Drought tolerance increases aphid resistance in native potato genotypes

Global climate change is restructuring ecological interactions, but it has not yet been fully resolved whether plant drought tolerance influences resistance to herbivorous insects. A proposed hypothesis predicts a trade‐off in which drought‐tolerant plants are more susceptible to herbivores, particularly under water limitation. We evaluated this hypothesis using eight native Chilean potato genotypes ( Solanum tuberosum Chilotanum group) that differed in their drought tolerance, evaluating their interactions with the potato aphid ( Macrosiphum euphorbiae Thomas) under well‐watered and drought conditions.

Aphid walking time on the leaf surface, which reflects the difficulty experienced by insects in locating suitable feeding sites and therefore provides an indicator of pre‐feeding plant resistance, varied according to the interaction between potato genotype and water regime. Under drought conditions, some genotypes exhibited longer walking times, whereas others showed little change, indicating that drought modifies host acceptance in a genotype‐dependent manner.

Electrical penetration graph (EPG) recordings were used to evaluate aphid feeding success after stylet insertion. Across all genotypes, aphids exhibited a reduction in phloem‐related activities as plant drought tolerance increased, indicating that drought‐tolerant genotypes imposed stronger barriers to successful phloem access and sustained feeding.

Aphid abundance and population growth rate under drought were not associated with plant drought tolerance. However, aphid per capita biomass decreased significantly with increasing drought tolerance, suggesting reduced insect growth on the most drought‐tolerant genotypes. These genotypes also exhibited drought‐induced increases in leaf trichome density, particularly in the abaxial midrib leaf region, which is consistent with an enhanced structural defence against aphids, possibly reducing water loss.

Taken together, these results demonstrate that drought tolerance is positively associated with multiple components of aphid resistance in Chilotanum potatoes. Rather than supporting a trade‐off between drought tolerance and herbivore resistance, our findings suggest that traits conferring resilience to water limitation may simultaneously strengthen plant defences against phloem‐feeding insects.