Superinfection by strains of tobacco streak virus

Abstract

Eight selected strains of tobacco streak virus varied in their reactions in cross-protection tests. Of the 28 possible pairs of strains, eight reciprocally protected tobacco against each other, eight unilaterally protected, and with 12 pairs, neither member protected against the other. When infected tobacco was susceptible to superinfection it was less susceptible than healthy tobacco except with two of the strains, which reduced susceptibility very little. Susceptibility to other viruses was retained, however. The capacity of strain WC to superinfect was not increased by selection. Nonsuperinfecting strains added to superinfecting inoculum decreased lesion numbers. Top particles seemed not to function in superinfection. The determinant for superinfection was carried in bottom particles in heterologous mixtures. Recombination of superinfecting capacity and lesion type occurred upon superinfection with heterologous mixtures of middle and bottom particles.