THERMAL-ANALYSIS OF DORMANT BUDS OF 2 MUSCADINE GRAPE CULTIVARS AND OF VITIS-LABRUSCA L MARS

Thermal analysis was used to determine if muscadine grape (Vitis rotun difolia Michx.) buds supercool and to determine the seasonal cold hard iness of several grape cultivars grown in Arkansas. Buds of the muscad ine cultivars Carlos and Summit, sampled from vines grown at Clarksvil le, Ark., produced low-temperature exotherms consistent with the numbe r of buds tested. Apparent hardiness of the buds increased from 5 Nov. 1993 through 7 Jan. 1994. Mean low-temperature exotherms (MLTE) were lowest on 7 Jan. and were -21.5C for 'Carlos' and -23.4C for 'Summit'. 'Mars' buds, sampled at Clarksville, Ark., and Winchester, Va., were included in the study and increased in hardiness during the same perio d. MLTE for 'Mars' from Arkansas were similar to those of the muscadin e cultivars on 7 Jan.; however, 'Mars' attained lower MLTE temperature s with vines grown in Virginia than with those in Arkansas. Location d ifferences in hardiness of 'Mars' are conjectural.