Identification of Resistance to Maize rayado fino virus in Maize Inbred Lines

Maize rayado fino virus (MRFV) causes one of the most important virus diseases of maize in America. Severe yield losses, ranging from 10 to 50% in landraces to nearly 100% in contemporary cultivars, have been reported. Resistance has been reported in maize populations, but few resistant inbred lines have been identified. Maize inbred lines representing the range of diversity in the cultivated types and selected lines known to be resistant to other viruses were evaluated to identify novel sources of resistance to MRFV. The virus was transmitted to maize seedlings using the vector Dalbulus maidis, and disease incidence and severity were evaluated beginning 7 days postinoculation. Most of the 36 lines tested were susceptible to MRFV, with mean disease incidence ranging from 21 to 96%, and severity from 1.0 to 4.3 (using a 0 to 5 severity scale). A few genotypes, including CML333 and Ki11, showed intermediate levels of resistance, with 14 and 10% incidence, respectively. Novel sources of resistance, with incidence of less than 5% and severity ratings of 0.4 or less, included the inbred lines Oh1VI, CML287, and Cuba. In Oh1VI, resistance appeared to be dominant, and segregation of resistance in F₂ plants was consistent with one or two resistance genes. The discovery of novel sources of resistance in maize inbred lines will facilitate the identification of virus resistance genes and their incorporation into breeding programs.