Question
Potato plant produces flowers,fruits and seeds.yet they reproduce
with the help of eyes on the patato tuber.why?

Answer
Hi Radha,
Thanx for your question.  The potato is a member of the solanum family just as are peppers, tomatoes, tobacco and eggplant.  Potato plants do bloom and the blooms have the potential to produce seed.  Potato plants can be started from these seeds.  Generally, though, we use the eyes of the potato because it creates clones which are direct copies of the plant as opposed to seeds which most likely will have come from a hybridized form of the potato and not breed true.  Which means the resulting plant from the seed will not generally be identical to the parent plant due to the genetic instability of hybrids.  Hybrids don't breed true.  They will throw back to a prior, less desirable generation.  The eyes of the potato tuber are merely growing sections like one would find on a number of tuberous or rhizomatous plants such as cannas, peonies, dahllias, etc.  Farmers find that using "seed potatoes" is much more efficient and predictable than growing from seed.  I hope this helps.
Tom