>>2351139>how many successive generations would need to pass before a distinct cultivar would form?It depends on how many traits you want to control and how many genes control said traits. After that, it's all just down to luck. Usually a single trait would take about 3-4 generation, but isolating more increases the time taken exponentially.
>cross-pollination of two distinct cucumber cultivarsYes, generally. Selective breeding of crops for specific traits is something that has been practiced for thousands of years by many people long before genetics were well understood. If a caveman can selectively breed crops by replanting and sharing the best tasting berries you can too.
>What about individual fruitThe seed is the only part of the fruit that has genes from both parents. The flesh of the fruit is made by the parent plant. If you plant the seeds from the parent's fruit the child's fruit may look different. Ideally, you would take pollen from the flowers of one plant and transport it to another to initiate the fruiting process. However, pollinators and wind can introduce pollen from the flowers of other members of the same species which could "taint" the genes you're deliberately trying to isolate. On top of this, many plants can self-pollinate which can produce seeds containing clones of themselves instead. As a result, you're be best off keeping the parents isolated from other members of the same species and even similar species who could hybridize with it, then pollinating the flowers manually, then picking and planting the seeds from the resulting fruit.
If you are interested in plant genetics I recommend reading up about Gregor Mendel. He was one of the first biologists who studied genetics using pea plants.
