A farmer has two homozygous varieties of tomatoes. One variety, called Little Pete, has fruits that average only 2 cm in diameter. The other variety, Big Boy, has fruits that average a whopping 14 cm in diameter. The farmer crosses Little Pete and Big Boy; he then intercrosses the F1 to produce F2 progeny. He grows 2000 F2 tomato plants and doesn’t find any F2 offspring that produce fruits as small as Little Pete or as large as Big Boy. If we assume that the differences in fruit size of these varieties are produced by genes with equal and additive effects, what can we conclude about the minimum number of loci with pairs of alleles determining the differences in fruit size of the two varieties?

It should be understood that the method used above by the farmers is known as artificial crossing, or artificial insemination when describing the act in animals.

This method is usually adopted to achieve an excellent results from two organisms of different traits.

In this case, the plant or crop with small fruits might have some needed traits like ability to withstand drought, which the other plants with big fruits does not have.

Therefore, the crossing will help to produced a plant which its fruit will be balanced with both traits.