Breeding Vegetables for Organic Systems

We are in the second year of three years of funding for organic breeding. The three breeding projects (late blight resistant tomatoes, bush tromboncino summer squash, OP broccoli) will extend beyond the timeframe of the grant with the earliest expectation of release being with broccoli materials in 2007. The tomato and summer squash projects have another seven years or so before we will see the first variety release.

There are two main considerations in breeding for organic systems. The first is the need for specific traits, such as resistance to diseases and pests, that may be controlled in conventional systems through the use of pesticides, but for which economic control measures are lacking in an organic system. The second is for adaptation to the cultural factors that are unique to organic systems such as soil fertility and weed management. On the second point, the fundamental question to me is whether breeding in organic systems is necessary to produce varieties adapted to those types of systems. From a breeding perspective, the interaction between variety and organic system is another form of genotype by environment interaction. It then follows that to obtain optimal varietal performance one must breed within the system of intended production. However, there are no data published to date that support this hypothesis. We plan to test this hypothesis by determining the factors that characterize an organic system, and conducting trials to determine how varieties interact with the key variables. Secondly, we will extend the breeding program to other vegetable crops where traits needed for organic systems are lacking.

For example, supersweet (sh2) sweet corn types have almost completely replaced sugary (su) hybrids for fresh market production. Supersweets are notorious for germination and emergence problems without the use of seed-applied fungicides. Thus, organic growers must limit their planting time to when soil conditions are optimal for germination, thereby limiting their ability to have an early offering in the market. We have nine supersweet sweet corn populations with diverse parentage, and have begun selection for improved germination and emergence without fungicidal protection in early season plantings. Other crops and objectives will be determined by input from organic growers.

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