New Techniques in Plant Breeding : Accelerating the breeding cycle

INTRODUCTION
In the last decennium several new plant breeding techniques have been proposed and developed. These techniques resemble, are derived from, or make indirectly use of genetic modification techniques. The new breeding techniques that are considered in this report share as common feature that in the final products (plants or plant parts) no genes that are foreign to the species are present. Application of these new techniques results in crop phenotypes that could also be obtained through conventional breeding or mutation breeding, but often in a much longer time frame

AGROINFILTRATION
Agroinfiltration is a technique using Agrobacterium as a tool to achieve temporarily and local expression of genes that are foreign to the species in a plant. This technique is applied for testing the reaction of target plants to transgenic proteins, or for functional gene analysis in plants. Cuttings or seeds of the selected plants that are Agrobacterium free may be used for further crop development.

VIRUS-INDUCED GENE SILENCING
Virus-induced gene silencing (VIGS) is a technique used for (transient) silencing of the expression of specific endogenous genes in plants. VIGS is mainly used for functional analysis of genes. The VIGS DNA vector is usually introduced into the plant using Agrobacterium or specific plant viruses.

REVERSE BREEDING
Reverse breeding is a novel breeding technique that makes use of genetic modification to facilitate breeding of F1-hybrids by suppression of meiotic recombination. In the final breeding steps the genes used for the genetic modification are crossed out, resulting in end-products that are completely free of genetic modification-related DNA sequences

ACCELERATED BREEDING FOLLOWING INDUCTION OF EARLY FLOWERING
Accelerated breeding is a novel breeding technique that makes use of genetic modification to speed up breeding by induction of early flowering. In the final breeding steps the genes used for the genetic modification are crossed out, resulting in end-products that are completely free of genetic modification-related DNA sequences.

COMBINING OF GENETICALLY MODIFIED AND NON-GENETICALLY MODIFIED PLANT PARTS BY GRAFTING
By combining genetically modified and non-genetically modified plant parts, products (like fruits or flowers) can be produced on non-genetically modified plant parts that are grafted on genetically modified root stocks. The combined genetically modified-non genetically modified plants usually have improved cultivation characteristics.

CISGENESIS
Cisgenesis is the production of genetically modified plants using donor DNA from the species itself or from a cross compatible species. The newly introduced DNA is an unchanged natural genome fragment containing a gene of interest together with its own introns and regulatory sequences, like gene promoter and gene terminator DNA sequences. The introduced DNA is free of vector DNA, with the exception of T-DNA border sequences that are flanking the cisgenic DNA sequences.

INTRAGENESIS
Intragenesis is the production of genetically modified plants using donor DNA from the species itself or from a cross compatible species. The difference with cisgenesis is that intragenesis allows the creation of new combinations of DNA fragments which are all originating from the species itself or from a cross compatible species. In intragenesis also the transformation vector itself can be composed of functional DNA fragments from the genome of the target crop species.

OLIGONUCLEOTIDE-MEDIATED MUTATION INDUCTION
Oligonucleotide-mediated mutation induction is a site-specific gene modification system that makes precise changes in a gene sequence without the incorporation of genes that are foreign to the species.



About Author / Additional Info:
Ph.D scholar, ICAR- Indian Agricultural Research Institute, New Delhi-110012