[From Jerry Parsons]
In the 30 years which I have been in San Antonio as a horticulturist for Texas Cooperative Extension, this system of cooperative testing and local marketing has introduced productive hybrid tomatoes (Spring Giant, Big Set, Celebrity, Jack Pot, Bingo, Carnival, Whirlaway, Heatwave, SunMaster, Surefire and Merced Now, most of these tried-and-proven superior varieties are no longer available for home gardeners to enjoy. How and why could something like this happen?
The short story is: There are only a few vegetable seed companies left in the world and they are eliminating the older, Texas-proven varieties in favor of new, "improved' hybrids. This elimination includes Merced, Heatwave , Surefire, SunMaster tomatoes and Green Comet broccoli. Remaining supplies will soon be depleted. Dr. Larry Stein and I, reworked the Extension Vegetable Recommendation list and sources after a long period of denial about the non-existence of Porter & Sons Seedmen in Stephenville, Texas, which used to be a major seed supplier for Texas gardeners. The Cooperative Extension Vegetable Recommendation list and sources can be found at:
http://aggie-horticulture.tamu.edu/PLANTanswers/vegvar.html
It has been removed from the market but next year (2010) I will be selling second generation seed of Merced at: http://plantanswers.com/parsons_preferred_seed.htm

PARSONS PREFERRED SEED
The seed available for sale and use in this listing is available ONLY from PLANTanswers.com and have been selected by Jerry Parsons, Texas A&M University System Professor and Extension Horticulturist-retired, for uniqueness of disease resistance, dependable yields, and quality fruit with special characteristics only found in this listing. Complete growing instructions are
Seed of the Texas SuperStar tomato varieties (Merced and Surefire) have been discontinued so those seed will soon be eliminated from the market. SunMaster and Heatwave have also met similar fates. However, the most recent SuperStar tomato named 'Tomato444' can be found in the list as BHN444 and a new tomato named SunLeaper (available from Stoke's Seeds Ltd. http://www.stokeseeds.com/cgi-bin/StokesSeeds.storefront) is showing promise as per our demonstrations at:
http://aggie-horticulture.tamu.edu/plantanswers/vegetables/2003falltomatotrials/index.html
So, we recommend for tomatoes this spring that gardeners use Carnival, Celebrity, SunPride and/or Tomato444 for seed-you-can-find home garden tomatoes. If gardeners will look around the Internet, they may also be able to find seed of Amelia and SunLeaper which have also performed well for San Antonio gardeners.

Here is a link that might be useful: Plant Answers