Abstract

Genome is the entity of an organism’s heredity information. It is encoded either in DNA or, for many types of viruses, in RNA. The genome includes both the genes and the non-coding sequences of the DNA.  Genomics is a new field in biology that is concerned with the whole genome analysis, from sequence to function and derived information. The year 2010 marks the 10^th anniversary of the first plant genome sequence (Arabidopsis thaliana). Triggered by advancement in sequencing technologies, many crop genome sequences have been produced, with eight published till date. To date, however, only the rice (Oryza sativa) genome sequence has been finished to a quality level similar to that of the Arabidopsis sequence. This trend to produce draft genomes could affect the ability of researchers to address biological questions of speciation’s and recent evolution or to link sequence variation accurately to phenotypes. The increasing availability of DNA sequence information enables the discovery of genes and molecular markers associated with diverse agronomic traits creating new opportunities for crop improvement among different classes of molecular markers, SSR markers have proven to be the marker of choice for a variety of applications, particularly in breeding. In addition, DArT (Diversity array technology) markers represent another high-through put marker system, which can be used to prepare the whole genome map even without the availability of sequence data. In recent years, ESTs or gene sequences have been used to identify SSRs, SNPs and genetic molecular markers have been developed in several cereal crops species. Marker assisted selection (MAS) is a powerful tool for the indirect selection of difficult traits at an early stage before production of the next generation, thus  speeding  up the process of conventional plant breeding and facilitating the improvement of traits that cannot be improved easily by conventional method Association mapping might offer more power than linkage analysis for identifying genes responsible for the variation in a quantitative trait . Functional genomics involves the identification of the function of genes per se or those derived from a known allelic difference conferring an improved phenotype. Several techniques like SAGE, MPSS and micro and macro-arrays, are available, for the estimation of mRNA abundance for large number of genes simultaneously.  Tilling has proven to be a practical, efficient, and an effective approach for functional genomic studies in numerous plants species. Eco-TILLING, which is a variant of TILLING, examines natural genetic variation in populations and has been successfully utilized in plants to discover SNPs including rare ones. Comparative genomics approach using bioinformatics tools might provide an opportunity for efficient transfer of information from model species and major crops to minor and orphan crops. Genomics research is generating new tools that could increase the efficiency and precision of crop improvement however high costs currently limit the implementation of genomic-assisted crop improvement particularly for minor crops. Nevertheless, marker-assisted breeding and selection will gradually evolve into genomic-assisted breeding for crop improvement .