Hemp growers in New York face the uncertainty of growing a crop that becomes illegal to sell because it unintentionally contains a higher amount of the psychoactive chemical THC than is allowable by state regulations.
Now a Cornell University study has revealed the cause behind some hemp plants’ tendency to “go hot” that could make it easier to cultivate hemp and stay within legal limits.
The culprit seems to be genetics, according to work done by Cornell researchers, and not a stress reaction to environmental conditions.
People thought “there was something about how the farmer grew the plant, something about the soil, the weather got too hot, his field was droughted, something went wrong with the growing conditions,” said Larry Smart, professor in the horticulture section of the School of Integrative Plant Science. “But our evidence from this paper is that fields go hot because of genetics, not because of environmental conditions.”
Smart was the senior researcher for the study published last month in the Global Change Biology-Bioenergy.
Jacob Toth, a doctoral student in Smart’s lab, and lead author of the paper, developed a test that found three genetic categories for hemp plants: one has two CBD-producing genes, another has one of those genes and one producing THC, and the third has two genes making THC. The ideal selection has only CBD, or cannabidiol, genes.
Toth said, “To keep THC levels low, ensuring a lack of THC-producing genes will be important for the development of future compliant cultivars. Molecular testing is also much quicker and less expensive than current methods, and it can be done on seedlings instead of mature plants.”
The research team carried out field trials in both Ithaca and Geneva. The researchers noted that when they obtained supposedly low-THC hemp seeds, their tests revealed two-thirds actually produced THC levels above the limits.
Both types of compounds are produced only in the female hemp plants, but farmers might unwittingly use male plants with the THC genes for pollination that carry THC trait to their offspring, thereby promoting its production.
The team also came up with genetic markers to identify the sex of plants earlier, as they are identical until they flower. The technology is not affordable for an entire field of plants yet, Smart said, but promises to be useful.
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