The beginning of the 20th century saw the rediscovery of Gregor Mendel’s work on the
inheritance of phenotypic traits in plants. Mendel’s work laid the foundations of modern,
scientific plant breeding by enabling plant breeders to predict how traits brought into
breeding lines would be inherited, and what had to be done to ensure that the lines would
breed true. As a result, scientific plant breeding from the early part of the 20th century
onwards brought huge increases in crop yield, without which current human population
levels would already be unsustainable.
In the following decades, science made great strides in the elucidation of the molecular
processes that underpin inheritance; genes, the units of inheritance, were linked with
proteins, DNA was shown to be the material of inheritance, the structure of DNA was
resolved, DNA polymerases, ligases and restriction enzymes were discovered, recombinant
DNA molecules were created and techniques for determining the nucleotide
sequence of a DNA molecule were developed.
Plant scientists were quick to exploit the new tools for manipulating DNA molecules
and also made the astounding discovery that a naturally occurring bacterium, Agrobacterium
tumefaciens, actually inserted a piece of its own DNA into that of a plant cell
during its normal infection process. As a result, by the mid-1980s everything was in place
to allow foreign genes to be introduced into crop plants and scientists began to predict a
second green revolution in which crop yield and quality would be improved dramatically
using this new technology.