The domination–isolation ratio conjecture for cubic graphs

Let $G$ be a cubic graph, with domination number $\gamma(G)$ and isolation number $\iota(G)$. Domination–isolation ratio conjecture. For every cubic graph $G$,

$$\gamma(G) \le 2\iota(G).$$

The conjecture would improve the general ratio bound discussed in the source, which is at most $15/7$ for cubic graphs; no resolution is given, so the question remains open.