Indian scientists have developed the first ever low-pungent mustard that is pest and disease-resistant. It is based on CRISPR/Cas9 gene editing, while being non-GM and transgene-free.
Significance of Gene Editing in Mustard Breeding
- Traditional mustard seeds (Brassica juncea) that are grown in India contain about 120-130 parts per million (ppm) of compounds called glucosinolates, which are a group of sulphur and nitrogen-containing compounds contributing to the characteristic pungency of their oil and meal.
- These compounds serve as natural defenders, protecting the plant from pests and diseases.
- In comparison, canola seeds have much fewer glucosinolates, around 30 ppm. These lower levels let the canola oil and meal have a specific pleasant taste.
- Oilseeds yield oil for cooking, and their leftover meal, a protein-rich ingredient, is used in animal feed. Rapeseed meal, rich in glucosinolates, is fed to livestock but requires mixing with grass and water.
- High glucosinolates are also known to cause goiter (swelling of neck) and internal organ abnormalities in livestock.
- Scientists have been working on a goal to develop mustard seeds that have fewer glucosinolates, similar to canola seeds.
- However, reducing glucosinolates in mustard seeds can weaken the plant’s overall ability to defend itself against pests and diseases, which presents a challenge.
Role of Gene Editing in Mustard Breeding
- Scientists directed their efforts toward modifying specific genes known as glucosinolate transporter (GTR) genes.
- These genes play a crucial role in how glucosinolates, important compounds in mustard seeds, build up.
- To achieve this modification, they employed a gene-editing tool called CRISPR/Cas9, which works like precision scissors to alter gene sequences accurately.
- In a particular mustard variety named ‘Varuna,’ the researchers focused on 10 out of the 12 GTR genes.
- Through these genetic modifications, they deactivated the proteins produced by these genes, resulting in a significant reduction in glucosinolate levels within the seeds.
Implications of Gene Editing on Plant Defense and Pest Resistance
- The modified mustard plants showcased glucosinolate levels in their seeds that were lower than the 30 ppm threshold set for canola-quality seeds.
- Interestingly, the leaves and the walls of the pods around the seeds displayed higher amounts of glucosinolates.
- This increase was attributed to a disruption in the transport of these compounds. This heightened accumulation of glucosinolates in the leaves and pods plays a crucial role in bolstering the plant’s ability to resist pests.
- As a result of these genetic modifications, the edited mustard lines exhibited robust defense mechanisms against both fungal and insect pests.