Loading...
Characterization of different stocks of macrobrachium rosenbergii and development of genetically improved strain through selective breeding
Giant freshwater prawn Macrobrachium rosenbergii (de Man, 1879) is an important species suitable for culture in inland and low saline coastal water bodies. Information on the genetic structure and variation among cultured species are essential for genetic approaches to optimize conservation strategi...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Ph.D Thesis |
| Language: | Undetermined |
| Published: |
Panangad
Department of Aquaculture, College of Fisheries
2010
|
| Summary: | Giant freshwater prawn Macrobrachium rosenbergii (de Man, 1879) is
an important species suitable for culture in inland and low saline coastal water
bodies. Information on the genetic structure and variation among cultured
species are essential for genetic approaches to optimize conservation strategies
and breeding programmes for improving stocks. DNA based markers can be
used to assess more precisely the genetic variations in the entire genome.
Natural populations of M. rosenbergii inhabiting the rivers in different
geographical areas of India show wide variation in morphological traits and
economic characters.
The present work envisages studying the genetic
diversity of wild populations of M. rosenbergii collected from different parts of
India through phenotypic characters and molecular marker studies. It also aims
to develop a superior strain by combining the desirable characters through
selective breeding.
In this study genetic characterization of Andhra Pradesh (AP), Orissa
(OR) and Kerala (KR) stocks of Macrobrachium rosenbergii were done with
RAPD and Microstellite markers. Marker analysis showed variation between
stocks and AP showed more genetic distance from OR and KR populations.Moreover KR stock from Achankoil River showed slight similarity with AP.
Phenotypic trait analysis was done with three stocks. Egg diameter,
larval hatch fecundity, larval rearing period, survival rate and larval length
were estimated. Highest egg diameter and hatch fecundity were shown by OR
and KR populations. AP showed minimum larval rearing period and maximum
survival rate. Maximum larval length was for KR.
Stress tolerance studies were conducted in V and X stage of
M.rosenbergii larvae with temperature, salinity, formaldehyde and ammonia to
estimate the relative differences in the ability of different populations to
withstand stressed conditions. Among base population KR population showed
highest tolerance towards temperature, salinity, formaldehyde and ammonia.Stage wise tolerance variations also found in all populations. X stage showed
more tolerance to all stressors except ammonia.
Comparison of other economically important parameters such as disease
resistance, quality of flesh, percentage survival, growth rate, percentage
morphotypes and head tail ratio were also done. Disease resistance was tested
with white tail virus and bacteria (Enterococcus aerogenes) by challenge study.
In both studies KR population exhibited better tolerance than other
populations. Prophenoloxidase activity and total haemocyte count was also
estimated in infected prawns to check the immune response. Here again KR
showed higher activity and count. Flesh quality of three populations was
estimated by carcass proximate analysis. In this study, no variation in body
composition was shown by three stocks. Percentage survival rate and weight gain of three populations in cage were estimated. Maximum survival rate was
found in AP and highest growth was found in KR stock.
Analysis of
percentage morphotypes of various populations showed the maximum OC for
AP and SM for OR stock, with no significant variations in percentage BC and
female prawns, head tail ratio, which was calculated to find out the yield of
meat revealed the least ratio for KR.
Large healthy prawns of the three stocks were selected from families
showing better performance. Breeding experiment was conducted to produce
six crosses viz. Andhra Pradesh (male)×Orissa (female) APOR, Orissa (male)
× Andhra Pradesh (female) ORAP, Andhra Pradesh (male) × Kerala (female)
APKR, Kerala (male) × Andhra Pradesh (female) KRAP, Orissa (male) ×
Kerala (female) ORKR, Kerala (male) × Orissa (female) KROR.
Different phenotypic characters and economically important traits of F1
generations of hybrids were also studied. KROR showed better egg diameter,
hatch fecundity, larval survival rate and larval length. But larval rearing period
was minimum for APKR. KROR showed resistance to viral and bacterial
diseases, which was similar to that of KR and better than other hybrids. In
cage culture APOR showed better survival rate, while growth rate was significantly higher for KROR, which was more than that of base populations.
Analysis of percentage morphotypes showed a similar pattern as that of base
populations. Lower head -tail weight ratio was shown by KROR, which was
lower than that of KR.
Estimation and comparison of heritability of weight of three better
performing hybrids were done. From the data it was found that maximum
heritability of weight was for KROR (.75) followed by APKR (.161) and
APKR exhibited no heritability.
|
|---|