What to say in one-minute presentation of a poster in a scientific conference?
I've seen this before and it can work very well. Your only task in the one minute slot is to convince people that they should come and see your poster. Say what you've been doing and why it's interesting. You could use your abstract as a starting point but don't just read it out. Keep the slide really simple with the paper title and authors and a single, striking figure.
Usually, in these "madness" sessions (that's what they're usually called on the conferences I'm familiar with), the one minute is more of an upper limit rather than a rough guideline. As such, your abstract may already be too long.
The main purpose of the one-minute-presentation is to serve as an appetizer for people to come and see your poster. Thus, while it serves a similar purpose as an abstract, an abstract should rather be more descriptive and matter-of-fact, whereas such a teaser presentation can easily be more on the "mystery" side, posing a question without answering how you solved it just yet.
A useful idea might be to pick an impressive graphic from your poster (one that makes the audience want to learn more), briefly describe your topic and give some hints, though not a full description, of the solution you present.
It may be better to start from your elevator pitch, rather than the abstract. If you don't have an elevator pitch, prepare that first.
The term "elevator pitch" comes from a scenario in which you happen to be in an elevator, or other situation allowing for a very short interaction, with somebody you want to influence. What do you say? The objective is not to deliver full details, but to get them interested enough to extend the interaction. See the Wikipedia article, or Forbes article.
The poster-at-conference version of the elevator pitch scenario is you find yourself in the elevator with an important professor in your field. You have less than a minute elevator ride to explain your research in such a way as to get the professor sufficiently interested to visit your poster.
Poster madness is just a very big elevator containing most conference participants who are likely to visit posters. It may be easier to think in terms of talking to one person first.