The effect of plant growth regulators, carbon sources and gelling agent on the callus regeneration of Malaysian rice MR219 (Oryza sativa L.)

Abstract

The development of a highly efficient tissue culture system for indica rice is crucial to speed up the implementation of gene editing in breeding programmes as well as to explore the roles of indica genes. However, because indica rice types are recalcitrant to in vitro response, there are only a few reports on the successful transformation process on indica rice due to recalcitrant response to in vitro response. The present study attempted to identify the effects of plant growth regulator (PGR), carbon sources and different concentrations of gelling agent on embryogenic callus induction and rice regeneration of Oryza sativa var MR219. The PGR used were 1 or 2 mg/L 6-benzylaminopurine (BAP) and 1-Naphthaleneacetic acid (NAA) and the carbon sources were 30 g/L sucrose and maltose. Three different gelling agent concentrations (3 mg/L, 6 mg/L or 9 mg/L) were evaluated. The highest frequency of friable callus induction (87%) was observed in callus induction media (CI) containing Murashige and Skoong media (MS) supplemented with 3 mg/L 2,4-dichlorophenoxy acetic acid (2,4-D) and 0.3 mg/L kinetin. Histological studies of the calli showed the presence of embryogenic calli with small intercellular spaces compared to non-embryogenic areas which developed on the hormone MS media. The highest regeneration frequency (50%) was achieved when friable calli were cultured on MS medium containing 3% sucrose, 1 mg/L BAP, and 1 mg/L NAA with 9% phytagel. The callus grown on sucrose media showed the highest number (66.13%) of albino plantlets, while the number of albino plantlets on maltose media was smaller (20%). In conclusion, this optimised mature embryo-derived callus of MR219 rice is responsive to regeneration and could be amenable to genetic transformation studies.