A new study has identified potential key genes responsible for the autoflowering trait in cannabis, providing insights into how this unique characteristic can be harnessed for improved cannabis cultivation.
Autoflowering cannabis plants have gained popularity among cultivators due to their unique features, such as shorter flowering times and adaptability to varying photoperiods. A groundbreaking scientific study, available on a preprint server, has made significant progress in understanding the genetic basis of these traits, which could revolutionise the cannabis cultivation landscape in the future.
The Autoflowering Phenomenon
Autoflowering cannabis plants distinguish themselves from photoperiod-sensitive strains by flowering automatically, irrespective of their exposure to light and dark cycles. This exclusive trait presents growers with several advantages, including:
- Enabling multiple harvests within a single growing season, thereby increasing yield
- Decreasing vulnerability to pests and diseases due to the reduced flowering time
- Enhancing adaptability to a wide range of environmental conditions, making cultivation more flexible
Methods
The researchers crossed an autoflowering cultivar with a photoperiod sensisitve cultivar, and conducted a thorough analysis of the genetic makeup of the offspring focusing on those with the autoflowering trait (Fig. 1). They utilised high-density genotyping, genome-wide association studies (GWAS), and gene expression analyses to identify and investigate candidate genes responsible for the autoflowering phenotype. By examining gene sequences and comparing them across different cultivars, the researchers were able to pinpoint specific genes that may play a crucial role in the development of the autoflowering trait.
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Key Findings: The Genetic Basis of Autoflowering
The researchers focused on two genetic loci (specific locations on chromosomes), known as Autoflower1 and Autoflower2, which were previously identified as being associated with the photoperiod-insensitive flowering trait. Recent mappings have shown that the Autoflowering1 locus is linked to two key genes, APETALA2 and PSEUDORESPONSE REGULATOR 37 (PRR37), which play crucial roles in the regulation of flowering time (Garfinkel et al., 2023; Leckie et al., 2023). In this study, the main focus was on the Autoflower2 locus and its potential role in autoflowering cultivars.
The study demonstrates that three key genes within this region, FLOWERING LOCUS T (CsFT1), EARLY FLOWERING9 (CsELF9), and ARGONAUTE5 (CsAGO5), are closely linked and likely play essential roles in the autoflowering phenotype:
- CsFT1: This gene acts as the central integrator of flowering time, with specific variants resulting in photoperiod-insensitive flowering. It is potentially the primary gene responsible for triggering flowering in response to environmental cues.
- CsELF9: Associated with earlier maturity, this gene could contribute to the rapid flowering observed in autoflowering strains, allowing them to complete their lifecycle more quickly than photoperiod-sensitive strains.
- CsAGO5: This gene is speculated to have a role in age-related flowering, ensuring that autoflowering plants begin flowering at the appropriate developmental stage, regardless of photoperiod exposure.
Is Autoflower2 a “Supergene”?
The close proximity and linked nature of these candidate genes within the Autoflower2 region raise the possibility that it may be a flowering time “supergene.” Supergenes have been observed in other species with complex phenotypes, such as Mimulus, Primula, fire ants, and butterflies. The tight linkage between CsFT1, CsELF9, and CsAGO5 might ensure the inheritance of photoperiod-insensitive phenotypes in C. sativa, providing a genetic basis for the autoflowering trait.
Implications for Cannabis Cultivation:
Deciphering the genetic mechanisms underlying autoflowering traits can profoundly impact cannabis breeding efforts, facilitating the development of:
- Novel strains featuring customised flowering times and photoperiod sensitivity, catering to specific cultivation requirements
- Enhanced adaptability to diverse environmental conditions, reducing the challenges faced by growers in different climates
- Boosted crop productivity through the possibility of multiple harvests per season, potentially increasing overall yield
This pioneering study opens the door to a more comprehensive understanding of the genetic basis of autoflowering cannabis traits, presenting an array of exciting possibilities for the future of cannabis cultivation. As researchers continue to unravel the complexities of Autoflower2 and its constituent genes, both growers and breeders are poised to benefit from the knowledge and advancements that emerge from these investigations.
Reference
Dowling CA, Shi J, Toth JA, Quade MA, Smart LB, McCabe PF, Melzer R, Schilling S. (2023). Dissecting the genetic basis of photoperiod-insensitive flowering in industrial hemp. bioRxiv. doi: 10.1101/2023.04.21.537862