Evaluation of Chilling Injury to Strawberry Plants Following Application of an Organic Fungicide

Fragaria ×ananassa ‘Camarosa’ (strawberry) plants were grown in a single hoop style high tunnel with straight, raisable sidewalls for vernalization at Mississippi State University’s R.R. Foil Plant Science Research Facility. In late February 2011, plants started flowering and on 5 March 2011, plants were exposed to a 15-h chilling event following a foliar application of an extract of Reynoutria sachalinensis [giant knotweed (Regalia®)] at 1× (10 mL·L^-1). Application was made 24 hours before the chilling event to strawberry plants with open flowers. Chilling event was simulated in an environmental growth chamber with initial temperature set at 16 °C and decreased by 4 °C per hour until reaching 0 °C and held for 8 hours. In addition to the spray treatment, there were two non-sprayed controls: one with plants left in the high tunnel (9.7 °C) and one with plants exposed to the chilling treatment. To assess chilling injury, total growth, yield, marketable grade, and antioxidant enzymes were determined. There were no significant differences in total growth, yield, or marketable grade regardless of spray or chilling exposure; however, there was an increase in glutathione-S-transferase in plants sprayed with Regalia® compared with non-sprayed plants. While Regalia® may not cause a quick response to protect ‘Camarosa’ strawberry plants from chilling temperatures, it does appear to enhance antioxidant activity in strawberry plants under moderate chilling conditions.