Comparison of agar and gum karaya as gelling agent for in vitro regeneration of rough lemon (Citrus jambhiri Lush.) plantlets from nodal explants

In the present study, attempt was made to compare agar with gum karaya as gelling agent in micropropagation of rough lemon (Citrus jambhiri Lush.). Initially nodal segments were cultured on agar-gel MS medium containing benzyladenine (BA), kinetin (KN), zeatin (ZN) (1.0–2.5 mg L^?1) and malt extract (200–1,200 mg L^?1) to standardize the medium. Maximum shoot regeneration (66.66%) was observed with KN 2 mg L^?1 with an average shoot length of 0.73 cm. Gum karaya and agar was then evaluated at different concentration and combinations in same medium. The shoot regeneration response on media gelled with 30 g L^?1 gum karaya was 62.49% with an average shoot length of 0.80 cm. Regenerated shoots were rooted on MS medium gelled with agar and supplemented with different concentrations (0.5–2.5 mg L^?1) of indole-3-acetic acid (IAA), naphthalene acetic acid (NAA), and indole-3-butyric acid (IBA). Maximum response (52.77 %) was observed with IBA 2.0 mg L^?1 with an average number of 2.58 roots/shoot. A maximum of 53.47% cultures showed root regeneration with an average number of 2.91 roots/shoot in 30 g L^?1 gum karaya-gel medium. Texture measurements revealed that firmness of gum karaya-gel medium was nowhere near to that of agar. However, in their capability of supporting growth and differentiation of explants they are equal to agar medium. Gum karaya forms less adhesive and gummy medium as compared to agar. This study indicates that gum karaya can be used as gelling agent in place of agar.