Regeneration of dihaploid chicory (Cichorium intybus L. var. foliosum Hegi) via microspore culture

In order to develop fully inbred chicory plants, dihaploid plants were raised from callus derived from microspores of three selected Witloof, Robin and Treviso types. Microspores were isolated from florets containing pollen at the uninuclear state and cultured in a modified MS medium plus 0.5mg/l 2,4-D, 0.5mg/l IAA and 2.0mg/l zeatin. During culture periods of up to 6 months, gametoplasts emerged from pollen grains, divided and started to form colonies and calli. These were subcultured on the same basal medium supplemented with 0.5mg/l BA and 0.5mg/l IAA. Shoot growth was enhanced on a low salt-containing medium supplemented with 0.4mg/l kinetin and 0.2mg/l IAA. Shoots were rooted on a half-strength Lepoivre medium plus 0.2mg/l IBA and finally transferred to soil. Florets were excised from 34 capitula, but only microspores from four of them developed into plants via callus. More than 450 plants were raised in the greenhouse and the field. Leaves from these plants were subjected to DNA fluorescence analysis via flow cytometry: a range of ploidy levels was detected. The cell composition of 44 of these plants was predominantly haploid, with a diploid background. Regenerant plant phenotypes were compared with the parent genotypes. The value of such haploids in commercial chicory breeding is discussed.