The Right Variety

Always select Leaf Mold-resistant varieties. The disease code is LM.

Here is the link to Johnny’s Selected Seeds Leaf Mold Resistant Varieties.
‍

Here is a small list of potential varieties.
Many other disease resistances exist, but we focus on Leaf Mold and Powdery Mildew for a simplicity/impact ratio.
If you have a specific disease issue, make sure to select a variety that is resistant to it.

Why ?

Leaf mold is a major issue in tunnel tomatoes. When it hits in July, you can say goodbye to a big part of your fall harvest. It represents losses up to $ 3 000 per bed.
You need excellent humidity control to mitigate its effects. Even then, it can strike and scrap the end of the season.

Rebelski - a must have

Some varieties, such as Rebelski, are resistant to Powdery Mildew (PM). Another disease that can destroy a fall harvest. 

Rebelski is nice because of its resistance to leaf mold and powdery mildew. There are not a lot of varieties that are resistant to both. That may limit your choices too much.

So choose LM resistant varieties. We will be able to tackle Powdery Mildew in another way.