Variability of sweet chestnut (Castanea sativa Mill.) in Montenegro according to morphological traits of fruits and UPOV descriptors

In this preliminary research phenotypic diversity of 40 chestnut trees in four natural sweet chestnut populations in Montenegro (Kostanjica, Ostros, Stoliv and Kostanjica) was investigated. The variations within and among the populations were analyzed based on fruit morphology traits and descriptors established by The International Union for the Protection of New Varieties of Plants (UPOV) in order to assess sweet chestnut genetic diversity. The research conducted in 2018 examined six measured and six derived fruit morphology traits as well as seven UPOV descriptors of fruit morphology and leaf bud burst phenology. The following morphometric traits were analyzed: Fruit weight, Fruit height, Fruit width, Fruit thickness, Scar length and Scar width. The following UPOV descriptors were examined: Fruit embryony, Degree of penetration, Fruit shape, Fruit size, Fruit color, Kernel color, Time of leaf bud burst. The results showed that the Mediterranean populations (Stoliv and Kostanjica) have smaller fruits than the sub-Mediterranean populations (Kostanjica and Ostros); their fruits have stronger pellicle intrusion and they exhibit polyembriony more frequently. The average value of Shannon’s diversity index for six UPOV descriptors was 0.66. Cluster analysis with the UPGMA method was used for classification of the tress into groups. Cluster grouping is in concordance with populations' geographical distribution. Sub- Mediterranean populations Ostros and Kostanjica formed 2 clusters with trees from both populations, and another two clusters were formed by trees from Mediterranean populations Kostanjica and Stoliv. Our results indicate a high variability within populations which is important for the conservation of genetic pool of the species. To fully comprehend the variability of sweet chestnut natural populations in Montenegro the research should be expanded on data provided by molecular markers like SSRs as well as further and more detailed assessment of morphological characters.