Re: Plant Breeding

> If you want to propagate a desired mutation in plant breeding, why would the method of self-pollination be used instead of crossing only with unrelated organisms?

Most mutations are recessive; this is a genetic self-protection mechanism, as most mutations are harmful. Therefore in order to propagate a desired mutation, it is best to breed the plant with other plants which share the desired mutation. Self-pollination provides a simple and easy way to do this.

Another method heavily used in horticulture is the propagation of a desired trait by using cuttings. The cuttings will grow into new plants which are clones of the original. I believe (but this is off the top of my head) that navel orange trees -- which have no seeds -- are propagated by cuttings. You can also combine traits without interbreeding by grafting a top with desired traits onto a set of hardy roots.

The analogous process in animal husbandry is inbreeding (when humans do it we call it incest), which has been used to preserve desirable traits in livestock for many centuries.