Optimization of the Marker‐Based Procedures for Pyramiding Genes from Multiple Donor Lines: I. Schedule of Crossing between the Donor Lines

Abstract

Recent exploitation of DNA markers of desirable trait genes facilitates construction of high‐degree, gene‐pyramided lines via assembling markers from multiple donor lines. In such a program, a plant that has all the target markers in a heterozygous state must be produced first. Efficient procedures for that are discussed. When pyramiding the genes onto the genetic background of a particular recipient line, the backcross should be performed separately for each donor before the crossing between the donors. The plants produced through the backcross should be crossed in a schedule with structure and disposition of the plants as symmetric as possible. When four such plants (A, B, C, and D) are produced, for instance, they should be crossed in a schedule like (A × B) × (C × D) in which the number of target markers of A plus B should be as similar as possible to that of C plus D. Ideal‐type schedules in the presence of four to eight donors are presented. A contrastingly different guideline applies when the donors themselves are crossed without the backcross; they should be crossed in a schedule with completely tandem structure in which donors with fewer target markers enter the schedule in earlier stages. The disposition of donors in the schedule should be modified in the presence of linked or redundant markers. Donors should be disposed in a pattern to minimize the occurrence of repulsion linkages. Formulae for the modification under a high redundancy are presented.

Microsatellite mapping of powdery mildew resistance allele Pm5d from common wheat line IGV1-455

“…Xgwm577 showed specific alleles for Pm5a, Pm5b and Pm5c, whereas a null allele was found for Pm5d, Pm5e and Mlxbd. Null markers are not as efficient as amplifiable markers in MAS because they cannot be screened in heterozygotes and therefore require at least two generations for detecting plants carrying target alleles (Ishii and Yonezawa 2007). To circumvent this disadvantage, Xwmc581 can be used in MAS for any of the three Pm5 alleles of Chinese origin.…”

Towards marker‐assisted selection in pulses: a review

“…2004). The possible breeding schemes that can be used for gene pyramiding involving MAS and required population size in each segregating population have been discussed in several recent reviews (Ishii and Yonezawa 2007a,b, Ye and Smith 2008a,b, 2009, Gupta et al. 2010).…”

“…Therefore, it is often cited that genetic markers can be deployed as an alternative to identify and select specific genes or combine multiple resistance genes (Brahm et al 2000, Fjellstrom et al 2004). The possible breeding schemes that can be used for gene pyramiding involving MAS and required population size in each segregating population have been discussed in several recent reviews (Ishii and Yonezawa 2007a,b, Ye and Smith 2008a,b, 2009. Marker-assisted pyramiding has been employed widely in cereal crops for combining multiple genes/QTLs controlling both qualitative (Huang et al 1997, Hittalmani et al 2000 and quantitative (Castro et al 2003) disease resistance.…”

Genetic Markers, Trait Mapping and Marker-Assisted Selection in Plant Breeding

“…In case if the goal is to select a BC 1 F 1 plant that is heterozygous for a target gene and homozygous for recurrent parent allele at one fl anking marker and heterozygous at the other with 99 % probability, the minimum number of BC 1 F 1 plants required would be about 100 when the target locus is at the distance of 5 cM from the fl anking markers. Ishii and Yonezawa ( 2007 ) have outlined various schemes for pyramiding two or more genes. For instance, one of the schemes involves crossing of multiple donors (~4) with a single recipient parent followed by separate backcrosses.…”