That mean old late blight strikes every year in my community garden and when I am foolish enough to think I can grow tomatoes at City College, so I am still on the lookout for a late blight resistant variety or two. Inland gardeners may escape this nasty disease, but it is thriving in cooler gardens near the coast.
Two years ago, in a trial reported in this blog, I grew several varieties that "someone" on the web said resisted late blight where they garden. Not a very scientific choice, but for several years, I tried the ones that wholesale seed companies and universities have been developing for resistance and none of those worked, so I was ready to try anything.
As a review, tomato late blight, which is the same as potato late blight, and which caused the Irish potato famine, is not soil borne, but carried by aerial spores from infected plants. It appears rather late (as in late blight) in the season. There are dark brown lesions on stems and leaves, followed by general collapse of the plants.Here are a couple of photos of plants with symptoms:
The fruit may start to show the greasy brown coloration near the stem while it is stil green, or after it ripens. This may spread to whole fruits. In any case, fruit on infected plants ripens poorly and isn't sweet.
The one variety that has been on the market for several years is 'Legend'. In my trials, it was the first to die. Here is the miserable dead plant of 'Legend' in 2009:
Of the others I tried in 2009, my best plants were 'Juliet', which now is sold with a notation that it has some resistance to "Blight." (Not very informative, since there is also an early blight, a disease much more common in the Eastern US, but an entirely different disease.) Here is 'Juliet' in 2009:
Although 'Juliet' had a touch of late blight, it produced a huge crop of these plum-type fruits--bigger than a cherry tomato, but smaller than a standard paste tomato. They were, however, perfect for the Broiled Tomatoes with Herbs and Cheese recipe I printed in Golden Gate Gardening.
In the past couple of years, late blight has been appearing on the East Coast as well as in the West. A few more supposedly resistant varieties have appeared, and I am trying 4 new ones:
Plum Regal F1 (Salsa/Sauce/Drying) 68 days
Golden Sweet F1 (Yellow Grape) 60 days
Mountain Magic F1 (Red, tall vine) 70 days
Defiant PHR F1 (Red, short vine) 70 days
So, I got them all from Johnny's Seeds, who may or may not have seeds of them left this year. They are all hybrids, and all relatively early. (The number of days doesn't count the 6 weeks or so to grow transplants, but anything under 75 is reasonably early.) The one I am most hopeful for is 'Defiant', since it has a formal "PHR" after the name, stands for "Phytopthora Resistant". (Phytopthora is the scientific genus name of the late blight fungus.) 'Defiant' is also said to resist 2 strains of the disease, so maybe it resists the strain we have while others didn't?
The plants will be potted up this week, planted out in May in one or possibly several San Francisco test sites. Stay tuned!