Abstract
The provisional standard of 1.1 mg/kg for deoxynivalenol (DON) in wheat was determined by Japanese government in 2002. Therefore, the endpoint in our research must be changed form disease severity to mycotoxin contamination. In this review, I proposed the following strategy for control of Fusarium head blight and mycotoxin contamination.
i) NIV chemotypes of F. graminearum were widely distributed in western part of Japan in 2002 and the isolation frequency was higher than that of DON chemotypes, and moreover, their virulence would be considerably high. Therefore, control of NIV in addition to DON is needed in Japan at least in the western part, and higher level of FHB resistance should be aimed for in wheat and barley breeding than ever.
ii) We found that seven chemicals; metoconazole, tebuconazole, captan, thiofanate-methyl, oxine-copper, copper-hydroxide and phosphorous acid would control DON and NIV. On the contrary, treatment of azoxystrobin significantly increased the level of DON and NIV compared to the control plots, even though it reduced disease severity of FHB. These results suggest that new fungicide evaluation system based on efficacy for mycotoxin contamination should be introduced.
iii) We demonstrated that sieve sorting and gravity sorting were effective to reduce DON and NIV level. In a country elevator, we need more simple ELISA system to check DON and NIV.
iv) In Japanese wheat production, non-till or minimum tillage is not essential and area of a wheat field is relatively small. Therefore, cultural practice to decrease residue is practical options. We are going to test cultural practices of top soil dressing, burning, up-cut rotary and carry out to decrease the rice residue which is primary inoculum source of Fusarium head blight.
v) Despite the importance of the disease, there are still unanswered questions concerning the epidemiology and disease spread. How far can the ascospore inoculum be moved from an infected field? How is a genetic diversity of Fusarium graminearum in a field? These information are key for rational management techniques. We investigated spatial distribution of Fusarium head blight and mycotoxin contamination in naturally infested field. The SSR (simple sequence repeats) markers that could clearly and reliably detect DNA polymorphism among Japanese isolates of Fusarium graminearum were developed. Molecular epidemiology using SSR markers could be a new approach.
