Root and Shoot Responses to Bird Cherry‐Oat Aphids and Barley yellow dwarf virus in Spring Wheat

Abstract

There is little information available that describes the effects of bird cherry‐oat aphids (Rhopalosiphum padi L.) and Barley yellow dwarf virus (BYDV) on cereal plant root systems. This 2‐yr field experiment was conducted to determine how spring wheat (Triticum aestivum L.) root characteristics, shoot characteristics, and grain yield respond to R. padi infestation, BYDV infection, or a combination of R. padi plus BYDV. Treatments were applied at the 2‐ to 3‐leaf stage. When measured at anthesis, plants that received R. padi treatments (300 aphid days) had about a 30% greater total root length (as measured with a minirhizotron) than control plants. Plants that received BYDV as well as those that received R. padi plus BYDV had about a 40% decrease in total root length when compared with the control. Root system characteristics at different soil depths responded differently to BYDV infection across the 2 yr of the study. In the first year, BYDV‐infected plants had less root length at all soil depths measured than plants that did not receive BYDV infection. In the second year, which was drier near anthesis, root lengths of both BYDV infected and uninfected plants were similar at the 0‐ to 18‐cm soil depth, while at deeper soil depths, plants that had BYDV infection had less root length than plants that did not receive BYDV infection. Plants that received either R. padi or BYDV had fewer tillers, less tiller height, and less shoot dry weight than control plants. The lack of R. padi × BYDV interaction for above‐ground variables suggests that shoots responded to BYDV in a similar manner regardless of whether or not they received R. padi treatment. Treatments consisting of R. padi infestation or BYDV infection reduced individual kernel weight by 8 or 22%, respectively. Infection with BYDV also caused a 53% reduction in the number of kernels per meter of row and a 62% reduction in total grain yield. We conclude that R. padi infestation caused acute injury to spring wheat plants while BYDV caused chronic injury. Most of the dependent variables measured in this experiment responded to BYDV in a similar manner regardless of whether or not the plants received R. padi treatment.