Acta Hortic. 1262. ISHS 2019. DOI 10.17660/ActaHortic.2019.1262.18 Proc. III International Orchid Symposium Eds.: Jongyun Kim et al. 133 Medium composition, coconut water, and chitosan effects on Phalaenopsis protocorm growth and development D. Sukma a , S.A. Aziz, N. Andini, H.A. Putri and S. Sudarsono Department of Agronomy and Horticulture, Bogor Agricultural University, Bogor, Indonesia. Abstract Protocorm multiplication through the regeneration of protocorm-like bodies (PLBs) is used to obtain clonal progenies of hybrid orchids. The aim of the present study was to identify effective media for commercial orchid propagation through PLB proliferation. We evaluated the effects of basal media and either coconut water or chitosan supplementation on the growth of PLBs and the proliferation of Phalaenopsis hybrid PLBs, using two experiments, with random complete block designs (RBCD). The first experiment evaluated the progeny of white (V3) × pink standard hybrid (KHM0421, population 1) and their reciprocal hybridization (population 2) and different medium compositions. The hybrid seeds germinated and developed into protocorms on a half- strength Murashige and Skoog (½ MS) medium supplemented with 15% coconut water (CW). The protocorms were then transferred to four different media: 1) ½ MS; 2) ½ MS + 15% CW; 3) 2 g L -1 complete fertilizer (CF); and 4) CF + 15% CW. Experiment two evaluated the effects of chitosan on the growth and proliferation of protocorms from population 1, using four different media: 1) ½ MS; 2) 2 g L -1 CF; 3) ½ MS + 5 ppm chitosan; and 4) CF + 5 ppm chitosan, supplemented with 15% CW. The first experiment showed that the protocorm from population 1 generated more PLBs (5.4 PLBs in 16 weeks) than that of population 2 (2.2 PLBs in 16 weeks). The best media for protocorm proliferation and plantlet regeneration was CF and CF + 15% CW. The results of the second experiment revealed CF + 15% CW was the best medium for protocorm multiplication and plantlet regenerations. Chitosan tended to have a negative effect on protocorm growth and did not increase protocorm multiplication or plantlet regeneration. The use of CF medium could benefit orchid propagation, as it was cheaper than the MS medium. Keywords: chitosan, coconut water, complete fertilizer (NPK 20:20:20), MS medium, protocorm-like bodies (PLBs) INTRODUCTION Phalaenopsis is one of the major flowering pot plant commodities in the Indonesian market. Based on the Indonesian ornamental production statistics data, orchids rank fifth after Chrysanthemum, Polianthes, rose, and jasmine. Based on Pusat Data dan Sistem Informasi Pertanian (2015), the hectarage used for orchid production in Indonesia has increased over the last ten years, as demand by both the local and export markets has increased. One potential problem of orchid growing in Indonesia is the limited production of domestic orchid propagules, resulting in the need to import orchid propagules from other countries, such as Taiwan, Japan, and Thailand. Local Phalaenopsis nurseries in Indonesia produce seedlings for their own use as well as importing seedlings from abroad. Although hybridization among Phalaenopsis cultivars is relatively easy, the harvested pods only contain a few seeds and thus germinate only a few protocorms (Sukma et al., 2015). In previous reports, hybridization of Phalaenopsis has resulted in large numbers of seeds and protocorms. However, self-pollination of the hybrids yielded only a few seeds or protocorms (Sukma et al., 2015). Therefore, clonal propagation of a E-mail: dsukma70@gmail.com