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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Plant Sci. | doi: 10.3389/fpls.2019.01126

Haplotypes at the Phg-2 locus are determining pathotype-specificity of angular leaf spot resistance in common bean

  • 1Molecular Plant Breeding, Institute of Agricultural Sciences, ETH Zürich, Switzerland
  • 2International Center for Tropical Agriculture (CIAT), Uganda
  • 3International Center for Tropical Agriculture (CIAT), Colombia

Angular leaf spot (ALS) is one of the most devastating diseases of common bean (Phaseolus vulgaris L.) and causes serious yield losses worldwide. ALS resistance is reportedly pathotype-specific, but little is known about the efficacy of resistance loci against different pathotypes.
Here, we report on ALS resistance evaluations of 316 bean lines under greenhouse and field conditions at multiple sites in Colombia and Uganda. Surprisingly, genome-wide association studies revealed only two of the five previously described resistance loci to be significantly associated with ALS resistance. Phg-2 on chromosome 8 was crucial for ALS resistance in all trials, while the resistance locus Phg-4 on chromosome 4 was effective against one particular pathotype. Further dissection of Phg-2 uncovered an unprecedented diversity of functional haplotypes for a resistance locus in common bean. DNA sequence-based clustering identified eleven haplotype groups at Phg-2; One haplotype group conferred broad-spectrum ALS resistance, six showed pathotype-specific effects and the remaining seven did not exhibit clear resistance patterns.
Our research highlights the importance of ALS pathotype-specificity for durable resistance management strategies in common bean. Molecular markers co-segregating with resistance loci and haplotypes will increase breeding efficiency for ALS resistance and allow to react faster to future changes in pathogen pressure and composition.

Keywords: Food security, Plant Pathology, Genome-wide association studies (GWAS), Pathotype-specificity, Common bean (Phaseolus vulgaris L.), Angular leaf spot, Pseudocercospora griseola, plant breeding

Received: 14 May 2019; Accepted: 15 Aug 2019.

Copyright: © 2019 Nay, Mukankusi, Bruno and Raatz. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Studer Bruno, Molecular Plant Breeding, Institute of Agricultural Sciences, ETH Zürich, Zurich, Switzerland, bruno.studer@usys.ethz.ch