Minimizing medium browning during in vitro cultures of herbaceous peony (Paeonia lactiflora Pall.)

Abstract

One of the major problems associated with peony tissue culture is the browning of culture media, which invariably leads to death of explants. All the five types of explant used in the present study resulted in media browning, which was maximum with leaf and ovary segments, while minimum with petiole segments and underground buds. Incorporation of chemicals into the medium and incubation under different conditions had a significant influence on media browning. Polyvinyl pyrrolidone (5.0 g/l) proved best chemical for controlling browning, while antioxidants (citric acid and ascorbic acid) failed to suppress the problem. Incubation of explants in a refrigerator for 48 h at 4oC was found best for minimizing the media browning of all explants types. Growing of stock plants under low light intensity drastically reduced the leaf segment media browning to 8.69% compared to 83.25% as observed with explants grown under open field conditions. Harvesting of leaves at different stages of development significantly reduced the media browning from a maximum of 89.09% with fully-expanded pink leaves to a minimum of 0.91% with unexpanded inner green leaves of terminal bud.