Development of amylose-free (amf) monoploid potatoes as new basic materialfor mutation breeding in vitro

For the induction and selection of double mutants with altered starch compo sition, a uniform (homohistont) amylose-free (amf) monoploid as basic plant is of vital importance. Therefore, new amf monoploids had to be developed via prickle pollination. And 26 monoploids were obtained which were screene d in vitro for vigour, leaf size and for the percentage of monoploid cells. The number of monoploid cells was underestimated at about 28%. Seven vigor ous monoploids were tested in vitro for tuberization capacity, which varied from 0 to 100%. After regeneration in vitro, 0 to 3.7 adventitious shoots per leaf explant were formed. The tuberization capacity of these shoots Var ied from 0 to 48. Two amf monoploids were selected which were vigorous and tuberized well in vitro. They are the basis for the application of an in vi tro mutation breeding protocol that should lead to the induction and select ion of new starch mutants in potato.