APOMIXIS AND NEW SELECTIONS OF WALNUT

Authors:	W. Guo-Liang, C. Yan-hui, Z. Peng-fei, Y. Yang Jun-qiang, S. Yu-qin
Keywords:	bagging isolation, apomictic rate, embryology, peroxide isoenzyme, economic characters, Juglans regia
Abstract: Walnut (Juglans regia L.), the most valuable nut crop in China, can be apomictic. The objective of this paper was to study apomixis in walnut. Techniques such as bagging isolation, cytology, embryology, isoenzyme analysis were used. Two improved strains were attained by conventional breeding. Four of the walnut cultivars examined had apomictic tendencies. Their average apomictic rate was 38.25%. The highest observed rate was 78.6%. Examination of the apomictic embryos showed that walnut has a single and a straight ovule. The non-fertilized ova divided by karyokinesis into two-cell original embryos which were the same size. These bi-cells then developed into an eight-celled, spherical embryo, which developed into an apomictic multicellular embryo. In the peroxide isoenzyme (POD) analysis of apomictic seedling leaves, two distinct enzyme bands emerged. Liaohe No.1 descendants that originated from apomixis had a higher uniformity of 86%. The economic nut characters of the apomictic strains were not significant different from the control but the yield was significantly higher because of increased fruit set.
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