Abstract:

This paper studied nutshell structure indexes (seal grade, thickness, density and mechanical strength) of different walnut cultivars which were harvested from various production localities, in different harvesting periods and at different tree-crown locations. The results showed that there were significant differences in shell structure indexes among different cultivars, especially between Juglans regia and J. sigillata. Except for a few cultivars, there were significant differences in shell density and thickness of the same cultivars produced in different regions for all other cultivars. Seven different harvesting time was implemented in this study. From early to late of the harvesting time, the shell seal grade of walnuts descended gradually; the shell density ascended at the early period but descended afterwards; and the mechanical strength had an ascending trend. The shell mechanical strength of walnuts grown on the sunny side was higher than that of those grown on the shady side; but the shell density of walnuts grown on the sunny side was lower. In summary, the cultivars, irradiation and harvesting time were the key factors that influenced walnut shell structure.

Key words: Juglans regia, Juglans sigillata, nut, nutshell, affecting factors, cultivar, production locality, harvesting periods