Analysis of morphological variability in Bosnia and Herzegovina’s autochthonous apple germplasm

Genetic variability of the autochthonous apple germplasm in Bosnia and Herzegovina (B&H) has previously been examined using ten SSR markers. The molecular analyses revealed a clear differentiation between traditional B&H cultivars and some of the most widely cultivated, modern cultivars in the region. In order to examine the morphological variability of autochthonous apple germplasm in B&H, a principal component analysis was used on data gathered during a three years field trial (2006-2008), which included 24 traditional B&H cultivars and 15 modern international cultivars, maintained at the ex situ apple collection ‘Srebrenik’ in Northeast Bosnia. Eighteen morphological characteristics were chosen for this study among a larger set of descriptors for apple defined by International Union for the Protection of New Varieties of Plants (UPOV) and International Board for Plant Genetic Resources (IBPGR). The objectives of the study were to identify the main sources of variability of morphological characteristics for all analyzed apple cultivars, to classify the cultivars according to main sources of variability and to assess the level of diversity of the analyzed traits for the autochthonous and international apple cultivars. The main sources of variability in the analyzed set of apple cultivars were mostly linked to fruit characteristics, such as fruit weight and fruit shape. An attempt to make a classification of cultivars and groups of cultivars through these characteristics generally failed due to overlapping of many traits between the autochthonous and international group. A separation between the two groups was observed when the classification was based on morphological traits such as tree habit (TH), tree vigour (TV) and scion/rootstock compatibility (SRC). This is very likely due to different selection pressure (preference and/or environment) between the groups. The assessment of the level of diversity revealed a higher diversity for all morphological traits among the B&H autochthonous apple cultivars. A pair-wise t-test revealed that the differences in values for Shannon index of diversity between the two groups were all significant (P<0.001). This can serve as an indication that B&H autochthonous apple cultivars represent an interesting potential for future apple breeding programs.