Answer: There are two blights that affect beans: halo blight and bacterial blight. Are you sure you are dealing with blight? Beans are also susceptible to mosaic virus, which causes puckered leaves and stunted plants that produce poorly. The virus is spread by aphids, so by controlling them you can help prevent the spread of the virus. Bean rust is a fungal disease that can cause serious damage.
I'm having trouble finding beans listed as resistant to blight. I found one bush bean, 'Grenoble' listed as resistant to halo blight. (Johnny's Seeds, http://www.johnnyseeds.com) Burpee sells a half runner called 'White Half Runner', but they don't list its disease resistance -- you might call their customer service department at 800-333-5808.
Finally, Vermont Bean Seed Co. has a large selection of beans, but they also don't list disease resistance. You might contact them directly: 803-663-0217. I'm not sure if any company will offer a 'guarantee' if disease resistance.
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