Uso de selección asistida con marcadores para resistencia a antracnosis en frijol común = Use of molecular marker assisted selection for resistance to anthracnose in common beans

La antracnosis causada por Colletotrichum lindemuthianum puede llegar a generar pérdidas hasta del 95% de la producción en fríjol (Phaseolus vulgaris L.), por eso es considerada una de las enfermedades más limitantes. Con el presente trabajo se inició un programa de mejoramiento utilizando selección asistida por marcadores. Se usó como parental resistente el cultivar Mesoamericano G2333, para incorporar a fríjoles volubles comerciales de Colombia los genes Co-5 y Co-42 , que confieren resistencia a C. lindemuthianum. Se obtuvieron progenies RC1F1 provenientes de cruces entre G2333 y siete parentales volubles tipo Bola roja y Rojo moteado cultivados en zonas productoras de fríjol de Cundinamarca y Boyacá. La selección de plantas RC1F1 se realizó con los marcadores moleculares SCAR SAB3 y SAS13, ligados a los genes Co-5 y Co-42 , respectivamente. En la evaluación genotípica de 1.271 plantas RC1F1, 608 amplificaron con SAB3 y 603 con SAS13. La segregación para cada marcador se ajustó a la razón 1:1 esperada en pruebas de chi-cuadrado (X2 = 2,38, P= 0,12 para SAB3 y X2 = 3,32, P= 0,07 para SAS13). Un total de 299 plantas RC1F1 amplificaron con ambos SCAR, ajustándose a la razón esperada (X2= 1,11, P= 0,78) y confirmando la segregación independiente. Estas plantas fueron seleccionadas para continuar el programa de mejoramiento, ya que se espera que porten los genes Co-5 y Co-42. Se logró implementar la selección asistida por marcadores para antracnosis, y acelerar la introducción y piramidación de genes de resistencia en fríjol de importancia económica en Colombia. = The anthracnose caused by Colletotrichum lindemuthianum is one of the most significant diseases in beans (Phaseolus vulgaris L.) and can produce yield losses up to 95%. In this study, a breeding program utilizing molecular marker assisted selection (MAS) was initiated. In order to obtain commercial Colombian climbing beans resistant to C. lindemuthianum, the program incorporated genes Co-5 and Co-42 taken from G2333, a resistant Mesoamerican cultivar. From the crosses between G2333 and seven cultivated Andean beans, were obtained progenies BC1F1. The cultivated Andean beans included Bola roja and Rojo moteado types gathered from Cundinamarca and Boyacá crops. The BC1F1 plants were selected using the SCARs molecular markers SAB3 and SAS13 linked to Co-42 and Co-5 genes, respectively. In a genotypic evaluation of 1.271 BC1F1 plants, 608 and 603 were amplified with SAB3 and SAS13, respectively. The segregation expected ratio (1:1) in X2 tests was obtained for each molecular marker indicating X2 = 2,38, P = 0,12 for SAB and X2 = 33,32, P = 0,07 for SAS13. The amplification with both molecular markers was obtained in 299 plants BC1F1, according to the expected ratio (X2 = 1,11, P = 0,78) adjusted to the independent segregation. These plants were selected to continue the breeding program. In this study, a molecular marker assisted selection was implemented and introduction of resistant genes into commercially important Colombian beans was accelerated

Molecular marker-assisted backcrossing of anthracnose resistance into Andean climbing beans (Phaseolus vulgaris L.)

Anthracnose, caused by the fungus Colletotrichum lindemuthianum, is considered a major constraint in the production of common bean (Phaseolus vulgaris L.). This study aimed to evaluate, in a backcross plant-breeding program, the efficiency of selecting plants resistant to anthracnose using marker-assisted selection (MAS) for two resistance genes, Co-5 and Co-42 derived from the resistance source G2333 based on the linked PCR based markers SAB3 and SAS13. The amplification of both markers was compared using DNAs extracted with two techniques, alkaline extraction, which is a fast, and inexpensive method for high throughput screening; versus a proteinase K based miniprep extraction, which is more time consuming but provides more DNA. To further evaluate the effectiveness of the markers in selecting for resistance, we compared the marker genotypes and observed phenotypes for 266 plants from eight backcross families inoculated with a field isolate of anthracnose. The Co-5 gene and SAB3 proved to be useful and the markers associated with Co-5 and Co-42 could be pyramided to give added levels of anthracnose resistance