Lecture 3 - Gathering Variability Flashcards
who was Seager Wheeler
made Marquis 10B wheat (most grown wheat variety for 30yrs) by identifying off-types and was crowned World Wheat King 5 times
what is economic yield
portion of plant biological yield that humans use
breeding
selecting plants with traits that are superior to those previously found in the population
where do alleles arise from when crossing
-mutations
-local and genome duplications (autopolyploidy)
allopolyploidy
when is there less genetic recombination
there is less recombination near centromeres/less distance because it causes blocks of alleles to be inherited together)
linkage blocks
blocks of alleles inherited together
what does genetic linkage cause
decreases ability to create variability
how does temperature affect recombination
it has different impacts in males and females
can affect crossover events and break linkage
what is required to get genetic recombination
mating systems (Sexual or asexual)
what determines the genetic structure of a population
mating systems
2 types of a population
natural and cultivated
how can knowing the type of reproduction of your crop be important for breeding decisions
determines the form of the end product and the breeding methods to be used
cultivar types (end products)
pure lines
multi-lines
hybrids
open pollinated (synthetics)
clonal
apomyctic
genetic characteristics of inbreeders (self-pollinated plants)
low recombinant genotype frequency
high local fitness
uniform populations
deleterious recessives rare
mating of outcrossing plants occurs between ______ individuals
unrelated
what is outcrossing plants typically considered to be in
Hardy-Weinberg equilibrium (random mating)
which parent do you know when you select
typically only known female. male is completely unknown due to pollen
genetic characteristics of outcrossers (outcrossing plants)
-high recombinant genotype frequency
-variable fitness
-can more readily adapt to new environments
-carry and hide deleterious recessives
-susceptible to inbreeding depression
2 types of asexual reproduction
vegetative propagation
apomixis
vegetative propagation
plant tissue other than seed is used to produce a clone (ex: cuttings and tissue cultures)
apomixis
plant embryos develop from megaspore mother cell without fertilization
genetic characteristics of asexual reproduction
-all progeny are identical to the parent plant (no genetic variation)
-can maintain a superior genotype
types of mutation effects on organisms
silent, missense, and non-sense
silent mutation
same amino acid coded for so there is no change in phenotype
missense mutation
change of amino acid produces a different protein which changes the phenotype
non-sense mutation
codon is changed to stop codon which prematurely stops translation and produces a different or lethal phenotype
what are the compounds in faba bean that cause favism (Acute Hemolytic Anemia)
Vicine and Convicine
plant breeders are only interested in mutations if they …..
affect a plants ability to reproduce or affect plant’s end-use quality
and occurs in cells that produce gametes
where do different alleles come from
-mutations
-variation in chromosome # (polyploidy)
genome
each basic set of chromosomes characteristic of a species
ploidy
the number of sets of these chromosomes
diploid
2 sets of chromosomes
haploid
1 set of chromosomes
polyploid
more than 2 sets of chromosomes
examples of a tetraploid (4x), hexaploid (6x), and octoploid (8x)
4x - durum wheat
6x - bread wheat
8x - strawberries
autopolyploid
multiple copies of the same genome in an individual (ex: alfalfa AAAA)
allopolyploid
several genomes within a single individual and acts like a diploid ex: bread wheat AABBDD
advantages to polyploidy
-increased vegetative vigour
-facilitates new gene combinations that wouldn’t occur in a diploid
-possibility of recessive is much lower
-can combine genomes to create new species
-allows duplicate locus differentiation
when can a triploid occur
when an accidental unreduced diploid gamete pairs with a normal haploid one or when you cross a diploid with a tetraploid
what happens when a triploid attempts to pair during meiosis
generates massive genetic imbalances upon cell division and typically produces a sterile plant
how are triploids maintained
seed propagation is only possible if it is a result of a diploid x tetraploid
otherwise vegetative propagation is necessary
examples of useful triploids
banana
seedless watermelons
some flowering plants
