Genome editing technology like CRISPR/Cas9 has emerged as an excellent and rapid plant
breeding tool for exploring basic plant biology as well as for increasing agricultural GDPs.
Although CRISPR-based genome editing has shown its applicability in different plant
genomes since 2013, the genus Brassica has come across this precise gene modification tool
only since 2015, owing to the polypoid and complex genome architecture. The globally
cultivated oilseed Brassica crops – Brassica napus (rapeseed) and Brassica juncea (mustard)
are rich in seed glucosinolate content. The presence of high amounts of seed glucosinolates is
known to be anti-nutritional and limits the value of the seed oil for human consumption and
the seed meal as animal feed. Over the last 6-7 decades, a major breeding objective in
rapeseed and mustard cultivars has been to bring down the seed glucosinolate content within
the Canola quality limit. However, such Canola quality rapeseed and mustard cultivars are
low glucosinolates in all parts of the plants rendering them vulnerable to generalist pests and
pathogens.
We recently reported CRISPR/Cas9-based editing of glucosinolate transporter (GTR) family
genes in Indian mustard to develop ideal lines with the desired low seed glucosinolate content
while maintaining high glucosinolate levels in the other plant parts for uncompromised plant
defense. The use of three gRNAs provided highly efficient and precise editing of four GTR1
and six GTR2 homologs leading to a significant reduction of seed glucosinolate content from
146.09 μmoles/g dry weight (DW) to as low as 6.21 μmoles/g DW. Detailed analysis of the
GTR-edited lines showed higher accumulation of glucosinolates in the aerial parts. When
tested against the pathogen Sclerotinia sclerotiorum and generalist pest Spodoptera litura, the
GTR-edited lines displayed a defense response at par or better than that of the wild-type line.
The GTR-edited lines were equivalent to the wild-type line for various seed yield and seed
quality traits. Our result presents a breakthrough in the breeding of oilseed Brassicas for oil
and meal quality without compromising the protection provided by glucosinolates to all the
vegetative parts of the plant.