Ploidy refers to the number of sets of chromosomes that an organism has in each cell. For example, humans are diploids, meaning that we have two sets of chromosomes—one from mom and one from dad. Plants, on the other hand, can have varying numbers of chromosomes without any detrimental effects. Breeders take advantage of this trait in developing new plants.
Polyploids can either be identified through genome size and ploidy surveys using a flow cytometer, or they can be developed through chemical mutagenesis using colchicine or oryzalin (active ingredient in the pre-emergent herbicide Surflan®).