Features Agronomy Other Crops
The potential of ethylene

Most plants produce it, many respond to its usefulness in growth and ripening
and others rest slowly in storage with it, but potatoes have yet to experience
the full benefits of being exposed to commercial applications of the product.
Now, researchers in Atlantic Canada are publishing the goods on ethylene and
how it can improve a number of aspects of a potato crop.

"Ethylene is responsible for many growth processes in plants including
the ripening process," explains Barbara Daniels-Lake, a potato researcher
with Agriculture and Agri-Food Canada in Kentville, Nova Scotia. "Ethylene
is a plant growth regulator and, in potatoes, we knew it could affect sprouting."

While Daniels-Lake was considering how ethylene affected sprouting, her colleague
from the Nova Scotia Agricultural College in Truro, Dr. Kris Pruski, investigated
how ethylene could control tuber size. They are working together along with
another researcher, Dr. Robert Prange, to study the effects of ethylene on stored
potatoes with each focussing on separate aspects of the plant growth regulator.

After four years of research, Pruski used the fact that ethylene creates uniform
sprouting to increase the number of stems which, in the field, will produce
more tubers that are smaller. In the case of seed potatoes, this is a valuable
tool because smaller tubers are better for seed and a higher number of tubers
means more seed is produced.

A low concentration (4ppm) was used on Russet Burbank, Shepody and Atlantic
in their trials. "Once the tubers are exposed to ethylene, sprouting is
suppressed," explains Pruski, "but when you remove the ethylene, the
tubers will sprout." So, if the ethylene is removed just prior to planting,
the tubers will sprout uniformly and in a timely manner. In the case of all
three cultivars, the average time to emergence was significantly shorter in
plants from the ethylene-treated seed than from the control. In addition, the
total yield was higher from seed stored in ethylene treatments. Pruski's research
indicated the increase was most significant if the tubers were harvested relatively
late.

However, using ethylene requires some finesse because the research conducted
by Daniels-Lake proved that ethylene has two effects on potatoes. She advises
that "ethylene causes potatoes to sprout and also prevents them from sprouting."
The key is knowing which process you want the ethylene to accomplish and then
delivering it to the tubers at the right time and at the right rate.

No one had looked at the commercial potential of ethylene as a sprout inhibitor,
says Daniels-Lake. "It has low toxicity, has an acceptable cost, serves
an important function to prevent potatoes from sprouting until needed and inhibits
sprouts in commercial applications where sprouts are undesirable, such as in
French fries." The researchers looked at many compounds to accomplish sprout
suppression, but found that ethylene was the most economical and practical.
However, she cautions that it can affect fry colour if not applied correctly.

The downside to news about a natural product that is multi-useful and economically
viable is that it is not available for commercial use yet. Ethylene is registered
for potatoes but the holders of the registration have chosen not to pursue its
commercial potential at this time.

Pruski is enthusiastic about the value of ethylene to growers, not just from
the point of view of what it can do, but also its economic value. "Ethylene
can be injected into the storage, so all a grower needs is a system that can
allow for the injection, has good ventilation and can accommodate the use of
this type of product," he says. The cost to use ethylene would be around
$3000 per year, he adds. Compared to other products or methods of sprout control,
"ethylene is relatively inexpensive."

If you are a seed grower or producing potatoes under contract for a processor,
ethylene could fit into your operation. Based on the work of Prange and Daniels-Lake,
it has been used in Europe for the past three years on table potatoes, but Canada
has been slow to embrace this new method. Although much of the research was
pioneered in Canada and ethylene has been used in the United Kingdom since 2003
as a sprout inhibitor, it is not in use here. An advantage of ethylene, according
to Daniels-Lake, is that it is a naturally occurring substance and growers are
not adding anything new to the potatoes that they do not already produce themselves.

Despite the excitement over how useful ethylene can be, the researchers are
quick to caution growers that when it becomes available, they must still use
it carefully. "For example, don't let other plants or fruit be exposed
to ethylene in storage," says Daniels-Lake. "Ethylene will cause many
fruits or vegetables to ripen faster or lose their leaves or flowers."
The other downside, which is no fault of the researchers who are promoting ethylene
as an alternative sprout inhibitor, is the slowness of the technology transfer.
Even though the product has been proven effective and would be an economical
and useful tool, growers cannot use it without PMRA registration approval and
commercial availability.

"This is such an easy and inexpensive way to prevent sprouting, yet growers
don't have access to it," laments Pruski. It may be a case of growers needing
to put pressure on regulators to get ethylene available sooner rather than later.
The suggestion is that the 'will' is not there to make it happen. At least in
the laboratory, ethylene has proven itself to be a useful tool in a couple of
diverse applications, but it just has not made it to the farmgate yet. -30-