Study on the Genetic Diversity of Germplasm Resources of Juglans sigillata in Northwest Yunnan

Purpose Germplasm resources of Juglans sigillata in northwest Yunnan were studied to reveal genetic diversity and genentic structure and to provide basis for scientific conservation and effective utilization of the genetic resources.

Method 332 samples from 13 walnut populations were taken in the analysis by SSR molecular markers technology. Genetic variance was revealed through AMOVA, and Mantel’s test was used to analyze the correlation between genetic distance and geographic distance.

Result (1) The expected heterozygosity ranged from 0.456 5 to 0.630 0, with an average of 0.528 6. The Shannon’s information index was between 0.852 9 and 1.336 7, with an average of 1.026 4 and the Nei’s gene diversity ranged from 0.442 1 to 0.622 5, with an average of 0.528 6. The data suggest a medium genetic diversity in this area. The genetic diversity level showed pattern of reduction from the northwest (Diqing and Nujiang) to the southeast (Lijiang and Dali). (2) The proportion of genetic differentiation among populations was 0.101 1, which means that genetic variation derived mainly from within populations. AMOVA analysis got the same result. (3) Cluster analysis showed 13 populations were divided into 4 groups at genetic identity of 0.85. Mantel’s test showed a significant correlation between genetic distance geographic distance (r=0.644 1, P=0.002 0).

Conclusion Medium genetic diversity and the particular genetic variation patterns of walnut germplasm resources in northwest Yunnan have been developed through long term of natural selection and human activities. The proportion of genetic differentiation among populations was low, showing the genetic variation derived mainly from within populations. For the selection and conservation of resources in the area, it should focus on the selection of families and individuals within populations based on the selection of selection of populations with rich genetic diversity.