Cucurbit Genetics Cooperative Report 10:33-34 (article 20) 1987
Inheritance of Littleleaf and Multi-branched Plant
Type in Cucumber
Todd C. Wehner
Department of Horticultural Science, North Carolina State University, Raleigh,
Jack E. Staub and Clinton E. Peterson
Department of Horticulture, U.S.D.A., University of Wisconsin, Madison,
Little-leaf is a plant type discovered in an inbred selection in Arkansas.
Goode et al. (1) reported that the F1 of several
crosses was normal, and the F2 (resulting from self-pollination
of the F1) segregated in a ratio which suggested a 3:1. It has
leaves, stems and flowers smaller than normal, and multi-branched vines.
The multi-branched habit is similar to the Cucumis sativus var. hardwickii
line, LJ 90430. The Goode et al. little-leaf line ('Little
John') holds up better than normal leaf lines such as 'Calypso' under the
rough treatment they receive during multiple harvest. It also seems to grow
better than the normal cultivars under dry or windy conditions. That is
at least partly due to the small, tough leaves on the plant.
Breeders are using the new plant type to incorporate the small leaf habit
and/or the multi-branched habit into commercially acceptable lines. Although
it appears to be a single-gene mutant, and the symbol ll has been
used as a symbol to represent the trait (2), no inheritance data have been
published. The objective of this study was to determine the inheritance
of the two most important traits of 'little-leaf', small leaves, and multi-branched
Methods. 'Little John' was crossed as the paternal parent to 'Wisconsin 2757' and the F1 were self-pollinated and backcrossed to each
parent to form 6 generations for testing: Pa (WI 2757), Pb (Little John),
F1, F2 BC1Pa, and BC1Pb. The
6 generations were tested in the field at Hancock, Wisconsin in the summer,
1986 using randomized, replicated and coded treatments to prevent bias during
evaluation. Data were checked for fit to the expected 3:1 ratio using a
Chi-square analysis. The multi-branched data were coded such that 0 to 2
= few, and 3 to 5 = many branches. Branching was also evaluated using generation
variances where phenotypic = F2 variance, and additive = 2(F2)-
(BC1Pa)-(BC1Pb) variances. Narrow-sense heritability
was calculated as additive/phenotypic variance.
Results. Multi-branched habit did not follow any single-gene inheritance
pattern we could determine. It must, therefore, be considered a quantitative
trait. Unfortunately, heritability of multi-branch was approximately 0 using
generation variances. In the cross of two other inbreds (data not shown)
the heritability was 0.61, but the data from several crosses we have studied
is extremely variable.
On the other hand, the littleleaf trait of 'Little John' is controlled
by a single recessive gene (Table 1). Some of the plants were misclassified
(see, for example, the F1 data) due to environmental variability
for leaf size. Thus, littleleaf can be considered a good marker, already
named ll, where 'Little John' carries the recessive mutant allele,
and WI 2757 (as well as most other cucumber lines) carries the dominant, wild-type
Table 1. Inheritance of littleleaf trait (ll) in the cross of
'WI 2757' (Pa) x 'Little John' (Pb).
- Goode, M.J., J.L. Bowers and A. Bassi, Jr. 1980. Little-leaf, a new
kind of pickling cucumber plant. Arkansas Farm Res. 29:4.
- Zijlstra, S. and A.P.M. den Nijs. 1986. Further results of linkage
studies in Cucumis sativus L. Cucurbit Genet. Coop. Rpt. 9:55.