Differential Varietal Responses in Faba Bean Concerning Pea Aphid and <i>Pea Necrotic Yellow Dwarf Virus</i> ( <scp>PNYDV</scp> ) When Intercropped With Oat

ABSTRACT The pest status of pea aphid ( Acyrthosiphum pisum H.) in faba bean ( Vicia faba L.) cultivation has gained importance because it transmits Pea necrotic yellow dwarf virus (PNYDV), a novel nanovirus in Europe. This study evaluated two faba bean varieties, ‘Fuego’ and ‘GL Sunrise’, grown under sole crop (SC) and intercrop (IC) conditions with oat ( Avena sativa L.) to assess their response to biotic stress by vector infestation and PNYDV infection. In a 2‐year field experiment (2021–2022), an additive, alternate row design with infector rows in each plot receiving regular releases of viruliferous A. pisum was used. ‘GL Sunrise’ consistently had lower aphid infestations than ‘Fuego’ in both cropping systems. Furthermore, intercropping with oat reduced vector movement due to the row barrier effect. In 2021, PNYDV was absent, so aphid pressure mainly resulted in nutrient depletion, with minor effects on nitrogen fixation and yield. Land equivalent ratios (LER) were slightly below 1.0. In 2022, PNYDV infection compounded by heat and drought led to a significant reduction in symbiotic N‐fixation and yield of V. faba in SC systems. In IC systems, the oat component benefited from the reduced competitiveness of both stressed V. faba varieties, and this additional oat yield resulted in LER values above 1.0. The IC system thus ensured a lower spread of aphids and PNYDV and greater yield stability. Due to the only moderate agronomic performance of GL Sunrise under Central German growing conditions, a further screening for stress‐tolerant faba bean genotypes is recommended.