Selectable Markers to Marker-Free Selection in Rice

Inadequate rice production worldwide is largely attributed to abiotic and biotic stresses, along with high sensitivity of cultivable plant germplasm. In the field of cereal biotechnology, rice engineering plays an important role in achieving tolerance to such stresses. Plant transformation and selection play crucial role in rice engineering. This review summarized the antibiotic, herbicide and metabolic selection marker genes (SMG) employed in diverse rice engineering studies. These SMGs are no longer required after the transformation has been achieved, hence undesirable at the commercial level. This study also included several strategies employed in rice engineering to eliminate such foreign DNA elements. These include co-transformation, site-specific recombination, transposon and CRISPR base approaches. CRISPR/Cas9 being simple and efficient, is considered a crucial step toward clean gene technology. Further ease and applicability of CRISPR/Cas9 in the embryos directly can help us to modify target genes with efficient marker-free selection in minimum time. Overall, this review summarizes and analyse the recent advances that have enormous potential in rice improvement.