Golden Dawn and Tondo di Piacenza were cultivated in the same garden and cross-pollination took place between them. The gardener raised these cross-pollinated F1 seeds into plants that produced fruits. The gardener was unaware of the genotypes of the parent plants and did not realise that cross-pollination had happened. State the phenotype of the fruits of the F1 plants and explain why this was unexpected for the gardener.
Two of these F1 plants were crossed by the gardener. Complete Fig. 1.1 with the F1 gametes, F2 genotypes and F2 phenotypes. State the ratio of fruit phenotypes in the F2 offspring.
Watermelons, *Citrullus lanatus*, are plants in the same family as courgettes. They produce large round edible fruits that usually have many hard seeds. Seeds are the structures formed when male and female gametes fuse at fertilisation. In the 1990s, a triploid ($3n$) watermelon plant was produced. To make the triploid watermelon plant, a normal diploid parent plant ($2n = 22$) was crossed with an artificially produced tetraploid plant ($4n = 44$). Triploid watermelon plants develop edible fruits, but these are sterile and have no seeds, so they are more pleasant to eat. Explain why the fruits of the triploid plants are sterile and do not contain seeds.
Watermelons are attacked by watermelon mosaic virus (WMV). In 1965, a WMV-resistant plant in the same family, *Cucurbita ecuadorensis* ($2n = 40$), was discovered growing wild in South America. State why a WMV-resistant variety of watermelon cannot be produced by breeding *Cucurbita ecuadorensis* with a normal diploid watermelon.
Outline how the WMV-resistant characteristic of *Cucurbita ecuadorensis* could be transferred to watermelon plants.