In vivo polyploidy induction in Dendrobium crumenatum through colchicine treatment

Abstract: Polyploidy induction plays a significant role in hybridizing and improving orchids (Orchidaceae). Induction of polyploidy can help to restore fertility by doubling of chromosomes and thus leading to the creation of allotetraploids which can help breeders develop improved hybrids and novel types by contributing beautiful floral or growth characteristics unobtainable from the diploid forms. The objective of the present study was to investigate the effective colchicine concentration and duration of exposure for the polyploidy induction in Dendrobium crumenatum via in vivo method, thus improving the flower characteristics. For the in vivo induction of polyploidy, D. crumenatum plantlets were chosen and subjected to eight different colchicine treatments. Treatments were based on colchicine concentration (0.05 and 0.1%) and the duration of exposure of plantlets to these doses of colchicine (24, 48, 72 and 96 hrs). The morphological characters, like shoot length, diameter of pseudobulb, number of leaves and width of leaves showed treatment mean values greater than their corresponding control plantlets. After analyzing the histogram peaks of in vivo treated samples, it was observed that the highest tetraploid induction (50%) was achieved with the treatment of 0.05% colchicine for 96 hours. Moreover, the maximum mixoploids (66.67%) were obtained from two different treatments; first, with 0.05% colchicine for 72 hours and second, with 0.05% colchicine for 48 hours. These results suggest that longer treatment duration of 96 hours with 0.05% colchicine leads to higher tetraploid induction while shorter durations of 72 and 48 hours with the same concentration of colchicine are more effective for producing mixoploids. Stomatal observations exhibited a lower stomatal density, but increased stomatal size in polyploids than diploids.