Infection Rates of Two Strains of Soybean Dwarf Virus of Ladino Clover Collected in the Pastures of the Tokachi District of Hokkaido

Abstract

Soybean dwarf virus (SDV) isolates were grouped into two strains, dwarfing (SDV-D) and yellowing (SDV-Y). ELISA is effcient assay to detect SDV in plants, but the two SDV strains are indisitinguishable in a polyclonal ELISA system. The infection rates of two SDV strains of ladino clover in the Tokachi district were investigated with back inoculation to soybean seedlings by manipulation of the foxglove aphid, Aulacorthum solani Kaltenbach. High percentages of ladino clover collected in annually damaged regions were infected with both strains, with a tendency for the proportion of SDV-Y infection to be high new pastures. Because the susceptibility of ladino clover to SDV-Y is more sensitive than to SDV-D, it is considered that the ladino clover was infested with SDV-Y first, and that the mixed infection with SDV-D increased later.