"the root of this issue" is correct and can be used in written English.
It refers to the underlying cause or origin of a problem or situation. Example: The root of this issue lies in the lack of communication between the two departments.
One thing we all agree on is that the root of this issue is inadequate research funding.
At the root of this issue is consumers' wariness about GM foodstuffs and GM organisms in general.
Now I'm fairly certain that the young Mr. Smith isn't hiding in his pool house waiting for me to defend his penchant for an A-line skirt but I am here doing just that because unfortunately the root of this issue reaches far beyond the fashion forward seventeen-year-old.
The root of this issue is often economic: National surveys show that twice as many children from the richest households attend primary school, compared to children from the poorest households.
The roots of this issue lie in the deeply held assumption of the beneficial quality of French civilisation for humankind.
"The roots of this issue run deep," he said, "and they don't relate solely to the United States failure to pay all of its dues on time".
While the protests have created a situation in which the lack of security has worsened the sexual abuse of women, the roots of this issue can be traced back to the society's failure to tackle sexual assaults directly.
It's not having the drugs—or having them and not knowing how to inject them that's at the root of this specific issue.
There is one thing each person can do however if you love horses, big cats, coyotes, and other wildlife, and you are still eating meat, you are participating in the problem that is at the root of this entire issue.
We could get all sad and huffy about this one animal (and I have to admit, I did for a bit after hearing this news), we could chastise this gentleman for killing this animal solely for sport and perhaps a bit of fame, but the root of the issue here isn't this one man and this one lion.
In his essay Mr Blair says while it is "right in the immediate term to concentrate on defeating Isis" in the longer term "another Isis will quickly arise to take their place unless we go to the root of the issue and deal with this ideology wherever and however it shows itself on a coordinated global basis".
