Scientists working to grow the best tomato

In the day when the mass production of food trumped everything else, plant breeders developed the "perfect" supermarket tomato. Thick-skinned and with a shelf life for the ages, it was a boon for growers, shippers and retailers.

But even non-foodie consumers realized that they were getting the short end of the stick. Those reddish orbs looked like the real thing but tasted like damp cardboard, and the supermarket tomato became a standing joke. It also spurred the rediscovery and celebration of the heirloom tomato, the antique, vernacular fruit that managed to capture not only the folksy history of a regional variety but also the warmth and memory of summer itself. The poster child was the brassy beefsteak Brandywine, but thousands of tomato varieties have survived thanks in large part to this renaissance.

As home gardeners across the land have discovered - especially in this year's June monsoon - heirlooms often fall down in key areas: They are sickly, they take forever to fruit, and the yield is low.

"Bacterial and fungal diseases can take down a home garden the quickest, especially if you don't have a vigorous spraying program," said Chelsey Fields, vegetable and herbs product manager at W. Atlee Burpee & Co. "They can wreak havoc on heirlooms."

If one generation of scientists could produce a cannonball tomato, a new generation of scientists is asking, "Where did the flavor go, and how can we get it back?" These questions have spawned leading-edge breeding programs whose aim is to create varieties that have all the flavor and nutritional advantages of the heirlooms but the vigor and bounty of the modern hybrid.

Hybridizers at the University of Florida have introduced two varieties designed to do just that. Garden Gem produces oodles of small oval fruits, perfect for eating whole off the vine, for throwing in salads or for marinara. One of its parents is Maglia Rosa, not strictly an heirloom but bred as a stable cross from gourmet cherry tomatoes.

Garden Treasure is a larger, slicing tomato derived from an heirloom named German Queen. German Queen is an impressive beefsteak, but once picked it gets soft quickly. "The hybrid tastes better than the heirloom [parent] because it's a little firmer," said Harry Klee, who heads the university's tomato breeding program. "It produces five times as much fruit and has a shelf life of a couple of weeks."

Taste itself is inherently subjective; some palates prefer something sweeter, others more tart, and that balance can change as we age. But it turns out that much of the flavor experience in a tomato can be quantified and chemically identified and thus manipulated in breeding new varieties.

We've long known that a tomato tango occurs between sugars (fructose and glucose) and acids (mostly citric but also malic and glutamic), but as Klee has written, these are just the foundation. A third element involves the more complex dance between our olfactory receptors and as many as 20 volatile organic compounds at work in tomatoes. They can be detected in the lab through gas chromatography. These aromatics have names only an organic chemistry buff would love, but they have a direct bearing on our lives with tomatoes. Hexanal conveys a green, grassy characteristic; 6-methyl-5-hepten-2-one is both fruity and floral. You want nutty and fruity? Reach for the 2-phenylethanol.

After 10 years of intensive work, "we know how much of all these compounds we want in the ideal tomato," Klee said. "The challenge now is how do you make them?" That is, assemble them deliberately in new tomato varieties. This will take another 10 years, he predicts.

Scientific advances are working in his favor: Since the first tomato genome was sequenced three years ago, Klee's team has worked with a scientist in Beijing to map the genomes of 250 heirloom varieties. This will help them assemble desired traits through genetic profiling (but not engineering).

Another boon has been the taste-testing data amassed by Klee's team over the past four years. In Gainesville, the summer is too hot for tomato cultivation, but the climate allows two harvests a year - in June and November. During those months, the project assembles 100 tasters drawn from the university's student body, faculty and staff to evaluate approximately 25 varieties over four weeks. This is a huge undertaking because it requires growing hundreds of plants from seed to maturity, but the scientists now have flavor ratings on 150 varieties since 2012.

As subjective as it might be, taste testing by engaged volunteers is important because science alone can't crack this nut. If you look at the lab analysis of an heirloom named Marmande, "the chemistry tells us that people should really like it, but they actually hate it because it's too soft, too mushy," Klee said.

