MULTILOCUS GENETIC STRUCTURE OF EUROPEAN CHESTNUT (CASTANEA SATIVA) HELLENIC CLONES AND GENETIC DIVERSITY OF ORCHARD POPULATIONS

Clonal identification and multilocus genetic structure of chestnut cultivars of two Hellenic orchard populations originating from distant geographic locations is reported, while genetic diversity of orchard populations is compared to that of wild ones in corresponding locations. Winter buds were sampled and nine loci (16 alleles) were revealed out of seven enzyme systems investigated. Results indicated that orchards are essentially low-number multiclonal plantations with respect to their grafted part. The percent unique genotypes in both orchards were estimated to be 21% of the total number of individuals, compared to 70-86% found in natural populations. A total of 650 pairwise comparisons has led to the identification of eleven unique clones present in orchard populations. Despite the significant distance among the orchards a common elite clone was identified. A clonal identification key was developed. The average probability that two trees may have the same genotypic multilocus array by chance alone is still high, indicating the need for future DNA fingerprinting. Evidence suggests the existence of a notable reduction of genetic diversity in orchard populations compared to wild ones in Greece. However, Hellenic orchards seem to possess higher amounts of genetic variability compared to western European ones. The implementation of these results in applied breeding research is discussed.