Don't know if you knew this but there are other places that have sweet onions too that are indigenous to their area.Texas has their 1015 Super Sweet(planted on Oct.15) and Washington has what's called Walla Walla's. I think Hawaii has a particular sweet onion too.
That's not a post Iíd expect from someone who likes to chide people for not reading posts before posting.
Expanding on what I wrote two posts before yours (where I commented on both 1015ís and Maui onions), none of the sweet onions we have in the US today are indigenous. It all started in 1898 when Bermuda onions were first planted in Texas. Ironically, the seeds were from the Canary Islands not Bermuda.
By the 1920's they were growing so many onions in Texas, the demand for seed brought in new, inexperienced seed growers who drove the Canary Island seed quality down. Per-acre yields in Texas became so low that growers began looking at other varieties Ė the most important of which was the Grano from Spain. Because of low yields, there have been few, if any, Bermuda onions grown commercially in the US since the late 1940's despite what you might see advertised at your grocery store.
One of the most important super sweet onions is the Granex, an F1 hybrid that was developed in Texas from the Excel Yellow Bermuda and the Texas Early Grano 951. This onion has a host of names including Vidalia, Maui, Noonday, etc.
The Grano 1015Y (a.k.a Texas 1015) is not a hybrid Ė rather an improved Grano 951 that was developed for resistance to pink root Ė not sweetness per se Ė while maintaining early maturity. Attempts to further improve the 1015Y have resulted in later maturity which is highly undesirable from a commercial growing perspective.
The Walla Walla onion, on the other hand was developed from seed brought from Corsica off the coast of Italy. Interestingly, Bermuda onions are also of Italian origin.