Pitcher plant's callus induction and plant regeneration for optimal culture medium

The pitcher plant (Nepenthes truncata) is an endemic plant that is now endangered due to over-collection from the wild and poor cultivation practices. However, just like other countries, the Philippines could develop technologies for pitcher plant breeding, conservation of biodiversity, and commercial purposes. Rasco and Delgado (UP Min) undertook callus induction and plant regeneration of N.truncata to determine the appropriate combination of explant and plant growth regulator for callus induction and for the optimal culture medium for callus proliferation and regeneration. Three types of explants were obtained from 5-month old axenic seedlings - leaf with pitcher, shoot tip, and nodal segments. These were tested in different concentration of naphthalene acetic acid (NAA) combined with different combinations of thidiazuron (TDZ). Findings of the study revealed the following: The experiments showed that the leaf proved to be the most suitable for callus induction among the explants, in 1/2 strength MS medium. Likewise, good callus formation was obtained from the combination of 0.5 mg L-1 NAA + 0.05 mg L-1 TDZ using the leaf. The main constraint of the research was the browning of callus after 3-4 months. To alleviate the problem, two culture media - 1/2 strength B5 and 1/2 strength MS - and two antioxidants/adsorbents - ascorbic acid and activated charcoal 1 - were tested against the controls (1/2 strength MS) without antioxidants/adsorbents using leaf as explants. The antioxidants/adsorbents did not seem to control browning but 1/2 strength MS when activated charcoal regenerated shoots in some treatments, with a maximum of 7.5 shoots per explants in the combination - 0.5 mg L-1 NAA + 0.05 mf L-1 TDZ. Peptone was also studied as an organic supplement for callus but its effect was found to be insignificant. The study found that the combination of NAA and TDZ gave the best results as culture media for the callus induction of N.truncata. Additionally, the two culture media could be used interchangeably. The best plant growth regulator combination for callus induction was determined to be 0.5 mg L-1 NAA + 0.05 mg L-1 TDZ, which gave the highest quality and efficiency measurements, as well as good results.