Assessment of chilling and heat requirements in some commercial cultivars and genotypes of kiwifruit in the west of Mazandaran

Information about temperature requirements in fruit trees has an important effect on productivity and determine suitable areas for their growing. The research was carried out via single node cuttings test in a randomized complete block design with three replications in Citrus and Subtropical Research Center in 2015-16. This study was conducted to determine the chilling requirements of Hayward and Tomuri cultivars and male and female golden genotypes using three chilling models (Chilling hours, Utah, Dynamic) and their heat requirements via Growth degree hours (GHD) method. Results showed that the chilling requirements of female and male golden genotype buds were 480 and 585 chilling hours respectively, and for Hayward and Tomuri cultivars were 692 chilling hours. The amount of buds heat requirements in the cultivar and genotype ranged from 2233 GHD in female golden genotype to 4066 GHD in Hayward cultivar. Hayward cultivar required 966 hours of chilling requirement for maximum flowering, meanwhile Tomuri, male and female golden genotype had a similar chilling for both vegetative bud break and flowering including 692, 585 and 480 hours respectively. With continued sampling, heat requirements reduced and significant negative correlation was found between chilling and heat requirements for bud break. From low chilling requirements of male and female golden genotypes, we can deduce that climatic conditions may be not limiting factor in the leading of them in growing area. It is thought that Utah and dynamic models may be more suitable than hour model to evaluate of chilling requirements.