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– Marker assisted selection • Fortify food with Vitamin A precursors • Case study: Maize and Vitamin A – Lower Vitamin A deficiency related diseases
29 30 5 04/03/2013 Visually scoring key precursors is difficult Marker Assisted Selection
• SNP markers that co segregate with the trait …
…candidates for linkage to the genes for the trait.
– SNP = single nucleotide polymorphism
– Marker SNPs need not be causal • SNPs correlated with B carotene production: • Goal: – 2 5 fold higher production – Maximize carotenoids and B carotenes • But: • Incorporating these genomic regions into maize
varieties could help reduce Vitamin A deficiencies – Color phenotype alone is unreliable
– Difficult to quantify precursors in high throughput – If adopted by local growers • Therefore: Use genotype instead of phenotype!
31 Harjes et al. 2008, Science 319: 330 333 32 -Breeding the yellowest kernels isn't going to work to
m aximize B-carotenes
-However, colour is an unreliable phenotype -Incorporating the SNPs that co-segregate with the trait of
Vitamin A production will reduce Vitamin A deficiencies Why do we care about genetic variation in crops? Irish Potato Famine (1845 1852)
• 750,000 1 million Irish died during the famine 1. Clues to past artificial selection – 1 2 million more emigrated – On what traits did our ancestors select? • Population of Ireland fell by ~25% 2. Future improvement of crops
– Is it possible to keep breeding better crops without
– Or is there insufficient genetic variation? • Many emigrants settled in Britain, USA & Canada
– Started cultural ties that last to this day
– Irish immigrants comprised ~25% of many major cities 3. Pest and pathogen management • Boston, Baltimore, Philadelphia, Toronto – Single largest ethnic group in Toronto in early 1850’s – Can we reduce crop loss to pests?
33 34 What happened? • Potatoes do not grow easily from seed
• They sprout easily from the
underground tuber (potato)
• Leads to clonal propagation
• This happens in your house if you
forget about potatoes in a cabinet
for too long ! • Social, economic, and religious discrimination,
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This document was uploaded on 01/27/2014.
- Winter '14
- Annotated Lecture S