Stevia rebaudiana is a unique plant that contains non-caloric natural sweetener and has gained much interest among Malaysians. In this study, the effect of different concentrations of N-methyl-N-nitrosourea (MNU) was assessed in inducing mutation in Stevia seeds to produce genetic variations, which is valuable for crop improvement. Stevia seeds were soaked in six concentrations of MNU (0.0, 0.13, 0.25, 0.38, 0.50, and 1.00 mM) for four different durations (15, 30, 45, and 60 min) at room temperature. As a result, application of MNU reduced the germination percentage and germination rate of Stevia seeds as compared to the control group. Prolonged exposure to the highest concentration of MNU recorded the lowest percentage of germination (2.5 ± 1.4%) and the lowest germination rate (0.21 ± 0.16). Tricots were observed among seedlings treated with 0.13, 0.38 and 1.0 mM of MNU for 30 min. Presence of seedlings with albino colour proved the mutagenic effect of MNU on Stevia genome. Based on the percentage of seedlings with chlorophyll mutation, the most effective and efficient mutagenic treatment to induce mutation was 60 min in 0.25 mM of MNU.
One of the top species in the aquaculture sector, known as striped catfish or Pangasianodon hypophthalmus, is an important and valuable freshwater fish in many countries. Due to the high demand for this species, their number has declined to "threatened" levels. Hence, the purpose of this study is to analyse the genetic variation of wild and cultured striped catfish collected from five producers in Asian countries; Thailand, Vietnam, Indonesia, India, and Philippines, by using mitochondrial DNA partial region data sequence; CO1 and cytochrome b gene. Population analyses using 395 base pairs length for CO1 and 275 base pairs length of cytochrome b partial region nucleotide sequence have shown no significance difference between wild and cultured striped catfish. Vietnam species had shown a wide range of genetic distance of the intrapopulation compared with other countries in the range of 0.000-0.040 for CO1 gene and 0.003-0.008 for cytochrome b gene. The Neighbour-joining method has also been used to construct phylogenetic trees using CO1 gene; the tree formed few subclades with mixed populations, and the tree using cytochrome b showed only Vietnam species divided into a few sub-populations. For the other four countries, Thailand, Indonesia, India, and Philippines were in the same group. Hence, this study's findings may provide a reference for inter and intra-relationships of P. hypophthalmus that may help in the aquaculture activity of this striped catfish.
The 16S rRNA gene is a housekeeping genetic marker that is available in almost all bacterial species and it is used in bacterial phylogeny and taxonomy studies. In many studies, the 16S rRNA gene is used in identification of certain bacterial species. Being a less conserved genetic marker, certain studies found it is a useful tool to infer the genome-wide similarity levels among the closely related prokaryotic organisms. Thus, this study aimed to compare the variation in the 16S rRNA partial region of Burkholderia spp. that infect the panicle of rice from eight different geographical areas. 58 sequences with total of 688 base pairs (bp) of 16S rRNA gene in B. glumae and B. gladioli were retrieved from public database based on several countries namely United State, Panama, Ecuador, Thailand, China, India, Korea and Malaysia. Then, the data sequences were analysed and validated using MEGAX and ABGD software respectively. The result of phylogenetic tree confirmed that B. glumae and B. gladioli were species that present in the panicle blight of rice. However, Data Analysis in Molecular Biology and Evolution (DAMBE) and Automatic Barcode Gap Discovery (ABGD) software were not able to detect substitution saturation and divergence between B. glumae and B. gladioli respectively based on the 58 sequences of the 16S rRNA partial region. Hence, it proves that 16S rRNA gene is an ineffective genetic marker to be used to differentiate the closely related species of bacteria from similar genus.
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