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Inheritance of Resistance to Verticillium dahliae in Diploid Interspecific Potato Hybrids

Verticillium wilt is a serious disease in potato and is caused primarily by the soilborne fungi Verticillium dahliae and V. albo-atrum. Host plant resistance to the disease offers an option for long-term, inexpensive, and environmentally sound control. High levels of resistance to stem colonization have been identified in two diploid hybrids between the cultivated potato and wild Solanum spp. An intercross between the two clones produced a 3:1 ratio of resistant to susceptible clones. A cross between a susceptible clone and one of the resistant clones also produced a 3:1 resistant:susceptible ratio. These data can be explained by a two-gene model, in which dominant alleles of both genes must be present to confer resistance. The two-gene model also explains data from previous research with wild Solanum spp. A simple mode of inheritance should improve the probability of producing resistant offspring when resistant hybrids are used as parents in a breeding program.