A comparative study on rooting of in vitro regenerated shoots in haploid, diploid and tetraploid purple coneflower (Echinacea purpurea L.)

Abstract

Haploid, diploid and tetraploid shoots of Echinacea purpurea L. sharing the same genome were cultured in medium and their rooting response to the composition of the culture medium was investigated. It was found that in medium without growth regulators, haploid shoots could initiate roots quite efficiently with the shortest time required for the emergence of roots and with the highest rooting rate; the response of the diploids was similar to that of the haploids and largely different from that of the tetraploids. The tetraploids obviously required longer time for the initiation of roots and had the lowest rooting rate. Supplementing the medium with 0.05 and 0.15 mg/L naphthaleneacetic acid or 0.1 and 0.3 mg/L indole-3-butyric acid (IBA) had little positive effect on the rooting of diploid shoots and, in some cases, had even negative effect on the rooting of haploid shoots, but enhanced effectively the rooting of the tetraploid shoots. By supplementing the medium with 0.3 mg/L IBA, the time required for the emergence of roots from the tetraploid shoots was shortened and the rooting rate was increased largely. As a result, healthy tetraploid plantlets with fully developed root system could be efficiently propagated.

Keywords

• Purple coneflower
• tissue culture
• haploid
• diploid
• tetraploid
• rooting