Marker Assisted

SelectionBiotechnology in Action

Traditional Tree Breeding

Selection of trees is based on visible traits (phenotypes)

Grafts or seeds are taken from the selected trees

Crossbreed the selections

Perform progeny testing

Select the best

Repeat

Time consuming and results are sporadic

Marker Assisted Selection (MAS)

Using DNA markers to assist in the selection of trees for breeding, testing, or production

DNA

Made up of nitrogen bases; adenine (A); cytosine (C); guanine (G); thymine (T)

Proteins are built based on the sequence of the nitrogen bases

AGTCAGTC represents different protein than TAGTAGCTA

Small fraction of DNA code for proteins

Most DNA represents non-coding sequences

Complete sequence is called a genome

MAS

Markers are not normal genes

Seldom have biological effect

Can be thought of as landmarks

Identifiable DNA sequence

Found at specific location on genome

Follow standard laws of inheritance

MAS (cont.)

Markers require DNA evaluation

Different kinds of markers exist

RFLPs; SNPs

All types vary in technical requirements amount of time, money, and labor needed

Information provided by each type of marker is different

Utilizing MAS

Many traits are genetically complex, involve many genes

Selecting individuals from a population based solely on phenotype would not produce desired offspring

Markers have been found that are always associated with the desirable phenotype

Example: Frost resistance in trees is a genetically complex trait

Markers have been used to identify off spring of parent trees with frost resistance.

MAS Frost Resistance

DNA is extracted from selected trees

Electrophoresis is used to identify individuals with desired marker

Marker indicates presence of frost resistance.

MAS Analysis

Marker for frost resistance

Individuals 1, 3, 4 and 6 have the marker for frost resistance in their genotype. Individuals 2, 5 and 7 do not have the frost resistance marker.

Future of MAS

Has the future to reduce the time it takes to create new seed plantation.

Could produce a “better” tree in years instead or decades

Only major species of trees will be utilized

Not enough studies to determine if process is cost effective on a commercial basis

May be utilized to save trees such as the American Chestnut