Abstract

Selectable marker genes conferring resistance to antibiotic and herbicide are routinely used in genetic engineering to discriminate between transformed and non transformed plants. Elimination of marker gene is important and will favour public acceptance of transgenic crop products.Various site specific recombination (SSR) systems have been developed for removing marker gene or short spacer sequences from the transgenic plants. Among them, Cre-LoxP recombination system is extensively used for the removal of selectable marker gene in developing marker free (SMG) transgenic plants. B.juncea is one of the most important sources of edible oil and it is productivity is severely affected by sap sucking mustard aphids (10-90% yield loss).To enhance the productivity of Indian mustard, development of aphid resistance is a long standing breeding objective which always assumed paramount importance and priority. RNAi is an emerging technique for developing resistance in plants against biotic stresses which include virus resistance, bacterial resistance as well as insect resistance. We have developed transgenic Cre lines under different germ line specific promoters and transgenic B. juncea aphid resistant lines expressing ds RNAs. While the molecular analysis and insect bioassay established potential of the aphid resistant transgenics, elimination of the selectable marker gene will make them more suitable for environmental release.