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percentage of fruit in larger size classes
than those produced by the nongrafted
scion varieties. Averaged over
all our trials, the differences in fruit
size distribution between grafted and
non-grafted were fairly small. In some
trials, however, plants on vigorous
rootstocks did have larger fruit. Some
published studies provide measures of
fruit quality, such as dissolved sugars,
pH, total dissolved solids, vitamin C,
lycopene, or even “taste-test” data.
Those studies indicate that the quality
of fruit from grafted plants seems to be
slightly inferior to fruit from the nongrafted
plants, though still commercially
acceptable. Our field trials focused on
yields, and we did not measure any
fruit quality data. However, we did
not notice any fruit defect problems in
grafted vines. Also, in 2018 we did cut
open both red and mature green fruit at
harvest to make sure that there were no
problems inside the fruit.
Variability From Trial to Trial or
Field to Field
A study in Florida with determinant
type cultivars has shown yield
increases of 25 to 42 percent using
certain rootstocks, but year-to-year
variability also increased as compared
to non-grafted plants. This variation
underscores the importance of
considering variable outcomes to
determine the feasibility of grafted
tomatoes here. Some fields will likely
benefit more from grafting than others,
and this may not always be predictable
in advance.
Economics
Costs of field establishment are
increased significantly with grafting.
Material costs for transplanting (seed
plus nursery costs) alone might be
$2,000 per acre or higher or more
than with conventional transplants.
However, we don’t yet really know what
the costs might be if this were adopted
commercially in California, so our plant
costs are based on small volume sales
prices. If we assume a cost of $0.40 per
grafted plant, then a yield increase of
19 percent at a market price of $6.55
per 25-pound box would pay for the
increased plant cost.
On-going and Future Work
Scion Cultivars
(Trial Years)
‘Bobcat’ (2016) ‘DRO137TX’ (2016-18)
‘Dixie Red’ (2016) ‘Maxifort’ (2016-18)
*‘Galilea’ (2016) ‘Arnold’ (2018)
‘HM 1794’ (2016-18) ‘Guardior’ (2018)
‘Quali T 27’ (2017-18) ‘Estamino’ (2018)
‘Quali T 47’ (2017-18)
‘Quali T 99’ (2017-18)
Other research projects looking
at grafting tomatoes are being
conducted in California. A United
States Department of Agriculture
(USDA)-funded project with
processing tomatoes is underway with
collaboration of Gene Miyao, UCCE
Yolo, Solano and Sacramento counties,
Zheng Wang, UCCE Stanislaus County
and myself, in addition to proprietary
research being conducted by the
industry. Rootstocks for heirloom
tomato production are being evaluated
by Margaret Lloyd, small farms advisor
with UCCE in Yolo, Solano and
Sacramento counties.
Acknowledgements
The California Department of Pesticide
Regulation provided partial funding
for this project but does not necessarily
agree with any opinions expressed, nor
endorse any commercial product or
trade name mentioned. In addition,
this project was supported by the
Specialty Crop Block Grant Program
at the U.S. Department of Agriculture
through Grant 14-SCBGP-CA-0006.
The contents of this report are solely
the responsibility of the authors and
do not necessarily represent the official
views of the USDA. We also thank
our grower-cooperators (Live Oak
Farms and Pacific Triple E), Growers
Transplanting Inc. for producing grafted
Rootstock Cultivars
(Trial Years)
Non-grafted Control
Table 2. Scion and rootstock cultivars used in our field trials.
*Note: Galilea is a roma/saladette type, while the other seven cultivars are all round types; all
but Dixie Red were developed for the Western U.S. mature green production system.
plants, and the following companies
that supplied the seeds: Monsanto/De
Ruiter Seeds, Gowan Seed Company,
Harris Moran Seed Company, and
Syngenta Vegetable Seeds.
For More Information
Additional information on our field
trials:
https://ucanr.edu/sites/veg_crop_sjc/
Grafted_tomatoes/
Detailed information on how to
undertake vegetable grafting is available
at: http://www.vegetablegrafting.org/
resources/grafting-manual/
List of tomato rootstocks including
disease resistances and where to order
seed: http://www.vegetablegrafting.org/
resources/rootstock-tables/solanaceousrootstock-table/
Comments about this article? We want
to hear from you. Feel free to email us at
article@jcsmarketinginc.com
22 Progressive Crop Consultant May/June 2019