DNA fingerprinting of wheat genotypes by RAM markers
Eyasu Tekie Teshale, Sangita Bansal, Avinash Mishra, Vijaipal and V.K. Ehanna
G. B. Pant University of Agriculture & Technology, Pantnagar 263145, Uttranchal, India.
Polymerase chain reaction (PCR) based randomly amplified polymorphic DNA (RAPD) markers were used to study the genetic relationship and genetic diversity among 27 Indian wheat accessions (17 hexaploids and 10 tetraploids). The size of PCR amplified products ranged between 0.03 and 3.0 kb. Out of the 103 amplified total RAPD bands, 82 (79.6%) were polymorphic. Within hexaploids, of the total 98 amplified bands, 64 (65.3%) were polymorphic whereas within tetraploids, of the total 103 bands, 78 (75.7%) were polymorphic. The similarity coefficient between hexaploids and tetraploids ranged from 0.630 to 0.952 and 0.400 to 0.966, respectively. Primers UBC-535, UBC-552, UBC-600, UBC-534 and UBC-386 showed maximum number of polymorphic bands. The primers UBC-18, UBC-535, UBC-337, UBC-600, UBC-572 and UBC-534 were found to give distinguishable number of unique RAPD markers. These six primers were able to distinguish some of the genotypes like, IC-82233, IC-99785, IC-35161-D, IC-35177-D and IC-35720-D. As the similarity matrix value showed, the tetraploid genotypes had more wider genetic distance value than hexaploids.
Key words: genetic diversity, RAPD, Indian wheat, PCR
Introduction
Wheat (Triticum aestivum) is the world's leading cereal grain and most important food crop. The genetic origin of wheat is a classic example of how closely related species combine in nature to form a polypIoid series. The species of Triticum are grouped into diploids (2n=2x=14), tetraploids (2n=4x=28) and hexaploids (2n=6x=42). Only two species of Triticum are commercially important: the hexaploid species, T. aestivum (the bread wheat and the principal wheat in commerce), and the tetraploid species, T.turgidum (the durum wheat that is used for making pasta). The total numbers of accessions in international and local gene banks around the world are estimated to be in excess of 400,000, although many accessions may probably be duplicated in the different collections. FAO has developed a set of descriptor for wheat to facilitate uniformity in describing wheat accessions in different gene banks and to assist breeders in locating genes specific breeding programs (Poelham and Sleper 1995). Knowledge of genetic diversity and relationship among a set of germplasm and the potential merit of the genetic diversity would be beneficial to all phases of crop improvement. Assessments of genetic diversity of the elite germplasm have been sought and used by plant breeders for numerous reasons e.g. genetic relationships, parent selection, germplasm management and protection among others (Lee 1995).Traditionally, the assessment of the genetic composition of crop germplasm has been conducted on the basis of morphological and phenotypic characters, which frequently lack the resolving power needed to identify individual genotypes. Estimation from biochemical markers viz. isozyme analysis may also be biased by the general consideration that only a minor portion of the genome is represented by these markers (Second 1982). In the last decade, molecular markers such as RFLP, RAPD, SCAR, AFLP etc. have been used to assess genetic variation at the DNA level, allowing an estimation of degree of relatedness between individuals without the influence of environmental variation (Miller and Tanksley 1990). Among the various techniques available, RAPD analysis is a potentially simple, rapid, reliable and effective method for detecting polymorphism in wheat (Vierling and Nguyen 1992). To date, no information is available on variation in Indian tetraploid and hexaploid wheat genotypes at the molecular level. In view of the above, we have done this study to evaluate genetic relationship between and within tetraploid and hexaploid wheat genotypes.