A mild systemic reaction to lettuce mosaic virus in lettuce: Inheritance and interaction with an allele for resistance

Abstract

In crosses of lettuce (Lactuca sativa L.) between parents producing a mild or susceptible reaction to lettuce mosaic virus, a single gene segregated. The heterozygote reacted in an intermediate manner. In crosses between mild-reacting and resistant parents, the mild reaction gene and the resistant gene segregated independently. The resistant and mild alleles together produced a new phenotype that is usually symptomless. The gene symbol proposed is Mi'Mi, where Mi' gives the mild phenotype. Breeding is in progress to combine the mild and resistant traits in new lettuce cultivars.