Features Production Research
Promising rootstocks could expand grafting markets

May 26, 2010, Wooster,
OH – Promising Ohio State University research on grafting may help pave the way
for expanded uses of the technique in tomato production systems.

May 26, 2010, Wooster,
OH – Promising Ohio State University research on grafting may help pave the way
for expanded uses of the technique in tomato production systems.

Grafting is a technique
whereby the root system (or rootstock) of one plant is fused onto the stem and
leaf (or scion) of another plant. The purpose is to match the field performance
characteristics (high yield, disease resistance, drought tolerance, etc.) with
a fruit that has high market demand.

In a three-year project,
Ohio Agricultural Research and Development Center scientists have found success
in using the technique to improve tomato cultivars. As a result of the
research, three promising rootstocks have been identified that could add to the
few commercial rootstocks currently available and expand tomato grafting into
such markets as organic and high tunnel tomato production.

“Rootstock breeding
programs are aimed at big producers, specifically for the hydroponic vegetable
market. There are several rootstocks on the market, but really only two that
are considered commercial standards,” said David Francis, an OARDC geneticist.
“Our research was aimed at soil-based production, either open field or high
tunnel, and targeted organic farms due to the high value of the produce. The
results of the research potentially will give growers interested in grafting
more rootstock choices.”

Francis bred 46
rootstocks by cross pollination of cultivated and wild tomato species and found
that three rootstocks show promise in carrying traits for field performance,
such as yield or disease resistance, while producing a desirable, marketable
fruit.

“The idea behind
developing rootstocks is to produce a plant that has more vigor than the
typical tomato, while not losing the fruit characteristics that consumers
like,” said Francis. “We were looking for a rootstock that performs
consistently better than the non-grafted plant as well as the commercial
rootstock standards.”

Francis said that when
it comes to rootstock breeding, the key to hybrid vigor rests with the parents
selected for crossing.

“The further away in
genetic relationship the parents are, the more vigorous the plants tend to be,”
said Francis. “That is, two cultivated plants with similar genetic backgrounds
will be less vigorous than a cultivated plant crossed to a wild species.” In
fact, the three rootstocks that performed the best were all crosses between a
wild South American species and a domesticated tomato.

The rootstock breeding
research is just one part of a larger grafting project to improve efficiency
and productivity in the tomato industry, which was valued at $67.5 million in
Ohio last year.

With the 46 rootstocks,
Francis was looking for such characteristics as seed size, uniformity of
germination, high yields, fruit quality, disease resistance, drought tolerance
and fruit size. Ten were eliminated due to poor seed characteristics.

“Of the 36 rootstocks
that advanced to the field, we came up with a list of nine that we thought were
acceptable in terms of those characteristics, especially yield and quality, but
ended up eliminating six of them because they didn’t graft as well as we would
have liked,” said Francis. “Certain combinations just don’t graft well.”

After two years of
promising results from the three chosen rootstocks, researchers hope to get at
least one more year of data from various field locations across the nation
before recommending the rootstocks for commercial production.

“If these rootstocks are
successful, commercializing them will definitely give growers more choices,
especially in an organic production system,” said Francis. “One of the
limitations in organic tomato production is weak uptake of nutrients. More
vigorous rootstocks can improve the production of quality fruit.”

Francis said he also
sees new commercial rootstocks improving organic tomato production from a
disease standpoint.

“Growers’ preferred
varieties are sometimes heirloom cultivars – old varieties that have very
little natural resistance to diseases,” said Francis. “There isn’t as strong an
effect when a rootstock is grafted to a hardy scion, but you graft a rootstock
to a weak scion and you definitely see an improvement in performance.
Resistance to soil-borne diseases and extra vigor helps the plant to stay
healthy and that has an impact on overall quality of the crop.”

For more information on
grafting, log on to http://oardc.osu.edu/graftingtomato/graft.htm.