The Andean common bean AND 277 has the Co-1 (4) and the Phg-1 alleles that confer resistance to 21 and eight races, respectively, of the anthracnose (ANT) and angular leaf spot (ALS) pathogens. Because of its broad resistance spectrum, Co-1 (4) is one of the main genes used in ANT resistance breeding. Additionally, Phg-1 is used for resistance to ALS. In this study, we elucidate the inheritance of the resistance of AND 277 to both pathogens using F-2 populations from the AND 277 x Ruda and AND 277 x Ouro Negro crosses and F-2:3 families from the AND 277 x Ouro Negro cross. Ruda and Ouro Negro are susceptible to all of the above races of both pathogens. Co-segregation analysis revealed that a single dominant gene in AND 277 confers resistance to races 65, 73, and 2047 of the ANT and to race 63-23 of the ALS pathogens. Co-1 (4) and Phg-1 are tightly linked (0.0 cM) on linkage group Pv01. Through synteny mapping between common bean and soybean we also identified two new molecular markers, CV542014(450) and TGA1.1(570), tagging the Co-1 (4) and Phg-1 loci. These markers are linked at 0.7 and 1.3 cM, respectively, from the Co-1 (4) /Phg-1 locus in coupling phase. The analysis of allele segregation in the BAT 93/Jalo EEP558 and California Dark Red Kidney/Yolano recombinant populations revealed that CV542014(450) and TGA1.1(570) segregated in the expected 1:1 ratio. Due to the physical linkage in cis configuration, Co-1 (4) and Phg-1 are inherited together and can be monitored indirectly with the CV542014(450) and TGA1.1(570) markers. These results illustrate the rapid discovery of new markers through synteny mapping. These markers will reduce the time and costs associated with the pyramiding of these two disease resistance genes.

Assessment of the stability and adaptability of a genotype to different environments is useful for recommending cultivars for known conditions of cultivation and should be a requirement in breeding programs. Twenty maize (Zea mays L.) cultivars were tested at eight locations in Minas Gerais by the National Center for Maize and Sorghum Research (CNPMS) of the Brazilian Enterprise for Agricultural Research (EMBRAPA) for two years. The experiments involved a randomized complete block design in which three procedures were used to analyze cultivar stability and adaptability. The level of association among the parameters obtained by the three methods was assessed using Spearman's rank correlation. Hybrids 'DINA 170', 'G-96C', 'C 505', 'DINA 70' and 'C 435' had a mean yield greater than 6,000 kg/ha. Eberhart and Russell's regression coefficient (betai) was negative and correlated significantly (P < 0.01) with Lin and Binn's superiority index (Pi), indicating that the most responsive cultivars tended to have smaller Pi. Pi did not correlate with Huehn's nonparametric measurements Si(2) and Si(3) nor with Eberhart and Russell's sigmadi² (P > or = 0.05), but correlated positively with Si(1) (P < 0.05), indicating that superior genotypes (with lower Pi) could also be stable, a finding not commonly reported in the literature. The stability parameters, Si(1), Si(2), Si(3) and sigmadi², correlated positively among each other (P < 0.01), indicating that the stability estimates of the Huehn's nonparametric model did not add important information to those obtained by the Eberhart and Russell's method. Estimates from the Huehn's method, however, showed that stability estimates from nonparametric models are useful alternatives to parametric models. 'DINA 170', which had a greater general mean, was characterized as a cultivar adapted to favorable environments, and was among the most productive in the different environments assessed. The cultivar 'G-96C' showed medium adaptation to all environments (ideal cultivar) and had good stability. Cultivars 'C 505' and 'C435' were alternatives for 'G-96C'. 'DINA 70' showed good adaptability but had low stability.

