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F1 Hybrids
Claudia Canales
The need for more food
• F1 hybrids • Fertilisers • Mechanisation (tractors)
U.S. maize yields in the last 100 years U.S. population growth in the last 100 years
8-fold increase in maize yield thanks to:
What is a maize F1 hybrid?
The first generation (F1) of a cross between from two uniform parent inbred lines
F1 Hybrid
Parent 1 Parent 2
X CROSS
Maize reproduction
Each kernel is a genetically unique individual
How do you make an F1 hybrid?
3 steps
1: Development of parental inbred lines
By self-pollinations until a good degree of uniformity is achieved. Selection for type and good parent potential is done as the lines are inbred.
Inbreeding depression
2: Test crossing: sets of two inbred lines are crossed (uniformly, with no selfing allowed)
How do you make an F1 hybrid? Cont.
Hybrid vigour
3: Production crossing: commercial production of F1 hybrid seed. Expensive and labour-intensive.
How do you make an F1 hybrid? Cont.
What are the advantages of F1 hybrids?
• It is uniform in appearance and behaviour: – enables farmer to treat and harvest crop at the same
time uniformity – has marketing advantages when sold to buyers with
strict quality standards)
• It has hybrid vigour (makes them more competitive with weeds)
• It is high yielding • It is selected for improved grain quality • A particular hybrid can be selected for specific
pest and disease resistance or drought tolerance
Maize F1 hybrids
P1 P2 C B
14 days P1 P2 C B
Maize
Parent 1 Parent 2 Parent 2 Parent 1 F1 Hybrids F1 Hybrids
Game introduction
• F2 generation of hybrid seed – variability and consequences
• Hybrid seed is more expensive than open-pollinated maize seed
• Farmers situated in a low potential environment and who cannot afford extra inputs such as fertilizer may not recover the costs of the hybrid seed
• Fresh hybrid seed needs to be bought every planting season (farmers cannot replant grain as seed without major reductions in yield, which might be a decrease of 30 % or more)
What are the disadvantages of F1 hybrids?
What are the disadvantages of F1 hybrids? Cont.
Parent 2
Parent 1
F1 Hybrid
F1 Hybrid seed selfed over several generations
Inbreeding depression
Hybrid vigour
F1 hybrid seeds vs landraces
• Genetic uniformity can be a problem if the conditions are bad (such as extreme weather conditions, new pest or disease)
• Traditional landraces are genetically very variable, and hence more resilient, although yields are lower
• Landraces are invaluable sources of genetic diversity
Consequences of hybridisation
• Bought seed vs seed saving
• (Lack of) Ability of individuals or government research institutions to produce in desired quantity and quality
• F1 hybrid production closely linked to the creation of private seed companies for commercial seed production (public versus private investment in plant breeding)
F1 hybrid seeds are not GM!! Why? Because they are produced by crossing two non-GM plants.
F1 Hybrid
Parent 1 Parent 2
X CROSS
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