Effects of Different Natural Extracts and Plant Growth Regulators on Plant Regeneration and Callus Induction from Pseudobulbs Explants through in vitro Seed Germination of Endangered Orchid Bulbophyllum auricomum Lindl.

Abstract

Bulbophyllum auricomum Lindl. is a rare orchid and has flowers with an attractive fragrance. The present study investigated the tissue culture method for micropropagation. Capsules derived from artificial self-pollination were obtained for the best seed germination in MS basal medium. Plant growth regulators (1.0 mg•L -1 of BAP and 2.0 mg•L -1 of NAA) were affected by callus induction from subcultured pseudobulb explants. For the callus subculture, different natural plant extracts were tested in 11 treatment media. Among them, MS medium with 150 mL•L -1 of coconut water was generally effective in fresh weight (1.75 ± 0.08) and (3.01 ± 0.20) of callus proliferation and PLBs induction at 1 and 2 months, respectively, followed by an MS combination of 30 g•L -1 of banana and 20 g•L -1 of potato extract. The results of a comparative study of different MS mediums containing plant growth regulators with a natural extract combination and MS medium supplemented with natural extract only showed that MS medium supplemented with a combination of natural extracts (150 mL•L -1 of coconut water) and plant growth regulators (2.0 mg•L -1 of BAP and 1.0 mg•L -1 of NAA) obtained the highest shoot regeneration (3.37 ± 0.17) and (6.41 ± 0.68) after 1 month and 2 months of culturing, respectively.

Micropropagation of Bulbophyllum Orchids

“…Optimum germination of around 90% was found when seeds were collected by 140 DAP [7]. In B. niphondii, fruit was harvested 12 months after pollination and stored at 10 0 C before use [10], in B. auricomum fruit was used 3-4 months after pollination [6] [12].…”

“…In several multiplication Bulbophyllum species, PGRs have been used. The cytokinin and auxin were reported to have increased the growth of shoots and leaves in B. auricomum [12], B. odoratissimum [9], B. macrantum [8] and also induces in vitro flowering in B. auricomum [6]. The addition of 1 mg.L -1 BAP with 0.5 mg.L -1 NAA was most responsive for shoot formation while 1 mg.L -1 KIN with 2 mg.L -1 NAA was the optimum concentration in root formation of B. auricomum [6].…”

“…Several Bulbophyllum are interesting because of their uniqueness, such as B.auricomum [6], B. fascinator [7], B. macrantum, and B. phalaenopsis [8]. Several of them are useful as medicine because they contain secondary metabolites such as B. odoratissimum which is known to contain bulbophythrins that show cytotoxic activity against several human cells cancers such as leukemia, hepatoma, lung adenocarcinoma and stomach cell cancer [9] and several listed as rare orchids such as B. niphondii [10], B. dhaninivatii [11], B. auricomum [12]. Based on CITES, Bulbophyllum is included in the Appendix II category [13].…”