Harsh environments and climate change hamper industrial hemp productivity. Under stress conditions, uniform germination and vigorous seedlings are key to sustaining crop establishment and performance. Trichoderma spp. are beneficial micromycetes, able to colonize plant roots and promote plant development even under abiotic stress conditions. Thus, the seed treatment with specifically selected Trichoderma isolates could be a useful strategy to enhance hemp seed germination and plantlet growth. In this view, a preliminary screening was performed with ‘Eletta campana’ cv. Nine out of 20 Trichoderma isolates enhanced the radicle growth (+66–111%); most of them resulted in good root colonization, but only four isolates significantly enhanced the shoot DW (+18–22%). Three isolates were selected for a pot experiment, compared to T. afroharzianum T22, to evaluate the effect on plant growth, root architecture, accumulation of photosynthetic pigments and stress-related compounds, and variation in antioxidant activity in 20-day-old plantlets. T. afroharzianum OR4 significantly promoted plantlet growth (+9% shoot DW and +11% leaf DW). The seed treatment had a low impact on the other variables studied, except in the case of foliar proline content, a marker of stress tolerance, that was greatly increased with T. afroharzianum T22 and T. atrobrunneum X44 (+32% and +17% DW).
Galletti et al. (Sat,) studied this question.