Good question. I'd imagine something like blight resistance would probably not be a simple case of a few specific genes we can just switch over.
It could also just be technology. This breeding program has been around for 50 years or so and CRISPR only really took off around 2011. In addition, the original CRISPR-Ca9 caused a lot of unintended changes in DNA and it's really critical that the new trees are morphologically equivalent to the original trees in order for the birds, insects, and animals that depended on them to resume their interactions. Newer technologies like CRISPR-Nickase are much more precise but also very recently developed
It actually is pretty "simple" in this case (the tree needs to produce a single chemical, oxalate oxidase). There is a program that has done this very successfully, and it just working through the regulatory process before wider distribution can happen. They have thousands of trees in (controlled) forest plots, including three generations of offspring.
That's the genetic engineering approach, but the Chinese ones have a different, more complex, less well understood, and potentially complementary resistance mechanism.
That's very interesting. The video I linked showed that blight resistant trees had a very specific response to grow extra tissue around the infection site to stop it from spreading further so I assumed it was more of a multi-pronged defense
Yes - the Asian ones that evolved with the fungus have a more complex strategy, making a purely breeding-based program challenging. Separately, some clever genetic engineering allows the trees to break down oxalic acid, which prevents the fungus from being able to efficiently attack the plant cells.
Indeed, part of the work being done by the team working on the genetic engineering approach is breeding Darling 58 with the Chinese backcrossed version.
It could also just be technology. This breeding program has been around for 50 years or so and CRISPR only really took off around 2011. In addition, the original CRISPR-Ca9 caused a lot of unintended changes in DNA and it's really critical that the new trees are morphologically equivalent to the original trees in order for the birds, insects, and animals that depended on them to resume their interactions. Newer technologies like CRISPR-Nickase are much more precise but also very recently developed