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Cucurbit Genetics Cooperative Report 3:52-54 (article 31) 1980

In Vivo Pollen Tube Growth as a Measure of Interspecific Incongruity in Cucumis L.

Y.O. Kho, A.P.M. den Nijs and J. Franken

Institute for Horticultural Plant Breeding, Wageningen, the Netherlands

Pollen tube growth in the style was studied in a diallel involving ten African species of Cucumis as well as C. sativus L. Several workers have studied interspecific relationships within the genus by assessing fruit and seed set and fertility of hybrid offspring. The present work extends this knowledge to the location of the barriers to pollen tube growth in the stigma, style and ovary. Moreover, almost all species in this study were represented by several accessions so that some insight was gained in intra-specific variability with respect to crossability. All accessions were identified taxonomically and are listed with their author.

For each combination in each year at least three flowers (and mostly a larger number) were pollinated. Pollen tube behavior was examined by UV microscopy of flowers three days after pollination.

Plants were grown in the summer in a glasshouse (25°C D/18°C N). Almost all crosses were repeated in three consecutive seasons. As there were no great discrepancies among the results in the different years, we combined all data. All species were monoecious except the cultivated melons. Only monoecious feral melons (type agrestis) were employed as female parent to avoid ambiguities due to emasculation. In most species the different accessions (Genebank numbers, Gbn) behaved similarly, so the results were pooled per species. Notable exceptions are C. sativus with five accessions and C. anguria with three. Four accessions of C. sativus can be tentatively designated as primitive or hardwickii-types. The fifth is C. sativus var. sikkimensis. The results of our investigation are in Table 1. For explanation of the figures, see the legends of the table. Some of the conclusions are as follows:

  1. Selfing pollinations and intraspecific crosses result in good penetration of pollen tubes into numerous ovules of all species.
  2. Part of the African species appear congruous.
  3. Cucumis myriocarpus and C. ficifolius appear unilaterally incongruous with most representatives of the African group. Cucumis myriocarpus, when used as a staminate parent, gives better results than in reciprocal crosses whereas with C. ficifolius, the reverse is true.
  4. Cucumis metuliferus is strictly separated from most of its relatives.
  5. All accessions of C. sativus are, to some extent, mutually congruous though not as fully as might be expected of a single species. There is even evidence for unilateral incongruity.
  6. Combinations between C. sativus and any of the African species exhibited restricted pollen tube growth, except several crosses of C. sativus x C. melo. The reciprocals of these crosses do not allow tube growth.
  7. Of all african species tested, C. melo appeared to be most promising for use as a bridge between several species with resistances and C. sativus.

More intensive investigations of the most useful combinations are in progress. More detailed results (a.o. on identification, variation between accessions, fruit and seed set, embryo culture, nature and fertility of obtained hybrids) will be published shortly.

Table 1. Pollen tube (p.t.) growth in the style in interspecific crosses in Cucumis L.

 

 

Male Parent

 

Female Parent

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

1

Cucumis africanus L.f., Gbn. 0162.0181.0330

4

3(4)

3(4)

3(4)

3(4)

2

2(3)

3(4)

4

1(2)

1(2)

1

2

1(2)

1(2)

2

2

C. anguria L., Gbn 0307.0310

3(4)

4

4

4

2

 

2

4

4

2

3(4)

1

2

2

2

2

3

C. anguria L., Gbn. 1758

2

4

4

 

 

1

1

2

4

1

1

1

1

2

 

 

4

C. myriocarpus Naud., Gbn. 0182.1776

2(3)

2

1

4

1

1

1

2

1

1

1

1

1

1

1

1

5

C. zeyheri Sond., Gbn. 1053

4

3(4)

2

3(4)

4

3

3

3(4)

4

1

2(3)

1

1

1(2)

 

1(2)

6

C. figarei Naud., Gbn 1707

3

 

1

3(4)

 

4

3

3

3

3

2

2

2(3)

2

2(3)

3

7

C. ficifolius A, Rich., Gbn. 1729

4

4

4

4

4

3(4)

4

4

4

3

2(3)

2

2

2

3

2

8

C. dipsaceus Spach., Gbn. 0163

4

3

 

4

4

3

3

4

4

3

2(3)

1

2

1

3

1

9

C. prophetarum L., Gbn. 1751

3

4

4

3

1

1

1

1

4

1

1

1

1

1

0(1)

0(1)

10

C. metuliferus Naud., Gbn. 0164.1734.1747

2

1

2

2

3

1(2)

1

2

2

4

2

2

2

2

2

2

11

C. melo L., Gbn. 0309.1777.1717

1

1

1

1

0(1)

1

1

0(1)

0(1)

1

4

0

1

0(1)

0(1)

1

12

C. sativus L., Gbn. 1739

1

1

 

1

 

0

1

0(1)

2

1

1

4

1

1

1

1

13

Gbn. 1811

3

1

1

1

1

0(1)

1

 

1

1

3

3

4

4

 

4

14

Gbn. 0777

3

3

2

2

3

1

1

1

 

1

4

3

3

4

4

4

15

Gbn. 1753

2(3)

0(1)

 

1(2)

3

1

1

1

3

1

3

3

 

4

4

3

16

Var. sikkimensis Hook.

2

1

1

2(3)

1(2)

0(1)

1

1

1

1

3

3

3

3

4

4

Legends: 0 = no p.t. in stigma; 1 = p.t. in stigma; p.t. in style; 3 = p.t. in ovary; 4 = p.t. in ovule; ( ) a few pollen tubes.

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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 23 October, 2009