Disease resistance is a tough thing to quantify because it varies so much from region to region. Studies often have different ratings for the same variety, plus there is a lot of anecdotal information out there.
I got tired of getting different answers, so I compiled 11 independent university or Co-op apple fire blight resistance studies, averaged the results, and normalized them. I only looked at varieties that were in 5 or more of the studies to ensure the data was statistically significant. The downside to this is that some newer, possibly better-performing varieties that haven't been in as many studies may have been excluded from this list.
This chart is just the top 20 fireblight resistant varieties, but you can filter and sort the full database based on the number of studies, average rating, and popularity.
Complete List of 133 Varieties
I also created a chart (below) comparing the Top 25 most popular apple varieties (based on average monthly Google search volume) against their fire blight resistance.
As you can see—and probably predicted—a lot of the popular grocery store apples are some of the worst performers when it comes to Fire Blight. This highlights the difference between breeding for "shelf stability/shipping" vs. breeding for "resilience."
A few interesting notes from the data:
The "PRI" Connection: The Purdue-Rutgers-Illinois breeding program dominates the top of the resistance list. You can see their signature naming convention in EnterPRIse, PRIscilla, William’s PRIde, and PRIma, but they also developed GoldRush, Jonafree, and Redfree, which all made the Top 20.
Scion vs. Rootstock: Keep in mind this tracks the resistance of the variety itself (the scion). While a resistant rootstock (like the Geneva series) is vital for keeping the tree alive, a resistant scion is what saves your harvest.
I am working on doing this for the other common apple diseases next. The goal is to compile them all together to come up with an "Overall Disease Resistance" score.
Also, if anyone knows of a study I did not reference, please send it my way so I can add it to the database.
5
