potato dextrose agar (PDA) and incubated for 7 days at 25°C in the dark (Cao et al. 2013; the e-Xtra description for details). Fusarium single-spore isolates were obtained from characteristic colonies (Leslie et al. 2006). Two single-spore isolates were selected for further study. The isolates were identified as Fusarium spp. based on microscopic morphology on PDA. Fusarium-like colonies were white to slightly yellow with abundant cottony mycelia. Single or two-celled (single septum) microconidia were reniform or oval, 8.0 to 9.6×4.0 to 6.0m in size. The elongated conidiophores bearing microconidia in monophialides were observed (Summerbell et al. 2002). Macroconidia were abundant, sickle shaped, 18.8 to 34.8×6.4 to 6.8m, with one to three septa (Taylor et al. 2019). For molecular identification, five regions of ITS, EF1-α, RPB1, RPB2 and β-tubulin genes were amplified and sequenced. Sequences of five different regions exhibited at least 97.98% similiarity with the corresponding DNA sequences in F. solani species complex (FSSC) (the e-Xtra description for details). The phylogenetic analysis based on the EF1-α, RPB1, RPB2 and β-tubulin region sequences revealed that the isolated strain in this study was clustered with only F. solani species in the phylogenetic tree for each region. Based on morphological and molecular analysis, the isolated fungal strains were identified as F. solani. Pathogenicity was confirmed by injecting a conidial suspension (106 spores/mL) of the isolated strains in to surface surface-disinfested leaf sheath of 2-year-old potted healthy plants. As a negative control, four plants were injected with sterilized water. All plants were kept in a greenhouse with controlled conditions: 26°C, 50% to 75% relative humidity. The similar rot symptoms were observed on the leaf sheathes in the inoculated plants 30 days after inoculation whereas the control plants remained asymptomatic. The fungi reisolated from the experimental plants were confirmed to be F. solani by morphology and sequences analysis, thus completing Koch’s postulates. To the best of our knowledge, this is the first report of F. solani causing leaf sheath rot of bush lily in China, where this pathogen has been reported to cause rot diseases of other economically important ornamental plants such as Phalaenopsis, Dendrobium according to the U.S. National Fungus Collections (Farr et al. 2020). In recent years, other Fusarium species have been reported to cause rot diseases on bush lily, including F. proliferatum and F. oxysporum (Farr et al. 2020). This study will also provide critical information on the causal agent for growers to implement disease management strategies.

Identifying Urban Functional Areas in China’s Changchun City from Sentinel-2 Images and Social Sensing Data

The urban functional area is critical to an understanding of the complex urban system, resource allocation, and management. However, due to urban surveys’ focus on geographic objects and the mixture of urban space, it is difficult to obtain such information. The function of a place is determined by the activities that take place there. This study employed mobile phone signaling data to extract temporal features of human activities through discrete Fourier transform (DFT). Combined with the features extracted from the point of interest (POI) data and Sentinel images, the urban functional areas of Changchun City were identified using a random forest (RF) model. The results indicate that integrating features derived from remote sensing and social sensing data can effectively improve the identification accuracy and that features derived from dynamic mobile phone signaling have a higher identification accuracy than those derived from POI data. The human activity characteristics on weekends are more distinguishable for different functional areas than those on weekdays. The identified urban functional layout of Changchun is consistent with the actual situation. The residential functional area has the highest proportion, accounting for 33.51%, and is mainly distributed in the central area, while the industrial functional area and green-space are distributed around.

Persistence of E. Coli O157:H7 in Urban Recreational Waters From Spring and Autumn: A Comparison Analysis

Persistence of E. coli O157: H7 (EcO157) in 48 water samples (24 Spring samples and 24 Autumn samples) from 3 urban recreational waters in Changchun City was investigated, and multivariate statistical analysis was performed to correlate survival data with water physicochemical properties and bacterial communities. Our data showed that EcO157 survived longer in Spring samples than in Autumn samples regardless of the lakes. Results revealed that recreational water physicochemical properties and bacterial community in Spring samples were different from those in Autumn samples. Mantel and Partial Mantel tests, as well as co-occurrence network analysis illustrated that EC salinity, TOC and bacterial community were correlated with survival time (ttd) (p < 0.05). Variation partition analysis (VPA) indicated that bacterial community, EC, TOC and TN explained about 64.81% of overall ttd variation in Spring samples, and bacterial community, EC, pH and TP accounted for about 56.59% of overall ttd variation in Autumn samples. Structural equation model (SEM) illustrated that EC indirectly positively affected ttd through bacterial community. The correlation between bacterial community and ttd was negative in Spring samples and positive in Autumn samples. TN appeared a direct positive effect on ttd in Spring samples. TP displayed a direct negative effect on ttd in Autumn samples. Our results concluded that there was seasonal variation in environmental factors that directly or indirectly affected the survival of EcO157 in urban recreational waters.