Influence of rootstock on the response of hass avocado trees to flooding stress

Abstract

In Chile, commercial avocado production has expanded to areas with poorly-drained soils that are low in oxygen. In these soils, improper irrigation design or management can limit fruit production and quality due to flooding of the root zone. The effects of soil flooding on stomatal conductance, transpiration, leaf chlorophyll content (estimated with a SPAD meter) and vegetative growth of one-year-old 'Hass' avocado trees (Persea americana Mill.) grafted onto one of three different seedling rootstocks were studied in a greenhouse. Trees grafted onto Mexicola, Zutano or Nabal rootstock were subjected to one of two flooding treatments: 1) non-flooded (control) or 2) flooded for six days. After the flooding period, flooded plants were removed from the flood water, placed in the same conditions as the control plants and their responses were measured during a six-day recovery period. Visible symptoms of flooding were desiccation of the shoot apex and leaf abscission. There were no consistent differences between rootstocks for stomatal conductance or transpiration during the flooding period. However, during the recovery period, trees on Mexicola rootstock had higher stomatal conductance and transpiration and appeared more vigorous than trees on the other rootstocks. Root, leaf and total plant dry weights and leaf chlorophyll content were significantly lower for flooded than nonflooded trees. The data indicated that 'Hass' avocado grafted onto Mexicola rootstock are able to recover from six days of soil flooding better than trees grafted onto Zutano or Nabal rootstocks.