Long life span, heterozygous nature and linkage drag often influence stacking of desirable genes from wild sources in conventional breeding for crop improvement. Recombinant DNA technology and transgenesis have enabled transformation of alien gene into plants across the kingdom barriers. The release of genetically modified (GM) crops into agricultural production has raised considerable debate, especially among the general public, politicians and bureaucrats. To meet this concern, cisgenesis & intragenesis were developed as new tools in crop modification and plant breeding. The cisgenesis/intragenesis concept imply that plants must be transformed with genetic material derived from the species itself or from closely related species capable of sexual hybridization and also foreign sequences such as ‘Selectable marker genes’ and ‘Vector backbone’ sequences should be absent.
Cisgenics/intragenics are developed through marker-free transformation and possess only plant-derived promoters and border sequences. Agrobacterium-mediated transformation is performed to avoid nonspecific integration and to have control over copy number. These are new alternatives to traditional and transgenic breeding. They can replace complicated introgression and induced translocations. The development of the intragenic vector concept and selectable marker excision strategies allows the transfer of genes without introduction of foreign sequences. Intragenic vector construction involves identifying functional equivalents of vector components within plant genomes and using these DNA sequences to assemble vectors for plant transformation. The European countries which show protest against transgenics are now using cisgenesis to improve crop growth. Intragenic vectors have been developed for potato, petunia, tomato, tobacco, apple, onion, rice, pine trees.
Success stories in cisgenesis/intragenesis include late blight resistant potato developed by introducing two broad-spectrum potato late blight R genes, Rpi-sto1 and Rpi-vnt1.1 from the crossable species Solanum stoloniferum and Solanum venturii in three different varieties. The generation of cisgenic barley by inserting one extra copy of the endogenous phytase gene (HvPAPhy_a) with its native promoter and terminator, showed a 2.6 - 2.8 fold increase in phytase activity.
To date, several different traits in various crops have been modified by cisgenesis/intragenesis. Since these genetic modifications are based on the sexually compatible gene pool, they carry a high potential for generating plants with environmental, economic, and health benefits that may be essential for meeting the global need for a more efficient and sustainable crop production.
3. HOLME, I. B., DIONISIO, G., BRINCH‐PEDERSEN, H., WENDT, T., MADSEN, C. K., VINCZE, E. AND HOLM, P.B., 2012, Cisgenic barley with improved phytase activity. Plant Biotechnol. J., 10(2): 237-247.
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