ISHS Acta Horticulturae 199: II International Workshop on Temperate Zone Fruits in the Tropics and Subtropics
THE TERMINATION OF SEED AND BUD DORMANCY IN PEAR BY APPLICATION OF CHEMICALS |
| Authors: | H. Lin, C. Lee, C. Lin |
| Abstract:
'Shinseiki' and 'Hengshan' are two major cultivars of pear (P y-rus serotina Rehd.) in Taiwan. Scions with flower buds of the long chilling 'Shinseiki' from highland orchards are grafted on water shoots of the short chilling 'Hengshan' in lowland orchards in central Taiwan in mid-January to mid-February. These scions produce a harvestable crop in June, whereas 'Hengshan' fruits are not mature until August-September. 'Shinseiki' fruits can be harvested again the following January and February—the third harvest from the same tree in less than a year. However, buds on the 'Shinseiki' scion cannot break normally the next spring. Therefore scions must either be grafted every year or treated with chemicals to enhance bud break. Cyanamide, thiourea, dinitro-ortho-cresol (DNOC) and potassium nitrate were tested for terminating bud and seed dormancy. Flower bud development was separated into 9 successive stages. Buds reaching stage 2 were considered to have broken. Thiourea (2%) was most effective in breaking seed dormancy in the cv. Liauli; chilling requirement of such seeds was 600 hours. The effect of 2% thiourea was equivalent to 360 hours of chilling; however, the treatment caused severe damage to the radicle and hypocotyl. Treatment with potassium nitrate (3%) and hot water (37°C) was equivalent to 240 hours of chilling. Cyanamide (2%) and thiuorea (0.2%) promoted some budbreak in 'Shinseiki' cuttings, and cyanamide promoted the rate and degree of budbreak in intact shoots of 'Hengshan', 'Shinseiki' and 'Liauli'. | |
