Is it possible to perform selection of plants without seeds?
Most commonly by breeding with a related plant - if there is one. Mutagenesis is an old technique that technically can work.

If one part of the plant has mutated, of course you can take cuttings or plant tissue culture samples.

strawberries can be bred and characteristics selected for.
https://en.wikipedia.org/wiki/Breeding_of_strawberries

A good example of a difficultto breeed plant is bananas
See
http://www.promusa.org/blogpost363-Who-s-breeding-bananas