The tomato crop

It is only in the 20th century that tomato (Solanum lycopersicum) became an important vegetable in commercial cultivation and home gardens. The wild relatives of tomato originated in western South America. Tomato domestication followed a two-step process; during the first step S. lycopersicum var. cerasiforme was developed in South America, and during the second step S. lycopersicum developed in Mesoamerica which was accompanied by a selection for fruit color, size, shape, and plant architecture. Until the late 19th century, tomatoes were grown as open-pollinated landraces, also known as heirloom tomatoes. In the 20th century, commercial breeding shifted to producing high yielding hybrids, which combined excellent characters from both parents. Hybrids carry resistance (R) genes against various types of pathogens which have been introduced in tomato varieties from one or more of its 12 wild relatives. However, R genes are not available against all types of pathogens. Tomato can be attacked by more than 200 different pathogens and the most important ones are briefly described in this chapter.