Rational subgroup conjecture for closed irreducible 3-manifold groups

Let $M$ be a closed, connected, ${\mathbf{P}^2}$-irreducible $3$-manifold with infinite fundamental group. Rational subgroup conjecture. Every subgroup of $\pi_1(M)$ which embeds in the additive group $\mathbf{Q}$ is cyclic. The source gives no resolution; this assertion is paired with the normalizer conjecture in an equivalent group-theoretic formulation.