Further Results of Linkage Studies in Cucumis sativus L.

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Cucurbit Genetics Cooperative Report 9:55 (article 16) 1986

Zijlstra, S. and A.P.M. den Nijs
Institute for Horticultural Plant Breeding (IVT), and Foundation for Agricultural Plant Breeding (SVP); POB 16, 6700 AA Wageningen, the Netherlands

Following earlier research (1). linkage studies for 5 pairs of genes have been continued at the Institute for Horticultural Plant Breeding (OVT). Involved here were the marker genes short petiole (sp), little leaf (11), glabrous (gl), compact (cp), umbrella leaf (ul), and long hypocotyl (lh). The mutants are designated as in the list in the 1985 CGC report.

The 3 pairs sp/11, gl/11, and sp/cp segregated independently (Table 1). Although the number of F2 plants was small for the pair sp/11 the chi-square values were low for both the monogenic segregation and the digenic segregation (linkage test). The F2 population from the pair gl/11 had too many individuals of the gl genotype but the X23 in the test of independence was satisfactorily low. The X23 in the combination of sp and cp indicated a very good fit to independent segregation.

A weak linkage was found between the genes sp and ul. The recombination percentage was calculated as 36%. However, this result should be considered with caution, because during the winter season, when the test was done, it is hard to distinguish between normal and umbrella leaf (ul). There were too many plants of the ul genotype in the F2 population. A strong linkage was calculated for the gene pair sp/lh. The recombination percentage was 18%.

It is remarkable that, of all the gene loci studied, only a few are in the same linkage group. The localization of the genes is to be continued.

Table 1: Segregation and size (N) of F2 populations for linkage test, recombination percentage and calculated chi-square ratio for the 9″3″3″1 ratio (X2) for5 pairs of genes.

Gene pair

Segregation
++
+-
=
—

N

%

X23
sp/11 73 23 16 124 50 50 2.95*
gl/11 79 25 49 162 50 50 1.16*
sp/cp 145 38 56 257 50 50 0.45*
sp/ul 97 81 47 239 36 36 8.73
sp/lh 131 54 47 245 18 18 69.24
*Significant at P = 0.05

Literature Cited

  1. Nijs, A.P.M. den and T.W. Boukema. 1983. Results of linkage studies and the need for a cooperative effort to map the cucumber genome. Cucurbit Genetics Coop. Rpt. 6: 22-23.