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Since 2002, papaya black rot has been spreading over several islands of Okinawa Prefecture, Japan. To devise a prevention strategy for the disease, microbiological research on the pathogen was conducted. Twelve strains were isolated from papaya infected with black rot showing symptoms such as water‐soaked lesions on stems and petioles, black spots on fruits, and rotted leaves turning yellow with necrotic spots. Through Koch's postulates, we confirmed that the isolated strains caused papaya black rot. Bacteriological assays showed that the strains have characteristics different from the type strains of Erwinia mallotivora, E. papayae, and E. psidii. Moreover, 16S rDNA sequence similarity searches showed that the isolated strains had less than 98.6% similarity with type strains. Additionally, phylogenetic analysis of 16S rDNA sequences suggested that the isolated strains were possibly a novel species belonging to the genus Erwinia, as the strains formed an independent cluster and had low sequence similarity with the type strains. Earlier studies indicated that papaya black rot is caused by E. cypripedii. Therefore, we propose to add the Erwinia sp. isolated in this study to the list of papaya black rot pathogens. [ABSTRACT FROM AUTHOR]

Powdery mildew disease was found on mango (Mangifera indica) in Okinawa Prefecture, Japan, in April 2013. During and after flowering, infected panicles, leaves, and young fruits became coated with a whitish powdery fungus. Fungal growth was usually severe on panicles, then plants became brown and defoliated. The fungal sample collected from conidia on diseased panicles was identified as Erysiphe quercicola based on morphology and rDNA-ITS sequence analysis. Inoculation with the isolate reproduced the symptoms on mango leaves and the fungus was reisolated from the inoculated leaves. In addition, the fungus infected Japanese oak (Quercus crispula), konara oak (Q. serrata), and ubame oak (Q. phillyraeoides). This is the first report of powdery mildew (udonko-byo in Japanese) on mango caused by E. quercicola in Japan. [ABSTRACT FROM AUTHOR]

In July 2013, a severe postharvest rot of mango fruits (cv. Lippens), with symptoms identical to stem-end rot caused by Lasiodiplodia theobromae or Neofusicoccum parvum, was found in Okinawa Prefecture, Japan. From affected fruit, Diaporthe species were consistently isolated. The isolates reproduced the original symptoms in healthy mango fruits after inoculation and were re-isolated from the inoculated fruits. Based on morphology and a phylogenetic analysis of rDNA-ITS, CAL, H3, EF1-α, and TUB, the isolates were classified into two Diaporthe species (Clade I and Clade II). In terms of susceptibility to procymidone, a registered fungicide against mango stem-end rot in Japan, the two Diaporthe species were less sensitive than previously reported mango stem-end rot pathogens and had MIC and EC50 values higher than the standard concentration applied. [ABSTRACT FROM AUTHOR]

A panicle blight with sclerotia was found on mango ( Mangifera indica L.) in Okinawa Prefecture, Japan, in March 2016. Water-soaked lesions with white mycelia developed on panicles in the flowering stage; softening and decay of panicles was followed by formation of sclerotia. The fungus isolated from these sclerotia was identified as Sclerotinia sclerotiorum based on morphology and analysis of rDNA-ITS sequences. The isolate reproduced the symptoms on mango panicles in an inoculation test and was reisolated from flower stalks. This is the first report of sclerotinia rot (kinkaku-byo in Japanese) on mango caused by S. sclerotiorum in Japan. [ABSTRACT FROM AUTHOR]

We isolated an antimicrobial compound from the aerial tissue of Geranium carolinianum and identified it as ethyl 3, 4, 5-trihydroxy benzoate (ethyl gallate) by 1H-NMR and 13C-NMR and gas chromatography–mass spectrometry. The antimicrobial activity of ethyl gallate against three potato pathogens was assayed by the paper disk method. The activity against Ralstonia solanacerum, Streptomyces scabies, and Streptomyces acidiscabies was observed at concentrations >200, >300, and >300 µg disk−1, respectively. These results suggest that the antimicrobial activity of Geranium carolinianum against soil-borne plant disease pathogens is partly related to ethyl gallate. [ABSTRACT FROM AUTHOR]

In a previous study, we found that a 70% aqueous ethanol extract of the fresh aerial tissue of Geranium carolinianum L. showed antimicrobial activity against the pathogen causing soil rot of sweet potato. As the appropriate time for cultivation of sweet potato and the growing period of G. carolinianum do not overlap in Okinawa Prefecture, Japan, the fresh aerial tissue is available in order to control soil rot of sweet potato. Thus, we examined the control effect of fresh aerial tissue against soil rot of sweet potato. The various trials (a single repetition of 20 m2) were performed in fields that had undergone 8 years of continuous cropping of sweet potato at Okinawa Prefectural Agricultural Experiment Station, Horticultural branch. After harvest, when the disease severity was evaluated by determining the necrotic area of the storage root, the incorporation of fresh aerial tissue (5000 kg 1000 m-2) into the soil was considered to be highly effective, with a protective value of 75.4. This result shows that G. carolinianum could be used as a biological agent for the control of soil rot of sweet potato. [ABSTRACT FROM AUTHOR]

A new antifungal compound, (3S)-4,6-dihydro-8-methoxy-3,5-dimethyl-6-oxo-3H-2-benzopyran (4), was isolated from Penicillium expansum. During the isolation procedure 4 was determined to be unstable and readily reacted with methanol, ethanol, and water, forming three new isochromans, (1S,3S)-6-hydroxy-1,8-dimethoxy-3,5-dimethylisochroman (1), 1-ethoxy-6-hydroxy-8-methoxy-3,5-dimethylisochroman (2), and 1,6-dihydroxy-8-methoxy-3,5-dimethylisochroman (3), respectively. (3S)-6-Hydroxy-8-methoxy-3,5-dimethylisochroman (5) was reisolated from P. expansum. In fungicide disk assays, compounds 1, 2, and 4 inhibited the mycelial growth of Lasiodiplodia theobromae at 100 microg/mL by 76%, 74%, and 69%, respectively.