yeah.. you can get a lot of seeds from one plant.. i would think that fifty would be easy.. just think about some schwag that you used to smoke, and think about all of the seeds that would come tumbling out, lol...
you can even just seed 1 or 2 buds if you dont want to seed the whole crop... just collect the pollen into a jar, and get a nice fine paint brush and paint the buds with it.. you want to pollunate the buds around the second week of flowering...
best of luck and happy breeding..