CREATION AND TESTING OF TRUE SYNTHETIC VARIETIES OF ONION (ALLIUM CEPA)

P. Goldschmied, R. Ellerbrock, E. Cobb, M. Mutschler

Most new onion varieties are hybrids created by the controlled cross of two inbred lines. Although the inbred lines are not fully homozygous, the resulting F1 hybrids are relatively uniform and maximized for "heterozygosity" and "hybrid vigor". Older onion varieties and homegrowns are open pollinated populations with varying degrees of heterozygosity, heterogeneity, and inbreeding depression, causing reduced vigor.

A third type of variety was produced - the synthetic variety. Synthetic varieties are created by intermating strategies that maximize heterozygosity, while maintaining cultural uniformity, and are then maintained for a number of generations by open-pollination. Therefore a synthetic variety has much of the heterozygosity and vigor of the F1 hybrid, but the seed production and cost advantages of an open pollinated variety.

Synthetics would not replace F1 hybrids, but would be of use in specific applications such as organic production, marginal areas, and developing countries. Seed companies could create their own synthetics by combining their superior breeding materials with known combining abilities.

A series of inbred lines of yellow/brown pungent storage onions with good adaptation to New York State, larger bulb size and good storability were used to create the 3 first synthetics, which were trialed in 2004. This investigation determines the potential of these synthetic varieties and demonstrates their value. It is also a first step in testing and adapting the synthetic seed production technique to commercial onion seed production. A second set of 6 new synthetics was produced in 2004, for trials in 2005.

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