The Andean cultivar Paloma is resistant to Mesoamerican and Andean races of Colletotrichum lindemuthianum, the fungal pathogen that causes the destructive anthracnose disease in common bean. Remarkably, Paloma is resistant to Mesoamerican races 2047 and 3481, which are among the most virulent races of the anthracnose pathogen. Most genes conferring anthracnose resistance in common bean are overcome by these races. The genetic mapping and the relationship between the resistant Co-Pa gene of Paloma and previously characterized anthracnose resistance genes can be a great contribution for breeding programs. The inheritance of resistance studies for Paloma was performed in F2 population from the cross Paloma (resistant) × Cornell 49–242 (susceptible) inoculated with race 2047, and in F2 and F2:3 generations from the cross Paloma (resistant) × PI 207262 (susceptible) inoculated with race 3481. The results of these studies demonstrated that a single dominant gene confers the resistance in Paloma. Allelism tests performed with multiple races of C. lindemuthianum showed that the resistance gene in Paloma, provisionally named Co-Pa, is independent from the anthracnose resistance genes Co-1, Co-2, Co-3, Co-4, Co-5, Co-6, Co-12, Co-13, Co-14, Co-15 and Co-16. Bulk segregant analysis using the SNP chip BARCBean6K_3 positioned the approximate location of Co-Pa in the lower arm of chromosome Pv01. Further mapping analysis located the Co-Pa gene at a 390 kb region of Pv01 flanked by SNP markers SS82 and SS83 at a distance of 1.3 and 2.1 cM, respectively. The results presented here showed that Paloma cultivar has a new dominant gene conferring resistance to anthracnose, which is independent from those genes previously described. The linkage between the Co-Pa gene and the SS82 and SS83 SNP markers will be extremely important for marker-assisted introgression of the gene into elite cultivars in order to enhance resistance.

The most effective strategy to manage bean anthracnose (ANT), caused by Colletotrichum lindemuthianum, is the use of resistant cultivars. There are more than 20 ANT resistance genes that have been identified and mapped in common bean (Phaseolus vulgaris L.) chromosomes. Moreover, quantitative resistance loci (QRLs) have been described through genome‐wide association studies (GWAS). Identification of pathogen‐responsive genes and proteins on a molecular level provides a better understanding of metabolic pathways involved in ANT resistance. In this study, we investigated typical resistance proteins located close to ANT resistance loci in the common bean reference genome. Among them, we checked for proteins with nucleotide‐binding and leucine‐rich repeat (NBS‐LRR) domains and kinase domains since most resistance genes encode proteins with these domains. In addition, proteins with kinase domains are known to operate as pattern‐recognition receptors that recognize pathogen‐associated molecular patterns (PAMPs) and activate an immune response. Based on the common bean reference genome (Version 2.1), the regions 500‐kb upstream and downstream of the physical position of each ANT resistance locus were considered for a candidate gene search. Thus, an integrated map of ANT resistance loci and candidate genes (encoding defense response‐related proteins) was constructed. This map contains candidate genes for all ANT resistance genes and QRLs previously described in the literature. A total of 256 NBS‐LRR proteins and 200 protein kinases were detected. The functions of the identified candidate genes in ANT response should be validated and studies should be performed to understand how they interact with metabolic pathways.

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 developing resistant cultivars. Here, we discussed the relationship between the diversity of C. lindemuthianum and common bean resistance genes against anthracnose disease. Indeed, several studies using a system of 12 differential bean cultivars have been carried out since 1991 to monitor anthracnose, reporting the constant appearance of new races. Colletotrichum lindemuthianum shows high virulence diversity, with 298 races distributed across 29 countries. In Brazil, we identified 89 races, with races 73, 65, and 81 as the most frequent. Moreover, we highlighted the common bean gene clusters, their unique location on chromosomes, and their relationship with races and resistance genes. The genetic mapping studies, molecular markers linked to anthracnose resistance alleles, and the specific races were integrated on the seven‐chromosome map using the reference genome of common bean. Recently, the ease of use of genome sequences and the development of molecular technologies have allowed molecular markers for marker‐assisted selection applied to anthracnose‐resistant cultivars. As a result, it is feasible that Mesoamerican genes Co‐5, Co‐4², Co‐6, Co‐16, and Co‐17, and the Andean genes Co‐1², Co‐1⁴, Co‐Bf, Co‐15, Co‐AC, and CoPv01^CDRK are well known to confer resistance to most races reported in Brazil and around the world. Thus, pyramiding these genes through molecular markers can help reduce the time and cost of introducing resistance genes in commercial common bean cultivars.