Institute of Vegetable and Floriculture Science, NARO

Phytopathology Unit

Plant diseases have been mainly controlling using a variety of agrochemicals. Continuous use of agrochemicals sometimes leads to the appearance of resistant pathogens, and arises adverse effects on beneficial microorganisms. In the Phytopathology Unit, we are studying on vegetable diseases caused by viruses, bacteria, and fungi, and developing integrated disease management in sustainable horticulture.

Tomato yellow leaf curl virus is a causative agent of the Tomato yellow leaf curl disease, and is transmitted by the whitefly Bemisia tabaci. We are promoting research to interfere with the virus transmission by viruliferous whiteflies by affecting the insect behaviors such as repellency and feeding action on a host plant.

The leaf mold of tomato became a problem because physiological races were occurred and overcame all resistant cultivars commercially available in Japan. Several fungicide-resistant strains were also occurred. We now focus on parasitic fungi and develop the microbial pesticide to promote sustainable vegetable disease management.

We have developed a novel hydroponic technique using organic fertilizer. The technique inhibits tomato bacterial disease and root rot disease. The phenomenon is similar to suppressive soil. Biofilm, which contains more than 10,000 species of microorganisms, develops on the surface of tomato roots. We research the mechanism of disease control and improve the system of hydroponic culture.


Tomato yellow leaf curl virus (TYCLV) disease (top left); tomato leaf mold disease (lower left); and root-borne disease control effect by organic fertilizer-utilizing hydroponics system.

Unit Leader

Kazuhiro NAKAHO

Unit Members



Yuichiro IIDA