ISHS Acta Horticulturae 557: VII International Symposium on Orchard and Plantation Systems
THE INFLUENCE OF FREEZE-THAW CYCLING IN COLD HARDINESS STUDIES ON APPLE ROOTSTOCKS |
| Authors: | J.P. Privé, M.I.N. Zhang, C.G. Embree, D. Hebb |
| Keywords: | cold stress, electrical impedance spectroscopy, whole plant regrowth |
| Abstract:
Three experiments were conducted to examine the influence of freeze-thaw cycling in low temperature studies on apple rootstocks. In the first two experiments, electrical impedance (Z) was used to evaluate the cold hardiness of apple root pieces, while whole plant regrowth was used in the third experiment. In the first experiment, root pieces of ‘Beautiful Arcade’ from cold-storage (no freeze-thaw cycling) were compared to roots taken from the field (4 natural freeze-thaw events). In the second experiment, root pieces of ‘Ottawa 3’ (O.3) were subjected to one, two and three controlled freeze-thaw cycles at temperatures of -3, -6, -9 and -12°C. In the third experiment, whole plants of O.3 were subjected to various treatments examining both the effects of freeze-thaw cycling and duration of exposure to cold. With this experiment, mortality and whole plant regrowth was used to assess plant recovery. Lethal temperature (LT50) levels from the first experiment were near -9 and -3°C for the cold-stored vs. the field treatments, respectively. Root tissue integrity, as measured by Z, was severely reduced with multiple events of freeze-thaw cycling in the second experiment. In experiment three, whole plants exposed to multiple freeze-thaw cycling had significantly lower survival rates, reduced leaf, shoot and root growth compared to those exposed to constant freezing temperatures of equal duration. All experiments confirm that freeze-thaw cycling is more detrimental to apple rootstock viability than periods of constant freezing. | |
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