From what I've read, both, Burpee & Ferry Morse (the 2 most popular brands for garden center shelves) boast that they do not use/sell genetically modified seeds. Of course, hybrids are a different matter; but hybridization is also a natural phenomenon that aids in species adaptation & evolution, so shouldn't be feared.
TBH, I shopped around for GMO seeds last year, just out of curiosity for knowledge, and I could not find any seed suppliers of annual or perennial crops that openly advertised available GMO products for home farmers/gardeners. The few I did find were mainly cotton, plus some grains grown for animal feed; and even they were only available to large scale farmers who are already contracted with the seed producer; or a company affiliated with the seed producer. It also seems that GMO seed prices are much higher than non-GMO, and there are more federal regulations for growers;which is why they're more likely to be used in large scaled operations that have specific insurance policies & compliance monitoring systems, instead of being sold at the
local garden centers & nurseries.
This was just the results of my research, which I would definitely not consider to be any type of formal, thorough, or official. I basically just wanted to learn
enough to keep me from being paranoid about the genotype whenever I bought seeds from a new company, or got some in trades.