ABSTRACT
Modern cultivars of crop plants usually represent a small fraction of the variation that exists in their gene pool. For example, it has been estimated that less than 5% of the genetic variation in tomato exists in the cultivated species, while the rest of the variation remains distributed among its wild relatives (Miller and Tanksley, 1990). Similarly, very narrow genetic base exists in other self-pollinated crops such as soybean and rice where breeding has been mainly confined within the primary gene pool (Singh and Hymowitz, 1999; Wang et al., 1992).
