Changes of lipid components during dormancy in `Hull Thornless' and `Triple Crown Thornless' blackberry cultivars

Abstract

Chilling requirements and changes in polar lipids of two blackberry cultivars ( Rubus spp.), `Triple Crown Thornless' and `Hull Thornless' were determined during dormancy and budbreak. Under field conditions, `Triple Crown Thornless' required lower chilling units (CUs) than `Hull Thornless' to overcome dormancy. `Triple Crown Thornless' and `Hull Thornless' achieved full budbreak after receiving 600 and 1000 CU (chilling units), respectively. Under cold temperature treatments, `Triple Crown Thornless' needed 400 CU, while `Hull Thornless' needed 600 CU at 4°C to obtain 100% budbreak. The shoots kept at intermittent 6/24°C (6°C for 16 h, and 24°C for 8 h) did not reach full budbreak even after receiving 1000 CUs. An increase in phospholipids and glycolipids was detected at the end of dormancy. The increase in phospholipids occurred prior to the increase in glycolipids. The percentage of 18 : 2 fatty acid decreased while that of 18 : 3 increased and there was approximately a fivefold increase in the 18 : 3/18 : 2 ratio observed at the time of budbreak. The increase in the 18 : 3/18 : 2 ratio could serve as an indicator of dormancy termination and growth resumption in blackberry.