February 2021 - 5

PEACH
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rootstock for Florida's ridge area would
be a deep-rooted plant, well-equipped
for drawing nutrients out of the sandy
soils - Chaparro calls them ancient sand
dunes - that drain so well. The Indian
River area, on the other hand, has " an
organic hard pan " that frequently fills
with water, flooding orchards. Indian
River trees are typically planted in
raised beds that are two trees wide, with
drainage ditches between the beds. The
flooding in the Indian River area would
lend itself to a rootstock with shallower
root system.
" We want vigorous systems in both
soil types, " Lesmes-Vesga said.
Genetic work
Lesmes-Vesga's research work involves
phenotyping peach root systems to
identify root systems adapted to the two
different soil regions. Chaparro, one of
the scientists overseeing Lesmes-Vesga's
work, said research is looking at the
root architecture of the various genetic
variations.
" We are evaluating peach relatives
such as almond (prunus dulcis) and
gansu peach (p. kansuensis) and more
distantly related species like bullace
plum (p. umbellata), Chickasaw plum
(p. angustifolia) and myrobolan plum
(p. ceracifera), " Lesmes-Vesga said.
His work also includes looking at
different fruit-bearing cultivars for
scions.
Right now, " basically, most of the
cultivated peach varieties in Florida are
low-chill. The most popular subtropical
varieties are the non-melting flesh
'UFSun,' 'UFBest' and the melting flesh
cultivar 'TropicBeauty,' " he said.
At IRREC, Lesmes-Vesga works at both
the laboratory and greenhouse since he
works with seedlings year-round. During
the cool months, red lights simulate
daylight to prevent the trees from going
dormant. Cuttings from the nursery
trees are rooted inside aeroponics
systems and stimulated with rooting
hormones.
" New rootstock and scion breeding
selections are made every year and
undergo tests to determine their
commercial viability, " he said.
" Rootstock testing requires a significant
investment of time and effort to
ensure that there are no major flaws in
germplasm nearing release. We expect
to release additional low chill peach
scion cultivars in the near future and
rootstocks at a later time. "
Implications elsewhere
Florida peach growing is much
different than other regions because of
the low-chill cultivars used, Chaparro
said. The ridge area in central Florida
is sub-tropical in climate, and the
peach varieties grow best with a
minimal number of chill hours - just
Dr. Jose X. Chaparro cooperates closely
with the USDA-ARS stonefruit rootstock
breeding program at Byron, Georgia
and we test some of their advanced
selections for nematode resistance on
site. However, we are also breeding lower
chill rootstocks for subtropical peach
production in Florida. "
Importance of investment
The hours of careful research in the
lab and greenhouse informs the peach
breeding program.
New rootstocks and scions bred by
The differences in root systems between
two peach rootstock cultivars in trials at
the University of Florida.
150-250. However, some of the other
cultivars in the Indian River area are less
low-chill, operating with about 50-150
chill hours.
" It is unlikely that a rootstock under
Florida conditions will be adapted
to high chill peach production areas,
Lesmes-Vesga said. " However, moderate
chill rootstocks with broad spectrum
root knot nematode resistance should
be useful in other moderate chill
locations with acidic soils such as
southern Georgia, Alabama, Mississippi
and Texas. Some of our germplasm is
currently under test in California.
" The stone fruit breeding program
at the University of Florida headed by
Chaparro are hoped to increase Florida's
peach production range, improve the
commercial trees' performance and
help Florida's stone fruit growers stay
profitable.
For Florida to get to its current
stage required decades of investment.
Chaparro is the state's third peach tree
breeder. After the state first launched
its breeding program in 1952, it was 24
years until the first commercial-quality
variety, Flordaprince, was released. The
program has focused on non-melting
flesh peaches with improved shipping
quality.
While his research continues,
Chaparro said he's concerned that
universities across the country have
lost fruit tree breeders since the 1980s
simply through attrition.
" We need more rootstock breeders, "
Chaparro said. " The number of
programs nationwide is significantly
lower. " FGN
FGN | FEBRUARY 2021 | 5
February 2021

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