Agriculture and Plant Genetics

Targeted Exchange Between Homologous Chromosomes - A New Tool for Precise Breeding (No. T4-1871)

Lead Researcher: Prof. Avraham Levy


As the world’s population grows, and climate changes, there is a strong need for breeding hardier crops in a precise fashion. The traditional method of introducing new traits to a plant via traditional breeding methods is a slow and stochastic process, which can require growing a large number of plants to screen for desired progeny. Additionally, it can be difficult to generate a new variety with only the desired traits without any extra undesired traits being introduced in the process. The reason being is the randomness of genetic recombination during reproduction and due to the genetic linkage between desirable and undesirable traits. Therefore, it would be of great value to precisely shuffle genetic elements between chromosomes in both somatic and meiotic plant cells at specific sites. The group of Prof. Avi Levy have recently devised a method for inducing site specific recombination between homologous chromosomes using CRISPR/Cas9. The technology has numerous applications including allelic replacement in somatic cells. As well as performing reciprocal exchanges of large homologous chromosomal segments at specific locations, enabling recombination events that are rare via traditional breeding. The technology also has great promise in relation to the regulatory environment; as the USDA has stated that it would not oversee multiple crops that were ‘gene edited’ by CRISPR/Cas9< color=#0000ff>[1]. Consequently, this technology has great value as a method for combining specific crop traits and for improving the accuracy of plant breeding in plants. < size=2> 

  • Inducing targeted Homologous Recombination
  • Improving Plant Breeding – through a higher precision of the exchange of chromosomal segments and through the use of smaller populations
  • Applicable with any nuclease system – Simply requires that the system generates a DSB in somatic cells of a hybrid plant. (e.g. TALENs, CRISPR/Cas9, …)

The research team led by Prof. Avi Levy at the Weizmann Institute of Science has developed a method to site specifically induce homologous recombination (HR) between chromosomes. The team has applied the innovation in tomato and in Arabidopsis plants. CRISPR/Cas9 was used to perform site specific double strand breaks (DSB) on homologous chromosomal sections. Then using a series of phenotypic and molecular assays, the Levy team could show the DSB repair events were due to HR (either crossover or non-crossover) rather than non-homologous end joining (NHEJ).   [1] With a free pass, CRISPR-edited plants reach market in record time. Nature Biotechnology 36, 6–7 (2018). https://www.nature.com/articles/nbt0118-6b