87 research outputs found
Isolating silkworm genomic DNA without liquid nitrogen suitable for marker studies
Genomic DNA was isolated from posterior silk gland of silkworms, Antheraea assama. Absolute alcohol was used as tissue fixing solution instead of grinding in liquid nitrogen, which yielded high molecular weight DNA (>40 kb). Samples yielded similar amount of DNA when fixed in absolute alcohol (400 μmg/g of silk gland tissue) and ground in liquid nitrogen (456 μmg/g of silk gland tissue). RAPD profile of the isolated DNA revealed high degree of polymorphism. The silkworms were analysed using 50 random primers among which 36 polymorphic primers gave 309 amplicons. The average amplicons per primer found to be 8.58 and 94.82% amplicons were polymorphic. Cluster analysis based on Jaccard’s similarity coefficients resulted in the formation of two main clusters with S9 on one cluster and the remaining strains on the other cluster. Jaccard’s similarity coefficients ranged from 0.122 to 0.863 indicating a high level of genetic diversity within muga silkworm collection. Isolated DNA was also suitable for cloning and restriction enzyme digestion. This method does not require liquid nitrogen for fixation, grinding or storage at -80°C, making it advantageous over other common protocols.Key words: Genomic, silkworms, muga, molecular breeding
Analysis of genetic diversity of muga silkworm (Antheraea assamensis, Helfer; Lepidoptera : Saturniidae) using RAPD-based molecular markers
Eleven populations of muga silkworm, Antheraea assamensis Helfer, the golden silk yarn producer of northeast India, was subjected to RAPD marker analysis in order to assess its genetic diversity. The genomic DNA extracted from muga silkworms were analysed using 50 random primers among which 36 polymorphic primers generated 309 bands. RAPD profile of the isolated DNA revealed a high level of genetic polymorphism. The average amplicons per primer was found to be 8.58, and 94.82% amplicons were polymorphic. Cluster analysis based on Jaccard’s similarity coefficients resulted in the formation of two main clusters with one population on one cluster and the remaining on the other cluster.Jaccard’s similarity coefficients ranged from 0.122 to 0.863 indicating a high level of genetic diversity within muga silkworm collection. The study concluded that, although there lays little morphological differences among the collected muga silkworm populations, the populations are highly polymorphic which might have enabled the silkworm to survive under a restricted geographical location, that is north east region of India only but under diverse climatic conditions for a long period. This study maybe useful in identifying diverse genetic stocks of A. assamensis, which may be conserved on a priority basis
Studies on secondary metabolites of Som ( Persea bombycina Kost), a primary host plant of muga silkworm (Antheraea assamensis Helfer)
The host plant selection behaviour or feeding preferences of the insects are largely mediated by the
presence and distribution of secondary metabolites in plants. Quantitative estimation of few secondary metabolites and
HPLC analysis of phenolic compounds were carried out from the leaves of Som plant (Persea bombycina Kost) which is
a primary metabolite of the shimmering yellow golden silk yarn producer, the muga silkworm (Antheraea assamensis
Helfer). β –sitosterol content in the tender leaves was significantly the highest (1.06%) over semi-mature or mature
leaves, whereas Chlorogenic acid content was more in medium leaves (2.06%). Phytic acid content was significantly
higher in mature leaves (2310.05 mg/100g), total phenol in tender leaves (1.946%), ADF in mature leaves (26.50%),
ADL in mature leaves and tannin in tender leaves (6.71%). Purified phenolic extract when subjected to HPLC analysis, 6
prominent peaks were observed and screening with standard indicates Peaks 1, 2, 3 and 6 correspond to Chlorogenic
acid, catechol, Morin and gallic acid, respectively.
Keywords: Som, Persea bombycina, Muga silkworm, Antheraea assamensis, secondary metabolites, HPLC analysis
Analysis of Genetic Diversity of Persea bombycina ‘‘Som’’ Using RAPD-Based Molecular Markers
The utility of RAPD markers in assessing genetic diversity and phenetic
relationships in Persea bombycina, a major tree species for golden silk (muga)
production, was investigated using 48 genotypes from northeast India. Thirteen
RAPD primer combinations generated 93 bands. On average, seven RAPD fragments
were amplified per reaction. In a UPGMA phenetic dendrogram based on
Jaccard’s coefficient, the P. bombycina accessions showed a high level of genetic
variation, as indicated by genetic similarity. The grouping in the phenogram was
highly consistent, as indicated by high values of cophenetic correlation and high
bootstrap values at the key nodes. The accessions were scattered on a plot derived
from principal correspondence analysis. The study concluded that the high level of
genetic diversity in the P. bombycina accessions may be attributed to the species’
outcrossing nature. This study may be useful in identifying diverse genetic stocks of
P. bombycina, which may then be conserved on a priority basis
Ionization yield measurement in a germanium CDMSlite detector using photo-neutron sources
Two photo-neutron sources, YBe and SbBe, have been
used to investigate the ionization yield of nuclear recoils in the CDMSlite
germanium detectors by the SuperCDMS collaboration. This work evaluates the
yield for nuclear recoil energies between 1 keV and 7 keV at a temperature of
50 mK. We use a Geant4 simulation to model the neutron spectrum assuming
a charge yield model that is a generalization of the standard Lindhard model
and consists of two energy dependent parameters. We perform a likelihood
analysis using the simulated neutron spectrum, modeled background, and
experimental data to obtain the best fit values of the yield model. The
ionization yield between recoil energies of 1 keV and 7 keV is shown to be
significantly lower than predicted by the standard Lindhard model for
germanium. There is a general lack of agreement among different experiments
using a variety of techniques studying the low-energy range of the nuclear
recoil yield, which is most critical for interpretation of direct dark matter
searches. This suggests complexity in the physical process that many direct
detection experiments use to model their primary signal detection mechanism and
highlights the need for further studies to clarify underlying systematic
effects that have not been well understood up to this point
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