Resistance to a Necrotic Strain of Soybean Mosaic Virus in Soybean1

Eighty-nine entries from soybean [Glyclne max (L.) Merr.] germplasm collection and 47 cultivars were evaluated for resistance to necrotic infection by a strain of soybean mosaic virus (SMV-N) in the field. Necrotic symptoms developed on 18 of the 136 entries with severity ranging from 4 to 86%. Many of the soybean cultivars evaluated were susceptible. Five resistant lines or cultivars previously identified as resistant to SMV-N in field test, ‘KEX-2,’ ‘Kumgangdaerip,’ ‘# 31926,’ ‘KAS 390-10,’ and ‘KAS 150-5,’ were crossed with either susceptible cultlvars ‘Kwangkyo’ or ‘Tachisuzunari’ to study the inheritance of resistance. All the F₂ progenies of these crosses segregated in a 3:1 ratio of susceptible to resistant plants, indicating that resistance was conferred by a single recessive gene.