Abstract

The chilling requirements of the male and female flower buds of 23 pecan nut cultivars were determined and compared for the tendency to protogeny/protandry during 2000 to 2004 winter periods by Weinberger’s standard and Richardson’s chill unit methods. Calculating the chilling hours below 7°C and chill unit (CU) values during the experimental winter periods, 555 to 660 h and 407 to 416 (CU) of chilling duration were obtained under subtropical conditions of Adana. There are some differences on dormancy release dates and chilling requirements of the female and male flower buds as well as some little differences between the chilling methods. In 2003 to 2004 winter period, the chilling requirements were changed between 208 to 338 CU and 250 to 436 h in male flowers, whereas, 203 to 389 CU and 250 to 484 h in female flowers. In this year, similar to the previous year, Moneymaker broke endodormancy of female buds primarily on 22^nd January and showed the lowest chilling requirements (203 CU and 250 h), while male flower bud dormancy release occurred on 12^thFebruary with 300 CU and 346 h of chilling. The male flower buds of Kiowa, Schley, and Texhan were found to be the lowest chilling requiring cultivars suitable to warm climatic conditions, whereas, the others require more. For the female flower buds, Harris Super, Mahan, Moneymaker and Wichita gave the lowest chilling requirements, while Desirable, Schley and Woodard gave the highest. Considering the tendency of the male and female flower buds to protogeny and protandry, Kiowa, Schley, Texhan, Pawnee and Woodard showed protandry, while Choctow, Moneymaker, Harris Super and Western showed protogeny in both years.

Key words: Pecan nut, male and female flowers, endodormancy release, subtropical conditions.