Summary
Heterosis, where crossbred offspring outperform both inbred parents in growth or yield.
In depth
Heterosis occurs when crossing inbred lines gives superior F1 hybrids, often explained by dominance (masking harmful recessives) and overdominance. Modern hybrid maize yields far more than open-pollinated varieties.
The benefit declines in later generations, so farmers buy new seed.
Hybrid vigour, or heterosis, was exploited by Shull and Jones in maize in the early twentieth century, and double-cross and single-cross hybrids drove a threefold rise in yields. Farmers must buy new seed each year because the next generation segregates and loses the effect. The mule, from horse and donkey, is a hybrid showing vigour but sterility.
Explanations include dominance (inbred lines carry different harmful recessives that are masked in hybrids), overdominance (heterozygotes outperform) and epistasis. Hybrid rice in China raised yields by about 20 percent. Inbreeding depression is the opposite effect.
Key idea: the vigour is greatest in the F1 and declines in following generations as heterozygosity falls.
Frequently asked questions
What is Hybrid Vigour?
Heterosis, where crossbred offspring outperform both inbred parents in growth or yield.
Which area of biology covers Hybrid Vigour, and how advanced is it?
Hybrid Vigour is one of the 54 topics in Genetics. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Homozygous and Heterozygous, Incomplete Dominance, Genomic Imprinting.
Can you give an example of Hybrid Vigour?
A mule (horse x donkey) is stronger than either parent but is sterile.
What should I learn before Hybrid Vigour?
Work through the Beginner topics in Genetics first, such as Heredity, Gene, Allele, then return to Hybrid Vigour. Advanced topics assume the Intermediate vocabulary.
What topics are related to Hybrid Vigour?
The closest topics to Hybrid Vigour are Homozygous and Heterozygous, Incomplete Dominance, Genomic Imprinting, Gene Pool. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Hybrid Vigour?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Hybrid Vigour. To practise the whole of Genetics, use the Genetics quiz.
How is Hybrid Vigour different from Homozygous and Heterozygous?
Hybrid Vigour: Heterosis, where crossbred offspring outperform both inbred parents in growth or yield. Homozygous and Heterozygous: Homozygous means two identical alleles for a gene; heterozygous means two different alleles. Read both side by side and note what each one explains.
How should I study Hybrid Vigour step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Homozygous and Heterozygous and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.