Genetic diversity, core collection construction and genotype–environment associations of Eucalyptus cloeziana F. Muell. (Myrtaceae) germplasm based on EST-SSR markers

Conservation and assessment of germplasm resources play a crucial role in forest genetics and breeding. Eucalyptus cloeziana F. Muell is esteemed as a valuable timber tree species in China owing to its substantial economic and ecological significance. Nevertheless, there has been a dearth of research on functional genomics and molecular breeding within this species. In this study, 20 fluorescent-labeled polymorphic EST-SSR markers were utilized to genotype 448 E. cloeziana individuals from 118 families originating from 19 provenances within the State-owned Dongmen Forest Farm of Guangxi province, one of the largest gene pools of Eucalyptus in Asia. The results unveiled a relatively high genetic diversity of E. cloeziana germplasm ( I  = 2.310; He  = 0.855) and low genetic differentiation among provenances, with the majority of genetic variation occurring within provenances (96.73%). Bayesian structure analysis grouped the tested accessions into three clusters: northern provenances, northern high-altitude provenances, and southern provenances. A core collection comprising 85 individuals (18.97% of the total breeding population of 448 individuals) was established through random non-repetitive sampling to diminish redundancy while uploading a high level of genetic diversity ( I  = 2.470; He  = 0.890). Three loci associated with environment (EC-e039, EC-e015, and EC-e089) were identified using latent factor mixed model (LFMM) and redundancy analysis (RDA). Two temperature variables (maximum temperature of the warmest month and mean temperature of the driest quarter) and two precipitation variables (annual precipitation and precipitation of the driest month) were identified as significant environmental factors influencing adaptive variation in the species. These findings highlight the close relationship between climate conditions and genetic variability, providing valuable insights for the management of forest species in the face of a swiftly changing environment.