Comparison of mid-Winter cold-hardiness and soluble sugars contents in the shoots of 21 highbush blueberry (Vaccinium corymbosum) cultivars

Abstract

SummaryCold-hardiness and the soluble sugars contents of the shoots of 21 highbush blueberry (Vaccinium corymbosum) cultivars (‘Berkeley’, ‘Bluecrop’, ‘Bluegold’, ‘Bluehaven’, ‘Bluejay’, ‘Burlington’, ‘Chippewa’, ‘Collins’, ‘Dixi’, ‘Duke’, ‘Herbert’, ‘Jersey’, ‘Nelson’, ‘Northblue’, ‘Northland’, ‘Polaris’, ‘Rancocas’, ‘Sharpblue’, ‘Sierra’, ‘Spartan’, and ‘Sunrise’) were compared in mid-Winter. The level of cold-hardiness was determined by measuring electrolyte leakage at various freezing temperatures and was expressed as LT50, the temperature at which the incidence of injury reached 50%, and as Tmax, the temperature at which the rate of injury was maximal. The LT50 and Tmax values for the shoots of all 21 highbush blueberry cultivars ranged from –31.8º ± 0.09ºC to –41.1º ± 0.12ºC, and from –29.7º ± 0.06ºC to –36.9º ± 0.13ºC, respectively. Tmax values were significantly positively correlated with LT50 values (r = 0.98**, P ≤ 0.01). Based on their levels of cold-hardiness in terms of LT50 values, the 21 highbush blueberry cultivars were ranked in order as follows: ‘Jersey’ > ‘Northland’ > ‘Northblue’ > ‘Dixi’ > ‘Berkeley’ = ‘Sierra’ > ‘Chippewa’ > ‘Bluegold’ > ‘Burlington’ > ‘Bluejay’ > ‘Spartan’ > ‘Bluecrop’ = ‘Polaris’ > ‘Sunrise’ > ‘Duke’ > ‘Rancocas’ > ‘Herbert’ > ‘Sharpblue’ > ‘Collins’ > ‘Bluehaven’ > ‘Nelson’. Cold-hardiness, as estimated by LT50 and Tmax, was highly negatively correlated with total soluble sugars content (r = –0.78**, P ≤ 0.01 and r = –0.69**, P ≤ 0.01 for LT50 and Tmax, respectively). Among the soluble sugars detected, fructose and glucose concentrations, in particular, were significantly positively correlated with the levels of cold-hardiness in the shoots of all 21 highbush blueberry cultivars, but sucrose and raffinose concentrations were not correlated with cold-hardiness. Knowledge of intra-species differences in mid-Winter cold-hardiness in relation to soluble sugars contents will be useful during the breeding and cultivation of highbush blueberries.