In the USA, Cornell University researchers have identified a gene in hemp that provides resistance to powdery mildew.
While hemp ( and cannabis generally) is a hardy crop, it is still prone to attack by a number of insect pests and fungal diseases. Among the latter is powdery mildew, with infected plants displaying white powdery spots on the leaves and stems. It’s not just unsightly – powdery mildew damages the tissues of leaves and decreases plant vigor, growth and cannabinoid yields.
Powdery mildew thrives in environments with high humidity and moderate temperatures – such as greenhouses – and is one of the most prevalent diseases afflicting Cannabis sativa.
Significant time and money are spent on preventing and dealing with the fallout of powdery mildew. What’s really needed are more cannabis strains developed that are resistant to it. And researchers from Cornell University say they are on the right track.
The researchers identified a hemp cultivar resistant to powdery mildew on a consistent basis and hypothesised there was a resistance gene in that line. The cultivar -‘FL 58’ – was crossed with a susceptible cultivar and the progeny evaluated; which displayed a range of susceptibility.
“We did genome sequencing of the resistant line and compared it with susceptible lines and found a gene mutation that is highly likely to be responsible for the resistance,” said George Stack, one of the lead researchers. “We now have molecular markers that can identify that gene for resistance and can be used for selection of breeding lines.”
As well as resulting in resistant plants that will greatly improve indoor production of cannabinoids, the gene could be bred into hemp cultivars for field-grown grain, fiber and cannabinoid plants.
A paper on the study: “Genetic Mapping, Identification, and Characterization of a Candidate Susceptibility Gene for Powdery Mildew in Cannabis Sativa L.” has been published in the journal Molecular Plant-Microbe Interactions.
The Cornell researchers aren’t done yet – they are continuing to try to identify more powdery mildew resistance genes and delving into the interactions between the gene identified and other factors in order to maximize genetic resistance.
