Effects of 2,4-dichlorophenoxyacetic acid, α-naphthylacetic acid on the variant formation of Valentine Hoya (Hoya kerrii)

Abstract

Valentine Hoya (Hoya kerrii) is favoured by many people for its richness in leaf shape, colour and flower fragrance. To increase the diversity and abundance of Hoya, leaf samples were transplanted into MS medium supplemented with 2,4-D and α-naphthylacetic acid (NAA) (concentration 4-7 mg/l) to create callus and induce mutations. Calli formation rate was observed at 100% after 15 days of culture in all treatments supplemented with growth regulators, while the control treatment showed no callus formation. The results of rapid callus multiplication showed that the callus-forming leaf sample obtained from the treatment of 5 mg/l 2,4-D gave the largest callus size (2.98 cm). The 45-day-old calli were transferred to MS + 1 mg/l IBA + 3.5 mg/l BAP regeneration medium, the time of shoot appearance for callus samples treated with NAA was 95 days after subculture with the highest regeneration rate of 66.67%, earlier than 2,4-D treated calli (225 days, 50% regeneration rate). The results of genetic divergence analysis using RAPD markers recorded a total of 330 DNA bands with molecular sizes ranging from 170 to 2700 bp. The poly morphism information content index
was calculated in the 0.23-0.40 range. Samples treated with 5 mg/l NAA had the lowest similarity coefficient of 0.455, growth parameters such as petiole diameter, dermal tissue thickness, vascular bundle area, and a number of wood bundles recorded in samples treated with 5 mg/l NAA were superior to those of the control.