Unknown growth on tomato and pepper Veins

Can anyone ID this? I'm seeing it on at least one of my tomato plant  seedlings  and I saw it bad on a pepper plant starter that I bought from a nursery.  It's a colorless growth on the veins under the leaves  

I didn't find any thing that looked like that at the Cornell U. site, if it isn't some sort of egg cluster, you might just have a new disease.

Cornell U.

To me, it kinda looks similar to a gall, but the galls I've seen are round and appear to be random on leaves, not selectively on the vein. Perhaps you have time to take a leaf to your local ag extension office and see what they say? I'm curious to know what it is.

Thanks for the responses. I sent an email with photo to my local ag extension so I'll see if they know.

I got a response from the  Colorado State University extension. Here is his answer:


"My best guess is that this is a non-infectious disorder called edema.

Tomato seedlings are usually grown in greenhouses where humidity is high.  Soil moisture is kept high.  As a result, plant roots may take up more water than is being transpired (released) into the humid atmosphere.  So there is an accumulation of water in leaves’ intercellular spaces.  Many leaf cells enlarge and block the openings (stomates) through which water vapor is normally transpired from the plant; thereby contributing to further water retention in the leaf. If this condition persists, the enlarged cells divide and develop elongate corky cells, accounting for the raised, crusty appearance.
On tomatoes, leaf undersides and veins are the most likely site of edema.   Supposedly there are some tomato varieties “resistant” to edema, though I’ve never actually seen a list of those varieties.
In any case, I doubt this will be an ongoing problem for your tomatoes.  You can always “pinch out” a few leaves that appear badly affected."

Neat! Thanks for sharing the response!