Use of Electrical Conductivity to Assess Irrigation Impacts on Grapevine Winter Hardiness

A simple method involving measurement of electrical conductivity of grapevine cane tissue was evaluated. ‘Sovereign Coronation’ vines on two sites were subjected to five irrigation treatments based upon reference evapotranspiration (ET0) and various crop coefficients (Kc): non-irrigated control; 100% ET0 × Kc = 0.75; 150% ET0 × Kc = 0.75 (ET0 × 1.12); 100% ET0 × Kc = 0.2 to 0.8; 150% ET0 × Kc = 0.2 to 0.8. ‘Chardonnay’ vines were likewise subjected to several irrigation treatments: non-irrigated control, early season deficit (irrigation until berry set), midseason deficit (irrigation until lag phase of berry growth), late season deficit (irrigation until veraison), and full season irrigation (irrigation until harvest). Cane samples were collected from December to March inclusive, and cane segments were subjected to multiple temperature treatments (−24, −26, −28, −30, −32°C) in addition to a non-treated control. Treated cane segments were thinly sliced and incubated in distilled water (t1) at room temperature and at 100°C (t2), after which the electrical conductivity (EC) was read. Two indices calculated from both EC values (ItA, ItB) were responsive to irrigation. However, there was little relationship between either ItA and ItB versus irrigation in ‘Sovereign Coronation’, likely because it is a very winter-hardy cultivar. Nonetheless, there was a relationship between both ItA and ItB versus irrigation in ‘Chardonnay’, whereby treatments to which high irrigation volumes were applied also had high ItA and ItB values, suggesting higher potential winter damage. In summary, the technique described herein is relatively inexpensive and not time-consuming and, therefore, may constitute a rapid method for assessment of grapevine winter injury.