Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/28/2003
Publication Date: 7/1/2003
Citation: Riedell, W.E., Kieckhefer, R.W., Langham, M.A., Hesler, L.S. 2003. Root and shoot responses to bird-cherry-oat aphids and barley yellow dwarf in spring wheat. Crop Science. 43:1380-1386. Interpretive Summary: Insects and disease, which routinely reduce crop quality and yields, cause decreased agricultural profitability. Thus, the elucidation of how these biotic stresses interact is of much theoretical and practical importance. Theoretically, biotic stress interactions are of interest because they provide insight into interrelationships between physiological processes. Practically, biotic stress interactions are important because they indicate best management practices for multiple stresses. Cereal aphid infestations and barley yellow dwarf virus continue to have considerable impact upon the productivity and profitability of agriculture. The effects of bird cherry oat aphid (BCOA) infestation or barley yellow dwarf virus (BYDV) infection on aerial portions of small grains have been studied extensively. However, there is relatively little information available on how below-ground portions of plants are affected by these two stress causing organisms. We felt that a field study of the influence of BCOA infestation and BYDV infection, alone and in combination, upon root and shoot characteristics of spring wheat would be a step toward understanding the mechanism of yield loss in plants damaged by these two stress-causing organisms. Increased understanding of how plants are affected by these organisms might help breeders develop tolerant or resistant lines, or may suggest new ways to manage the crop to reduce the yield loss to these organisms. Our results suggest that BYDV was much more detrimental to spring wheat root growth and yield than BCOA alone. Root stunting caused by BCOA or BYDV may be an important factor contributing to the reduction in grain yield suffered by plants when they are damaged by these organisms. Reduced root length may also make damaged plants more susceptible to other physical stresses such as drought.
Technical Abstract: There is little information available that describes the effects of bird cherry-oat aphids (Rhopalosiphum padi L.) and barley yellow dwarf (BYD) 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, barley yellow dwarf virus (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 percent 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 percent decrease in total root length when compared with control. Root system characteristics at different soil depths responded differently to BYDV infection across the two years 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, 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 x 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 percent, respectively. Infection with BYDV also caused a 53 percent reduction in the number of kernel m-1 of row and a 62 percent 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.