Submitted to: Plant Cell Tissue and Organ Culture
Publication Type: Book / Chapter
Publication Acceptance Date: 11/20/2000
Publication Date: 6/15/2001
Citation: Repellin, A., Baga, M., Jauhar, P.P., Chibbar, R.N. 2001. Genetic enrichment of cereal crops via alien gene transfer: new challenges. (book chapter in Plant Cell Tissue and Organ Culture, Kluwer Academic Publishers.). Plant Cell Tissue And Organ Culture 64:159-183. Interpretive Summary: Transferring desirable genes from related (sometimes unrelated) species into drop plants is the main method of crop improvement. Traditionally, such genes are incorporated by crossing an appropriate donor with a crop cultivar. However, these procedures are lengthy and often tedious. Moreover, in some cases sexual hybrids cannot be obtained because of insurmountable crossability barriers. In the last decade, the development of novel gene-transfer techniques that allow direct delivery of a desired foreign gene into an otherwise superior cultivar has added new dimensions to crop improvement programs. In this invited article (invitation to Prem Jauhar), we describe briefly cereal crop improvement by hybridization methods. The article focuses mainly on the contributions of modern tools of genetic engineering to cereal improvement. We discuss the current challenges that need to be overcome in order to realize the full potential of biotechnology for crop improvement.
Technical Abstract: Genetic improvement of crops has traditionally been achieved through sexual hybridization between related species, which has resulted in numerous cultivars with high yields and superior agronomic performance. Conventional plant breeding, sometimes combined with classical cytogenetic techniques, continues to be the main method of cereal crop improvement. Through the introduction of new tools of biotechnology, crossing barriers have been overcome, and genes from unrelated sources have become available to be introduced asexually into plants. Cereal crops were initially difficult to genetically engineer, mainly due to their recalcitrance to in vitro regeneration and their resistance to Agrobacterium infection. Systematic screening of cultivars and explant tissues for regeneration potential, development of various DNA delivery methods and optimization of gene expression cassettes have produced transformation protocols for the major cereals, although some elite cultivars still remain recalcitrant to transformation. Most of the transgenic cereals developed for commercial purpose exhibit herbicide and/or insect resistance, traits that are often controlled by a single gene. In recent years, more complex traits, such as dough functionality in wheat and nutritional quality of rice have been improved by the use of biotechnology. The current challenges for genetic engineering of plants will be to understand and control factors causing transgene silencing, instability and rearrangement, which are often seen in transgenic plants and highly undesirable in lines to be used for crop development. Further improvement of current cereal cultivars is expected to benefit greatly from information emerging from the areas of genomics, proteomics and bioinformatics.