Genetic identification and evaluation of cold-resistant germplasm resources in Populus tomentosa

Objective  This paper identifies the resources of Populus tomentosa in Shuozhou City, Shanxi Province of northern China, compares and analyzes the genetic structure and genetic diversity differences of the populations of poplar in Guanxian County, Shandong Province of eastern China, and evaluates the cold resistance of the existing poplar in Shuozhou City.

Method Using 370 individuals in Shuozhou City and 441 clones in Guanxian County, SSR molecular markers were used to carry out the identification of poplar resources, population genetic structure and genetic diversity analysis, and to evaluate the growth index and low temperature tolerance.

Result Using 13 pairs of primers, 370 individuals of P. tomentosa were divided into 183 clones. A total of 67 allelic variations were detected, with an average of 5 allelic variations per locus, and the polymorphism information content ranged from 0.306 to 0.735. Compared with the Guanxian County Germplasm Resource Bank in Shandong Province, it was found that the same clone resources were not preserved during the ex-situ preservation of P. tomentosa. The difference in genetic diversity was not significant. The 624 clones preserved in the two sites can be divided into seven clusters. The 183 extant clones in Shuozhou City were classified into five classes by cold tolerance evaluation, including 47 cold hardy clones in classⅠ, and the cold hardy poplars also had higher tree height and wood volume growth.

Conclusion Natural selection has caused the north and south germplasm repository of P. tomentosa to eliminate part of the germplasm that deviates from the environment of the preservation site, and to retain the germplasm resources that are suitable for the environment of the preservation site. The genetic structure of two populations differs considerably, indicating the need to collect, conserve and use forest germplasm resources in different regions. The existing female asexual lines in the germplasm repository of Shuozhou City, Shanxi Province, are valuable cold-tolerant breeding resources, which are of great value for the construction of a suitable population of northern poplar and the genetic improvement of high rotation.