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Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Trade Journal Publication Acceptance Date: 4/12/2004 Publication Date: 7/12/2004 Citation: Pastor-Corrales M. A. 2004. Review of coevolution studies between pathogens and their common bean hosts: Implication for the development of disease-resistant beans. Ann. Rep. Bean Improvement Coop. 47: 67-68. Interpretive Summary: Studies conducted by various scientists using traditional and molecular tools reveal that the virulence and genetic diversity of certain pathogens of the common bean (Phaseolus vulgaris), such as those that cause rust, anthracnose, angular leaf spot, and perhaps other diseases, can be separated into distinct groups that mirror the genetic diversity of their host. Andean and Middle American strains of these pathogens have evolved with (adapted to) Andean and Middle American beans, respectively. These studies also suggest that certain combinations of Andean and Middle American host-resistance genes may result in beans with durable resistance to these variable pathogens Technical Abstract: The genetic diversity of the cultivated common bean (Phaseolus vulgaris L.) is organized into two distinct gene pools, Andean and Middle American that appear to have originated separately in the Andes region of South America, and in Central America and Mexico, respectively. Morphological, biochemical, and molecular attributes differentiate these two gene pools. The Andean pool is comprised of large-seeded beans while the Middle American pool is constituted of small and medium-seeded beans. It is significant that the diversity of cultivated common bean cultivars parallels the diversity of their wild bean ancestors. Research results from various laboratories reveal that the diversity of the pathogens causing angular leaf spot - ALS - (Phaeoisariopsis griseola), anthracnose (Colletotrichum lindemuthianum) and rust (Uromyces appendiculatus) segregate into two distinct groups, one Andean and another Middle American, that mirror the diversity of their bean host. This separation has been attained with virulence assays that included Andean and Middle American bean differential cultivars, isozymes, RAPDs, random amplified microsatellites, and restriction fragment length polymorphism of the amplified ribosomal intergenic spacer region. This separation has been documented for isolates from wild beans from South America and Mexico, as well as for isolates from cultivated beans from South, Central and North America, the Caribbean and Africa. The high specificity found among the ALS, anthracnose and rust pathogens for certain bean cultivars suggested that disease resistance genes from Andean beans could be used to manage Middle American races of these pathogens. Similarly, genes from Middle American beans could be used to manage Andean races of these pathogens. Thus, bean cultivars having appropriate combinations of Andean and Middle American disease resistance genes, attained through gene pyramiding, could provide durable resistance to all races of these pathogens. |
