Abstract
The common bean (Phaseolus vulgaris L.) is the world’s most important legume for human consumption. Anthracnose (ANT; Colletotrichum lindemuthianum) and angular leaf spot (ALS; Pseudocercospora griseola) are complex diseases that cause major yield losses in common bean. Depending on the cultivar and environmental conditions, anthracnose and angular leaf spot infections can reduce crop yield drastically. This study aimed to estimate linkage disequilibrium levels and identify quantitative resistance loci (QRL) controlling resistance to both ANT and ALS diseases of 180 accessions of common bean using genome-wide association analysis. A randomized complete block design with four replicates was performed for the ANT and ALS experiments, with four plants per genotype in each replicate. Association mapping analyses were performed for ANT and ALS using a mixed linear model approach implemented in TASSEL. A total of 17 and 11 significant statistically associations involving SSRs were detected for ANT and ALS resistance loci, respectively. Using SNPs, 21 and 17 significant statistically associations were obtained for ANT and angular ALS, respectively, providing more associations with this marker. The SSR-IAC167 and PvM95 markers, both located on chromosome Pv03, and the SNP scaffold00021_89379, were associated with both diseases. The other markers were distributed across the entire common bean genome, with chromosomes Pv03 and Pv08 showing the greatest number of loci associated with ANT resistance. The chromosome Pv04 was the most saturated one, with six markers associated with ALS resistance. The telomeric region of this chromosome showed four markers located between approximately 2.5 Mb and 4.4 Mb. Our results demonstrate the great potential of genome-wide association studies to identify QRLs related to ANT and ALS in common bean. The results indicate a quantitative and complex inheritance pattern for both diseases in common bean. Our findings will contribute to more effective screening of elite germplasm to find resistance alleles for marker-assisted selection in breeding programs.
Highlights
Common bean (Phaseolus vulgaris L.) is an annual legume crop with a relatively small genome of 473 Mb [1]
Anthracnose is caused by the specialized hemibiotrophic fungus Colletotrichum lindemuthianum (Sacc. and Magnus), which co-evolved with common bean into Andean and Mesoamerican races [6,7]
Based on the Bonferroni threshold (p-value: 1.24 x 10−5; -LogP: 4.904) used to control type I error, it was observed that non-random associations extended up to 100 cM for the common bean genome and declined rapidly from that distance
Summary
Common bean (Phaseolus vulgaris L.) is an annual legume crop with a relatively small genome of 473 Mb [1]. It is the most important grain legume for direct human consumption [2,3]. Yield losses caused by the ANT pathogen are extremely high in common bean, reaching up to 100% [5]. ALS leads to crop losses of up to 80% and is found in more than 60 countries worldwide [8,9] This disease is caused by the hemibiotrophic fungus Pseudocercospora griseola (Sacc.) Crous & Braun Phaeoisariopsis griseola (Sacc.) Ferraris) [10], and can be identified by angular necrotic spots on plant leaves and pods [11]
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