Relationship between Polyploidy and Leaf Shape in Colchicine-derived Periclinal Chimeras of Catharanthus roseus (L.) G. Don

Abstract

The development of tetraploids is one of the useful methods for breeding horticultural plants. However, it is difficult to obtain the perfect tetraploid by chromosome doubling on colchicine treatment. In this study, the colchicine treatment of seedlings of Catharanthus roseus induced chimeras with each tissue of L1, L2, and L3 layers composed from 2x or 4x. The percentage of polyploids containing chimeras was the highest with 24-hour treatment with colchicine at 10 mM (DMSO 5%). Regarding the relation between ploidy of L1–3 layers in the leaf of the obtained polyploid and the leaf width/leaf length ratio, the ploidy of L1 and L3 layers was not involved in the leaf width/leaf length ratio. Leaves with an L2 layer of 4x were roundish and the leaf width/leaf length ratio was significantly higher than in leaves with an L2 layer consisting of 2x. Therefore, the ploidy of the L2 layer was involved in the determination of the leaf shape.