Transgene-free genome editing in potato, a clonally propagated crop - strategies and future prospects

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein (Cas)-based genome editing technology has come out as very precise and effective tool for targeted modification in the gene of interest and offers unprecedented potentials in crop improvement. However, in the present regulatory framework for commercialization of genome edited crops, in many countries including India, the edited lines must be transgene-free. In India, only site directed nuclease (SDN) I and SDN II category of genome edited events which are transgene-free are permitted for commercialization. Potato is a vegetatively propagated crop, having autotetraploid genome and is highly heterozygous in nature. Removal of the transgene from potato genome of edited lines through genetic segregation, either by crossing or selfing, is not the appropriate method as the elite background of the genome gets disturbed due to heterozygous nature of the crop. Every individual seed of potato, i.e. true potato seed (TPS) behaves like a different individual than the parental line and is unable to maintain the genetic identity. In this review article, we have discussed several strategies that can be enacted for generation of transgene-free genome edited lines in potato. This article will provide deeper insight and enhance understandings about the optimum use of CRISPR as non-GMO technology in the genetic enhancement of potato and to adopt the best strategies in editing this important tuberous, clonally propagated crop.