Growth comparison of two stem-cutting types in induced mutation through gamma irradiation of Hoya lacunosa.

Hoya is one of the popular houseplants that has acquired many enthusiast collectors worldwide. Its center of origin ranges from Southeast Asia region, India, China, Japan, until Australia. Hoya lacunosa is a native Indonesian Hoya. Among other Hoyas, Hoya lacunosa is easy to grow and fast-growing into long vines. The white cinnamon-scented blossoms are considered its best feature. Improvement of its growth habit into more compact shape, leaf shapes, and flower features would be desirable for both nursery growers and plant hobbyists. Induction mutation are one of the breeding methods available, best applied to improve one or few target traits. Unlike in seed crops, mutation breeding in vegetatively-propagated crop may utilize various plant propagules, e.g. cutting. For each propagule option, their response to gamma exposure varies widely, but information on this matter is still scarce. Better understanding on suitable propagule options would highly improve the success of a breeding program. Since Hoya is mostly propagated by stem cuttings, two types of plant materials are used in this experiment: rooted and fresh cuttings. We aimed to compare the growth response of both types after different levels of gamma irradiation exposure. Five samples of Hoya lacunosa rooted cuttings were each provided for 10 irradiation levels. Similar number of samples and levels were provided for fresh stem cuttings. Irradiation treatment was executed using Gamma Cell-220 facility. Treated plant cuttings were grown in pots in PRTPR Pasar Jumat, South Jakarta, Indonesia. Plants of 10 Gy dose were the earliest in sprouting new stems and leaves, even compared to control. Up to 3 months after planting, no new growth was observed on plants irradiated with dose above 30 Gy (rooted cuttings) and 20 Gy (fresh cuttings). In conclusion, rooted cuttings of Hoya lacunosa has recovered better and produced new shoots faster. This research may provide valuable information to design more efficient future breeding strategies in time and resources, especially for vegetatively-propagated plants of high economic value. [ABSTRACT FROM AUTHOR]