Endofity korzeni świerka pospolitego oraz podatność drewna różnych jego pochodzeń na rozkład przez Armillaria ostoyae i Heterobasidion parviporum
AbstractThe thesis presents the results of quantitative and qualitative research on the diversification of the mycobiota of Norway spruce roots and their impact on health of the trees, and an assessment of susceptibility of the spruce to the root pathogens Armillaria ostoyae and Heterobasidion parviporum depending on the amount of phenolic compounds in the wood. The research on the distribution of fungal endophytes was carried out at 9 locations, based mainly in national parks (The Babia Góra National Park, The Gorce National Park, and The Tatra National Park). The roots were collected from 45 healthy spruces and 27 wilting ones. The fungi were isolated from 4 types of roots (fine, thin, medium and thick) on Potato Dextrose Agar (PDA) growth media using two methods of chemical disinfection. The fine roots were divided into two groups, one of which was chemically disinfected, and the other one rinsed. The research on susceptibility of the spruces to the root pathogens was carried out at 22 research locations, of which 19 were based in mountain areas and the other 3 were located at the Białowieża National Park. The root samples from 392 spruces were pulverized into sawdust and placed in test tubes; after sterilization they were inoculated with 2 strains of A. ostoyae and 2 strains of H. parviporum. The susceptibility of spruce wood to decay by Armillaria and Heterobasidion was assessed based on decline of dry matter after 3 months of cultivation. Qantitative analysis of phenols was taken by means of extraction of these compounds from the pieces of sawdust with diameter lower than 0,1 mm from 99 spruces, and then their content was assessed by means of colorimetric method using a spectrophotometer. Ferulic acid was used as an equivalent in determining the content of phenolic compounds. In order to assess antiradical abilities of the tested extracts the DPPH radical test was taken. The mycobiota of spruce roots was highly diversified, quantitatively and qualitatively, among healthy and wilted trees at the same locations as well as between locations. The analysis based on the Jaccard and Sørensen’s indexes (analysis of species and amount accordance) showed greater resemblance between fungal associations found in forest complexes located closer to each other. A lower resemblance between such associations was also found in between lower and upper subalpine forests, which could indicate a significant role of local climatic conditions in frequency of distribution of some fungal species. The type of roots had also a significant impact on the spectrum of fungi inhabiting them. The thicker the roots, the lower was the amount of species and number of roots inhabited by the fungi. The most inhibited were the fine roots which were not disinfected chemically. Dark septate endophytes (PAC) were identified by means of genetic tests as 6 species: Phialocephala fortini, P. subalpina, P. turiciensis, P. letzii, P. sphaeroides, and Acephala applanata, and were the dominant fungi on the roots of spruce. They were found on all the trees and at all the locations, inhabiting mainly the fine and thin roots. Most often the fungi are mutualistic. However, the research results show that the fungi can become weak parasites, especially in case of highly weakened and wilted trees. There are three indications that support it. The frequency of occurrence of the fungi on the wilted trees was statistically significantly higher than on the healthy trees. Furthermore, only on the wilted trees the PAC strains were frequent on medium roots, whereas they did not inhabit the medium roots of healthy trees or they were not frequent there. Likewise, defensive reaction of the trees against inhabitation by, among others, P. subalpina, known for its pathogenity, at locations at the Babia Góra National Park proves that in some circumstances this influence can be adverse. The hypothesis can be made that differences in roots inhabitation of the specific spruces by the PAC endophytes can be related to the defensive reaction of the tree against the pathogenic strains, or the lack of other fungi that could inhibit the virulence of some of the PAC strains. The combination of rinsing and chemical disinfection of fine roots proved very useful in analyzing the interactions between fungi in rhizosphere and the roots. As the fungal endophytes did not percolate from the surface of the root to the inside, it can be evidence of defensive reactions of the tree against the fungi. Also the presence of saprophytes