Interaction Between Flooding or Drought Stress and Potato Leafhopper Injury in Alfalfa

Abstract

Potato leafhopper is a predominant biotic stress in alfalfa production, whereas drought and flooding are frequent abiotic stresses. Controlled environment studies were conducted to examine the interaction between flooding or drought stress and potato leafhopper (PLH, Empoasca fabae [Harris]) feeding damage on seedlings of two cultivars of alfalfa (Medicago sativa L): one susceptible to PLH, one resistant to PLH. Flooding treatments reduced shoot dry matter accumulation approximately 50% in the absence of PLH in both cultivars and significantly reduced root dry matter in one cultivar. Drought stress significantly reduced shoot dry matter and increased root dry matter. PLH feeding combined with either flooding or drought stress reduced root dry matter accumulation but not shoot dry matter. Flooding injury and PLH feeding injury showed an additive negative response for root dry matter accumulation. Flooded and non-stressed plants accumulated less root total non-structural carbohydrates (TNC) when subjected to PLH feeding. Responses of the two cultivars were similar across all biotic and abiotic treatments. The results clearly show that the most damaging physiological response of seedling alfalfa to PLH feeding is a sharp decline in root growth and TNC accumulation. This suggests that seedlings that have experienced even minor root waterlogging damage may be especially susceptible to damage by PLH feeding. Accepted for publication 23 April 2002. Published 2 May 2002.