Phenotypic Variability of Brachiaria Decumbens After Exposure to Gamma Irradiation
Brachiaria decumbens (Signal grass) has been used for many years as grazing pastures for ruminants. Its toxicity to small ruminants is the main limitation to utilization of this grass. Many researchers have reported several methods to control or alleviate this problem. Since there is a potential...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2003
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/10632/1/FP_2003_1.pdf |
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| Summary: | Brachiaria decumbens (Signal grass) has been used for many years as grazing
pastures for ruminants. Its toxicity to small ruminants is the main limitation to
utilization of this grass. Many researchers have reported several methods to
control or alleviate this problem. Since there is a potential to use mutagenesis
techniques to obtain variability of the plants, the objective of this study is to
observe the phenotypic variability of Signal grass after mutagenic induction with
gamma radiation. Further studies can be conducted to make a selection of
variants which are free from toxicity. Brachiaria decumbens seeds were irradiated at doses of 1 00, 200, 300, 400, 500,
600, 700, 800 and 900 Gy to determine the appropriate doses for mutagenic
treatments of the grass. The results showed that, B. decumbens seeds were less
sensitive to gamma ray than most other species and the LD50 was found to be
between 800 to 900 Oy.
In order to observe the effects of gamma radiation on phenotypic variability of
the grass, the grass seeds were exposed to 900 Oy gamma radiation. Results
showed that gamma radiation at 900 Oy increased variability in morphological
characteristics and nutrient contents and an obvious phenotypic mutant was
detected.
There were significant increases in variabilities of morphological characters
(tiller numbers, leaf length, leaf width, leaf weights, stem weights., leaf-to-stem
ratio and internode lengths) and nutrient contents (Crude Protein, Ether Extract,
Crude Fibre, Acid Detergent Fibre, Neutral Detergent Fibre and Ash) among the
treated plants. There was also a positive skew of the frequency distribution curve
for the treated plants to the right, indicating that mutagenic radiation can cause
increased variability, which allows greater selection potential for desired
characteristics.
DNA Polymorphism in the mutant cannot be detected through RAPD. The
mutant showed significantly higher leaf width, leaf-to-stem ratio and crude
protein compared to control plants. |
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