Inheritance of the necrotic and mosaic reactions in sorghum infected with a 'Johnson grass' strain of sugarcane mosaic virus

Abstract

When 30 sorghum inbred lines were inoculated with a 'Johnson grass' strain of sugarcane mosaic virus, seven reacted with systemic necrosis whereas 23 developed systemic mosaic symptoms. Nine F1 populations, 11 F2 populations, and 17 F3 populations derived from one F2 were tested for reaction to the virus. The results are consistent with the hypothesis that inheritance of the type of reaction is controlled by a single gene. The gene does not appear to have been reported previously, and the alleles are designated N, n. Presence of the dominant allele results in systemic necrosis, whereas presence of the homozygous recessive results in systemic mosaic symptoms. Colour of the necrosis, i.e. whether red or tan, is controlled by another single gene, probably the factor for purple (P) or tan (p) plant colour. The N and P genes do not appear to be linked.