I assume this is a technique that is used to create mutants?
I don't think it's unheard of. Delhi 76 is a flue cured tobacco that was created by treating Delhi-34 with gamma radiation.
Delhi 76
Colchicine doubles the chromosome number. I've used it before in anther culture of rice. For anther culture the idea is that your taking a haploid cell, doubling its chromosome number so the cells are diploid then regenerating a new plant via tissue culture. It allows for the rapid creation of a homozygous line if used for anther culture. If you are starting with a diploid organism/cell (i.e. seed) the doubling of the chromosomes creates a polyploid (it would double the ploidy level in existing polyploids like tobacco as well).
It's a common practice used in horticulture/ag to try and get bigger flowers, leaves, etc. Of course it's also been one of the things that has sparked the interest of home Cannabis growers as well (to each their own I suppose) and there appears to be a fair amount of info on the net for what works in that species.
Just doing a quick google search I'm seeing colchicine levels recommended for tobacco anther culture, but didn't see anything in a very short search for seed treatment....at about .1% concentration so for tobacco trying a gradient around that level might be a good place to start. Too much colchicine to the seed is lethal, to little and the chromosomes don't double. A person would have to try a concentration gradient to see what works unless there is already published info out there. Colchicine is toxic to people and animals so caution should be used.
Just as a little trivia they use colchicine to treat gout in people. I had knee problems once and some quack of a doctor gave me a prescription for gout pills without testing me for gout. At that point I was in enough pain I took the pills without questioning much. About a week latter I'm at work and one my one of my friends is joking with me about taking colchicine for gout. I thought he was full of it until I went home and looked the medication up, it was colchicine marketed under a different drug brand name. Boy was I pissed... Turns out I don't have gout either.
It would be a nightmare from a geneticists perspective (I'm grateful I work on a diploid species), but from an agricutural perspective it could be good. Cultivated strawberries are mostly octoploid some are even decaploid (10n). A person would be looking more at the phenotype than trying to figure out the actual genetics in this case - i.e. what gives a bigger plant, increases nicotine, etc... I know they use colchicine a lot with orchids and other species to get larger flowers and bigger plants.
