ANAND AGRICLTURAL UNIVERSITYB. A. COLLEGE OF AGRICULTURE

Topic: Gene Pyramiding

GP-501 :- Principles Of Plant breeding (2+1)

Course Teacher: Dr. J. N. Patel

Prepared By,

Dhanya A J, [ Reg. No: 04-2348-2014 ], M. Sc. (Agri) Plant Molecular - Biology & Biotechnology

Introduction The development of molecular genetics

and associated technology like MAS has led to the emergence of a new field in plant breeding-Gene pyramiding.

The term gene pyramiding is used in agricultural research to describe a breeding approach to achieve pest control and higher crop yield.

Gene pyramiding aims at the derivation of an ideal genotype that is homozygous for the favorable alleles at all n-loci. Molecular markers aid in selecting the best plants with which to proceed.

Gene Pyramiding

MAS based gene pyramiding could facilitate in pyramiding of genes effectively into a single geneticbackground.

Gene pyramiding or stacking can be defined as a process of combining two or more genes from multiple parents to develop elite lines and varieties.

orPyramiding entails stacking multiple genes leading to the simultaneous expression of more than one gene in a variety.

Strategies For Gene Stacking / Pyramiding

Iterative Procedure / Sexual Hybridization

Re- Transformation

Co- Transformation

Iterative Procedure / Sexual Hybridization

A plant harboring one or more transgenes is cross-hybridized with another plant containing other transgenes. Development of a multi-stack hybrid occurs via iterative hybridization. Examples of commercial stacksMaize:   Agrisure™ Viptera™ 3220 (Bt11 x MIR162 x TC1507 x GA21)Cotton:  Roundup Ready™ Flex Bollgard™ II (MON88913 x MON15985)

MethodsSexual Hybridization

The gene pyramiding scheme can be distinguished into two parts (Figure 1). The first part is called a pedigree, which aims at cumulating of all target genes in a single genotype called the root genotype.

The second part is called the fixation step which aims at fixing the target genes into a homozygous state i.e. to derive the ideal genotype from the one single genotype

Backcrossing for Gene Pyramiding

Re- Transformation

Examples of commercial stacksCotton:  Bollgard™ II 

A plant harboring a transgene is transformed with other transgenes.

Re-transformation.A plant harbouring transgene A is retransformed

with transgene B

Co- Transformation

A plant is transformed with two or more independent transgenes. The transgenes of interest are in separate gene constructs and delivered to the plant simultaneously. Examples of commercial stacks

Maize:   NaturGard™ Knockout™ (Bt176), BtXtra™ (DBT418), YieldGard™ (MON810, MON809, MON802), Herculex™ I (TC1507), Herculex™ RW (59122), Agrisure™ CB/LL (Bt11)Soybean: Vistive™ Gold

Single-plasmid Co-transformation.Transgenes A and B are linked on one piece of DNA and transferred together into a plant.

Multiple-plasmid co-transformation. Transgenes A and B are on different pieces of DNA that are transformed together into a plant

Conclusion

Gene pyramiding is an important strategy for germplasm improvement.

Molecular marker genotyping can facilitate the gene pyramiding process by reducing the number of generations that breeders must evaluate to ensure they have the desired gene combination.

Reference

http://www.isaaa.org/resources/publications/pocketk/42/

Gene Pyramiding Using Molecular Markers- Francis et al., 2012

http://agbiosafety.unl.edu/education/backcross.htm

Gene pyramiding-A broad spectrum technique for developing durable stress resistance in crops.- Joshi et al., 2010