Lecture 9 Flashcards
centres or origin for crops:
Fertile Crescent in southwest Asia, Middle East, china, mesoamerica, andes, Amazonia, eastern and northern america
domestication
people grow plants on purpose for food and selected for particular traits
goosefoot
native to North America, 2500 years ago it was grown as a cereal, now its a weed
when did selection of crops begin
11,000 years ago
artificial selection; corn example
pick the seeds from the plants we like; corn was artificially selected for large cobs with seeds permanently attached to the cob, wild corn wants to spread seeds, reduced dormancy so all seeds germinate at the same time, one main stem because its easier to harvest, reduced shade avoidance to grow in rows,
stupid plants
crops are “stupid plants” because they are incapable of competing and allocating resources to responses. we want them to put all resources into producing seeds or growing. they can’t compete, we make the decisions for them.
teosinte
wild corn; highly branded stem, seeds disperse, variable seed dormancy, seeds germinate at different times
TB1 and TGA1 genes
genes in the regulatory region of corn, small changes to these genes cause massive changes between corn and teosinte because changing these genes changes the regulation of all genes in the region; only 5 changes to genome required to change teosinte into corn
TB1 gene function in teosinte
branched gene; maize tb1 mutant is branched; TB1 is a transcriptional repressor, expressed differently in corn and teosinte, more in corn less in teosinte; TB1 represses growth from auxiliary meristems in corn, not enough of it in teosinte to restrict branching
glume
protective kernel covered with lignin and silica providing protection in teosinte, no good for corn because we want access to the seeds
TGA1 gene function
positively regulates glume, more TGA1=more glume
evolutionary differences are often due to:
variation in regulatory genes which have major affects on multiple aspects of a phenotype
polyploid corp examples
banana, canola, cotton, oat, potato, sugar cane, wheat, sweet potato; commercial plants are polyploidy
Emmer wheat
pasta wheat; low in gluten protein; not sticky
T. aestivum wheat
bread wheat; high levels of gluten protein; sticky which is important in bread dough to trap CO2 in and rise
cultivated wheat:
wheat is an allopolyploid of distinct diploid and tetraploid species
how does cultivated wheat “act” as a diploid during meiosis
bread wheat genome is hexaploid (AABBDD) but acts as a diploid during meiosis pairing only chromosomes from the same genomes. homologous pairing A with A, B with B, etc. this ensures stable inheritance of the complete wheat haploid genome (ABD) from one generation to the next
Brassica species
includes a lot of vegetables including canola, rutabaga, cabbage, turnip, Brussels, kohlrabi. exists as 3 separate species but closely related, interbred to produce 3 allopolyploid species
B. oleracea
cabbage, kale, broccoli, brussel sprouts, cauliflower
B. nigra
black mustard
B. rapa
Chinese cabbage, turnip
B. juncea
allopolyploid; Indian mustard
B. napus
allopolyploid; canola, rutabaga
B. carinata
allopolyploid; Ethiopian mustard
glucosinolates
anti-insect compounds found in mustard which gives it its bitter flavour
what % of mustard seed is grown in canada
90%
sinapis alba
not from the brassica family; white mustard, used to make yellow mustard condiment
garlic mustard
European herb, invasive in North America, colonizes ecosystems and displaces native species, highly competitive with plants like trillium in ontario; produces a chemical which kills neighbouring plants
Canola
CANadian Oil Low Acid; hybrid variety of rapeseed (brassica); developed/breeded in Canada to reduce bitter tasting glucosinolates
Brassica oleracea
species that contains cabbage, kale, broccoli, Brussel sprouts, cauliflower, all same species fo plant just bred with different phenotypes selected. each one is a different mutant
Broccoli
proliferation of shoot apical meristems
cabbage
many leaves overlap and surround the terminal flower bud
brussel sprouts
cabbage development among stem at auxiliary meristems
cauliflower head
mass of inflorescence meristems; something stops cauliflower from further development so it never goes from inflorescence to floral meristems
AP1 and CAL1
together, they promote transition fro inflorescence meristem to floral meristem in arabidopsis
why does cauliflower not transition to floral meristems?
double mutant; AP1 and CAL1 both have a stop codon in the middle of the coding region of the gene therefore it is exactly the same situation as the lab test of arabadopsis double mutant
Landraces
genetically distinct, locally adapted varieties of a crop, before modern agriculture seed stocks were maintained by individual farmers resulting in 100’s of landraces
traditional plant breeding
farmers are trying to select traits, don’t want genetic variation but it still happens because the seeds are collected from multiple plants on the field
scientific plant breeding
genetically improved crops; start of 20th century; use single individuals as founders to produce purebred offspring; same as traditional just improved, farmers didn’t realize they were genetically modifying plants, same outcome, faster
2 major methods of scientific plant breeding
1 Cross-pollination of inbred lines plus recurrent backcrossing
2 Heterosis/hybrid vigour
Cross-pollination of inbred lines plus recurrent backcrossing
- two varieties, high yield and disease resistant
- breed plants to get F1 generation
- test and select for high yield & resistant individuals
- backcross for variety 1
- test and select
- repeat backcross to variety 1 and selecting multiple times
- result is a wheat variety mostly made up of variety 1 DNA with Variety 2 disease resistance genes
inbred
breeding of very closely related individuals
Molecular Plant Breeding
similar to cross-pollination of inbred and backcrossing, but instead of testing for traits, scientists follow molecular markers linked tightly to traits of interest
heterosis or hybrid vigor
produces a hybrid better than the parental lines
cross 2 low-yield inbred parental lines
resulting F1 hybrids out yield parental lines
genetic basis of hybrid visor is not known
Darwin first noticed hybrid visor in corn
how much did corn yields increase from 1930-1997
1-8 metric tons
60% due to hybrid lines
40% due to weed control and fertilizer use
hybrid crops examples:
tomatoes, corn, lettuce, spinach, other leaf crops
history of crop heights
pre 1940- bred to be tall to compete with weeds
1940- first herbicide invented
post 1940- bred to be shorter to remain upright in wind and rain
Norman Borlaug
sparked and sustained the green revolution (US plant pathologist); improved wheat and rice; increased crop yields worldwide, reduced hunger, death and political unrest; won Nobel Peace Prize
transgenic plants
insert one or more genes into plant genome
benefits of transgenic vs cross pollination and backcross
faster, more controlled add only desired genes, gene sequencing provides more info, useful in research
transgene or gene transformation methods
gene gun
agrobacterium
gene gun transformation method
grow plant tissue culture in dish
shoot tissue with DNA coated particle
DNA integrates into plant genome
cells divide in tissue culture dividing genes with them
as the plant grows, plants are selected for ones that properly display the gene of interest (some display the gene better than others)
grow the plant and use it as a seed source
Agrobacterium
creates a tutor like structure on the plant causing the cells to divide rapidly
Agrobacterium transformation method
insert gene of interest and a marker gene into t-DNA, transform back into agro, agro transfers t-DNA into plant cells, t-DNA inserts randomly into plant genome, screen for transgenic plants expressing gene go interest correctly, result: transgenic plant of GM plant
