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In 2018, a bacterial disease complex composed of bleached spots and soft rot–blight on onion seedlings was observed in nursery beds in Changnyeong, a major onion-producing county in South Korea. Four bacteria isolated from the diseased lesions were identified: Pseudomonas viridiflava, Acidovorax avenae subsp. avenae, Pantoea ananatis, and Xanthomonas axonopodis, respectively. We referred to the four strains as a “bacterial disease complex” because they were isolated from the same sample with multiple symptoms. We examined the synergistic activity among the four strains to understand their relationships and roles. We monitored in vivo bacterial population density and disease progression after artificially inoculating the bacteria on onion seedlings at a temperature of 22 or 28°C. The disease pattern progressed sooner at 28 than at 22°C (by an average of 4 to 6 days). The rate of disease progression induced by inoculation of P. ananatis alone was consistent with that induced by coinoculation of P. ananatis with the other strains, regardless of the temperature (22 or 28°C). The in vivo growth of P. ananatis on onion seedlings was not different after inoculation alone versus together with the other strains. The rate of disease progression induced by P. viridiflava was similar when inoculated alone and when inoculated with other tree strains at 28°C, but disease progression induced by inoculation alone was slower at 22°C. The in vivo growth of P. viridiflava or X. axonopodis on onion seedlings decreased rapidly or gradually, respectively, when inoculated with the other strains. Coinfection with the other three strains had repression effects on the growth of P. viridiflava, a slight effect on X. axonopodis, and no effect on P. or A. avenae subsp. avenae in vivo. These results indicate that the strains coexist or interact antagonistically, rather than synergistically, depending on the conditions. These results were consistent with the results of the in vitro growth inhibition assay, in which P. viridiflava growth was inhibited by X. axonopodis or P. ananatis. These results also confirmed that X. axonopodis is present on bleached spots and P. viridiflava on soft rot–blight lesions, and that P. viridiflava and P. ananatis cause soft rot–blight but do not coexist. A. avenae subsp. avenae is a minor causative pathogen of bleached spots on onion seedlings, but it is not significantly affected by temperature and has no antagonistic or synergistic interactions with X. axonopodis.

Realizing a clinical-grade electronic medicine for peripheral nerve disorders is challenging owing to the lack of rational material design that mimics the dynamic mechanical nature of peripheral nerves. Electronic medicine should be soft and stretchable, to feasibly allow autonomous mechanical nerve adaptation. Herein, we report a new type of neural interface platform, an adaptive self-healing electronic epineurium (A-SEE), which can form compressive stress-free and strain-insensitive electronics-nerve interfaces and enable facile biofluid-resistant self-locking owing to dynamic stress relaxation and water-proof self-bonding properties of intrinsically stretchable and self-healable insulating/conducting materials, respectively. Specifically, the A-SEE does not need to be sutured or glued when implanted, thereby significantly reducing complexity and the operation time of microneurosurgery. In addition, the autonomous mechanical adaptability of the A-SEE to peripheral nerves can significantly reduce the mechanical mismatch at electronics-nerve interfaces, which minimizes nerve compression-induced immune responses and device failure. Though a small amount of Ag leaked from the A-SEE is observed in vivo (17.03 ppm after 32 weeks of implantation), we successfully achieved a bidirectional neural signal recording and stimulation in a rat sciatic nerve model for 14 weeks. In view of our materials strategy and in vivo feasibility, the mechanically adaptive self-healing neural interface would be considered a new implantable platform for a wide range application of electronic medicine for neurological disorders in the human nervous system., Electronic implantable devices should be soft and stretchable, such that nerves can adapt mechanically and autonomously. Here, the authors present an adaptive self-healing electronic epineurium which can form compressive stress-free and strain-insensitive electronics-nerve interfaces.

The African spear or cylindrical snake plant (Sansevieria cylindrica) is commonly used as an ornamental indoor succulent plant. In May 2019, we observed bacterial blight in S. cylindrica grown for interior decoration and air purification in Jinju, South Korea. These symptoms eventually led to leaf desiccation. Similar leaf blight symptoms have been frequently documented on social media; however, as an imported species, the pathogens of S. cylindrica have not been reported in South Korea. Based on pathogenicity tests; levan production, oxidase production, pectinolytic activity, arginine dihydrolase production, and tobacco hypersensibility tests; analytical profile index API tests; and phylogenetic analysis based on multi-locus sequence analysis using the 16S rRNA, gyrB, rpoD, and rpoB gene sequences, we identified the causative pathogen as Pseudomonas sp. This study is the first to report leaf blight caused by Pseudomonas sp. on S. cylindrica.

Anthracnose was observed on postharvest avocados (Persea americana) in a commercial market in Jinju, South Korea, in 2019. Symptoms included soft rot and sunken lesions leaking necrotic fluid. Oran...

