EVALUATION OF FREEZING TOLERANCE OF CUMIN (CUMINUM CYMINUM L.) UNDER CONTROLLED CONDITIONS

Abstract

Freezing tolerance of cumin ecotypes was investigated under controlled condition.. Six cumin ecotypes (India Rajestan and five Iranian: Ghoochan, Sabzevar, Khaf, Ghayen and Torbate Heydarieh) were subjected to six temperature treatments including 0, -3, -6, -9, -12 and -15 oC. Treatments were arranged in a completely randomized design with three replications. Following three weeks of acclimation plants were transferred to a thermogradient freezer and treated with the above temperatures. The cell membrane integrity was determined after freezing through electrolyte leakage (EL) and the temperature causing 50% leakage (LT50el) was evaluated. For recovery plants transferred for three weeks to glasshouse and at the end of recovery period for each ecotype survival percentage, lethal temperature causing 50% mortality (LT50su), plant height, leaf area and dry matter were determined. The effect of ecotypes and freezing temperatures was significant for most traits. The minimum (20.1%) and maximum (85.3%) EL was observed at 0 oC and -15oC, respectively. Decreasing the freezing temperature reduced plant survival. Ghoochan and Ghaen had greater survival compared to other ecotypes. Plant height decreased significantly under lower temperatures and greater plant height observed for Iranian ecotypes. Plant dry matter and leaf area decreased by 90% and 86% at -12 oC, respectively as compared to non frozen control (0 oC). However, there were no significant differences among cumin ecotypes for dry matter and leaf area. Based on this study, EL could be an easy and efficient method in evaluating the freezing tolerance of cumin ecotypes.