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Grey mould is an important necrotrophic fungal pathogen that causes huge economic losses in agriculture. Many types of bacteria are used for biological control of grey mould via competition for space or nutrients and/or the production of antifungal metabolites. Oxalate is a key component of virulent necrotic fungal pathogens. In this study, we isolated non-antifungal oxalate-degrading bacteria (ODB) from the surfaces of oxalate-rich spinach and strawberries to investigate their ability to control necrotic fungal pathogens such as grey mould. A total of 36 bacteria grown on oxalate minimal (OM) agar plates were tested for oxalate-degrading activity. Five isolates exhibiting the highest oxalate degradation activity were subjected to molecular identification using 16S rRNA gene sequencing. Two isolates exhibiting non-antifungal activity were subjected to disease suppression assays using Arabidopsis-Botrytis systems. The isolate Pseudomonas abietaniphila ODB36, which exhibited significant plant protective ability, was finally selected for further investigation. Based on whole-genome information, the pseudomonad oxalate degrading (podA) gene, which encodes formyl-CoA transferase, was analysed. The podA - mutant did not inhibit Botrytis infection and oxalate toxicity; the defects were recovered by podA complementation. Purified PodA-His converted oxalate to formate and eliminated oxalate toxicity. These results indicate that P. abietaniphila ODB36 and PodA enzyme are associated with various aspects of grey mould disease inhibitory effects.

This is the first report of bacterial center blackening in muskmelon fruit caused by Pseudomonas oryzihabitans, which is known as an opportunistic pathogen of humans and warm-blooded animals. The aim of this study was to investigate the microbiological characteristics of this infection. Bacterial center blackening, which can cause aversion in consumers, was observed in muskmelon fruit in South Korea in the fall of 2017. Symptoms included severe black pigmentation in the pulp surrounding the seeds inside muskmelon fruit. Dark brown pigmentation and gram-negative, non-spore-forming, rod-shaped pseudomonads were consistently recovered from the black pigmented pulp tissue of muskmelons. The symptoms after artificial inoculation were the same as those of the natural infection, while the control fruit exhibited no symptoms of infection. Using pathogenicity tests, analytical profile index (API) tests, whole-cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), and 16S rRNA gene and gyrB region sequencing, the dominant species was identified as P. oryzihabitans. The recent outbreak indicates that P. oryzihabitans poses a potential threat to the global production and transportation of muskmelon as well as food safety., (Copyright © 2018 Elsevier B.V. All rights reserved.)

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]