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Anthracnose, caused by the fungus Colletotrichum lindemuthianum (Sacc. and Magnus) Briosi and Cavara, is a major disease affecting the common bean (Phaseolus vulgaris L.), potentially causing yield losses of up to 100%. Utilizing resistant cultivars is the most effective approach for disease control. This study aimed to characterize the genetic resistance of two cultivars, TU and Michigan Dark Red Kidney (MDRK), to anthracnose. Inheritance tests were performed on F2:3 families from the TU (R) × AND 277 (S) cross using C. lindemuthianum race 3, and on F2:3 families from the crosses TU (R) × Kaboon (S) and TU (R) × Perry Marrow (S) inoculated with race 39. Inoculation with three races of C. lindemuthianum showed that MDRK carried the allele of the Co-1 locus. However, inoculation of F2:3 families from the MDRK × TU cross with race 1545 revealed that MDRK's resistance to this race is conditioned by two dominant genes (Co-1 allele on Pv01 and another allele on Pv04). Segregation results from inheritance tests using F2:3 families with the TU resistant cultivar fitted to a 1RR:2RS:1SS ratio, indicating the presence of a single dominant gene in the TU cultivar. Both the Mesoamerican TU and the Andean MDRK cultivars represent valuable sources of resistance to C. lindemuthianum and can be incorporated into common bean breeding programs to enhance disease resistance.

Anthracnose caused by Colletotrichum lindemuthianum is one of the most critical diseases in the common bean (Phaseolus vulgaris L.). The characterization and localization of pathogenic fungal races are essential for understanding pathogen population dynamics and recommending strategies to develop resistant cultivars. As resistant genotypes are the most economical and ecologically safe means of controlling plant diseases, there have been efforts to characterize resistance genes in common bean. Several studies using a system of 12 differential bean cultivars have been carried out to monitor anthracnose since 1991, reporting the constant appearance of new fungal races. C. lindemuthianum shows high virulence diversity. The objective of the present study was to review the relationship between C. lindemuthianum races and the common bean pathogenic processes involved in the risk of developing anthracnose disease. As a result, 89 races occurred in Brazil, wherein 73, 65, and 81 of C. lindemuthianum are the most frequent. Furthermore, we built a map with the anthracnose resistance loci, molecular markers, and their respective physical position. The accessibility to the genomes and sequencing technologies permits molecular markers for marker-assisted selection applied to anthracnose-resistant cultivars. This study could be used as a reference for future resistance mapping studies and as a guide for selecting resistance loci in breeding programs aiming to develop common bean cultivars with durable anthracnose resistance.

Anthracnose is a severe disease of common bean that, under favorable conditions, can cause a 100% yield loss. For effective resistance breeding, the virulence and genetic variability of the causal pathogen, Colletotrichum lindemuthianum, must be understood and the emergence of new races monitored to ensure the development of broad-spectrum, durable resistance. In the present study, 28 isolates of C. lindemuthianum collected in Pernambuco, Brazil, were characterized: i) for their pathogenicity on a differential common bean cultivar set, ii) for their genetic variability, based on the Internally Transcribed Spacer (ITS) region sequences, and iii) for their ability to cause anthracnose on a selection of 20 common bean accessions. The 12 differential cultivars were inoculated with the 28 isolates, identifying 16 races of C. lindemuthianum: 2, 3, 8, 9, 10, 64, 65, 72, 73, 75, 81, 85, 89, 117, 139, and 331. Except for race 81, all were reported for the first time in Pernambuco; this was the first report of race 139 in Brazil and of race 331 in the world. The ITS region sequence of 17 isolates revealed the presence of 27 SNPs, four SNPs in the ITS 1 region, and 23 SNPs in the ITS 2 region. Of the 20 common bean accessions screened for resistance with the 16 isolates of C. lindemuthianum, the Andean accessions ‘Praia’ and ‘Africano 4’ were the most resistant. The broad resistance detected in some common bean accessions indicates their utility as potential sources of resistance to C. lindemuthianum, particularly in areas where Mesoamerican beans and Mesoamerican races of the pathogen are predominant.

