Genotype × Environment Interactions of Industrial Hemp Cultivars Highlight Diverse Responses to Environmental Factors

Abstract

Core Ideas Some hemp traits are more strongly affected by environmental factors than others. Multi‐environment testing is an integral part of hemp cultivar development. Water availability can have a significant impact on yield and other traits. Starting with the 2014 Farm Bill, hemp (Cannabis sativa L.) is being re‐introduced as an industrial crop in the United States. Since the crop has been absent for over 70 yr, little is known regarding the genetic mechanisms controlling economically relevant traits. Particularly, with federal legality of the crop hinging on a stringent tetrahydrocannabinol (THC) content of 0.3% or less, it is necessary to assess variance in this trait due to environmental effects and genotype × environment interactions (GEI) to avoid running afoul of federal law. Understanding how physical and biochemical traits respond to the environment also plays a strong role in selecting and developing appropriate cultivars for production in diverse growing regions. In 2016 we performed cultivar trials in multiple environments in Colorado to assess performance characteristics of a diverse set of germplasm from breeding programs across Europe and Asia. From these data, we were able to identify traits nearly entirely controlled by genetic factors, like days to maturity and THC and cannabidiol (CBD) production. We also identified traits strongly influenced by the environment and GEI, like grain yield, plant height, and water use. Individual cultivars also exhibited widely varying degrees of sensitivity to the environment. This underscores the importance of continued work to characterize genetic control of hemp traits to expedite breeding of cultivars that are well‐adapted to target growing regions.

Recent advances in Cannabis sativa genomics research

“…There are only two published cannabis GWAS studies, one of which is ongoing and the other reporting marker‐trait association using a limited number of SNPs (B. J. Campbell et al ., 2019; Henry et al ., 2020; http://multihemp.eu/). The paucity of studies is likely a consequence of the previous limited accessibility of cannabis genetic diversity and insufficient marker density.…”

Impact of Growth Stage and Biomass Fractions on Cannabinoid Content and Yield of Different Hemp (Cannabis sativa L.) Genotypes

“…However, the CBDA, differs in respect to DW yield between growth stages. Campbell et al [39] reported, that 83% of variance in CBD/A content resulted from genetic effects, making genotype selection important when seeking high CBD/A contents. Environmental factors such as the positive correlation between CBD/A content and water availability found by Calzolari et al [23] slightly increase CBD/A content, but the change was small enough that inflorescence yield is far more important to overall yield than a slight change in CBD/A percentage [39].…”

Development and validation of genetic markers for sex and cannabinoid chemotype in Cannabis sativa L.

“…Hemp ( Cannabis sativa L.) is a multiuse crop grown primarily for grain, fiber, and cannabinoids. In recent years, there has been a resurgence in the study of hemp in the United States and across the world in fields including genomics (Grassa et al, ; Laverty et al, ), agronomics (Campbell, Berrada, Hudalla, Amaducci, & McKay, ), and novel end‐uses (Turner, Sloan, & Currell, ; Wang & Xiong, ). The market for hemp (defined as <0.3% tetrahydrocannabinol; THC by dry weight) and marijuana (>0.3% THC), is expected to surpass $26 billion in the US by 2025 (Global Cannabis Report: 2019 Industry Outlook, ).…”