Abstract
Three nucleic acids were found in 5% polyacrylamide gel electrophoresed with extracts from several cultivars of Japanese pear (Pyrus spp.) that had no symptoms. They were cultivar-specific, and were detected from bark, leaf, petals and flowers plus petals. They were not digested by DNase I and were resistant to RNase A in 2×SSC buffer, but were susceptible to RNase A in 0.1×SSC buffer. These nucleic acids were absorbed by CF-11 cellulose in 15% ethanol. These results indicate that the three nucleic acids were double-stranded (ds) RNA. Molecular weights were estimated at about 1.08, 0.97, 0.90×106 daltons according to electrophoresis with dsRNAs of the rice dwarf virus as a marker. Several cultivars that have these dsRNAs had genetic relationships. The results of investigating the transmission of dsRNAs to the next generation by crossing showed that dsRNAs were detected in 31/40 when only the seed parent had dsRNAs, in 12/12 when only the pollen parent had dsRNAs, and in 5/5 when both parents had dsRNAs. These dsRNAs were transmitted high frequently to the next generation through both ovule and pollen, but transmission of dsRNAs by grafting to other cultivars without dsRNAs did not occur. These results suggest that the dsRNAs from Japanese pear are similar to dsRNAs derived from the phytocryptovirus group.
