how let's start with the female parent plant young watermelon seedlings are
treated with a chemical called colchicine which prevents proper
splitting of the chromosomes during mitosis and results in plants that are
tetraploid containing four copies of each chromosome
when these tetraploid plants undergo meiosis instead of creating a haploid
daughter cell with only one copy of each chromosome they actually create a
diploid daughter cell with two copies of each chromosome
if you cross this with haploid pollen from a normal water Mountain plant you
wind up with a triploid watermelon progeny and watermelons do not like
having three copies of each chromosome these three copies of each chromosome
can't properly separate during meiosis leading two unsuccessful fertilization
leading to a watermelon plants they can't properly produce seeds now I think
that's a pretty tasty genetic trick
go forth to science