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A study of the traits associated with the biocontrol activity of Phlebiopsis gigantea

Mgbeahuruike, Anthony Christian (2009). A study of the traits associated with the biocontrol activity of Phlebiopsis gigantea. Uppsala : Sveriges lantbruksuniv.
ISBN 978-91-86197-24
[Licentiate thesis]

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Phlebiopsis gigantea has routinely been used for the biocontrol of the conifer pathogen, Heterobasidion annosum s.l. but the mechanism for the biocontrol action has not been properly understood. In the present work, 64 isolates of P. gigantea were screened for traits important for the biocontrol of H. annosum. Growth rate and the interaction patterns of H. annosum s.l. and P.gigantea were studied in both carbon rich (Hagem) and low carbon media (Norkrans). Laccase assay and wood degradation capabilities were performed on the 64 isolates. Data was analyzed with multiple regression and principal component analysis. Results showed a significant effect of culture composition on the outcome of the interaction, 90 % of the isolates were able to displace H. annosum s.s. in sawdust media after 20 days, as compared with only 4% recorded in the glucose rich Hagem media. High growth rate on sawdust, a lignified carbon source, correlated with high growth rate in ferulic acid, a lignin precursor (P = 0.078), high growth rate in xylan, a hemicellulose (P = 0.001) and percentage weight loss in pine (P = 0.01). Interaction in sawdust correlated with high wood degradation capability in pine and spruce with P-values (P = 0.01, P = 0.03) respectively, high growth rate in xylan (P = 0.01), laccase production (P = 0.08), interaction in Hagem (P = 0.01) and mean growth rate at 10 °C (P = 0.001). Additionally, the role of hydrophobin in the competitive interaction was further investigated. The genomic sequence of Phlebiopsis gigantea hydrophobins 1 and 2 (Pgh1 and Pgh2) from a subset of isolates selected on the basis of geographical origins and antagonistic abilities was investigated. Similarly, the expression of Pgh1 and Pgh2 under different substrate conditions was also studied using quantitative PCR. Sequence analysis was performed with Clustal W and inspected with Megalign (DNA Star). Expression data was analyzed using the relative quantification method- 2-ΔΔCt and tested for effects of isolates, genes and culture conditions using the general linear model (GLM) procedure in SAS. There was a close sequence similarity between hydrophobin genes of isolates having different antagonistic capabilities and from different geographical sources. Higher transcript levels of Pgh1 and Pgh2 were recorded in submerged cultures compared with aerial conditions. The effect of substrate on the expression of the two genes (Pgh1 and Pgh2) was statistically significant (P = 0.0001). Differences in transcript levels of Pgh1 and Pgh2 were also observed among isolates belonging to different antagonistic categories. Overall, the results suggests that the antagonistic and competitive advantage of P. gigantea, hinged on the ability of the isolates to degrade the different structural components of wood. A significant correlation was also found between some high antagonistic isolates and the expression of hydrophobin genes (Pgh1 and Pgh2). The significance of these results in the biological control is discussed.

Authors/Creators:Mgbeahuruike, Anthony Christian
Title:A study of the traits associated with the biocontrol activity of Phlebiopsis gigantea
Year of publishing :2009
Number of Pages:41
ALLI. Differential screening of Phlebiopsis gigantea isolates for traits associated with biocontrol of the conifer pathogen Heterobasidion annosum (Submitted ) II. Differential expression of two hydrophobin genes (Pgh1 and Pgh2) from the biological control agent Phlebiopsis gigantea
Place of Publication:Uppsala
ISBN for printed version:978-91-86197-24
Publication Type:Licentiate thesis
Full Text Status:Public
Agrovoc terms:fungi, biological control agents, genes, gene expression, heterobasidion annosum, root rots, disease control, biological control, sawdust, growing media, pcr
Keywords:Biocontrol, Interaction, Heterobasidion annosum, Phlebiopsis gigantea, hydrophobins, Quantitative PCR, sawdust
Permanent URL:
ID Code:2109
Department:(NL, NJ) > Dept. of Forest Mycology and Plant Pathology
(S) > Dept. of Forest Mycology and Plant Pathology
Deposited By: Anthony Mgbeahuruike
Deposited On:22 Sep 2009 00:00
Metadata Last Modified:02 Dec 2014 10:16

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