Identification and mapping of major-effect flowering time loci Autoflower1 and Early1 in Cannabis sativa L.

Authors: TOTH, JACOB - Cornell University; STACK, GEORGE - Cornell University; Carlson, Craig; SMART, LAWRENCE - Cornell University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2022
Publication Date: 9/21/2022
Citation: Toth, J., Stack, G., Carlson, C.H., Smart, L. 2022. Identification and mapping of major-effect flowering time loci Autoflower1 and Early1 in Cannabis sativa L. Frontiers in Plant Science. 13. Article e991680. https://doi.org/10.3389/fpls.2022.991680.
DOI: https://doi.org/10.3389/fpls.2022.991680

Interpretive Summary: There are many hemp (Cannabis sativa) varieties available for industrial, oilseed, and medicinal uses. As the hemp industry has expanded, there has been a rapid expansion of new varieties selected for flowering time, i.e., the critical daylength required for the initiation of flowering. Flowering time is an important trait because, if known, hemp varieties can be matched with latitude for efficient cultivation. Alternatively, if grown under greenhouse conditions, the optimal photoperiod required to initiate flowering can be reproduced. Unfortunately, the genetic control of flowering time is poorly understood, and this makes genetic selection a long and iterative process. Therefore, we used genetic mapping to identify two genes that control hemp flowering. Identification of the genes gives plant breeders molecular tools to accelerate breeding and selection of cultivars that are uniform, suited to specific environmental conditions, and which meet industry needs.

Technical Abstract: Flowering time is an important trait for all major market classes of hemp (Cannabis sativa), affecting yields and quality of grain, fiber, and cannabinoids. C. sativa is usually considered a short-day plant, flowering once night length reaches a critical threshold. Variations in flowering time within and across cultivars in outdoor grown populations have been previously identified, likely corresponding to genetic differences in this critical night length. Further, some C. sativa are photoperiod insensitive, colloquially referred to as autoflowering. This trait has anecdotally been described as a simple recessive trait with major impacts on phenology and yield. In this work, the locus responsible for the autoflower trait (Autoflower1), as well as a major-effect flowering time locus, Early1, were mapped using bulked segregant analysis. Breeder-friendly high-throughput molecular marker assays were subsequently developed for both loci. Also detailed are the flowering responses of diverse cultivars grown in continuous light and the result of crossing two photoperiod insensitive cultivars of differing pedigree.