EVALUATION, ENHANCEMENT, GENETICS AND BREEDING OF LETTUCE, SPINACH, AND MELON
Location: Crop Improvement and Protection Research
Title: Following the genes that make resistant plants: shared tools for breeding and pathology
| Rauscher, Gilda |
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2009
Publication Date: June 1, 2009
Citation: Rauscher, G.M. 2009. Following the genes that make resistant plants: shared tools for breeding and pathology. Phytopathology 99:S185.
Although plant pathology and breeding are distinct disciplines with unique perspectives, they frequently share a common goal: that of identifying and understanding durable resistance, the kind of resistance that will not be overcome quickly and will remain effective against a wide array of isolates. While pathologists strive to discover the sources of resistance, it is the breeder's function to deploy and make them useful to the agricultural community. This function has become of paramount importance for improving the productivity and sustainability of agriculture and reducing its environmental impact.
Two of the main challenges breeders face are time and diversity. Crop variety development is a lengthy process; it may take up to 20 years to introgress a single gene into a commercial variety. The limited durability of most R-genes makes it even more important to identify and deploy new sources of resistance rapidly. Pathogen diversity also plays a major role in plant breeding. In pathosystems with a wide array of isolates, or subject to fast pathogen evolution, the deployment of single resistance genes may not be as functional as the use of multilines or pyramiding genes. The identification of the correct phenotypes is crucial during the breeding process, but it can be difficult and time consuming, especially when desirable and detrimental genes are linked. However, the use of molecular markers such as AFLPs, RFLPs, SSRs and SNPs can accelerate the process of surveying the genome for the correct array of resistance genes in a breeding progeny, making it more efficient than the traditional method of inoculation for phenotyping and substantially shortening the breeding time.
Molecular markers have become increasingly popular in the search for major R-genes, QTLs and even those genes involved in resistance pathways. To date, a wide array of major R-genes have been mapped, characterized and cloned. Structural similarities between R-genes have allowed for identification of resistance clusters, making it easier to recognize areas of the genome desirable for breeding. This, in turn, has the potential to enhance the durability of resistance as it has been shown that linked R-genes tend to act synergistically. Furthermore, when resistance clusters are mapped in model pathosystems, synthenic areas can reveal the location of resistance in related species, giving clues of chromosomal segments that may be important to explore for breeding.