ABSTRACT
As with other tomato disease resistances, breeders have developed cultivars with virus resistances that are conferred by single dominant genes. In the previous chapter, Table 13.1 provides a summary of the virus resistance genes that have been utilized in breeding. Cultivars with tomato mosaic virus resistance are common, especially in greenhouse tomatoes. Some varieties with spotted wilt virus resistance have been developed although virulent races have overcome many of the genes deployed in the past. More recently, cultivars with resistance to tomato yellow leaf curl virus (TYLCV) have been developed and the best of these utilize major vertical genes as opposed to horizontal genes. More details are available in the sections for each of these diseases. There has been considerable work done on tomato virus resistance using genetic transformation and the potential for commercial impact from these approaches may be nearer than is the case for other types of pathogens. But cultivars have yet to be deployed with genetically engineered resistances. Some references involving genetic transformation will be mentioned but an adequate treatment of this topic is beyond the scope of this writing. Several book chapters have information on tomato virus and other resistance(s) (Dixon 1981, Tigchelaar 1986, Watterson 1986, Lukyanenko 1991). Herein, the primary goal will be to relay new information and provide reasonably thorough coverage of virus diseases where genetic information on resistance has been reported. Information on sources of resistance, inheritance, virus strains, inoculation techniques, 458and the status of breeding efforts will be given for each disease that are presented alphabetically.
