Cucurbit Genetics Cooperative Report 4:56-57 (article 29) 1981
Y. O. Kho, J. Franken and A. P. M. den Nijs
Institute for Horticultural Plant Breeding, P. O. Box 16, Wageningen, The Netherlands
Pollen tube behavior and fertilization in selected crosses between species of Cucumis were studied at different temperatures in glasshouses of the I. V. T. phytotron in the summer season of 1980. This investigation follows the large scale crossability program reported earlier (1). Plants were grown in plastic containers, as this improved flowering. The following cross pollinations were carried out at 20, 23, and 26°C constant: Cucumis sativus (Gbn 1811) x respectively C. melo cv. Gulfstream, C. ficifolius (Gbn 1729) and two accessions of C. metuliferus (Gbn 0164 an Gbn 1802); and C. metuliferus (Gbn 0164 and Gbn 1802) x respectively C. melo cv. Gulfstream and C. sativus (Gbn 1811). For the crosses C. ficifolius (Gbn 1729) x respectively C. sativus (Gbn 1811) and C. melo cv. Gulfstream, pollinations were also made at 17°C constant. Pollen tube growth was examined in vivo by UV microscopy three days after pollination. Fruits were dissected and checked for possible ovule and embryo development, using a binocular microscope.
In general, the pollinations under controlled temperature conditions in the phytotron did not give better results that earlier work in the glasshouse as far as pollen tube growth is concerned. However, to some extent a temperature effect could be noted for three parental combinations which are listed in Table 1. 26°C proved beneficial for pollination and fertilization in C. metuliferus x C. melo. Four fruits were obtained, containing seeds of different size. Globular and heart shape embryos were found in one fruit only. Placed on an agar medium, some embryos developed cotyledons but no growing point. The same cross involving a different accession of C. metuliferus did not reveal any temperature dependence. It may, therefore, be rewarding to test many accessions of C. metuliferus for their crossability in crosses with C. melo.
A temperature effect also appeared to exist for the pollinations on C. ficifolius (Table 1). One fruit was obtained at 20°C following pollination with C. sativus and five and three fruits respectively at 20 and 23°C when C. melo cv. Gulfstream used as pollen parent. The fruits, harvested about five weeks after pollination, only contained seeds without an embryo. The structure of the tissues found in the embryo sacs could often not be determined. Perhaps these seeds were too old, as fruits harvested two weeks after pollination in the cross C. ficifolius x C. melo contained seeds with a small embryo (0.05 mm). These embryos did not develop further when put on an agar medium; larger scale experiments are necessary to decide whether such embryos may or may not be cultured on plantlets.
Table 1. Temperature effect on pollen tube growth and fertilization of 4 different species crosses in Cucumis L.
Cross combination |
Temp (°C) |
Number pollinations |
No. fruit used for UV tests |
Pollen tubes in |
Remarks |
| C. metuliferus (Gbn 0164) x C. melo cv Gulfstream |
20 |
16 |
4 |
style |
no fruit set |
|
23 |
19 |
6 |
style |
no fruit set |
|
|
26 |
21 |
5 |
ovary |
fruits with small globular embryos |
|
| C. metuliferus (Gbn 1802) x C. melo cv Gulfstream |
20 |
31 |
10 |
style |
no fruit set |
|
23 |
29 |
9 |
style |
no fruit set |
|
|
26 |
28 |
12 |
style |
no fruit set |
|
| C. ficifolius (Gbn 1729) x C. sativus (Gbn 1811) |
17 |
15 |
10 |
ovary |
no fruit set |
|
20 |
57 |
19 |
ovary (micropyle)* |
one fruit; not determinable tissues in seeds |
|
|
23 |
49 |
19 |
ovary |
no fruit set |
|
|
26 |
29 |
18 |
style (ovary) |
no fruit set |
|
| C. ficifolius (Gbn 1729) x C. melo cv Gulfstream |
17 |
17 |
10 |
stigma (style) |
no fruit set |
|
20 |
58 |
16 |
style (ovary) |
fruits with determinable tissues in seeds; small embryos in seeds of 14 days old fruits |
|
|
|
23 |
40 |
17 |
micropyle |
fruits with determinable tissues in seeds; small embryos in seeds of 14 days old fruits |
|
26 |
22 |
12 |
ovary |
no fruit set |
*(…) a few pollen tubes.
Literature Cited
- Kho, Y. O., A. P. M. den Nijs and J. Franken. 1980. Interspecific hybridization in Cucumis L. II. The crossability of species, an investigation of in vivo pollen tube growth and seed set. Euphytica 29:661-672.