Submitted to: Encyclopedia of Applied Plant Science
Publication Type: Book / chapter
Publication Acceptance Date: 3/19/2003
Publication Date: 6/1/2003
Citation: JAUHAR, P.P. CYTOGENETICS AND CROP IMPROVEMENT: CHROMOSOME ENGINEERING. ENCYCLOPEDIA OF APPLIED PLANT SCIENCE. 2003. p. 167-179. Interpretive Summary: Genetic improvement of our crop plants has been achieved mainly through conventional plant breeding. Among other techniques, hybridization with land races or related species helped produce high-yielding superior varieties of food, fiber, oilseed, and other crops. Wild relatives of crop species are invaluable sources of genes for resistance to various pests and diseases. These genes have been and are being used for genetic enrichment of various crops, particularly cereals like wheat. The advent of the tools of cytogenetics in the early 1930's facilitated wide hybridization of wheat with its annual and perennial relatives and resulted in introgression of desirable alien genes into wheat cultivars that sustain humankind. Various cytogenetic tools such as wide hybridizations, coupled with manipulation of chromosome pairing between wheat and alien chromosomes, employed for transferring desirable alien chromatin into wheat were termed "chromosome engineering". This article covers some important aspects of chromosome engineering as applied to genetic improvement of cereal crops, particularly wheat. When published in the Encyclopedia of Applied Plant Science, the article will provide basic concepts and useful information on wheat improvement technology to researchers, teachers, and students worldwide. The techniques employed in chromosome engineering of wheat could be adapted to other crops.
Technical Abstract: Sustained crop improvement has been achieved mainly through traditional breeding including hybridization with land races and related species, resulting in high yielding superior cultivars of food, fiber, oilseed, and other crops. Wild relatives of crop species are rich reservoirs of genes that have been and are being used for genetic enrichment of various crops, especially cereals. Thus, adoption of the tools of cytogenetics since the 1930's facilitated wide hybridization of wheat with its annual and perennial relatives and resulted in wheat cultivars with alien genes. The pioneering work of Sears in which he transferred a chromosome segment carrying a leaf-rust resistance gene from a wild grass, Aegilops umbellulata, into common wheat, heralded the era of chromosome engineering, facilitating the utilization of wild resources for wheat improvement. Cytogenetic manipulations, including those based on suppression of the Ph1-enforced chromosome pairing regulation, for engineering desirable alien chromatin helped introduce disease and pest resistance into wheat cultivars. This article covers main facets of chromosome engineering as applied to genetic improvement of cereal crops, particularly wheat. This is not only because of the vital importance of wheat for humankind but also because a great deal of the chromosome manipulation work done on wheat and the technologies applied are of relevance to other crops.