Gene flow among wild and cultivated common walnut (Juglans regia) trees in the Qinling Mountains revealed by microsatellite markers

Abstract

Patterns of gene flow and gene introgression can be used to assess the risk of genetic pollution of wild forest trees from widespread cultivated trees. A comprehensive understanding of the genetic relationships and levels of gene flow among wild and cultivated common walnut (Juglans regia) has become an urgent issue. Using twelve microsatellite markers, we investigated the genetic diversity and gene flow between cultivated and wild trees of J. regia in the Qinling Mountains, China. A high level of genetic variation was detected in both cultivated and wild trees. The mean number of alleles per locus was 17.5. Observed heterozygosity (HO) and expected heterozygosity (HE) were 0.777 and 0.800, respectively. Pollination of mother trees was not by nearest neighbors, and a paternity of 60.7% of offspring evaluated could not be assigned to a local, sampled tree. Pollen flow from cultivated trees to wild trees was infrequent (5.4%), and selfing rates ranged from zero to 25.0%. Male parents were located from 0 to 1005 m from their female partners, with an average pollination distance of 285.1 m. These results are discussed in light of the cultivated species' diversity, outlining the frequent spontaneous genetic contributions from the wild to the cultivated compartment. In addition, the pollen flow parameters provide useful information about the dynamics of pollen movement within J. regia populations.

Molecular Characterization of Local Walnut (Juglans regia) Genotypes in the North-East Parnon Mountain Region of Greece

“…In recent investigations, the observed heterozygosity has been reported within the range of 0.57 to 1.00 (with an average of 0.80) as noted by Eser et al [53], 0.633 to 0.895 (with an average of 0.75) according to Balapanov et al [20], 0.548 to 0.927 (with an average of 0.803) in the research conducted by Zhou et al [54], 0.39 to 0.80 (with an average of 0.60) in a study by Orhan et al [48], and 0.250 to 0.833 (with an average of 0.514) as documented by Bujdoso and Cseke [55]. In this study, the average Ho ranged from 0.00 to 0.84, with a mean of 0.47, which agrees with the Ho of around 0.5 reported by Aradhya et al [56] for the region of Eurasia, while for walnut populations from Central Asia, Western Asia, and the Middle East, Pollegioni et al [57] found 0.559.…”

Hybridisation of Malus sylvestris (L.) Mill. with Malus × domestica Borkh. and Implications for the Production of Forest Reproductive Material

“…[37], between different cherry species (Prunus avium L. and Prunus fruticosa Pall.) [38], between cultivated and wild apricots (Prunus armeniaca L.) [39], between cultivated and wild common walnut (Juglans regia L.) [40] and many other species. Hybridization has also been demonstrated in some typical forest tree species, e.g., between field elm (Ulmus minor Mill.)…”