Genetic Diversity of Intensively and Extensively Managed Chestnut (Castanea sativa) Orchards in Greece

Chestnut (Castanea sativa) orchards in Greece can be broadly classified in two categories: intensively managed (commercial cultivars grafted on selected rootstock established on agricultural land in the vicinity of rural communities) and extensively managed (local scions grafted on wild trees demarcating areas within natural forests, away from rural communities). The genetic diversity and multilocus genetic structure of two intensively and two extensively managed orchards is reported and compared based on 17 isoenzyme loci. Results indicated that intensively managed orchards present a high number of unique genotypes (85% of the total number of individuals), while extensively managed orchards have a rather low-number of unique genotypes (21% of the total number of individuals). In one intensively managed orchard, interspecific C. sativa × C. crenata hybrids were identified in 22% of the individuals studied. Genetic diversity parameters were higher in the intensively managed orchards evidently as a result of the higher number of alleles present (mean average number of alleles per locus in the intensively and the extensively managed orchards was 2.31 versus 1.50 respectively). The genetic diversity of intensively managed orchards is comparable to that of adjacent natural populations and higher than the diversity reported in western European orchards. It is postulated that the greater number of unique genotypes in intensively managed orchards may reflect the traditional arboricultural practices of the local growers. It can present an obstacle regarding the nut uniformity for industrial processing; nevertheless it may be beneficial under climatic change scenarios. The implementation of the above results for further selection and breeding is discussed.