Genetic relationships and diversity revealed by AFLP markers in Mexican common bean bred cultivars

Landraces and bean (Phaseolus vulgaris L.) cultivars grown in Mexico are diverse, as are consumer preferences and agroecological production environments. Mexican common bean cultivars were analyzed using amplified fragment length polymorphism (AFLP) fingerprinting to examine the genetic relationships within and among races, based on the genotyping of 112 bred cultivars developed in Mexico. Molecular analysis of dry bean germplasm will be useful to corroborate previous cultivar characterizations and establish the genetic basis of improved germplasm, to facilitate the use of that diversity, and to implement the use of markers in selection. Germplasm included 111 cultivars belonging to Mesoamerica (25), Jalisco (39), Durango (28), and Nueva Granada (19) races, which are commonly cultivated throughout the bean-producing areas of Mexico. A Mexican P. coccineus species cultivar (Blanco Tlaxcala) was also included for comparison. Broad genetic diversity was found within bean races, and diversity values between races were similar. Most of the Nueva Granada germplasm was clearly different from that of all other races, whereas the P. coccineus cultivar was distinct from all P. vulgaris cultivars. A dendrogram based on the AFLP analysis did not clearly match with that made on the basis of racial classification. This mismatch was probably due to genetic recombination between Andean (Nueva Granada) and Mesoamerican (Jalisco, Durango, and Mesoamerica) gene pools. Utilization (if contrasting parents for specific crosses has also contributed to broadening the genetic basis of common bean.