Genre of music in iPhone does not match those in iTunes

I have changed genres on iTunes so that I do not end up with many different genres.

All have changed as I wanted to on iTunes. However when I sync my music to my iPhone there are quite a lot of songs that show a different genre to that what is displayed in iTunes. I have looked in the actual iTunes library and the genre shows what I have changed it to so I cannot work out why my iPhone is ignoring the change.

Any advice, please?!