An evaluation of freezing tolerance of winter chickpea (Cicer arietinum L.) using controlled freeze tests

Abstract

Nezami, A., Bandara, M. S. and Gusta, L. V. 2012. An evaluation of freezing tolerance of winter chickpea ( Cicer arietinum L.) using controlled freeze tests. Can. J. Plant Sci. 92: 155–161. Chickpeas (Cicer arietinum L.) are subject to freezing injury and/or winter kill. Field testing for freezing tolerance evaluation is slow, unreliable, and highly variable; thus an artificial freeze test that correlates with field survival is required. Our objective was to develop a reliable and simple artificial freeze test to evaluate the freezing tolerance of winter chickpeas. Four cultivars with varying levels of freezing tolerance were grown and cold acclimated under low irradiance (150 µmol m−2 s−1) and high irradiance (400 µmol m−2 s−1). Acclimated whole plants or excised leaflets were subjected to six tests to determine the LT50 temperature (lowest temperature to kill 50% of the plants). In two tests, following the freeze test, whole plants were held at 20°C/15°C (day/night) for 3 wk for re-growth analysis. LT50 was estimated from both axillary buds and foliage re-growth and from foliage re-growth. The LT50 was also assessed on excised plantlets from whole plants frozen to a series of test temperatures. LT50 was determined by re-growth of plantlets held for 1 wk at 20°C in test tubes or by electrolyte leakage following thawing at 20°C. Excised plantlets were frozen to the same temperatures used for the whole plants. LT50 was determined by re-growth in test tubes for 1 wk or by electrolyte leakage. Results from excised plant parts from frozen intact plants or plantlets excised prior to the freeze test were similar to those estimates derived from re-growth analysis of plants frozen whole. Freeze test employing excised plantlets offers high precision and the ability to screen large populations. Plants grown and cold acclimated under an irradiance of 150 µmol m−2 s−1 were not as freezing tolerant as those grown and cold acclimated under an irradiance of 400 µmol m−2 s−1.