Tomatoes, wilt, blight
I live in the Denver area, and for the past few years have successfully grown tomatoes and other veggies from seed. This year I bought a "Mighty Mato" Brandywine grafted onto a root of a "wild tomato" from a local nursery. It was oversized for this time of year, but I was curious. Looked good except for a few yellow leaves at the bottom. Was assured this meant nothing. Here is the path: 1. Put potted plant in area it would live (new SF box with new planting mix) 2. Wait 3 days before transplanting 3. Transplant per instructions, not covering plant above existing roots 4. Within 2 days, 50% of plant is yellow and wilting from the bottom up. I say it's a blight or wilt. Garden center accepted it back gracefully and gave me credit, but insist the only reasons could be inconsistent watering or planting above rootball and said it couldn't put out so much new growth if it had a fungus. We have drip irrigation and live near the garden center, so it should not have been a shock. Is it something that could contaminate my garden?
Despite what they say, it may have been a blight or wilt. Plus, tomatoes respond well to being planted deeply, as the stem grows new roots - but I have to admit I do not have any experience with grafted tomatoes and perhaps they are different.
Blights and wilts are most often brought home from a plant bought at a nursery. Some watering methods in a greenhouse can encourage rapid spread from one pot to another due to splashing water. If it had only been recently infected, it would have grown normally until the disease took a good hold.
But, to be fair, it could have been many other things, such as a pre-existing disease in your soil left over from last year, transplant shock (even if a plant is well watered, shock can occur especially if the plant is older when transplanted) or the rootball may have dried out which causes the soil around it to repel water rather than absorb it even when watered regularly.
You will probably not know for sure, but a sure sign will be if the next plant also succumbs in the bed. This will mean that the bed is infected and you will need to avoid planting nightshade vegetables there for a year or two.