# Mycorrhizal symbiosis drives tolerance to potato cyst nematodes

## TL;DR

Mycorrhizal fungi help potato plants tolerate nematode damage, with tolerant cultivars showing stronger responses and changes in sugar transporter genes.

## Contribution

Demonstrates that mycorrhizal fungi are essential for host tolerance to nematodes, not just complementary.

## Key findings

- Tolerant potato cultivars lose yield in sterile soils under nematode pressure.
- Arbuscular mycorrhizal fungi increase tuber biomass during nematode parasitism.
- Sugar transporter gene expression varies in tolerant cultivars, suggesting a role in tolerance.

## Abstract

Host plant tolerance to pathogens is increasingly relevant as resistance sources and control options become scarce. Arbuscular mycorrhizal (AM) fungi are known to enhance plant stress tolerance, but it remains unclear whether they are essential for, or complement, innate tolerance. We observed that potato cultivars described as tolerant to G. pallida suffered yield loss under nematode pressure when grown in sterile soils, indicating a lack of tolerance. The introduction of Rhizophagus irregularis increased tuber biomass during nematode parasitism, with cultivars commercially labelled as tolerant exhibiting a stronger response to AM fungi. The data suggest cultivar differences in mycorrhizal responsiveness with the differential expression of a range of plant sugar transporter genes in “tolerant” cultivars inferring a role of sugar allocation in host tolerance. Overall, AM fungi are critical for conferring tolerance against G. pallida and revealing the underpinning genes may provide useful targets to explore in current commercially desirable yet intolerant cultivars.

•Potato cultivars labeled as tolerant lose yield under nematode pressure in sterile soils•Arbuscular mycorrhizal fungi improve tuber biomass during nematode parasitism•Tolerant cultivars show stronger mycorrhizal responsiveness than intolerant ones•Sugar transporter gene expression suggests a role in tolerance mechanisms

Potato cultivars labeled as tolerant lose yield under nematode pressure in sterile soils

Arbuscular mycorrhizal fungi improve tuber biomass during nematode parasitism

Tolerant cultivars show stronger mycorrhizal responsiveness than intolerant ones

Sugar transporter gene expression suggests a role in tolerance mechanisms

Natural sciences; Plant biology; Interaction of plants with organisms; Molecular plant pathology; Agricultural science