Occurrence of Dothistroma needle blight in Lithuania and Belarus: The risk posed to native Scots Pine forests

Abstract

Dothistroma needle blight (DNB) caused by the ascomycetous fungus Dothistroma septosporum is an important pine disease in Europe. In this study, we determined the distribution and abundance of D. septosporum in local Scots pine forests and plantations in Lithuania and neighbouring Belarus by combining morphological observations and molecular tools. This is the first valid report on the occurrence of D. septosporum in Belarus, based on detailed morpho-cultural and molecular characteristics. Currently, in both countries only the asexual stage of D. septosporum is found on needles of the native Scots pine and on various ornamental exotic pines planted in botanical gardens and arboreta. Our results show that P. sylvestris may now be considered the most common host with varying susceptibility to D. septosporum. Phylogenetic analysis revealed the presence of three different ITS haplotypes among Lithuanian and Belarusian D. septosporum isolates. Mating type (MAT) genes analysis showed that two mating types (MAT1-1 and MAT1-2) occur in both countries, indicating a high probability of D. septosporum sexual reproduction. Isolates from Lithuania were represented by the idiomorph MAT1-1 and MAT1-2 in the ratio of 1:1, while isolates from Belarus were dominated by the idiomorph MAT1-1 (ratio 3:1). Our results also demonstrate the importance of DNB monitoring for prevention and control of disease outbreaks in Lithuanian and Belarusian Scots pine forests in the future.