Development of a Molecular Marker to Track APA Introgression in Common Bean For Bruchid Resistance

In common bean (Phaseolus vulgaris), the main seed storage pests are the bruchid beetles. Adult females lay eggs on the outside of the seed, and the larvae hatch and bore into the seed to feed. Damage done to the seed by the larvae has a large impact on seed quality and yield. Arcelin (ARC), phytohaemagglutinin (PHA), and α-Amylase inhibitor (α-AI) make up a group of linked seed storage proteins that form the APA locus on chromosome Pv04. This locus is associated with bruchid resistance in common bean and tepary bean (Phaseolus acutifolious).

A major breeding objective is to introduce bruchid resistance into common bean from a resistant tepary genotype, G40199, by introgressing the resistant APA locus into susceptible common bean backgrounds. Here we developed a molecular marker that can be used to track the introgression. A group of four resistant (containing the G0199 APA locus) and four susceptible genotypes were used as source materials to develop the marker. A set of primers to the α-amylase inhibitor locus amplified a DNA fragment that showed a 45 base pair insertion/deletion that distinguished the common bean and G40199 APA loci. Further amplification and sequencing of the APA locus shows the existence of different variants in the α-amylase and arcelin loci from the G40199 source.

This enhanced locus characterization and insertion/deletion marker may preclude the need for bruchid resistance screening early in the breeding process and help better understand how this resistance is introgressed in common bean.