Cold Hardiness in Rubus 1

Abstract

More than 80 raspberry and 42 blackberry genotypes were evaluated for cold hardiness after controlled laboratory freezing in January 1990. Red, yellow, black, and purple raspberry cultivars ( R. idaeusL., R. neglectusPeck), blackberry cultivars ( R. allegheniensisPorter, R. ursinusCham & Schldl.) and other Rubus species selections were examined. Tso's, the temperatures where 50% of the samples were killed, were calculated for cane (cambial region), bud and bud base of each genotype. Red, purple, and black raspberries had a lower T ₅₀values than did blackberries. The T ₅₀value of Rubus idaeusL. cv. Burnetholm canes was -34C. Hardy summer bearing red raspberries, 'Canby' and 'Puyallup' had a T ₅₀value of -30C; 'Canby' buds -26C; Puyallup -20C. The T ₅₀values of fall fruiting red raspberries, such as 'Zeva Remontante,' 'Indian Summer,' 'St. Regis,' and 'Fallred,' ranged from -23 to -25C. Several purple raspberries ( Rubus neglectusPeck cvs. Brandywine, Royalty) were quite cane hardy, with T ₅₀values lower than -33C. The buds and bud bases of these purple raspberries, however, had T ₅₀values at most -25C. Canes of several black raspberries ( R. occidentalisL. cvs. New Logan, Bristol) had T ₅₀values of -28C; buds -27C and -17C, respectively. 'Bristol' offspring had T ₅₀values as much as 15C less than the parent. Canes of the hardiest blackberry cultivar, ( R. sp. cv. Black Satin) had a T ₅₀value of -23C; buds were -19C. In many raspberry and some species genotypes examined, the region of the bud at the axis at the cane was less hardy than were tissues within the bud scales. The T ₅₀values of canes of most cultivars ranged from about 2 to 15 degrees hardier than buds.