Abstract

A collection of 28 populations of naturalized white clover in Argentinean and Chilean Patagonia, and two white clover cultivars, was used to select two groups of contrasting cold tolerance genotypes: 96 cold-sensitive and 96 cold-tolerant. The objective was to form an association-mapping population. Sixty young plants of each population were cold stressed progressively at -2, -4, -6 and -8 ºC for 48 hours and the damaged plants recorded. The records were fitted to the Weibull distribution and the three most tolerant and the three most sensitive populations were selected using the LT50 value (Lethal Temperature for 50% of the population) to choose the contrasting genotypes. The white clover populations showed a broad genetic variability for cold tolerance, which allowed the selection of 192 genotypes with divergent coldtolerance and formation of the association-mapping populations. Keywords: Cold tolerance, naturalized populations, Weibull distribution, plant survival