Estimation of chilling and heat requirements of different cultivars of blackberry in field conditions in East Mazandaran.

In order to determine the chilling and heat requirements of blackberry (Rubus sp.) cultivars, three thorny (Tupy, Marion, Silvan) and two thornless (Merton and Red immature) cultivars after the onset of dormancy and after exposing the chilling requirement were collected of the Blackberries collection from Sari Agricultural Sciences University (SANRU) and evaluated in a greenhouse via RCBD at three replication at 2019. Then the chilling and heat requirement models were calculated. Results showed differences in chilling requirements of thorny and thornless blackberry cultivars in field conditions. The highest percentage of the first bud burst related to thorny cultivar Silvan after 500 hours chilling. Marion and Tupy, and Red immature burst in 700 hours of chilling but Merton thornless burst after 900 hours. Also, the minimum day number for 50% bud burst in all cultivars was obtained in 700 hours of chilling. It should be noted that only thorny cultivars have reached full bloom and therefore are the most suitable cultivars for the development in eastern of south of Caspian Sea region. Thornless cultivars did not reach full bloom even after receiving 900 hours of chilling. The heat requirement required for 50% of buds to bloom varied from 6324 GDH in thornless Merton cultivar to 1116 GDH in Tupy cultivar. Using complementary treatments like as Hydrogen cyanamide to improve bud burst can be helpful.