Effect of Water Stress and Cabbage Aphid Feeding on Ethiopian Mustard Brassica carinata Physiology

Water deficit represents a critical abiotic constraint that impairs fundamental physiological processes in plants.Water deficit as a single stressor influences aphid's performance indirectly through changes in plant physiology.The present study was conducted in a greenhouse to investigate the effects of water stress and cabbage aphid (Brevicoryne brassicae) feeding on the physiology of Ethiopian mustard (Brassica carinata).In addition, the study examined how drought-induced changes in host plant physiology influence aphid performance.A factorial experiment was conducted to evaluate the individual and combined effects of drought stress and aphid infestation.Four levels of drought stress and two aphid infestation treatments were arranged in a randomized complete block design with 10 replications.Water stress had a significant effect on Ethiopian mustard physiology and cabbage aphid performance.Transpiration rate, photosynthetic rate, and stomatal conductance of B. carinata leaves decreased significantly as water stress increased.Transpiration rate, photosynthesis, and stomatal conductance of B. carinata leaves were reduced by 55.62%, 61.26%, and 63.53% in water-stressed plants.On the other hand, feeding by cabbage aphid significantly reduced transpiration rate, photosynthesis, and stomatal conductance on B. carinata leaves.Under conditions of water deficit, B. brassicae demonstrated significantly higher fecundity and an accelerated population growth rate (r m ).The findings suggest that drought stress has the potential to change the physiology of the B. carinata plant and cabbage aphid population dynamics.The interaction effect of water stress and aphid feeding significantly influenced the photosynthetic rate, transpiration rate, and stomatal conductance of B. carinata plants.