Lecture 18 - Selecting Flashcards
what is the difference between indirect and direct selection
indirect is selecting for something using a correlated trait (more of an estimate)
upside of doubled haploid method
get homozygous individuals with few generations
downside of doubled haploid method
need lab set up, need lots of variation to make up for 1 recombination, not all crops like to go through it
objective of single seed decent method
to advance a segregating population to homozygosity as quickly and efficiently as possible
single seed decent method
one seed is taken from a single plant in a F2 population. Seeds are bulked and planted to produce next gen and repeated until homozygosity (no selection during this time). Visual selection then occurs in a space plant nursery and are then handled as pure-line selection
problem associated with genetic drift
genetic drift can occur if F2 population is not big enough
how can single seed decent method be sped up
create stressful conditions through:
- changed light regime
- packing plants tightly
- adjust water and fertilizer regime
- change temp
- tissue culture
what is the backcross breeding method used for
to improve an otherwise desirable cultivar that is deficient in one or a few key characteristics
what characteristics are most easy to use the backcross breeding method
qualitative traits that are easily phenotyped and controlled by 1 gene
backcross breeding method
cross good cultivar with cultivar with desired trait and keep backcrossing the progeny with good cultivar until most of the offspring genetics are from the good cultivar but have that one desired trait. Plant is then selfed to get homozygous plants
where is the backcross breeding method best suited to
greenhouses as very small populations are required
what modifications well a recessive trait need in the backcross breeding method
will have to determine what plants have recessive trait using a marker, test crossing, or selfing
will also need to self and test at the very end
end product of the backcross breeding method
progeny nearly identical to recurrent parent but with the desirable trait from the donor parent
backcross breeding is considered a _________ breeding procedure
conservative
advantages of backcross breeding
- improvements are made in stepwise fashion and previous gains are not lost
- selection only needed for trait transferred
- can get away with small population
-works for both selfing and outcrossing crop
disadvantages of backcross breeding
- major improvements not likely
- not well suited to traits with low heritability
- linkage drag (desirable trait may bring other negative traits with it)
backcross breeding can be sped up using _________ _______
molecular markers
