Genetic Variations Among Families of Selectively Bred <i>Macrobrachium rosenbergii</i> (De Man) By RAPD-PCR Analysis

Abstract

Giant freshwater prawn, Macrobrachium rosenbergii is an important freshwater crustacean widely cultured in several countries including India. Of late, its production has come down due to slow growth rate and disease occurrences. The ICAR-Central Institute of Freshwater Aquaculture (ICAR-CIFA), Bhubaneswar in collaboration with the WorldFish, Malaysia has initiated a selective breeding programme for growth improvement of this species. In the present study, two groups of families (I. six numbers of families for growth and II. six numbers of families for disease resistance) were selected for experimentation from the families produced in the fourth generation of selection programme. Each group consisted of two extreme sub-groups of three families in each with higher and lower growth (based on weight) under group I and, susceptible and resistant families (based on larval survival following challenge with Vibrio harveyi) under group II. RAPD- PCR was used to evaluate the genetic variations between and within groups separately. Twelve selected decamer primers were used to amplify DNA fragments of three individuals of each family and data were analyzed by POPGENE version 1.31 software. In group I, a total of 102 bands were scored by the primers out of which 41 bands (40.19%) found to be polymorphic. Genetic diversity within the group varied from 0.0272  0.0965 to 0.0463  0.1316. UPGMA dendrogram of this group based on Nei’s genetic distance showed that families 5 (low growth family 2) and 6 (low growth family 3) are distantly related to high growth families. In the second group of disease resistance, 35 bands (36.46%) were found to be polymorphic out of 96 bands scored. Genetic diversity varied between 0.0301 ± 0.0957 to 0.0438 ± 0.1381 within this group. UPGMA dendrogram showed that families 1 (susceptible group 1) and 2 (susceptible group 2) are distantly related to three resistant families. Thus, the present results showed the existence of genetic variations in both growth and disease resistance traits that could be utilized in the selective breeding programme in M. rosenbergii.