Arbuscular Mycorrhizal Fungi in Viticulture: Should We Use Biofertilizers?

Aim: Arbuscular mycorrhizal (AM) fungi are a group of symbiotic soil fungi known for their role in promoting host-plant growth by improving nutrient uptake, providing pathogen protection, and increasing tolerance to common vineyard soil abiotic stressors such as salinity, extreme pH, and low water availability. Use of commercially produced AM fungal inoculants, known as fungal biofertilizers, is growing in viticulture, but remains untested under field conditions. Here we discuss factors that affect the performance of fungal biofertilizers and scenarios where they may be more, and less, advantageous.

Key Themes:

• Fungal biofertilizer use is increasing globally, but does their use translate to improved grapevine performance under vineyard conditions?

• What are the key considerations for incorporating AM fungi into vineyard management?

Impact and Significance: While the importance of AM fungi for plant performance is well known, inoculation with fungal biofertilizers does not increase plant growth or yield consistently. This may be due to context dependency of the AM symbiosis, which can be affected by vineyard management practices like fertilizer use and tillage. Where AM fungi are not limiting, as in most vineyard soils, adding inoculants when compatible fungi are abundant may be redundant. However, in situations where soil fungi may be limiting, such as in greenhouse propagation nurseries using near-sterile media, or in fields with a history of heavy fertilizer use, AM fungal additions may be warranted.