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#marker-assisted selection

3 public questions tagged with this topic.

Plant Breeding 4

MAS is most effective when markers are:

Efficiency of marker-assisted selection hinges on recombination frequency between marker and causal gene influencing linkage disequilibrium persistence. If marker is loosely linked at 20 cM, crossover occurs in 20% gametes each generation, decoupling marker allele from desired trait allele, leading to false positive selections and loss of target and reduced genetic gain. Tightly linked markers situated within 1-2 cM or preferably gene-based intragenic markers such as functional SNPs in coding region show recombination below 1%, ensuring near-complete co-segregation with trait across breeding c

Ref: Michelmore RW. 1995 Molecular dissection – tight linkage. Collard & Mackill 2008 tightly linked effectiveness

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Plant Breeding 4

Marker-assisted selection avoids:

Phenotypic selection suffers from confounding effects of environmental variation, microclimate heterogeneity, soil fertility gradients, and developmental stage, which obscure genetic differences especially for low heritability traits governed by many QTLs. DNA markers represent fixed sequence differences that are independent of external environment, plant age, and tissue, expressed constitutively in genome regardless of moisture or pathogen pressure. Therefore selection based on marker genotype is unaffected by seasonal fluctuations, field heterogeneity, or inoculum pressure that may cause esc

Ref: Tanksley et al. 1989; Xu Y. Molecular Plant Breeding – MAS avoids environmental influence

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Plant Breeding 4

Co-dominant markers are preferred in MAS because they:

Codominant markers reveal both alleles at locus simultaneously, displaying two distinct bands in heterozygote versus one band in each homozygote on gel or capillary electropherogram. This dosage information is invaluable in marker-assisted breeding because breeder can identify heterozygous carriers Aa that contain one copy of recessive or dominant donor allele while retaining recurrent background, and distinguish from homozygous donor AA that may exhibit drag penalty or lack recurrent adaptation. In backcrossing, BC progeny segregate 1:1 Aa:aa, and only heterozygous carrier advances, allowing

Ref: Collard BCY & Mackill DJ 2008 Marker-assisted breeding review: co-dominant heterozygote detection. Euphytica

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