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Signs and symptoms of root rot in Eucalyptus pellita plantations in Indonesia

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Agustini, Luciasih (2009) Signs and symptoms of root rot in Eucalyptus pellita plantations in Indonesia. Research Master thesis, University of Tasmania.

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Abstract

This thesis investigates the identity of fungi causing root rot in Eucalyptus pellita
plantations in Indonesia. It explores the question of how to detect root-rot infected
E. pellita trees from their crown symptoms and whether root-rot disease can be
detected at an early stage in the cycle of disease development.
This study described and identified the fungi associated with root-rot disease in
E. pellita, putatively caused by a species of Phellinus. Macro- and microscopic
observations and DNA analysis were used to describe sporocarp morphology and
the fungal cultures growing from the symptomatic root samples. Results showed
that at the 12 sites investigated, and contrary to expectations, species of Phellinus
are less commonly associated with root-rot disease than are Ganoderma philippii
and G. mastosporum. There were several potential fungal agents of root rot present
at any one site; the sporocarp types observed and the external appearance of the
roots were not consistently good indicators of the active pathogen as isolated from
roots.
A visual assessment method to assess the crown condition of trees in
plantations of E. pellita was developed. Eight aboveground variables were used as
indicators to classify the E. pellita crowns into five different classes. Repeatability,
reproducibility and reliability of this method were examined by conducting
repeated surveys. Analysis of the data showed that the crown variables adequately
discriminated between crown-condition classes when they were assessed by
experienced assessors. However, in repeated surveys which were conducted by less
experienced assessors, the crown variables did not sufficiently discriminate
between crown-condition classes. Applicability of the method to indicate root-rot
incidence and severity at individual-tree level was tested during the first survey.
An aboveground assessment of crown-condition using the methodology developed
does indicate, at the plot level, the incidence and severity of root rot. At the tree
level, the aboveground variables were not significantly correlated with root-rot
incidence and severity, as indicated by Spearman correlation (a = 0.05). There was
an approximate probability of one out of two that poor crown health was associated
with visible signs and symptoms on the roots exposed around the tree. Probability
of these indicators for estimating root-rot incidence and severity in an individual
tree is 61.4% and 41.6%, respectively.
A pathosystem model of Eucalyptus nitens trees artificially inoculated with Armillaria luteobubalina was set up to investigate early physiological responses associated with root-rot infection. Trees were inoculated with two different isolates of A. luteobubalina. Root systems were either wounded or left intact before inoculation. Three photosynthetic parameters, i.e. photosystem II yield (`F_v`/`F_m`), chlorophyll content and photosynthetic rate (`A_max`) were assessed during six-months of observation. Photosystem II yield was the most sensitive to root-rot infection. A significant difference in `F_v`/`F_m` between the unwounded control and other treatments was observed. Chlorophyll content and photosynthetic rate (`A_max`) decreased for all trees, including controls, during the period of the experiment. The decrease was more marked in treated than control trees. The root systems of inoculated trees were examined and reisolations of A. luteobubalina from symptomatic roots were carried out to confirm infection with Armilllaria of E. nitens trees. This preliminary trial of a model pathosystem was successful and did indicate that there were detectable physiological changes associated with early infection by Armillaria. However the experiment required a longer duration for more widespread physiological changes to be detected.
The findings of this project reinforce the importance of comprehensive efforts to reduce the severity and incidence of root-rot disease, especially in terms of early detection. These efforts include the correct identification of fungal causal agent/s, the regular monitoring of crown condition, the application of physiological indicators such as photosystem II yield (`F_v`/`F_m`) to detect stress in plants, including that caused by root rot. Further studies are required to scale up these findings to an operational and cost effective level of plantation management. Pest management strategies, especially for root rot, such as site-hazard rating, species-site matching and mixed-planting systems are discussed in reference to plantation expansion in Indonesia.

Item Type: Thesis (Research Master)
Copyright Holders: The Author
Additional Information:

Thesis (MAgrSc)--University of Tasmania, 2010. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:59
Last Modified: 02 May 2017 03:03
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