UNITED STATES DEPARTMENT OF AGRICULTURE
AGRICULTURAL RESEARCH SERVICE
WASHINGTON, D.C.  20250

with

THE ARKANSAS AGRICULTURAL EXPERIMENT STATION
FAYETTEVILLE, ARKANSAS  72701

and

WISCONSIN AGRICULTURAL EXPERIMENT STATION
MADISON, WISCONSIN  53706

RELEASE OF WISCONSIN WILD PETALOID MALE STERILE
CARROT CYTOPLASM

The Agricultural Research Service, United States Department of Agriculture, the
Arkansas Agricultural Experiment Station and the Wisconsin Agricultural Experiment
Station, announce the release of a Wisconsin Wild petaloid male sterile carrot cytoplasm.

Cytoplasmic diversity has been considered to be a desirable attribute in the production of
F₁ hybrids ever since the southern corn leaf blight epidemic two decades ago. Even
though most breeders agree with this concept, the vast majority of carrot hybrids
produced in the United States are in one cytoplasm, i.e., the Cornell cytoplasm. For this
reason, the Agricultural Research Service, with cooperating Experiment Stations,
announces the release of the Wisconsin Wild cytoplasm.

Wisconsin cytoplasm was derived from a small population of petaloid male sterile wild
carrots found growing near Madison, Wisconsin in the summer of 1970. This population
of wild carrots was examined because of the unusual pale pink color of the flowering
umbels. Closer examination of individual flowers revealed that they were petaloid male
sterile and were phenotypically very similar to petaloid male sterile produced by the
Cornell cytoplasm.

Four sterile plants were recovered by digging and keeping the root-ball intact. Individual
plants were then transplanted into 20 cm pots and placed in an air-conditioned
greenhouse. The best survivor of transplanting was then caged with a bouquet of flowers
from the inbred MSU 5931M, a maintainer of sterility in the Cornell cytoplasm. The
pollen source was kept in water and periodically replaced to insure an adequate
continuous supply. The F₁ seed were sown in the field at two locations; in muck soil at
Palmyra, Wisconsin and in mineral soil at Madison, Wisconsin. The F₁ roots, easily
identified by their white color and exceptional vigor, were planted in the greenhouse after
cold induction. Backcrosses were made to MSU 5931M and outcrosses to MSU 9541M,
MSU 2710M, and MSU 10374M, all inbred maintainers of petaloid sterility in the
Cornell cytoplasm. Progenies of these crosses were grown at Palmyra in 1972 and the
vernalized roots were planted in the greenhouse in November. Populations of all

crosses were classified for sterility and were backcrossed to the appropriate recurrent
parent.

All of the 43 F₁ plants from the cross, Wisconsin Wild x MSU 5931, were petaloid with
no anther-like structures. Seventy-five BC₁ plants to MSU 5931M, grown in the
greenhouse in the winter of 1972, were petaloid (Table 1) and sterile.

Progenies from crosses to other petaloid maintainers (Wisconsin Wild x MSU 5931M) F₁
x MSU 2710M, (Wisconsin Wild x MSU 5931M) F1 x MSU 9541M and (Wisconsin
Wild x MSU 5931M) F₁ x MSU 10374M were all completely petaloid. These three
crosses could be considered BC₁ progeny with respect to maintenance, since they are all
maintainers for the Cornell petaloid. If we look at the progenies in this light, it is
possible to consider these crosses together. This combined BC₁ population of 270 plants
(Table 1) consisted of all petaloid steriles providing good evidence that petaloid sterility
is maintained in the Wisconsin Wild cytoplasm by the same genotypes that maintain
petaloidy in the Cornell cytoplasm.

The cross to the MSU 670C line, a known restorer of Cornell sterility, produced nine
male-sterile plants and one male-fertile plant. This indicated that fertility in Wisconsin
Wild cytoplasm can be restored by the same genotypes as those that restore in the Cornell
cytoplasm. Based on these data, we conclude that behavior of the new cytoplasm is
similar, if not identical, to the Cornell source with regard to petaloid sterility. No data
were secured on other effects of this new source of cytoplasm.

Table 1. Maintenance of Wisconsin Wild Petaloid Male Sterility by Cornell Maintainers

The individual florets produced by the Wisconsin cytoplasm appear phenotypically
identical to those produced by the Cornell cytoplasm. Individual florets have anthers
replaced by petal-like structures that produce no pollen, thereby producing 100% male
sterility in the primary and high order umbels. The sterility appears to be maintained or
restored by the same maintainers or restorers as the Cornell cytoplasm.

Inquiry regarding seed availability for the Wisconsin cytoplasm should be directed to
P.W. Simon, USDA, ARS, Department of Horticulture, 1575 Linden Drive, University of
Wisconsin, Madison, WI 53706.

When this germplasm contributes to a new cultivar, it is requested that appropriate
recognition be given to its source.