TILLCANN: A TILLING platform in Cannabis sativa for mutation discovery and crop improvement

Cultivation of Cannabis sativa is increasing because of its therapeutic value and recognition as a multi-purpose and sustainable crop. Targeting Induced Local Lesions in Genomes (TILLING) is a versatile reverse genetics approach that unlocks induced variation through mutagenesis to accelerate the development of new cultivars and contribute to the functional validation of genes. Increasingly efficient next-generation sequencing technologies and genomic resources have combined to make TILLING by sequencing (TbyS) an attractive technique that can be applied in cannabis. Here we describe the development of a mutagenesis protocol for C. sativa and the development of the TILLCANN platform composed of 1,633 M2 families. As a demonstration of the functionality of the platform, we used TbyS to perform a high throughput screening of novel mutations in amplicons for genes associated with important agronomic and biochemical traits in a set of 512 M2 families. We confirmed 14 of the identified mutations and calculated an average mutation frequency range of 1/263 to 1/320 kb. We found that heterozygous mutants in the cannabis homologue of Class II TEOSINTE BRANCHED 1/CYCLOIDEA/PCF (TCP4) are linked to alterations in leaf number and morphology. We expect that the novel genetic variability unlocked in the TILLCANN platform for performing forward or reverse genetic screens can significantly boost breeding programs geared toward both medicinal cannabis and industrial hemp.