Submitted to: Sugar Journal
Publication Type: Abstract Only
Publication Acceptance Date: 5/30/2003
Publication Date: 6/25/2003
Citation: Tai, P.Y., Miller, J.D., Morris, D.R. 2003. Electrolyte leakage test for evaluating sugarcane freezing tolerance. Sugar Journal.
Technical Abstract: Measurement of electrolyte leakage was used to evaluate freezing injury of sugarcane foliage. Two Saccharum species, S. officinarum and S. spontaneum, five commercial cultivars and four commercial cultivar x S. spontaneum hybrids were exposed to 4 o C for six days in a growth chamber. Leaf segment samples (about 7.5 cm long) from the first complete leaves (top, middle and base of each leaf blade) were cut to determine if any leaf segment by genotype interaction occurred. After being washed with deionized water, two to four pieces per leaf segment were placed in a glass tube and submerged for 1 hour in a -2 o C ethylene glycol cooling bath and then a small ice cube was added into the tube to induce freezing. The samples were again immersed in the bath at -2 o C for one more hour followed by immersing at -3 o C and -4 o C for one hour each. The samples were thawed in a refrigerator overnight and incubated in 10 ml of deionized water with shaking at room temperature for four hours. Electrolyte leakage from leaf segments was measured with a conductivity meter. The leaf segments were removed from the glass tubes and frozen at -80 o C for one hour. The frozen leaf segments were returned to the glass tubes and incubated for four hours to obtain a measurement of total electrolyte leakage. The percent leakage (%) was expressed by (electrolyte leakage after freeze test/total electrolyte leakage) x 100. A test using top leaf segments only was conducted to determine lethal temperature LT50 (50% leaching) under a range of sub-breezing temperatures that were cooled in a gradual decrease of 1 o C each hour from -2 o C to -11 o C. Results indicated that there was no significant interaction between leaf segment and genotype, but there were significant differences among three leaf segments with the top being the highest % leaching while the base being the lowest. Based on the results from electrolyte leakage measurements, freezing tolerance varied among genotypes with S. officinarum clones from tropical region having the least resistance to freezing injury and the S. spontaneum clones from the higher latitudes having the most resistance while the freezing tolerance of the hybrid clones tested was intermediate to the two parent groups. The correlation between the visual rating on green leaf tissue after being exposed to natural frost injury and the measurement of electrolyte leakage was significant and negative (r = - 0.67*). The electrolyte leakage test can be used as an objective measurement of freezing tolerance in genetic and breeding studies in sugarcane.