Abstract:

Research on the phenological phase and phenotypic plasticity of leaves and fruits of walnut ‘Qingxiang’ was carried out, to clarify the effect of climate change on walnut phenological phase in large scale and to provide a basis for high quality walnut cultivation and understanding walnut population differentiation. The phenological phase and phenotypic plasticity of compound leaves, multiple fruit rate on single branch and nut surface of walnut ‘Qingxiang’ from different growing regions of warm temperate zone, northern subtropics and southern subtropics in China were observed. The average genetic similarity coefficient of walnut ‘Qingxiang’ from different regions was 0.998, indicating high purity of the test material. The phenological phase of walnut ‘Qingxiang’ was coincident from warm temperate zone to southern subtropics, but the fruit development time increased from 125 d to 150 d. Leaflet number of compound leaf ranged from 5-9 pieces to 5-11 pieces, lateral leaflet edge shape was from elliptic to narrow elliptic, with tip shape changed from sharp point to gentle point. The multiple fruit rate on single branch was from 2.22% to 7.43%, and lines and pits on nut surface became more and deeper. In the migrating cultivation of walnut ‘Qingxiang’ from warm temperate zone to southern subtropics, its growth period becomes longer, the lateral leaflet edge shape is changing from round to long gradually with more sharp tips, the fruit-bearing number on single branch increases, and the smoothness of nut surface is weakened. So, the phenological phase and phenotypic characteristics of leaves, multiple fruit rate on single branch and nut surface of walnut ‘Qingxiang’ show quite strong phenotypic plasticity. From the transformation trend of Juglans regia to J. sigillata, we speculate that the differentiation of the two species may be caused by environmental factors.

Key words: walnut, phenological phase, leaves, fruits, phenotypic plasticity