STRUCTURE AND GENETIC VARIATION OF DIPLODIA MUTILA ON DECLINING ASHES FRAXINUS EXCELSIOR IN POLAND
W. Kraj, T. Kowalski, M. Zarek
This study encompassed 137 cultures of Diplodia mutila isolated from necrotic tissue of 3- to 20-year-old trees of Fraxinus excelsior with decline symptoms, originating from three geographic regions of Poland differing by climatic conditions. Fungus identification was conducted on the basis of morphological traits of cultures and confirmed by analysis of ribosomal DNA sequences. The structure and genetic variation of D. mutila populations was determined with the use of RAMS markers. Neighbor Joining analysis of ITS sequences of the examined isolates showed the greatest similarity to sequences of D. mutila isolated from F. excelsior and deposited in GenBank. Intra-population variation expressed by Dice coefficient and Shannon index was high and increased along with the shifting of a population’s location from mild climate (northern Poland) to more severe climate, characteristic for upland and mountainous areas (southern Poland). The mallest genetic distance was shown by pairs of populations close to one another, inside individual regions. AMOVA showed great share (91%) of genetic variation inside a population, whereas variation was very small between populations (6.4%) and regions (2.6%). Principal component analysis showed grouping of fungus populations in accordance with their geographic location.