Thanks to decades of breeding, modern tomato varieties have a lot of great properties for grower and consumer alike. However, modern strains sometimes have less flavor than older heirloom varieties. This has prompted attempts to try to breed a tomato with all the taste of yesteryear along with all the benefits of more recent cultivars.
A panel at a meeting of the American Association for the Advancement of Science addressed the issue. A number of scientists on the panel are trying to change things with biochemistry and genetics.
One of the things being considered is the relationship between smell (generated by volatile chemicals in the tomato) and taste.
Harry Klee of the University of Florida has put together a collection of over 200 tomatoes, some heirloom, some the mainstream agricultural strains. Using those, his team has characterized the volatile chemicals present in each, coming up with a list of about 68. They've also put about 100 of those tomatoes to the test with a panel of tasters, who rated their appeal and flavor. Interestingly, he has discovered along the way that some of the heirloom varieties, assumed to be more tasty, actually have less flavor than might be expected.
The end result is that the team has what you might consider a statistical recipe for a good tomato. Generally, what consumers like is perceived sweetness. In general, the perceived sweetness was roughly in line with the amount of sugar present, but not always. Klee pointed out two varieties (Matina and Yellow Jelly Bean) that had similar levels of sugar, but one was perceived as twice as sweet as the other--the one with slightly less sugar.
The difference was the concentration of various volatiles in the tomatoes, which are quite often derivatives of carotenoids, chemicals most closely associated with carrots. The derivatives were considered fruity and floral, and were correlated with both perceived sweetness and likeability. Fortunately, the pathways that convert the carotenoids into these derivates are fairly well understood.
Klee's team has started identifying alleles that enable production of a variety of volatiles in heirloom strains, and started introducing them into high-production commercial strains. According to him, a single cross can give heirloom flavor with double the yield of the original heirloom strain--not enough to get commercial growers to switch, but a step in the right direction. Further breeding and, if necessary, some genetic engineering may return the heirloom genes to the modern tomato.