The most effective strategy to manage bean anthracnose (ANT), caused byColletotrichum lindemuthianum, is the use of resistant cultivars. This study aimed to evaluate resistance reactions of common bean accessions toC. lindemuthianumraces 2, 9 and 1545, and to perform genome-wide association study (GWAS). Hence, 89 accessions were phenotyped and genotyped through genotyping by sequencing (GBS). As a result, 48 accessions resistant to all evaluated races were identified. Moreover, single-nucleotide polymorphisms (SNP) significantly associated with resistance were identified in new regions of chromosomes Pv03, Pv05 and Pv06, and also at the beginning of Pv04 and end of Pv11, where other resistance genes have been previously found. In reference genome these regions contain model genes encoding resistance proteins as kinases, leucine-rich repeats, receptor-like protein, copper transport protein, pentatricopeptide repeats, calcium-dependent protein kinases, and ethylene-responsive transcription factors. The genomic regions associated to ANT resistance found in this study should be validated for further use in marker assisted selection and gene pyramiding. Together with new sources of ANT resistance our findings show promise for further crop improvement.

One of the significant challenges of common bean breeding is developing cultivars with high yields under drought conditions. The present study attempted to map quantitative trait loci (QTLs) and identify molecular markers that are linked to drought tolerance in the common bean. We evaluated 160 recombinant inbred lines (RILs), derived from the cross between the carioca cultivars IAPAR 81 (drought tolerant) and LP97-28 (susceptible to drought). In 2014 and 2015, two experiments were conducted (DS—drought stress, and NS—no drought stress). In the DS experiment, water suppression was performed at the flowering stages R5 to R6. The results of our experiments showed that drought conditions play an essential role in reducing most of the traits that were evaluated. RILs under drought conditions reduced the grain yield by 62.03% and 24% in 2014 and 2015, respectively. We identified 15 quantitative trait loci distributed on the chromosomes Pv01, Pv02, Pv03, Pv07, Pv08, Pv09, Pv10, and Pv11, related to grain yield, seed yield per day, 100-seed weight, number of pods per plant, plant height, number of days for flowering, and number of days to maturity. The characteristics of seed yield per day, 100-seed weight, and number of days to maturity showed that QTLs colocalized on Pv07. Identifying QTLs that are linked to drought tolerance in the RIL population IAPAR 81 × LP97-28 is of particular importance for common bean breeding programs seeking to improve carioca beans that are cultivated in regions with drought conditions, such as Brazil.

Abiotic stress is a limiting factor for common bean (Phaseolus vulgaris L.) production globally. The study of the genotypic, phenotypic, and bio-climatic variables in a broad set of accessions may assist the identification of genomic regions involved in the climatic adaptation of the common bean. We conducted a genotyping-by-sequencing analysis using 28,823 SNPs on 110 georeferenced common bean accessions from Brazil to discover associations between SNPs and bio-climatic indexes. The population structure analysis clustered the accessions into two groups corresponding to the Andean and Mesoamerican gene pools. Of the 19 bioclimatic variables, 17 exhibited a significant association with SNPs on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, Pv09, Pv10, and Pv11 of common bean. Ten candidate genes were associated with specific bio-climatic variables related to temperature and precipitation. The candidate genes associated with this significant Pv09 region encode a Platz transcription factor family protein previously reported to be an essential regulator of drought stress. The SNP markers and candidate genes associated with the bio-climatic variables should be validated in segregating populations for water stress, which could further be used for marker-assisted selection. As a result, bean breeding programs may be able to provide advances in obtaining drought-tolerant cultivars.

Salmonella enterica is one of the most common pathogens associated with produce outbreaks worldwide; nonetheless, the mechanisms uncovering their interaction with plants are elusive. Previous reports demonstrate that S. enterica ser. Typhimurium (STm), similar to the phytopathogen Pseudomonas syringae pv. tomato (Pst) DC3000, triggers a transient stomatal closure suggesting its ability to overcome this plant defense and colonize the leaf apoplast. In order to discover new molecular players that function in the stomatal reopening by STm and Pst DC3000, we performed an Arabidopsis mutant screening using thermal imaging. Further stomatal bioassay confirmed that the mutant plants exo70h4-3, sce1-3, bbe8, stp1, and lsu2 have smaller stomatal aperture widths than the wild type Col-0 in response to STm 14028s. The mutants bbe8, stp1 and lsu2 have impaired stomatal movement in response to Pst DC3000. These findings indicate that EXO70H4 and SCE1 are involved in bacterial-specific responses, while BBE8, STP1, and LSU2 may be required for stomatal response to a broad range of bacteria. The identification of new molecular components of the guard cell movement induced by bacteria will enable a better understanding of the initial stages of plant colonization and facilitate targeted prevention of leaf contamination with harmful pathogens.