limited to the rinsed fine roots from the healthy trees, and its presence in the chemically disinfected fine roots of the wilted trees can be an indication of the poor health of the roots. The simultaneous inhabitation of fine and thin roots by both the PAC fungi and the genera Trichoderma and Tolypocladium, and Sordariacaea family, is an indicator of the present and future poor health of the spruces. Armillaria ostoyae occurred only in some of the tree stands, usually colonizing a small number of medium and thick roots, and on some trees it occurred only on the root neck. As a weakness pathogen, the fungus preferred trees that had been already significantly weakened by other conditions. The presence of Heterobasidion parviporum was, however, not detected on the roots of the tested spruces. It cannot be excluded that the roots infected by Heterobasidion were placed in the deeper layers of soil, and so they were beyond the reach during the sampling of the roots. The differences in the intensity of decay of the spruce wood, primarily by Armillaria and, to the lesser extent, by Heterobasidion, were usually bigger within location than between locations. As the result, changes within population of the spruces had a bigger impact on the decay of the wood than the changes between populations. The intensity of decay of the spruce sawdust depended on the fungal species. The decay of the sawdust induced by H. parviporum was about 2 times bigger than by A. ostoyae. The differences in the decline of dry matter of the sawdust between the strains of the same species were statistically insignificant. A high differentiation in the intensity of decay of the sawdust from different trees was observed. In case of Armillaria the maximum decline of dry matter of the sawdust was 3 times higher, and in case of Heterobasidion 4 times higher, in comparison to the minimum value. As the health of the spruce tree stands deteriorated, the intensity of decay of the wood by Armillaria decreased, and the intensity of decay by Heterobasidion augmented. Phenolic compounds had a significant impact on the intensity of decay of the spruce wood and diminished for about 25% the decline of dry matter of the sawdust which was induced by A. ostoyae and H. parviporum. The amount of phenolic compounds increased with deterioration of health of the spruces, and its higher presence in the wood was a defensive reaction of the trees against the pathogens. A. ostoyae and H. parviporum differed in reactions to the presence and antiradical activity of phenolic compounds in the wood of the healthy and wilted trees. In case of Armillaria the presence of phenols in the wood of the healthy trees was not significantly related to the intensity of decay of the wood. Yet, in the wood of the weaken trees it slightly inhibited the process, and in the wood of the wilted trees, it stimulated the decay. Such a reaction of the pathogen might have been induced by antiradical activity of phenols. The increase of the occurrence of phenols always limited the intensity of decay of the wood by H. parviporum. This indicates a significant difference in the ability to neutralize phenolic compounds by these fungi and explains the ability of Armillaria to decay sapwood of conifers and the difficulties in inhabiting these trees by Heterobasidion. Moreover, phenolic compounds even in a low concentration inhibited germination and limited the length of germ tubes of conidia of H. parviporum. This explains the difficulty in obtaining positive and repeatable results in artificial infection of older trees during field tests. The number of spruces susceptible to infection by H. parviporum spores, in which the amount of phenols in the wood was less than critical value (less than ED100) was 22%. The low amount of phenolic compounds in the wood of spruce (less than ED100) significantly stimulates its decay by Armillaria, and only slightly the decay by Heterobasidion. In the second group of trees, with the higher amount of phenols (ED100 or more) these pathogens (especially H. parviporum) reacted inversly and decayed the spruce wood more slowly.
|Other language title versions||The mycobiota of Norway spruce roots and susceptibility of its wood to decay by Armillaria ostoyae and Heterobasidion parviporum|
|Publisher||Uniwersytet Rolniczy im. Hugona Kołłątaja w Krakowie, MNiSW |
|Publishing place (Publisher address)||Kraków|
|Book series /Journal (in case of Journal special issue)||Zeszyty Naukowe Uniwersytetu Rolniczego im. Hugona Kołłątaja w Krakowie. Rozprawy, ISSN 1899-3486, (0 pkt)|
|Publication size in sheets||7.5|
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