Tuesday, March 11, 2014

Breeding Workshop: trials, selections, breeding methods

Variety Trials: breeding to see what works (and what doesn't)

Jim Myers extolled the benefits of on-farm trials in his pre-conference workshop. It turns out that with participatory plant breeding, a cooperative arrangement that appeals to my grassroots heart, the variety trial is central to understanding and developing a new crop for a particular area. Myers held up a copy of an old AFES variety trial publication as an example of the kind of information breeders need to know and develop. He explained that it was important for:
  • getting to know the crop
  • expanding market potential, attracting new customers
  • addressing crop stresses
  • identifying organic info
  • on-farm variety trials for vegetables, herbs, etc. (Here Myers talked about a publication from the Organic Seed Alliance that he authored about creating on-farm experimental designs for useful variety trials. The OSA has many helpful publications on everything from policy to seed production, worksheets and webinars.)
There are two basic trial methods, the observation trial and the replicated trial.

Observation trials are okay for evaluating disease resistance or discrete traits (color growth, habit, fruit size and shape, earliness), productivity, and adaptation to the locale. An example might be planting one-row plots of 10-30 feet. Observation trials are repeated over years in the same place.

Replication trials remove variation casused by differences in the local environment & provide repeated measures. They require randomization, such as in the variety's placement within the plot.

Siting a trial: get as uniform a section as possible. Consider soils, wind direction, even elevation, shade, moisture/wet or dry spots.

Traits to evaluate depend upon intended use and kind of crop: processing, fresh market, home garden/

On-farm trials in their simplest form: plant several varieties side by side and keep notes. This requires planning!

On-farm trials II:
Arrange among a group of farmers to grow an extended set of varieties, each grower grows a set on their farm. The advantage here is that a broader set can be looked, but it requires not only more planning but also coordination, and it should include a common variety to serve as a yardstick. Varietal performance may be affected by differences in location and cultural practices, too.

NOVIC (or, see the Northern Organic Vegetable Improvement Collaborative)

Mother Daughter Experimental Design: this is a statistical plot design that maximizes the amount of information obtained from diverse environments.

mother site: complete randomized block design with at least three replications
daughter sites: single replicates on at least three collaborating farms

Where to find the genetic variation?

From commercial sources:
  • seed catalogs
  • Native Seed Search
  • Seed Savers Exchange
Exchange with other growers:
  • seed swaps
  • community seed banks/libraries/sanctuaries
  • Plant introduction collection (not a catalog: up to you to maintain seed or accession acquired)
  • NSL # is storage of last resort, very hard to get
  • PVP; has to be deposited in GRIN, but not available until patent runs out
  • Tomato Genetic Resource Collection (genetic stocks housed at UC Davis, regular tomatoes housed at Geneva, New York)
Methods of recombination:
  • natural crossing
  • artificial 
  • selection methods: mass selection, half-sib selection, bulk breeding, pedigree selection, single-seed descent, backcross breeding
Myers went into detail about each of these, but in particular the methods of selection. The technical aspects of the workshop were impressive and I will leave them aside, as the detail was considerable, but for those who are interested in pursuing breeding vegetable varieties, he recommended a few books, among them:

Breed Your Own Vegetable Varieties: The Gardener's Guide to Plant Breeding and Seed Saving, by Carol Deppe.

The Organic Seed Grower:  A Farmer's Guide to Vegetable Seed Production, by John Navazio.

There is also a book he co-edited but did not mention, Organic Crop Breeding.

No comments: