Screening for efficient cold hardening in a breeding population of Salix using near infrared reflectance spectroscopy

Abstract

The inheritance of cold hardening components - the timing of onset and the inherent rate - was studied in Salix spp. This was achieved by characterising the F2 population of a cross between an early-and-rapidly hardening clone and a late-and-slowly hardening clone. The cold hardiness of stems was estimated using the infrared reflectance spectra of dried and homogenised samples. This method was first calibrated against the freeze test method. The timing of growth cessation was used to determine the onset of cold hardening. In the F2 progeny, traits were partly recombined as indicated by the occurrence of clones with early-and-slowly hardening characteristics. The frequency distributions of clones also indicated that the timing of onset and the inherent rate of hardening were independently inherited traits. None of the clones exhibited the desirable late-and-rapidly hardening characteristics, combining a long growing period with effective cold hardening. This is not surprising since few F2 clones exhibited late hardening.