Articles
TWO APPROACHES TO IN VITRO SCREENING OF RASPBERRY CULTIVARS FOR COLD HARDINESS
The aim of this work was to study the possibility of screening raspberry genotypes for cold hardiness in vitro. Two different approaches were examined; determining cold hardiness after low-temperature acclimation treatment, and using accumulation of sugars as a biochemical indicator of hardiness.
Raspberry cultivars ‘Festival’, ‘Titan’ and ‘Willamette’ grown on three media were exposed to three acclimation treatments (0, 2 and 4 weeks cold temperature). During acclimation, plants were analysed for soluble carbohydrate content.
After acclimation, cold hardiness (LT50) was determined by controlled freezing of the plants.
Total soluble carbohydrates, sucrose, glucose, fructose and raffinose accumulated during cold hardening.
The hardiest cultivar ‘Festival’ contained more soluble carbohydrates, sucrose and raffinose, but less glucose and fructose than the other cultivars.
The results indicate the importance of sucrose on cold hardening in raspberry.
The amounts of total soluble carbohydrates, sucrose and raffinose correlated with cold hardiness in these cultivars and might be used as an indicator of hardiness when screening raspberry cultivars for cold hardiness in vitro.
No cultivar differences in cold hardiness were detected in non-acclimated plants.
Four weeks acclimation (including 2 weeks at +15°C, 2 weeks at +2°C, 24 h at -2°C and 3 days at +2°C) on MS basal culture medium without growth regulators discriminated best between the cold hardy cultivar ‘Festival’ and less hardy ‘Titan’ and Willamette.
It was apparent from this study that in vitro screening of red raspberry germplasm cold hardiness is promising as a preliminary indicator of hardiness.