New Early Maturing Synthetic Onion Populations for Northern Latitudes

Currently Wisconsin onion growers must compete with western US growers (California, New Mexico, Washington), as well as the global onion market (primarily Mexico and South and Central America) to supply fresh onions year-round for the domestic market. Increased availability of long-day early maturing onion varieties for Wisconsin and other northern US (latitudes greater than 38°N) areas would enable these growers to retain more of this market for longer periods of time. Although early maturing onions typically yield less than later maturing varieties, the economic incentive to be earlier to market is advantageous for Wisconsin growers. For example, a Wisconsin grower can secure $0.50 to 2.00 more per 50lb bag for a delivery of onions in mid-August than in mid-September, which could translate into a 10-20% differential, depending on the year.

The University of Wisconsin Onion Breeding Program currently has five early onion synthetic populations that are being prepared for release. In our current field trials, all five populations are reaching maturity as early (two populations) or markedly earlier (three poulations) than most of the selected commercial varieties. Our program is committed to the goal of releasing material that can be used as germplasm by other breeders and the commercial seed industry for cultivar development.

The Wisconsin early onion synthetic (WEOS) population breeding project was started in 1996 following evaluation of selected OP cultivars and several of the program’s inbred lines. The project grew to include older Wisconsin breeding lines, inbred lines, additional OP cultivars, as well as germplasm from six accessions from the USDA-NPGS GRIN collection. By 2002, five EOS populations were established, which have now completed several breeding cycles, ranging from four to seven. The number of families per population ranges from one to seventeen.

During the growing seasons of 2009 and 2010, we compared each population with six commercial varieties that spanned a range of average days to maturity (90 to 120 days). Three of the WEOS groups (2, 3, and 5) approached or reached maturity markedly before the earliest maturing cultivars included in the trial. These results suggest the potential for the Wisconsin Early Onion Synthetic populations to be of value for onion breeders in northern latitudes.