Response of the spring wheat-cereal aphid system to drought: Support for the plant vigour hypothesis
Abstract
Drought affects both crops and their pests, but the effect of the interaction between drought and pests on crops has not been sufficiently understood. The aim of this work is to determine (i) the response of spring wheat (Triticum aestivum) to three watering regimes (soil water capacity of 70, 50 and 40%) and aphid (Metopolophium dirhodum) infestation, and (ii) how drought affect aphid population growth.
Seedlings of one drought-susceptible (Quintus) and one drought-tolerant (Septima) cultivar were used, and changes in leaf structural and morphophysiological traits were measured. The age-stage, two-sex life table approach was used to determine aphid population growth.
The plant stress and plant vigour hypotheses in this system were tested by analysing correlations between leaf traits and aphid life table parameters. Drought stress negatively affected parameters related to plant vigour (reduced biomass, decrease in Ψ(π100) and increased resource allocation in structural defence trichomes) regardless of the stress tolerance of the cultivar, although the level of stress was generally greater in Quintus than in Septima.
Plants perceived the stress caused by the aphids as significant only under high drought stress, as the physiological response of increasing growth and osmolyte accumulation was triggered under these conditions. This response also benefited the aphids; hence, the population growth of the aphids was most severely affected under moderate drought stress.
The reproductive rate was negatively affected by trichome density and positively affected by leaf biomass and Ψ(π100); these findings provide support for the plant vigour hypothesis for the spring wheat seedling-rose-grain aphid study system.