Tuesday, March 11, 2014

Conference Workshop: On tomatoes and breeding lines: purple, yellow, rose

Jim Myers has worked on several species and varieties, but lately has caused a stir in the gardening world for his work with the Indigo Rose purple tomato, released by Oregon State University in 2012. To tomato lovers like me, this is pretty exciting, as it represents a new range of color and antioxidants available in these delicious fruit. But Myers was here to tell us about breeding vegetables in general. (Tomatoes, one of the most popular garden plants, are largely self-pollinating.)

Managing & selecting self-pollinated crops:
  • one individual can represent variety, but more than one is better
  • roguing and selection
  • isolation distances
Maintaining stock seed:
  • take 50-100 single plant selections from a finished variety
  • grow as progeny rows, using say, 50 seeds from your plant selection
  • inspect each plant for deviations, rogue off-type plants (roguing means weeding the rogues, the plants that don't conform to the type you are looking for)
  • eliminate progeny rows with high frequency of off-types
  • harvest by progeny row
  • composite seed (mixed-up seed) from progeny rows to make up foundation seed
  • grow every year or when regeneration of variety required
Roguing and selection
  • source of off-types
  • seed mixes
  • outcrossing
  • spontaneous mutation (can come off the same plant)
Examples of off-types
  • ovals and strings in beans or peas
  • plant / fruit / flower colors that don't match the variety
  • growth habit
  • pod fiber
  • sterile off-types
  • disease resistance (could be a good thing! or the off-type could show a lack of disease or pest resistance, and so not be so good)
Isolation distances
  • depends on geography barriers, pollinators, prevailing winds
  • can isolate in time as well as space
  • no isolation needed between beans and peas (10-50 ft)
  • isolation may be needed for: endive, escarole, lettuce; tomato and eggplant (10-50 ft)
  • isolation required: peppers (75-100ft)
Myers also discussed the requirements for cross-pollinated crops and how they differ from self-pollinated crops. Cross-pollinators usually produce many small seeds, while self-pollinators usually produce a smaller amount of very large seeds (although this isn't a hard and fast rule). 
Managing & selecting cross-pollinated crops
  • many individuals to prevent inbreeding
  • maintenance
  • isolation distances
maintaining stock seed:
  • keep population sizes large: below 30-50 plants inbreeding depression will occur (plants will become weakened due to lack of sufficient genetic variety)
  • grow variety in extreme isolation (caged production ensures isolation where land is limited)
  • continuous mass selection (trimming extremes in variation)
Isolation distances:
  • depends on geography barriers, pollinators, prevailing winds
  • is the crop insect or wind pollinated?
  • can isolate in time as well space (two weeks is offten enough time)
  • Cole crops, mustard greens, radish, kale, turnips, cucurbits, scarlet runner beans, onions, carrots, celery, chicory: .5-2 mi
  • sweet corn: 66-1,320 ft
  • table beet & chard: 1-2- mi (same color) 1.5-3 if different color, 3-5 mile if different types
  • spinach .5-3 miles
Unripe Indigo Rose tomato, an open-pollinated variety incorporating anthocyanins in the skin of its ripe fruit and released by Oregon State University. For more on the variety, see OSU's FAQ page. This and other, similar tomatoes are now available from many seed companies.


Tomatoes have three growth habits, controlled by a single gene: determinate, indeterminate, and semi-determinate. For example, Micro Tom is a tiny variety about 8" tall developed using regular breeding methods, which grows no taller. This is a determinate variety. An indeterminate is the norm for tomatoes, and is the vining ever-growing habit that most tomatoes will exhibit. A semi-determinate will fall somewhere in between. One attendee showed quite a bit of interest in the idea of breeding a northern-adapted variety from a small tomato such as Micro Tom.

Kurt Wold, another of the attendees at the conference and owner of Pingo Farm and Zone 1 Grown seed company, has many Russian varieties. He suggested that these cold-weather, short-season, early tomatoes make a good place from which to start breeding for Alaska's needs. He also has a small determinate variety, which would be better to start from than Micro Tom, he said, as it is already adapted to a northern climate. Myers agreed: starting with a variety that already has some of the characteristics you want will save a lot of time.

Cooperative breeding projects

In concluding his workshop, Myers asked his audience if there were any cooperative breeding projects in which people might be interested in participating. The local turnip breeding project already has a lot of adherents, and several more signed up during the conference, but others expressed interest in tomatoes, sweet or flour corn, and fava beans.

CES will set up a listserve to notify members about participatory plant breeding efforts/inquiries. For more information, contact Steve Seefeldt, CES agriculture agent for the Fairbanks area. (474-2423)

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