A rapid and efficient protocol for genotype-independent, Agrobacterium-mediated transformation of indica and japonica rice using mature seed-derived embryogenic calli

Key message A rapid, highly efficient and reproducible protocol has been developed that can cater to diverse rice cultivars owing its success to the use of the popular surfactant, Silwet L-77, during co-cultivation. Functional genomics have advanced in rice with the availability of high quality and well annotated genome data, coupled with characterizing several genes by genetic manipulation. Several protocols have been put forth for the later over the years with significant improvements. Since different cultivars of rice respond differently to different protocols of genetic transformation, there is always room for further improvements. In the present study, we have attempted to highlight important factors leading to successful transformation in rice. An efficient, rapid and reproducible protocol independent of genotype specificity has also been developed to genetically transform rice using scutellum-derived embryogenic calli from mature seeds by Agrobacterium-mediated transformation. The protocol has been tested on six diverse cultivars of indica rice and one cultivar of japonica rice, achieving a total transformation efficiency up to 94%, in some cultivars. The protocol involves use of a popular surfactant, Silwet L-77, which dramatically enhances the efficiency of the Agrobacterium-mediated transformation. Combined with variety specific, high efficiency callusing and regeneration media and optimal hygromycin strength, significant improvement has been achieved in both transformation and regeneration efficiencies across different cultivars. The proposed protocol is also shorter, and shoot regeneration is achieved in around two months starting from the beginning. The protocol may be easily improvised and adapted for several other varieties of rice.