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#genetic 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

MAS selects plants based on:

Marker-assisted selection replaces unreliable phenotypic screening with direct interrogation of DNA sequence polymorphisms linked to trait-controlling loci. Instead of measuring disease severity in field that depends on weather and inoculum load, MAS uses polymerase chain reaction amplification of SSR, SNP, or SCAR markers situated within few centimorgans of target gene, detecting presence of donor allele regardless of environment, plant stage, or dominance interactions. Segregating individuals are genotyped at seedling stage, selection made before flowering, accelerating backcross programs an

Ref: Tanksley SD 1989 BioTechnology – RFLP; Collard & Mackill 2008 Philos Trans – MAS based on DNA markers

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Plant Breeding 3

Single Seed Descent (SSD) emphasizes selection in:

Single Seed Descent maintains genetic diversity by advancing one random seed from each F2 plant forward without selection until homozygosity increases. Active natural or artificial selection during early segregating generations would favor competitive or early flowering types and eliminate potentially superior recombinants whose phenotype is not yet expressed due to heterozygosity and dominance masking. By postponing rigorous phenotypic evaluation to F5-F6, when lines approach 94-97% homozygosity under selfing, additive genetic variance becomes fixed and heritability rises substantially. In F6

Ref: Goulden CH. SSD method – Crop Breeding; Nature Plants Speed breeding, Watson et al. 2018

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