Cucurbit Genetics Cooperative Report 7:100-101 (article
Monogenic Inheritance of Andromonoecy in Tetraploid Cucumis
ficifolius A. Rich
Visser, D.L. and A.P.M. den Nijs
Institute for Horticultural Plant Breeding (IVT), P.O.B. 16, 6700
AA Wageningen, The Netherlands
Spontaneous fruit and seed set was observed in one out of ten
plants of Cucumis ficifolius A. Rich (Genebanknumber 2061,
IVT collection from Kenya), grown under isolation in an insect
proof glasshouse in the summer of 1981. Under our conditions
this monoecious wild species normally sets fruit only after
artificial pollination. The single exceptional plant was selfed
and used as pollen parent in crosses with several sibs of the
Thirty plants of a progeny obtained after selfing were examined
in 1982, and all possessed perfect flowers in addition to
staminate ones, so they were andromonoecious. Fruits set
following inadvertent self pollinations contained on average 35
seeds. Not a single pistillate flower was observed on any of the
30 plants. All 27 plants of a progeny of a sib cross were
monoecious, as was the selfed progeny of the monoecious female
parent of this cross. The andromonoecious character thus
appeared to be a recessive mutant character.
To investigate the inheritance of the trait, three monoecious
plants of the sib cross were selfed and backcrossed with
andromonoecious plants out of the self progeny of the putative
The resulting offspring was classified for sex expression, shown
in Table 1. From the results it can be concluded that a single
recessive gene governs andromonoecy in this species. We propose
to designate the gene: andromonoecy, symbol a. This
symbol is the same as in melon and watermelon, whereas in
cucumber the symbol m has been given priority (2).
Table 1. Segregation of andromonoecious sextype in crosses in C.
Number of plants
F2 (monoecious x andromonoecious)
(monoecious x andromonoecious) x andromonoecious
Counting of metaphase plates in root tips revealed 48 chromosomes
in accession Gbn 2061, so it is a tetraploid like almost all
accessions of C. ficifolius in our collection (Kroon,
unpublished results). The apparently disomic inheritance of gene a testifies to the allotetraploid nature of the species.
Meiotic chromosome studies of related tetraploid species revealed
allotetraploidy (1), but no genetic segregation data have so far
been presented to support this conclusion.
Monoecy is the prevalent sex expression in the genus Cucumis, C. melo excepted, and we have never before
observed andromonoecy in any wild species of our collection.
Rosa (3) considered monoecy as primitive in C. melo, from
which the andromonoecious condition of the cultivated melons
evolved. Our finding of one andromonoecious individual in one
out of nine accessions of C. ficifolius presents another
case of parallel evolution in the sex expression of the
- Dane, F. and T. Tsuchiya. 1979. Meiotic chromosome and pollen
morphological studies of polyploid Cucumis species. Euphytica
- Robinson, R.W., H.M. Munger, T.W. Whitaker and G.W. Bohn. 1976.
Genes of the Cucurbitaceae. HortScience 11:554-568.
- Rosa, J.T. 1928. The inheritance of flower types in Cucumis and Citrullus. Hilgardia 3:233-250.