To affect DNA inside a seed, or other plant tissues, the type of radiation would need to be "energetic" enough for single photons to actually break chemical bonds in the DNA.
Energetic radiation has shorter wavelengths than less energetic radiation.
Here are the kinds of radiation, listed In decreasing order of energy:
X-rays & gamma
UV
visible light
Infrared
microwave & HF & VHF & UHF
radio waves
You can observe the effect of sunlight on plastic: the UV in sunlight breaks down the chemical structure of the plastic, over years of exposure.
If you screen all the UV out of sunlight, it doesn't break down the plastic.
Visible light doesn't have enough energy per photon to break chemical bonds in plastic.
X-rays and gamma radiation can affect DNA and cause mutations.
Very short wavelength UV could do that, if you could focus enough short UV to penetrate the seed coats. In fact, enough short-wavelength UV can sterilize bacteria. As with X-rays, it would be tricky to find just the right the amount of radiation (dose) that would cause a measurable number of mutations vs. causing death.
Regular UV might have some genetic effect, especially if you don't insist it be a measurable effect or detectable by conventional science. But I don't think enough UV could get through a seed coat to affect the genes, without cooking the seeds from heat.
Visible light doesn't cause mutations because, even if you focused huge amounts of light on a seed, and managed to penetrate the seed coat without cooking it thermally, photons of visible light don't have enough energy to break chemical bonds.
Infrared (IR) has even less energy than visible light (per photon), and can't cause mutations.
IR can heat things up but not change their chemistry (until they scorch and burn).
Microwaves have even less energy than IR, and can't cause mutations.
TV and radio waves don't cause mutations.
From visible light on down, they can cause heat but not chemical changes.