Cucurbit Genetics Cooperative Report 8:7-8 (Article 3) 1985
A.P.M. den Nijs and I.W. Boukema
Institute for Horticultural Plant Breeding (IVT), P.O. Box 16, 6700 AA Wageningen, The Netherlands
During a visit of the first author to the Ukrainian Research Institute of Vegetable Gardening in Charkov, USSR, Dr. M.C. Efimov demonstrated the use of the ‘short petiole’ recessive character for marking maternal lines in hybrid pickling cucumber seed production. Because of its expected value in linkage studies, seed was requested, and Dr. Efimov generously supplied us with some seeds of the mutant line ‘1753’ through the N.I. Vavilov All Union Institute of Plant Industry in Leningrad.
Because this mutant has not yet been described, we present here some data on its morphology, genetic basis and first results of linkage studies. The petioles of the first true leaves of the mutant are very short (1 to 2 cm) (Table 1) and the leaf blade smoothly narrows to the petiole. The later leaves usually also have petioles shorter than normal. The effect of the mutant can be distinguished clearly in the seedling stage by judging the first true leaves. There also appears to be an effect of the mutant on stem elongation, since especially under winter light conditions the internodes below the first and usually the second true leaf don’t develop, resulting in an opposite arrangement of the first leaves. Differences occurred in vigor and fertility of the mutant plants, so we selected a typical fertile individual for crosses with other marker lines.
Results of our crosses to date with the mutant corroborate Efimov’s information, that the character is governed by a single, completely-recessive gene. This is illustrated by the segregation of the F2 progeny of a cross between our short petiole line and a glabrous (gl) line. The monohybrid ratio for the short petiole character in this cross was 267 : 83 (x2 = 0.31, 0.5 < p < 0.7). In a different cross with a compact (cp) line we obtained 258 : 92 (x2 = 0.31, 0.5 < p < 0.7). On the basis of this evidence we officially propose the designation short petiole for Efimov’s mutant, symbol sp. The dihybrid ratio obtained in the above-mentioned F2 of the cross sp x gl was 194 : 73 : 69 : 14 (X2 = 3.90, 0.2 < p < 0.3). This perfect fit to the expected ratio demonstrates that sp and gl are independent from each other. We obtained dihybrid ratios in F2s of the cross sp x cp and also of cross sp x lh (long hypocotyl), which clearly did not fit the expected ratio of 9 : 3 : 3 : 1, but we are not ready to conclude linkage because we surmise that the expression of these genes may interact with that of sp. This will be the subject of further study. Crosses of sp with other marker lines are in progress.
Table 1. Petiole length (cm) of the first four true leaves of mutant and normal plants segregating for the short petiole (sp) gene tested in summer, 1983.
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Leaf node |
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|
Genotype |
1 |
2 |
3 |
4 |
|
sp sp |
1.9 |
1.8 |
6.7 |
3.2 |
|
Sp sp |
15.0 |
14.2 |
16.2 |
16.1 |
|
Sp Sp |
15.2 |
15.9 |
17.6 |
17.8 |
|
sp sp as percent of Sp- |
21 |
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