Colchicine-induced polyploidy in the azalea cultivar Coral Bells

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Virginia Polytechnic Institute and State University

Lateral buds of the azalea cultivar Coral Bells were treated twice a day on either the second, third, fourth, fifth, or sixth day following the terminal pinch with one of 3 colchicine concentrations (.25%, .5%, .75%). The remaining plants were pinched the same day and the consecutive day treatments were started 2 days after the pinch. Plants were treated for 2, 3, or 4 consecutive days.

Colchicine-induced polyploidy was found in the first and second histogenic layers but not in the third layer and a completely polyploid shoot was not isolated. Evidence indicates the formation of sectorial and periclinal cytochimeras. Within the single and the consecutive day treatments, none of the 3 colchicine concentrations or length of treatments were decisively different from each other. However, the single day treatments, when combined, induced a significantly higher number of polyploid L-1 layers compared to the consecutive day treatments. It was found that as the concentration and/or length of treatment increased, there was a decrease in the number of viable vegetative buds.

Morphological changes were not observed within treated material. Induced polyploidy in the second histogenic layer resulted in the formation of polyploid pollen which could be used as a new source of germplasm.