Evaluation of impact of pine bark extracts on mycelial growth of Lophodermium seditiosum in vitro | Skuju koku mizas ekstraktu ietekmes uz Lophodermium seditiosum micēlija attīstību in vitro novērtējums

letton. Pētījumā novērtēta skuju koku mizas ekstraktu ietekme uz priežu brūnās skujbires izraisītāja Lophodermium seditiosum (Minter, Staley and Millar) augšanu un attīstību in vitro. Pētījumā novērtēta skuju koku mizas ekstraktu ietekme uz priežu brūnās skujbires izraisītāja Lophodermium seditiosum (Minter, Staley and Millar) augšanu un attīstību in vitro. Pārbaudīti parastās egles (Picea abies (L.) H. Karst.) un parastās priedes (Pinus sylvestris L.) mizas ekstrakti, kas iegūti ekstrahēšanas procesā, pielietojot dažādus polāros šķīdinātājus (ūdens, etanols, sārmaini ūdens šķīdumi). Konstatēta atsevišķu priedes mizas ekstraktu inhibējoša ietekme uz L. seditiosum micēlija augšanu, turpretī egles mizas ekstrakti nekavēja vai pat stimulēja L. seditiosum augšanu in vitro. Visefektīvāk micēlija augšanu kavēja 0,1 % priedes mizas etanola ekstrakts, kā arī 1,5 % priedes mizas nātrija sārma ūdens ekstrakts. Ekstraktu inhibējoša ietekme uz sēnes attīstību novērota līdz otrajai augšanas nedēļai. Konstatētas ekstraktu ietekmes atšķirības uz dažādu sēnes izolātu augšanu. Ekstraktu inhibējošais efekts uz sēnes augšanu skaidrots ar ekstraktos sastopamo fenola savienojumu antifungālajām īpašībām.

anglais. Lophodermium seditiosum (Minter, Staley and Millar) is one of the main needle pathogens in forest nurseries and young pine plantations causing Lophodermium needle cast on pines. Every season in forest nurseries Scots pine (Pinus sylvestris L.) seedlings are treated with fungicides to prevent infection. As these chemicals have an impact on the environment and use of some of them is not allowed after forest planting research is required into new agents for protection of seedlings against needle cast. Since conifer bark extracts, especially phenolic compounds, are known to have antifungal effects, we tested those on Lophodermium seditiosum under laboratory conditions. We tested three methods of adding extracts to agar media – addition of unsterilized extract, addition of autoclaved extract and addition of filter paper previously impregnated with extract. The method using impregnated filter paper showed the best results. Comparing Scots pine and Norway spruce (Picea abies (L.) H. Karst.) bark extracts we observed that spruce extract did not show any inhibition of L. setitiosum colony growth or even stimulated it, though some of the spruce bark extracts had a greater total amount of phenols in comparison with pine extracts. The largest L. seditiosum colony growth inhibition was obtained using pine bark ethanol and sodium hydroxide water extracts, and the effect of these extracts was maintained for more than two weeks. Sodium hydroxide water extracts at high concentration (1.5 %) showed inhibition of fungal growth. It was speculated that fungal growth is reduced by inhibiting its cellulaze enzyme activity due to tannins most likely present in these extracts or by possible increase of pH in the medium due to extract addition. 0.1 % pine bark ethanol extract had a significant effect on L. seditiosum mycelial growth in most of experiments, though its effectiveness varied among different L. seditiosum isolates. As this extract was rich with phenolic compounds which are reported to have antifungal effects, it was assumed that phenolic compounds are causing fungal inhibition. This extract will be tested on seedlings under field conditions to evaluate its effectiveness in practical forestry.