Overcoming limitations of conventional breeding with fast gene discovery in maize

12 Sep 2022 --- As agriculture faces severe challenges of cutting yield losses during extended periods of heat and drought while shifting to sustainable food models, the topic of how to adapt crops to changing climate conditions is paramount.

This summer has seen major drought, flooding, heatwaves and record temperatures worldwide, signifying how the rapid onset of climate change is making life difficult for global farmers.

Maize breeding
Scientists at VIB-UGent Center for Plant Systems Biology in Belgium say that conventional breeding programs are labor-intensive and time-consuming.

Instead, they have teamed up with Flanders Research Institute for Agriculture, Fisheries and Food (ILVO) to develop a fast gene discovery pipeline in maize to advance breeding programs.

“Conventional breeding has contributed greatly to the adaptation of crops to their environment but is starting to show its limitations,” says Christian Lorenzo (VIB-UGent Center for Plant Systems Biology).

“When trying to improve complex traits like crop yield, effects are often limited or insignificant, making this a slow process. But climate change is forcing us to develop more productive crops with fewer resources,” he says. 

Conventional breeding entails the crossing of varieties that contain the desired traits in their genome. A complex gene network often controls traits essential for plant survival and susceptible to environmental stress, such as growth and yield. 

Breeders might need to combine multiple growth-stimulating properties to achieve significant growth improvement, says the university. 

Conventional breeding entails the crossing of varieties that contain the desired traits in their genome.BREEDIT breeding
Finding the right combinations to obtain optimal results under varying field conditions is time-consuming. With molecular biology, agronomic traits can be linked to specific genes rather than genomic regions, narrowing down the genomic targets for breeding.

“We have now developed a pipeline in which CRISPR-mediated gene editing of multiple genes simultaneously is combined with different crossing schemes to identify the key genes involved in trait enhancement. In other words, BREEDIT is a support platform for breeding using innovative gene editing techniques.”

CRISPR-Cas9 is an established gene-editing technique to modify the plant’s genetic material with high precision. The molecular scissor Cas9 is directed to a predetermined position in the target gene by a guide molecule – gRNA – where a small genetic alteration is induced.

The BREEDIT team has developed a strategy to edit up to 60 genes in all possible combinations. Introducing 12 gRNAs at once into a Cas9-expressing parent generates a multiplex gene-edited maize plant. 

Implementing a crossing scheme with plants containing a different set of gRNAs leads to a diverse collection of edited maize plants that can be screened for improved agronomic traits.

“BREEDIT provides us with a tool to quickly identify promising gene edits to improve agronomic traits in crops. Especially for complex traits such as yield, gene editing-assisted breeding will become increasingly important to keep up with the changing environment,” says Prof. Dirk Inzé, lead of the BREEDIT project.

Edited by Gaynor Selby