Abstract
Key message A major QTL for angular leaf spot resistance in the common bean accession G5686 was fine-mapped to a region containing 36 candidate genes. Markers have been developed for marker-assisted selection. Common bean (Phaseolus vulgaris L.) is an important grain legume and an essential protein source for human nutrition in developing countries. Angular leaf spot (ALS) caused by the pathogen Pseudocercospora griseola (Sacc.) Crous and U. Braun is responsible for severe yield losses of up to 80 %. Breeding for resistant cultivars is the most ecological and economical means to control ALS and is particularly important for yield stability in low-input agriculture. Here, we report on a fine-mapping approach of a major quantitative trait locus (QTL) ALS4.1GS, UC for ALS resistance in a mapping population derived from the resistant genotype G5686 and the susceptible cultivar Sprite. 180 F3 individuals of the mapping population were evaluated for ALS resistance and genotyped with 22 markers distributed over 11 genome regions colocating with previously reported QTL for ALS resistance. Multiple QTL analysis identified three QTL regions, including one major QTL on chromosome Pv04 at 43.7 Mbp explaining over 75 % of the observed variation for ALS resistance. Additional evaluation of 153 F4, 89 BC1F2 and 139 F4/F5/BC1F3 descendants with markers in the region of the major QTL delimited the region to 418 kbp harboring 36 candidate genes. Among these, 11 serine/threonine protein kinases arranged in a repetitive array constitute promising candidate genes for controlling ALS resistance. Single nucleotide polymorphism markers cosegregating with the major QTL for ALS resistance have been developed and constitute the basis for marker-assisted introgression of ALS resistance into advanced breeding germplasm of common bean.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-015-2472-6) contains supplementary material, which is available to authorized users.
Highlights
Common bean (Phaseolus vulgaris L.) is the most important grain legume for direct human consumption (Broughton et al 2003), rich in protein, iron and zinc (Sathe 2002; Hemalatha et al 2007; Martinez Meyer et al 2013)
In order to validate quantitative trait locus (QTL) reported in various Andean germplasm, 180 F3 (65 families) of the Sprite × G5686 population were evaluated with the P. griseola pathotype 31-0
Molecular characterization and multiple QTL analyses confirmed a major resistance source (ALS4.1GS, UC) explaining 75.3 % of the phenotypic variation for Angular leaf spot (ALS) resistance, which was previously tagged with the Simple sequence repeat (SSR) marker Pv-ag004 (Mahuku et al 2009)
Summary
Common bean (Phaseolus vulgaris L.) is the most important grain legume for direct human consumption (Broughton et al 2003), rich in protein, iron and zinc (Sathe 2002; Hemalatha et al 2007; Martinez Meyer et al 2013). Around 111,000 years ago, common bean diverged from a common ancestor into two different gene pools: large-seeded Andean and small- to mediumseeded Mesoamerican beans Snap beans for green pod harvest are mainly of Andean origin (Gepts and Bliss 1985; Myers and Davis 2002). Following the two gene pools of common bean, Mesoamerican and Andean, the pathogen evolved in each gene pool separately (Guzman et al 1995; Crous et al 2006). Since P. griseola is highly variable (Abadio et al 2012), breeding for a broad ALS resistance involves genes of Andean and Mesoamerican origin or introduction of resistance genes from the secondary gene pool (Mahuku et al 2003). Only few resistance genes have been tagged with closely linked markers
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