The Use of Simple Sequence Repeats for Detecting Genetic Diversity in Egyptian and Exotic Bread Wheat

Abstract

The cultivated wheat (Triticum aesti- vum L.) belongs to tribe Triticeae of the family Poaceae. It is the first impor- tant cereal crop as the main source of hu- man diet (FAO, 1985). Approximately, ninety five percent of wheat's grown today are hexaploid wheat which comprising three genomes A, B and D (Harti and Jones, 2001). Genetic diversity is consid- ered one of the most important factors for crop improvement. Modern breeding process has dramatically narrowed the variation of important traits, especially among common wheat cultivars which are widely used in breeding programmes. It is important to investigate genetic diversity of wheat to assess its usefulness for breed- ing programmes. However, there are in- herent problems with the use of data on morphological traits, the latter being lim- ited in number and greatly influenced by the environment and by genotype X envi- ronment interactions. Molecular markers are a promising tool for evaluating genetic diversity among plant materials, as the phenotype and physiological markers are not accurate enough and often depend on environmental conditions. Many different DNA marker systems were used for diversity analysis. As far as the ability of polymorphism detection is concerned, the most useful markers were random ampli- fied polymorphic (RAPDs) (Kuczynska et al., 2001; Mukhtar et al., 2002; Weber et al., 2005; Irzykowska et al., 2005) and simple sequence repeats (SSRs), also termed microsatellites, have been pro- posed as one of the most suitable markers for the assessment of genetic variation and diversity among wheat varieties, because they are multiallelic, chromosome-specific and distributed evenly throughout the plant genome (Prasad et al., 2000; Stachel et al., 2000; Huang et al., 2002; Roder et al., 2002, Landjeva et al., 2006; Chabane et al., 2007; Salem et al., 2008). Microsa- tellites were also successfully used to identify quantitative trait loci (QTLs) (Parker et al. 1998), to tag resistance genes (Peng et al., 1999; Borner et al., 2000) and to detect polymorphisms be- tween the accessions of diploid and tetraploid wheat (Hammer et al., 2000; Pestsova et al., 2000; Fahima et al., 2002).