Hübriidvigor

Hübriidvigor, also called heterosis, is the phenomenon whereby offspring resulting from crosses between genetically distinct individuals exhibit greater biological fitness than either parent. Fitness can include higher yield, faster growth, increased fertility, or greater resilience, depending on the species and trait.

Hübriidvigor is most commonly observed in agriculture, where hybrids often outperform parental lines. In crops such as maize, rice, and wheat, F1 hybrids can show higher yields or improved stress tolerance. In livestock, crossbred animals may display faster growth, better fertility, and greater adaptability.

The genetic basis of hybrid vigor is multifactorial and not fully understood. The main explanatory models are the dominance hypothesis, which posits that deleterious recessive alleles are masked in the hybrid; the overdominance hypothesis, which suggests certain heterozygous genotypes confer superior performance at specific loci; and epistatic interactions among genes that create favorable allele combinations. In practice, multiple mechanisms likely operate together.

Applications and limitations: In plant breeding, F1 hybrids are produced by crossing two distinct lines to exploit heterosis. Hybrids offer uniformity and strong vigor, but require controlled pollination and ongoing production of new seed. Hübriidvigor is sometimes environment-dependent and may decline in unfavorable conditions. Vigor can also break down in subsequent generations due to recombination and segregation.

Historical notes: The concept and its practical value were demonstrated in maize in the early 20th century by Shull and East, leading to widespread adoption of hybrid breeding in agriculture.