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ISHS Acta Horticulturae 555: II International Symposium on Edible Alliaceae

PRESENT STATUS OF HAPLOID INDUCTION IN ONION: ANALYSIS OF PROCEDURE AND ITS LIMITATIONS

Authors:   B. Bohanec, M. Jakse, B. Javornik
Keywords:   Allium cepa, gynogenesis, chromosome doubling, colchicine, oryzalin
DOI:   10.17660/ActaHortic.2001.555.10
Abstract:
Gynogenic haploid induction in onion has been known since 1989, and recent research in our laboratory has been focused on studies related to improving haploid induction techniques, genetic determination of homozygosity and ploidy of regenerants, optimization of diploidization techniques and genetic analysis of haploid plants. We concluded that the technique of culturing ovaries or whole flowers is superior to ovule culture and that one step flower culture requires a significantly lower level of manpower for similar induction efficiency. Haploid induction frequency can be improved by altering media components, using thidiazuron, phenylacetic acid or by solidifying the media with gellan-gum. However, genotype has the major effect on induction frequency. In a recent analysis of 39 different long day accessions, responsiveness from 0 to 22.6 % (4.16% average) was achieved, with individual plant response up to 51.7%. We showed that esterase isozyme system can be efficiently used for determining homozygosity and flow cytometric studies were optimal for determining ploidy level. Gynogenic plants were predominantly haploid, in vitro plantlet treatments with oryzalin (3 days, 10 µM optimum) was more efficient than colchicine treatments. The genetic stability of regenerated plants was analyzed using random amplified polymorphic DNA (RAPD) analysis; most gynogenic lines were completely genetically uniform, with a few exceptions detected, exhibiting novel RAPD bands.

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