Beyond texture, a cherished tomato must have something even more amorphous: nostalgia. This is the magic driving another tomato breeding program in New Jersey, a state where the tomato is a cultural icon. At Rutgers University's agricultural research farm in Pittstown, hybridizer Tom Orton has been trying to capture the lost flavor of a famous old variety named, simply, Rutgers.

It was introduced in the 1930s as a general-purpose globe tomato that could be used by the state's then-thriving canning industry but also for market farmers and home gardeners looking for a flavorful and reliable tomato. It was so versatile that it could be used for slicing, juicing or canning. Commercial tomato varieties today are much more narrowly designed for their utility.

You can still find the Rutgers in seed catalogs, except it is not the original; genetic drift over the generations has brought a variety that is undoubtedly different from the first hybrid, now lost to time.

But Orton has taken the parents of Rutgers, a variety named Marglobe and a proprietary variety held by Campbell Soup, and crossed them to produce a new offspring aimed at capturing the now more imagined than remembered flavor of the original.

But each seedling is different and must be evaluated. In the past five years, Orton has taken his selections and crossed them across five generations to produce genetically stable plants that will grow true from seed. He's down to three finalists that have had to jump through all the hoops of acceptance, from disease resistance to the host of physical qualities that a tomato must have beyond flavor. These include color, shape, aversion to cracking and scorching, and the interior architecture of walls and the gel cavities.

I recently met his colleague Jack Rabin at the Snyder farm in Pittstown to taste the shortlisted finalists. We abbreviated their actual identification numbers to No. 1, No. 3 and No. 6.

We agreed that No. 3 had the edge in terms of its flavor concoction, which I ranked as 6 on a scale of 7 for acid, sweetness, texture and flavor. These are great tomatoes, and I look forward to growing the one that is finally introduced. Rabin agreed with me that the flavors would have been more intense had all three not been suffering from what appeared to be a surfeit of irrigation before harvest; they were grown at another farm for an annual taste-testing festival at the Snyder farm. The ones on the farm weren't ready on that day.

Incidentally, after tasting dozens of tomato varieties that day, I can say that any diced tomato that sits on a plate becomes soft and difficult to like after a couple of hours, and that the palate can only handle about half a dozen before the taste nuances are lost.

Meanwhile, Burpee is getting ready to introduce a better version of the soft Marmande, named Madame Marmande. "It resists cracking in the garden and you get a nice yield," Fields said. Burpee's most famous improved heirloom is Brandy Boy, around since 2003.

Flavor is linked to dietary goodies such as minerals, antioxidants and vitamins, and Klee's ultimate goal is to produce commercial varieties that consumers will want to eat, to improve public diet and nutrition. The key is to create a superior tomato that can be mass-produced so that it is cheap enough for everyone to buy. But the path to a better supermarket tomato is through the garden.

Gardeners will put up with traits that large commercial growers see as flaws, which is why the breeders are happy to offer their seeds to home and market gardeners. "It's an easier target to hit than is the commercial tomato," Klee said.

The reason so many folks grow tomatoes at home - other than the bragging rights - is that as frustrating as the enterprise can be, this is the only true way to get the tastiest tomatoes, freshly picked and vine-ripened. But it starts with superior varieties, and thanks to plant breeders such as Orton and Klee, some great new tomatoes combining the best of old and new are just around the corner.

The top heirlooms

The University of Florida rated the top five heirloom tomatoes.

Heirloom tomatoes are open-pollinated varieties, meaning you can save the ripe seed and the plants will grow true to type the following season. Many developed regionally within the United States or came with immigrants from other lands, imbuing them with cultural value. Purists regard heirlooms as being at least 50 years old. Some of the top five rated in the University of Florida's variety trials don't meet that criterion but are still true-bred gourmet varieties.

1. Maglia Rosa: A pink mottled cherry type developed by breeder Fred Hempel of Artisan Seeds in Sunol, Calif. Its parents are Black Cherry and Speckled Roman.

2. Garden Gem: A red cherry type uses Maglia Rosa as one of its parents and is one of two new introductions by the university.

3. Early Red Chief: A bush type, with large red fruits and an early crop.

4. Super Sioux: A flavorful old red slicing tomato valued for its classic tart taste, heat tolerance and resistance to cracking.

5. St. Pierre: An old French variety, a standard but flavorful red slicer.