Abstract:
Wild guppies have potential in developing various strains with attractive colour patterns, tail
types and tolerance to wide range of environment conditions, resistance to disease conditions
due to high immunity. Application of molecular genetic markers, are important to identify
diversity among wild guppies which are economically beneficial to ornamental industry and to
implement conservation of these valuable genetic resources. Major histocompatibility complex
(MHC) genes are highly polymorphic gene family and exon 2 of class II B gene is functionally
important in immunity and disease resistance. Hence, in the present study attempts are made to
assess the genetic and morphological diversity of wild guppy of Sri Lanka with special
reference to immune related MCH class II B gene. A total of 238 wild guppies were collected
from 10 regions to represent different agro-ecological zones of the country. The standard length
in between 13-24 mm was selected (179 fishes) to collect morphological data and genomic
DNA was extracted from muscle tissue using Chelex 100 DNA extraction kit. A PCR based
method was used to amplify exone 2 region of candidate gene with forward (5’GTG GAT TTC
AGA GAA TAT GCA 3’) and reverse (5’ TGA TTT ATC CAG AGC GGT TTG 3’) primers.
Touch down PCR was followed to amplification in the temperature range of 47 to 45 .
Selected fish sample consisted of 43.6% of male fishes and 56.4% female fishes. Significant
association existed in tail types and colour patterns versus region. Highest variation of tail
pattern types was recorded from Buttala region and 40.8% of guppies consisted round tail type.
High variation of colour pattern is observed from Badulla region. 58.7% fishes had brownish
gray colour pattern and 43% had golden upper body colour pattern. Variation of upper body
colour in all regions was similar. PCR protocol was optimized. There was a morphological
diversity between wild guppy fishes in different regions of Sri Lanka. Exon II in MHC class IIB
region was amplified and optimized PCR protocol for further studies. Sequence variation based
on Single Nucleotide Polymorphism (SNPs) and differences of immune response of wild guppy
population is yet to be analyzed.
