Comparative morphometric study and relationships between the Caucasian species of wild pear (Pyrus spp.) and local cultivars in Georgia

Morphological diversity in Pyrus spp. occurring in wild populations in Georgia has been evaluated and their relationships to local and introduced pear cultivars were determined using statistical discrimination between taxa, based on leaf and fruit traits. Eight native for Georgia wild species of pear - P. caucasica Fed., P. balansae Decne., P. salicifolia Pall., P. demetrii Kuth., P. georgica Kuth., P. ketzkhovelii Kuth., P. sachokiana Kuth., P. syriaca Boiss. - and the non-native European pear - P. pyraster (L.) Burgsd. - have been compared with 36 local and introduced pear cultivars. A total of 237 individuals were sampled in natural habitats, living collections and peasant grounds in different regions of Georgia. The individuals were evaluated for 27 morphological traits, which included 6 quantitative and 6 qualitative leaf and shoot descriptors and 14 qualitative fruit descriptors. Shape of the leaf blade was analysed using Fourier outline shape analysis method. 20 harmonics of Fourier coefficients per leaf and 10 leaves per individual were used. Multivariate Canonical Discriminant Analysis showed close relations between cultivars and 4 wild species - P. caucasica, P. balansae, P. pyraster and P. ketzkhovelii. According to hierarchical cluster analyses, the endemic species P. caucasica and P. balansae, native for Georgia, are aggregated only with 15 domesticated Georgian aboriginal local cultivars. P. pyraster and P. ketskhovelii clustered with different introduced and local cultivars. Crossing of these two wild taxa might have been first domestication events of pear in prehistorically times. Local aboriginal Georgian edible pear cultivars might have been originated from the native wild species of pear, P. caucasica and P. balansae. Many other pear cultivars in Georgia are associated with P. communis, probably originated through breeding selection in past historical times and resulting from recent activities of breeding stations in Georgia. (C) 2011 Elsevier GmbH. All rights reserved.