March 2022 - 10

Pair of muscadines have superior cold tolerance
By Margaret Worthington
and Amanda McWhirt
University of Arkansas
Muscadine cold hardiness was put
to the test during the winter of 2021 in
Arkansas. During the week of Feb. 16,
2021, arctic air moved into parts of the
mid-south and Texas. Temperatures in
Arkansas reached as low as -20° F in the
northern part of the state. Muscadine
production has typically been discouraged
in areas that frequently experience winter
temperatures below 10° F because of
damage to trunks and cordons starting
around 10° F and cane and trunk
mortality occurring at 0° F.
Muscadine buds are quite cold
tolerant, and damage to vascular tissue
ultimately results in cordon and trunk
injury following low temperatures. This
vascular injury is evidenced by common
symptoms like trunk splitting and the
development of aerial roots, which
indicate a break in the plant's " plumbing "
system.
The University of Arkansas Fruit
Research station located in Clarksville,
Arkansas, is on the far northern range
of where muscadines can reliably be
grown in the southeastern U.S. Cold
temperatures at the fruit research
station reached -15° F during February
2021, which allowed us to evaluate cold
hardiness of the muscadine advanced
Image 1. Noble muscadine vine in summer of 2021 at the University of
Arkansas Fruit Research Station in Clarksville, Arizona, showing no symptoms
of cold injury following temperatures of (-)15° F on Feb. 16, 2021.
Photo: Margaret Worthington
selections and cultivars we have planted.
Following this weather event, the
processing muscadine cultivars 'Carlos'
and 'Noble' had little or no evidence of
winter cold injury resulting in cordon
death in Clarksville (Image 1).
This is in contrast to other processing
or fresh-market cultivars that had severe
cold injury to cordons or were killed to the
ground including: 'Black Beauty,' 'Doreen,'
'Fry,' 'Granny Val,' 'Ison,' 'Nesbitt,' 'Southern
Home,' 'Sugargate,' 'Summit,' 'Supreme' and
'Tara.' On cold-injured muscadine vines,
Image 2. Muscadine vine with cordon cracking and
resprouting at the soil line following temperatures of
(-)15° F on Feb. 16, 2021, in Clarksville, Arizona.
Photo: Margaret Worthington
we saw plants resprout from the ground
in some locations and a lack of bud break
higher up the cordons, which indicated
damage occurred during the February
freeze (Images 2 and 3). Many other vines
broke bud normally, but collapsed later
in the season, as transpiration rates and
water requirements increased with rising
temperatures and a developing fruit crop
(Image 4). By contrast 'Carlos' and 'Noble'
went on to produce full crops during the
summer of 2021 (Image 5).
These observations following -15° F
temperatures add new understanding
about the cold hardiness potential of
'Carlos' and 'Noble.' Arkansas fruit
breeders John Clark and Jim Moore
had previously reported several
muscadines surviving temperatures down
to -7° F during the winter of 1989-1990
in Arkansas and North Carolina State
University breeder Ron L. Goldy saw
muscadine vines survive temperatures
down to -9.4° F in the winter of 1984-1985
in North Carolina. By contrast, 100%
of muscadine vines were killed to the
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March 2022

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