Investigating population dynamics of the chestnut blight in North Macedonia through time (1995-2000 and 2022).

Abstract

INVESTIGATING POPULATION DYNAMICS OF THE CHESTNUT BLIGHT FUNGUS IN NORTH MACEDONIA THROUGH TIME (1995-2000 AND 2022) Mihajlo Risteski1*, Kiril Sotirovski1 1Ss Cyril and Methodius University in Skopje, Hans Em Faculty of Forest Sciences, Landscape Architecture and Environmental Engineering *mihajlo.risteski@gmail.com The plant pathogenic fungus Cryphonectria parasitica and the infamous disease known as chestnut blight were initially discovered in the USA in 1904 on Castanea dentata and were recorded already in the late 1930-ties in Italy, on European sweet chestnut. Ever since, it has been disseminated in all European chestnut regions and has reached the eastern area of distribution of chestnut - Georgia, Azerbaijan and Iran. In 1950-ties, cankers showing “spontaneous healing” yielded isolates of the fungus expressing decreased virulence and sporulation. The phenomenon was named hypovirulence and is caused by mycoviruses of the genus Hypovirus. Ever since, scientists and practitioners have used hypovirulent isolates as a method for control of this devastating disease. It was additionally discovered that vegetative incompatibility between isolates of the fungus, is a restricting factor both for immediate suppression of growth of cankers and for the dissemination of hypovirulence within subpopulations of the fungus. Thus, vegetative compatibility (vc), and related aspects such as mating type (MAT), have been subjected to extensive research, both in Europe and the USA. In North Macedonia, in the period 1995-2000, C. parasitica from all larger chestnut populations was collected, isolated and analyzed for vc type diversity and MAT. Of the 786 isolates, the most dominant vc type was EU-12 (94 %), and only other 4 vc types were discovered (EU-1, EU-2, EU-10, EU-22). Regarding MAT, 96 % of the isolates were MAT-1. Hypovirulence incidence varied between subpopulations, ranging from 63 % (Skudrinje) to much lower or completely absent in others, while on the national level incidence was 19,5 % of 488 screened isolates. During 2022, over 500 samples have been collected from the same locations and will be subjected to analyses for the same aspects, with the main objective - comparison with data derived from previous research. We herewith present preliminary data and expected results. Keywords: Castanea sativa, Cryphonectria parasitica, hypovirulence, mating type, vc types