Discuss examples from Crop Science on new cultivar releases
1946 Stiff Stalked corn synthetic - 16 lines
SYN1 - highest yield
SYN2 - little yield reduction
SYN3 - stable yield
Sometimes natural selection will change composition-disease, drought, winterkill.
Synthetic used for alfalfa - grasses
Synthetic used by farmers who do not want to buy seed each year.
Marginal corn areas
Synthetics need to be constituted after several years.
1. Constituted from reproducible units of cross-pollinated crop (clones, inbreds)
2. Materials used are selected from performance in combining ability or progeny tests
3. The cultivar is constituted by random intermating of the units
4. The component units are maintained so synthetic can be reconstituted
Starting with Source Nursery
-> Several thousand plants. Develop inbreds
Superior plants inbred to fix traits
>25/50 superior clones grown in isolation
Self each, Intermate (polycross), Seed is bulked by clone
Superior clones identified in progeny test
> 4-10 clones put together as synthetic. Bulked as SYN0
Equal quantities of seed harvested from each clone/plant
SYN1 Open pollinated
Synthetics used in 1.) marginal areas where hybrids too costly, 2.) farmers can not buy seed every year, 3.) hybrid systems not available, and 4.) alfalfa, corn, sugar beets and sunflower.
Breeder maintains SYN0 parents.
Hybrids used to use T Cytoplasmic male sterility S/C CMS Southern Corn leaf blight reverted to machine emasculation.
· · Single cross 75% A x B
· · Highest yielding modified single (A x A') x B
· · 3 way cross 20% (A x B) x C
· · Double cross (A x B) x (C x D) marginal areas
Corn yields in 1930=20 bu/acre 1995 140 bu/acre 59% genetics- 23% weed control-19% fertilizer
Flint, dent, sweet corn, floury, popcorn and waxy corn.
Corn production 247 MT USA, 125 MT China, Bz 33 MT
QPM Quality Protein Maize- twice the lysine and tryptophan. 15% corn acreage in Ghana is QPM.
Reid Yellow Dent became very popular US variety. First major US hybrids US 13(1919) and Iowa 939.
1908 East planted hybrid and got 202 bu/acre.
1915 Funk Bros. Stated hybrid corn breeding program.
1918 First double hybrid produced
1920 Henry Wallace started a corn breeding program. Pioneer Hi-bred
1992 250 private hybrid seed companies. 22 million bags of hybrid seed sold- $60/bag.
HFCS High fructose corn syrup replaced sugar as major sweetener in the US.