When large-fruited tomato plnnts are crossed with small-fruited tomato plants the small size predominates in the F1. A cross of a plant with fruit weighing 1.1 g with one whose fruit weighed about 500 g produced F1 offspring whose fruit weighed on average 10.5 g and the F2 generation had fruit weighing an average of 11.1 g.

From "Dissecting the Genetic Pathway to Extreme Fruit Size in Tomato Using a Cross Between the Small-Fruited Wild Species Lycopersicon pimpinellifolium and L. esculentum var. Giant Heirloom" Genetics, Vol. 158, 413-422, 2001

Patrick Alexander

Also, it is more probable that the F2 generation will have individuals that are outside of the parental range if the parents are more similar in size. A cross of a 500g fruit weight variety with a 300g fruit weight variety is more likely to produce F2 offspring with fruit weights over 500g or under 300g than a cross of a 500g fruit weight variety with a 1g fruit weight variety is to produce F2 offspring with weights over 500g or under 1g.

Even though the frequencies of such offspring would differ among crosses (the frequencies will depend on the genetic, environmental and interaction effects for both the means and variances of fruit weight), if enough F2 offspring are produced one could find some that have weights outside of the parental range.

The likelyhood of getting segregants larger than either in the F2 tends to encrease as the degree of relatedness of the parental lines decreases.