INHERITANCE OF RESISTANCE IN PI 260418 AN ANDEAN BEAN RESISTANT TO MOST RACES OF THE BEAN RUST PATHOGEN.

Authors: Pastor Corrales, Marcial - Talo

Submitted to: Bean Improvement Cooperative Annual Report
Publication Type: Trade Journal
Publication Acceptance Date: 3/1/2005
Publication Date: 7/1/2005
Citation: Pastor-Corrales, M. A. 2005. Inheritance of resistance in PI 260418 an Andean bean resistant to most races of the bean rust pathogen. Ann. Rep. Bean Improvement Coop. 48:

Interpretive Summary: Bean growers have various alternatives to manage the economically important bean rust disease of beans. Although genetic resistance is the most economical and practical strategy to manage this disease, the attainment of effective resistance is difficult due to the high number of different strains that the bean rust pathogen possesses. Available rust resistance genes are effective against some but not all strains. An Andean bean known as plant introduction (PI) PI 260418 was discovered to be resistant to all but one of 90 strains of the bean rust pathogen. We have recently conducted inheritance studies to determine the number of genes that control the rust resistance in PI 260418. To accomplish this we crossed the rust-resistant PI 260418 with the rust susceptible bean known as Pinto 114 and then we evaluated the populations resulting from this cross with 14 different strains of the rust pathogen. The results indicated that the rust resistance in PI 260418 was controlled by a single dominant gene. This is the gene that provided resistance to all 14 different strains of the rust pathogen used in this study. This information will be used principally by bean beans scientists working throughout the world in the development of improved and rust resistant dry and snap beans.

Technical Abstract: Host resistance is a very effective strategy for the control of the bean rust disease caused by the fungus Uromyces appendiculatus. However, the achievement of effective resistance is complicated by the high virulence diversity of the rust pathogen. This pathogen has many different strains that often change from one location or year to another. That is why bean varieties that are resistant in one location or year may be susceptible in another. Although several rust resistance genes have been identified in common bean, most of these genes are effective against some but not all strains. In addition, these genes are present in bean cultivars with small and medium size seeds that belong to the Middle American gene pool. Recently a plant introduction (PI), known as PI 260418, was shown to be resistant to all but one of 90 strains of the rust pathogen. This is a large-seeded common dry bean from Bolivia that belongs to the Andean gene pool. To elucidate the genetics of rust resistance in PI 260418, this rust-resistant bean was hybridized with the susceptible bean known as Pinto 114. A total of 14 different strains of the bean rust pathogen were used to evaluate the progenies resulting from the cross between PI260418 and Pinto 114. The results indicated that the resistance in PI 260418 to the 14 strains was controlled by a dominant allele at a single locus. However, preliminary results, not shown here, indicate that the resistance in PI 260418 to other strains of the bean pathogen may be controlled by two additional unlinked loci.