Variability of Puccinia komarovii var. komarovii isolates from Impatiens parviflora DC. and its occurrence in the Drawa and Wigry National Parks in Poland

Small balsam ( Impatiens parviflora DC.), an invasive plant native to central Asia, is currently one of the most extensive invasive plants in Central Europe, including Poland. Its expansion may affect populations of native species, such as touch-me-not balsam (Impatiens noli-tangere). It is particularly dangerous in legally protected areas, where the possibilities of eradicating it are very limited. There is some hope for stopping its expansion by using pathogens as a biological weapon. In this case, useful may be host-specific rust fungus Puccinia komarovii var. komarovii . Our three-year observations of I. parviflora infection severity by P. komarovii var. komarovii carried out in Poland in Drawa National Park (DNP) and Wigry National Park (WNP) showed the higher incidence of rust on leaves in DNP, where the median blade infestation for two years was 51% of leaf coverage. In contrast, for three years in WNP, the median blade infestation amounted to only 25%. The most severe symptoms occurred during the summer months. However the percentage of leaf coverage by pathogen exhibited fluctuations depending on the year, implying an influence of environmental conditions that stabilized the infection each season. Molecular analyses, in addition to confirming the infection of the tested plants by P. komarovii var. komarovii , enabled the characterization of its population based on comparative analysis of ITS and LSU sequences. Clear differences were found between the studied isolates and P. komarovii from I. glanduliferae and I. brachycentra . There was no diversity among our isolates, but they differed from the sequences of Polish isolates originating from I. parviflora available in GenBank, which indicates some diversity of rust in a relatively small area. It probably results from sexual reproduction and may enable rapid adaptation of the pathogen to the region or host plant, or it may indicate certain “entry points” to Poland, where the isolates arrived from their native place of occurrence.