The following code
\documentclass{amsart}
\usepackage[math-style=TeX]{unicode-math}
\setmathfont{Minion Pro}
\begin{document}
\[ a = \sqrt{ b } \]
\end{document}
is compiled by LuaLaTeX as
Why is that? Minion Pro .otf from Adobe Reader distribution is installed system-wide, TeXLive 2016 is fully updated, OS is openSUSE Tumbleweed.
update: out of academic interest I have downloaded a pirated copy of Minion Math, v 1.021, to obtain a similar result with \setmathfont{Minion Math}:
According to the explanations below the behaviour with Minion Pro is to be expected, the behaviour with Minion Math speaks of the faulty font. The question can be closed, I suppose.





\setmainfonta general text font will not work, as you see. – David Carlisle Oct 02 '16 at 21:27