Genetics and mapping of a new anthracnose resistance locus in Andean common bean Paloma.

BACKGROUND: 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. RESULTS: 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. CONCLUSIONS: 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.

Divergência genética em germoplasma de feijoeiro comun coletado no estado do Paraná, Brasil / Genetic divergence in germplasm of common bean inParaná State, Brazil

O presente trabalho teve como objetivo avaliar a divergência genética entre 63 cultivares crioulas de feijão comun )Phaseolus vulgaris L.) coletados no estado do Paraná no período de 2001 a 2001. O experiemnto foi conduzido em área experimental localizada no município de Toledo, Pr, no ano de 2002. O delineamento experiemntal utilizado foi o de blocos casualizados com três repetições. os dados obtidos em cada característica foram submetidos à análise de variância considerando-se o efeito da cultivar como fixo. A análise multivariada foi usada para avaliar a divergência genética entre os genótipos utilizando-se as variáveis Canônicas e o método de agrupamento com base na Distância Generalizada de Mahalanobis (D2ii). As cultivares mais divergentes foram Carioca Pitoco e Jalo Vermelho e as mais similares foram Carioca Pitoco e Carioca. Esses resultados evidenciaram a existência de variabilidade genética nas cultivares de feijão utilizadas pelos agricultores e os que métodos e análise multivariadas demonstraram eficiência em detectá-la separando em grupos diferentes as cultivares Carioca e Jalo. As cultivares Carnaval (33), Carioca Pitoco (16), Pérola (14) e Carnaval (27), por apresentarem maiores produtividades e serem mais divergentes, são indicadas para gerar populações em programas de seleção interpopulacional

The present work had objective to evaluate the genetic divergence among 63 traditional cultivars of thecommon bean (Phaseolus vulgaris L.) collected in Paraná state in the period 2001-2002. The experimentwas carried out in an experimental area in 2002 in the county Toledo, PR. The experimental design was arandomized block with three replications. The Multivariate was used to evaluate the divergence amongthe genotypes, utilizing the Canonic Variable analysis and clustering, based on the GeneralizedMahalanobis Distance (2'iiD) for the quantitative variables. The results demonstrated that the mostdivergent cultivars were Carioca Pitoco and Jalo vermelho, whereas the most similar were Carioca Pitocoand Carioca. These results point out the existence of genetic variability in common bean cultivars usedby farmers, and multivariate analysis methods demonstrated efficiency to detect them, separating thecultivars Carioca and Jalo in different groups. Therefore, in order to compose the interpopulation selectionprograms the Carnaval (33), Carioca Pitoco (16), Pérola (14) and Carnaval (27) cultivars are recommendbecause they are the most divergent ones and possess one of the best averages in productivity