Hybrid Vigor

Definition: The increase in vigor of hybrids over their parental inbred parents (heterosis)

Hybrid

• A cross of two or more inbreds

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Hybrid Seed Production

Inbreds

• 5 or more generations
• Decreased vigor
• Increased uniformity
• Recessive genes are manifested

Common Crosses

• Single
  • Advantages
    1. Tend to be more uniform
    2. May have higher level of disease or insect resistance
  • Disadvantages
    1. Higher cost
    2. May yield less than a double-cross
• Double
  • Advantages
    1. May be more buffered against stress conditions
    2. May have more complete grain fill
    3. Lower seed cost
    4. Generally have higher seed quality
• Three-way
• Modified

Hybrid Production Systems

Cytoplasmic Mate Sterile System (CMS)

1. Need to transfer sterile cytoplasm to A line Transfer.gif
2. Parents involved: CMS_Comp.gif

• A line (CMS)
• B line (Maintainer)
• R line (Restorer)

Nuclear Encoded Male Sterile System (NMS)

• Sterility gene is linked to herbicide resistance
• 50% of the female plants are sterile

Chemical Hybridizing Agent (CHA) cha.gif

• Involves use of a gametocide

Self Incompatibility System (SIS) Incomp.gif

• Dominant
• Recessive

Photosensitive Male Sterile System (PMSS)

Thermosensitive Male Sterile System (TMSS)

References:

Principles of Seed Science and Technology. 3rd Ed. L.O. Copeland and M.B. McDonald. Chapman and Hill, New York, 1995