To what extent do wild apples in Kazakhstan retain their genetic integrity?
Kazakhstan belongs to the center of origin of apple. Malus sieversii (Ledeb.) M. Roem., the ancestral progenitor of the cultivated apple is native to this region. Pressure on the natural habitats of this wild apple has been intensified due to agriculture, grazing, and urbanization in the last century. For decades, M. sieversii in Kazakhstan has been subjected to the “Red Book of the Kazakh SSR” and today, this species is threatened with extinction. Wild apple undergoes exceptional losses in habitats, and the risk for losing the genetic integrity becomes worse due to increasing cultivation of cultivated apples and frequently occurring crosspollination events. The present study was focused on the current state of M. sieversii in Kazakhstan, the level of its diversity, its genetic integrity, and the identification of regions where future activities for conservation will have a good chance of success. A total of 311 M. sieversii samples of 12 populations collected in the wild, 16 previously selected wild apple genotypes, and 50 grown cultivars were studied using 16 simple sequence repeat (SSR) markers for genetic analysis. The results suggest that the level of genetic diversity is high. The differentiation between the populations was low, although the within-population heterozygosity was relatively high. A significant number of hybrids (8–95%) between M. sieversii and cultivated apples were found suggesting frequent crop-to-wild gene flow. The percentage of pure wild apple genotypes was highest in Krutoe truct and Tauturgen. These sites should be taken into account for future in situ long-term preservation activities.
KeywordsMalus sieversii Microsatellite markers Genetic diversity Population structure
The research was funded by the Grant on the subpriority “Fundamental Studies in the Area of Natural Sciences,” Budget Program 101 of the Scientific Committee of the Ministry of Education and Science of the Republic of Kazakhstan (grant no. 1105/GF4). We gratefully acknowledge Dr. S.V. Chekalin for collecting Malus sieversii samples and providing information on the wild apple germplasm. We also acknowledge R. Gläß for her technical assistance and Dr. F.O. Emeriewen for improving the English language of the manuscript.
Data archiving statement
All data are provided in Table S3.
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