Distribution and infection rate of satsuma dwarf virus in Mie Prefecture, Japan

Abstract

Strains of satsuma dwarf virus (SDV) occurring in Mie Prefecture were examined, and at the same time, the disease symptoms on the rind of citrus mosaic virus (CiMV) sub-strain were also examined. SDV-free trifoliate orange (Poncirus trifoliata (L.) Raf.) rootstocks were planted in plots where the SDV strain, the CiMV sub-strain, and the navel orange infectious mottling virus (NIMV) strain occur. The relationship between the SDV strain and the infection rate was determined. The CiMV sub-strain occurred most frequently in Mie Prefecture, followed by the SDV strain. An isolate of the NIMV strain was detected in two orchards in Mie Prefecture. This is the second occurrence of the NIMV strain recorded in a field outside of the original field in Wakayama Prefecture, following an occurrence in Ehime Prefecture. This is also the first report of mixed CiMV substrain and NIMV strain infection in citrus. The results indicate that the CiMV sub-strain is widely distributed outside Wakayama Prefecture. Moreover, isolates of the CiMV sub-strain, which hardly induce mosaic symptoms in the fruit rind, were widely distributed. Trifoliate orange seedlings were planted near infected citrus trees growing on trifoliate orange rootstocks. SDV infection occurred within one year of planting. Whether the difference in infection rate was caused by differences in viral strains or by environmental factors in the field remains unknown.