Vegetative growth and freezing tolerance of white clover (Trifolium repens L.) genotypes from Svalbard

Abstract

Vegetative growth and freezing tolerance of two genotypes of white clover ( Trifolium repens L.) collected at Svalbard (latitude 78°39' N, longitude 16°23' E) were studied in a daylight phytotron at controlled temperature and humidity. For comparison, two genotypes of a new Norwegian cultivar, Norstar, and one genotype of the cultivar AberHerald were included in the experiments. The genotypes from Svalbard gave higher dry-matter yields than the genotypes of Norstar, and one of them also exceeded the AberHerald genotype in dry-matter production at the temperatures studied, constant 12°C and alternating 15 9°C and 12 6°C (12 12 h). The genotypes from Svalbard were more tolerant of freezing than all the other genotypes. After a successive hardening treatment at 6°C and 0.5°C they obtained LT 50 values (temperature for 50% survival) of -16°C. The origin of these genotypes is not known, but their high productivity and freezing tolerance may make them useful for further breeding of white clover for marginal conditions. © 2001 Taylor & Francis.