First report of susceptibility of Cannabis sativa to Nacobbus celatus

Abstract

This study constitutes the first report of Cannabis sativa susceptibility to the endoparasitic nematode Nacobbus celatus. Driven by recent regulatory changes, medicinal cannabis cultivation is expanding rapidly across Argentina and the wider region. This growth necessitates the identification of emergent phytosanitary threats in established intensive agricultural zones, such as the La Plata Horticultural Belt, which has high production potential. In a completely randomized design, rooted cuttings of C. sativa var. ‘Pachamama’ were grown in 10-liter pots containing tyndallized soil and inoculated with 5,000 eggs of a population originally collected from Colonia Urquiza (GenBank AM412748), which represents the type lineage for the recently described species N. celatus. After a 90-day cultivation cycle, parasitized plants developed between 35 and 50 root galls and reached a Reproduction Factor (RF) of 2.64, confirming that C. sativa is a susceptible host. The infection severely compromised crop performance, causing a statistically significant 24.1% reduction in dry flower yield (p<0.01). Although individual cannabinoid concentrations per gram remained unaltered, the biomass drop led to a critical decrease in total cannabinoid production per plant, falling from 4,541.04 mg in healthy controls to 3,479.64 mg in parasitized individuals. Furthermore, cannabinol (CBN) was consistently absent in all infected plants (0 b) compared to controls, suggesting that nematode-induced stress and functional syncytia alter the rate or phenological timing of secondary metabolite maturation. These findings establish a critical precedent for the medicinal cannabis industry in the Americas, suggesting that the expansion of this crop into regions where the Nacobbus aberrans species complex is endemic requires a precautionary approach and the development of specialized integrated pest management strategies.