In 2018, bacterial shoot blight was observed on Asian pear trees (Pyrus pyrifolia) in an orchard in Jinju, South Korea. The young pear shoots were infected and showed shoot blight symptoms: the shoot tips shriveled and turned tan in color, and this spread from the shoot tip down the stem and into the leaves. The causal pathogen was isolated from the diseased lesions and identified as Pseudomonas cerasi based on API tests and multilocus sequence analysis (MLSA) using the 16S rRNA, gyrB, rpoB, and rpoD gene sequences. The symptoms after artificial inoculation were identical to natural field symptoms, whereas negative control plants were asymptomatic. Bacteria were re-isolated from the artificially induced lesions on blossoms and shoots, and their identity was confirmed by rpoD sequencing. This is the first report of bacterial shoot blight on pear tree caused by Pseudomonas cerasi Griffin in the world.

In 2018, severe bacterial blight was observed on Dracaena sanderiana plants imported and cultivated by a commercial nursery in Jinju, South Korea. This indoor plant is popularly grown for indoor air purification to prevent sick building syndrome (SBS). The diseased plants had severe blight symptoms, with leaf chlorosis and crumpling of stem and leaves. To identify the causal agent, we performed bacterial isolation, pathogenicity tests, physiological analysis, sequencing of the 16S rRNA region and recA gene, and phylogenetic analysis; the bacterial pathogen was identified as Burkholderia cepacia. This is the first report of bacterial blight on D. sanderiana caused by B. cepacia. Although there is no clear epidemiological information on the inoculum source, the recent occurrence of the disease indicates that B. cepacia is a potential threat to the production of indoor dracaena plants, which are increasingly used for air purification in SBS. Because D. sanderiana is grown in indoor living spaces, B. cepacia infection could threaten human health as well.

Salmonella enterica outbreaks in sprouts originate from contaminated seeds; conventional prevention technologies have been reported from many research institutes. In this study, we applied a biological control approach to inhibit S. enterica growth using the seed-dwelling non-antagonistic bacteria. We isolated non-antibacterial seed-dwelling bacteria from vegetable sprouts. A total of 206 bacteria exhibiting non-antibacterial activity against S. enterica were subjected to alfalfa sprout development tests. Eight isolates exhibiting no deleterious effect on the growth of alfalfa sprouts were tested for S. enterica growth inhibition on alfalfa seeds and sprouts, and an isolate EUS78 was finally selected for further investigation. Based on 16S rRNA, gyrB, and rpoB gene sequence analyses, strain EUS78 was identified as Erwinia persicina. In population competition, the S. enterica population increased by3 log CFU/g after 6 days of alfalfa sprout growth, whereas S. enterica growth was significantly inhibited by treatment with EUS78 (P .05). This effect of S. enterica growth inhibition by EUS78 was sustained until the end of the alfalfa sprout harvest. Overall, bacterial strain EUS78 significantly reduced S. enterica growth on alfalfa sprouts in a manner consistent with competitive exclusion. These findings led us to monitor EUS78 behavior on seeds during early sprout development using fluorescence and scanning electron microscopy. Strain EUS78 initially colonized alfalfa sprout seed coat edges, cotyledons, and finally root surfaces during early sprout germination. As alfalfa sprouts grew, EUS78 bacterial cells established colonies on newly emerged plant tissues such as root tips. The results of this study suggest that strain EUS78 has potential as a biological control agent to inhibit S. enterica contamination in the sprout food industry.

Sweet crab apple (Malus coronaria) is a popular ornamental tree planted in gardens and urban forests in South Korea. In 2018, severe symptoms were observed on street plantings of sweet crab apple in Jinju, South Korea including shoot blight: shoot tips, twigs and foliage of infected trees turned brown, and dried completely. The causal agent isolated from the disease lesions was identified as Pseudomonas viridiflava based on biochemical tests, pathogenicity, and 16S rRNA and rpoD gene sequencing. On artificial inoculation, this pathogen not only caused shoot blight on sweet crab apple, but also bulb rot and leaf blight on onion. Here, we report the occurrence of bacterial shoot blight caused by P. viridiflava in sweet crab apple for the first time in the world.

Over a 3-year period (2015–2017), sclerotium rot was observed on purple wood sorrel (Oxalis purpurea) in the exhibition field of Gyeongsangnam-do Agricultural Research and Extension Services, Jinju, South Korea. Infected plants exhibited blight and rot symptoms. White mycelial mats spread over lesions, and numerous sclerotia formed on the petiole near the soil line. Sclerotia were globoid in shape, 1–3 mm in size, and white to brown in color. The optimum temperature for mycelial growth and sclerotium formation on potato dextrose agar (PDA) was 30 °C and the hyphal width was 4–8 μm. Typical clamp connections were observed in the hyphae of fungi grown on PDA. Molecular identification was conducted by sequencing and analysis of the complete internal transcribed spacer (ITS) rDNA sequence of the causal fungus. On the basis of mycological characteristics, molecular identification, and pathogenicity to host plants, this fungus was identified as Athelia rolfsii. This is the first report of sclerotium rot on purple wood sorrel caused by A. rolfsii.