Warmenhuizen, The Netherlands
2006
Bejo Zaden/De Groot en Slot have developed two onion
cultivars that are resistant to downy mildew (Peronospora
destructor). At the De Groot en Slot symposium “The onion
and its relatives” held on 17 and 18 November in Broek op
Langedijk, the Netherlands, these onion cultivars were shown to
the onion sector for the first time. A major advantage of these
new onion cultivars is the lower environmental impact associated
with their cultivation. Accordingly these cultivars will
contribute to a more environmentally-friendly image of the onion
sector.
Downy mildew has
been a considerable problem in onion cultivation for many years.
Although chemical control is effective, the substances used are
highly detrimental to the environment. In response to this there
has been an increasing demand for resistant cultivars throughout
the world. Breeders and researchers from Bejo Zaden/De Groot en
Slot mounted a search for natural sources of resistance. These
were found at the start of the 1980s in the ornamental shallot
species Allium roylei. Since 1985 this resistance has
been included in onion breeding programmes. Traditional breeding
programmes resulted in the first cultivars in 2002. This falls
within the usual period of 15-20 years to breed a new cultivar.
Two resistant cultivars
The first two mildew-resistant hybrids (one
in the “Rijnsburger group” and one in the “American group”) have
passed a series of internal tests over the past few years, and
exhibited highly favourable results compared to existing
cultivars without this resistance. In 2005 a small quantity of
seed was harvested from both cultivars, but it will take several
more years to build up sufficient seed stocks to satisfy market
requirements.
Over the next
few years, Bejo Zaden/De Groot en Slot will use the seed
available to set up their own field trials in several crop
production areas.
The advantages of mildew
resistance are:
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