Somatic mutations during rapid clonal domestication of Populus alba var. pyramidalis

For many clonally propagated species, the accumulation of somatic mutations is the principal driver of declines in yield and quality. However, somatic mutations may also promote genetic diversification. Thus, elucidating somatic mutation rates and patterns is important to understand the genetic basis undergirding the emergence of commercially valuable traits and developmental processes. In this study, we studied the effect of short-time clonal domestication of Populus alba var. pyramidalis, a species that has been propagated by cutting for the last 67 years. We found that: (1) the somatic mutation rate for P. alba var. pyramidalis is 9.24 x 10(-9), which is higher than rates observed in related species; (2) there were more mutations near heterozygous regions, and a larger proportion of CpG and CHG sites were associated with somatic mutations, which may be related to the blocking of DNA repair by methylation; and (3) deleterious mutations were not shared by multiple individuals, and all occurred in heterozygous states, demonstrating the strong selective pressures that act against deleterious mutations. Taken together, the results of our study provide a global view of somatic mutation that will aid efforts to understand the genetic basis of commercially valuable traits and to improve clonally breeding species.

Automated summary

This study investigates the somatic mutation rates and patterns in Populus alba var. pyramidalis, a clonally propagated species that has been domestically cultivated. The study finds that the mutation rate in this species is higher than in related species, with mutations predominantly occurring near heterozygous regions. The presence of CpG and CHG sites suggests a potential involvement of methylation in blocking DNA repair. Additionally, deleterious mutations are not shared among individuals and occur in heterozygous states, indicating strong selective pressure against harmful mutations.