Authors
Fumihiko
Suzuki
and
Michiyoshi
Arai
,
National Agricultural Research Center for Kyushu Okinawa Region, 2421 Suya, Koshi, Kumamoto 861-1192, Japan
; and
Junichiro
Yamaguchi
,
2 Saga Agricultural Experiment Research Center, Saga-gun Saga 840-2205, Japan
ABSTRACT
In 2001, field isolates of Pyricularia grisea resistant to scytalone dehydratase inhibitors of melanin biosynthesis (MBI-D) were reported in Saga prefecture, Kyushu. Among 1,175 isolates collected from six prefectures of Kyushu in 2002 and 2003, 647 were resistant to MBI-D fungicides, each due to a single point mutation of the scytalone dehydratase (SDH) gene. On the basis of repetitive element-based polymerase chain reaction (rep-PCR) fingerprint data, the haplotypes of the resistant isolates showed high genetic diversity, indicating that the resistance existed in a multigenetic background. Three predominant haplotypes mainly contributed to the widespread resistance in Kyushu; haplotype Sa4 was observed frequently in Saga, Sa18 was predominant in Oita and Miyazaki, and Sa5 was widely distributed among all four prefectures. Also, phylogenetic analysis showed that both the resistant and sensitive isolates were clustered together in a closely related group. These results suggest that isolates possessing the SDH mutation would have been selected and then multiplied rapidly in each region of Kyushu as a result of the widespread introduction of MBI-D fungicides in a short period.
