Institute for Plant Protection, NARO

Development of a new selective medium to effectively isolate and distinguish bacterial leaf spot and leaf blight pathogens of cruciferous family

-In response to high demand for the inspection methods of seed-borne diseases-

National Agriculture and Food Research Organization(NARO) has developed a selective medium for isolating pathogenic bacteria that cause seed-borne bacterial leaf spot and leaf blight disease, which is a major global problem in cruciferous vegetable production. This technology can be used as an accurate and efficient seed inspection method, contributing to the stable production of cruciferous vegetables and the export of vegetable seeds, which is an important industry in Japan.


Bacterial leaf spot disease (including bacterial leaf blight) of cruciferous vegetables occurs in radish, cabbage, broccoli, cauliflower, Chinese cabbage, turnip, etc. and its damage has become a major issue not only in Japan but also worldwide in terms of stable production of cruciferous vegetables.

Since this disease is transmitted by pathogenic bacteria attached to seeds, securing healthy seeds is the most important control measure. Japan exports vegetable seeds, and there are occasions when export destination countries request a "phytosanitary certificate" for bacterial leaf spot disease on cruciferous vegetables. In order to investigate whether seeds are contaminated with pathogenic bacteria, it is necessary to isolate bacteria from seed samples using selective media and to confirm the pathogenicity of the isolated bacteria.

In January 2022, NARO released the "Standard Operating Procedure (SOP) for testing Bacterial leaf spot pathogens on radish seeds" for domestic seed inspection organizations using existing selective media and improved media. However, there are multiple species and strains of bacterial leaf spot pathogens, each of which grows differently on existing selective media. Hence it was difficult to distinguish between bacterial leaf spot pathogens and other seed-borne bacteria in some seed samples.

In order to solve this problem, NARO has developed two new selective media that can selectively identify cruciferous bacterial leaf spot pathogens. Two types of selective media developed this time are more effective in selectively growing cruciferous bacterial leaf spot pathogens compared to existing selective media, making it easier to identify pathogenic bacteria. In the future, we will revise the SOP by adding a newly developed selective medium and publish it as a more accurate and efficient method.


Inoue Y. (2022) Three semi-selective media for Pseudomonas syringae pv. maculicola and P. cannabina pv. alisalensis. Applied Microbiology and Biotechnology,

For Inquiries