| Summary: | 碩士 === 國立中興大學 === 森林學系 === 85 === China fir (Cunninghamia lanceolata) has long been damaged by Leaf Blight of
China Fir, a common disease which attacks the species from seedlings in nursery
to saplings in the plantation. Plantations at ages 7~8 are particularly suscep-
table. The causal agent of disease was isolated and identified as Pestalotia
shiraiana P. Hennings.
Current study involves seedlings of open-pollinated single-tree families
from a local seed orchard in Taiwan. Seedlings were grown in both growth chamb-
ers and greenhouse. Before artificial inoculation of the
fungus, young seedlings
(less than one year)were regularly measured for plant heights.
Three weeks after
inoculation, these seedlings were investigated for their disease-resistance and
growth traits.
For growth traits: in the growth-chamber experiment, five families were
involved for the study. Analysis of variance results showed that plants in dif-
ferent chambers behaved differently in their growth, which suggested a G×E
interaction effect. In the greenhouse experiment, where 13 families were used,
heritability estimates were high, which implies large between-families varia-
tion. Thus early selection was possible.
For disease-resistance traits: susceptibility degrees were calcu-lated in
both experiments. Results showed that there was a significant between-families
variation. However, two symptom traits (healthy/sick, whether the number of
infected leaves are more than 10 leaves)showed inconsistent results between the
two experiments. Linear logistic model for the growth-chamber
experiment did not
show significant result. However, the same statistical model
applied in the data
analyses of greenhouse experiment clearly demonstrated that there were signifi-
cant difference in resistance among 15 families.
In growth-chamber experiment, we have also measured green- and oven-dried
weights of above- and below-ground parts of the plants. It was found that the
T/R ratio showed significant difference among seedlings of different classes of
susceptibility classes. The larger the T/R ratio, the plants
showed more serious
signs of damage. In the greenhouse experiment, plant height just prior to inoc-
ulation showed positive correlation with individual*s susceptibility degree.
These results are valuable information and worthy for further investigation.
In general, results demonstrated that early testing of genetic entries of
Cunninghamia lanceolata for disease-resistance to Pestalotia shiraiana P.
Hennings was possible.
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