Physiological and Morphological Responses of Susceptible and Resistant Barleys to Bird Cherry-Oat Aphid Feeding

The bird cherry-oat aphid (Rhopalosiphum padi [Linnaeus, 1758]) is considered a key pest of cereal crops worldwide, causing direct damage through sap feeding and by acting as a vector for viral diseases. Managing aphids is challenging because of their biology and potential resistance to insecticides. Developing resistant barley genotypes is a sustainable strategy for managing BCOA. In this study, we assessed responses of susceptible “Morex” and resistant “BCO R001” barley, Hordeum vulgare L. genotypes to different initial BCOA densities (0, 50, 100 or 200 aphids.plant-1). Physiological and morphological parameters were measured weekly for four weeks after infestation. Chlorophyll content, photosynthetic rate, plant aerial fresh and dry weight were greater for the resistant cultivar at lower aphid abundances and up to three weeks after infestation. Carbon assimilation curves (A/Ci) of infested “BCO R001” were similar to controls 15 days post infestation, differing from Morex. However, BCOA infestation of 50 aphid.plant-1 for two weeks negatively impacted the fitness of both genotypes. Initial resistance by BCO R001 to BCOA infestation can allow growers and natural enemies more time contributing to more effective and sustainable management of BCOA infestations.