Cucurbit Genetics Cooperative Report 10:8 (article 7) 1987
Cordate, a Leaf Shape Gene with Pleiotropic Effects
on Flower Structure and Insect Pollination
R. W. Robinson
Horticultural Sciences Department, New York State Agricultural Experiment
Station, Geneva, NY 14456
Very few leaf shape genes are known for the cucumber. A new cucumber
mutant with distinctive leaf shape was induced by thermal neutron radiation
of seed of the cultivar Lemon. Leaves of the mutant have a cordate, nearly
round shape with revolute margins and no serration. It is easily recognized
at the first true leaf stage and at any later stage of development.
The mutant is late to flower and its open pollinated flowers usually
have reduced fruit set. The open pollinated fruit are often parthenocarpic,
although hand pollinated flowers can have good fruit and seed set. The short
calyx segments of the mutant tightly clasp the corolla, preventing it from
opening fully, thereby restricting insect pollination and reducing fruit
set until the plant develops to the stage that parthenocarpic fruit form.
In view of its induction by radiation, the mutant may represent a small
deletion or other chromosomal aberration, but it is inherited as a single
gene with disturbed segregation. Cordate-leaved plants breed true when selfed.
Hybrids of normal x cordate are nearly normal in appearance, but have reduced
leaf lobing. Fewer than 25% cordate individuals occurred in most but not
all F2 populations, the combined segregation data being 616 normal:
155 cordate (p for 3:1 = 0.1-.001). The symbol cor, for cordate,
is assigned to the mutant.
Another cucumber mutant with cordate leaves occurred spontaneously in
Russia. The Russian mutant was not available for allelism tests with cor, but they are presumably different since the Russian mutant was reported
to have normal flower structure and seed production (1)
- Gornitskaya, P. 1967. A spontaneous mutant of cucumber variety Nezhinskii
12. Genetika 3(11):169.