Grain legumes are considered major sources of dietary proteins, calories, certain minerals and vitamins, and they are the most widely cultivated and consumed crops worldwide. Among them are the common beans, whose major production volumes came from landraces cultivated in traditional farming systems. The objective of this study was to evaluate the phenotypic diversity of a set of common bean landraces from Mexico based on the agromorphological traits and nutritional composition of the grain in the context of traditional farming systems. Different field and laboratory data were collected and complemented with secondary information published in refereed journals and research reports. The results showed that there are significant differences in the morphological and physiological traits of the plant, pod and grain among groups of common bean landraces of different geographic origins, which were associated with different indigenous groups. Similar patterns were observed in the contents of anthocyanins, polyphenols, flavoinds and minerals as well as antioxidant activity. In the evaluated population groups in each region, there are outstanding populations in terms of agromorphological traits and the nutritional value of the grain that can enable a participatory breeding initiative guided by regional objectives. Some populations from Sierra Norte, Oaxaca, presented higher values in Zn and Fe, and populations from Estado de Mexico exhibited high polyphenol and flavonoid values but stable agronomic behaviour.

A core collection of the common bean (Phaseolus vulgaris L.), representing genetic diversity in the entire Mexican holding, is kept at the INIFAP (Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias, Mexico) Germplasm Bank. After evaluation, the genetic structure of this collection (200 accessions) was compared with that of landraces from the states of Oaxaca, Chiapas and Veracruz (10 genotypes from each), as well as a further 10 cultivars, by means of four amplified fragment length polymorphisms (AFLP) +3/+3 primer combinations and seven simple sequence repeats (SSR) loci, in order to define genetic diversity, variability and mutual relationships. Data underwent cluster (UPGMA) and molecular variance (AMOVA) analyses. AFLP analysis produced 530 bands (88.5% polymorphic) while SSR primers amplified 174 alleles, all polymorphic (8.2 alleles per locus). AFLP indicated that the highest genetic diversity was to be found in ten commercial-seed classes from two major groups of accessions from Central Mexico and Chiapas, which seems to be an important center of diversity in the south. A third group included genotypes from Nueva Granada, Mesoamerica, Jalisco and Durango races. Here, SSR analysis indicated a reduced number of shared haplotypes among accessions, whereas the highest genetic components of AMOVA variation were found within accessions. Genetic diversity observed in the common-bean core collection represents an important sample of the total Phaseolus genetic variability at the main Germplasm Bank of INIFAP. Molecular marker strategies could contribute to a better understanding of the genetic structure of the core collection as well as to its improvement and validation.

Mexico has various types of common bean (Phaseolus vulgaris L.) and a long history of breeding in multiple commercial classes. In this study, our goal was to evaluate a wide collection of commercial cultivars of common beans from Mexico, including Azufrado, Bayo, Flor de Mayo, Flor de Junio, Pinto, and black bean types, to discover their level of relatedness with 32 simple sequence repeat (SSR) markers. Eight panels of end-labeled fluorescent SSR loci were used in an automated detection system and 85% of loci were read. A total of 204 alíeles were detected in the study, showing the diversity among the Mexican cultivars. Through population structure and principal components analyses, Andean and Mesoamerican genotypes as well as three subgroups within the Mesoamerican genepool were distinguished. The divisions corresponded to a group of Andean cultivars, two subgroups of the Durango-Jalisco (DJ) complex, and one group equivalent to race Mesoamerica. This latter race was much less diverse than the DJ complex and had little gene flow with other groups. This study shows the value of fluorescent SSR markers for evaluating commercial cultivars of common beans. Given the importance of Mexico as a primary center of origin for common beans, as a major market for the crop, and as the second largest producer in Latin America, this study has implications for the global evaluation of common bean cultivars.

Molecular Approaches to Genetic Diversity 50 Section Species Mexican states of distribution P. coccineus L. subsp. striatus

En el norte de Tamaulipas, México se cultivan entre 30 mil y 100 mil hectáreas con maíz (Zea mays L.) cada año. La superficie varía debido a la incidencia de factores bióticos (plagas de insectos, hongos toxígenos) y abióticos (alta temperatura, salinidad del suelo, sequía), así como la disponibilidad de agua para riego. Por tal razón, alternativas culturales, genéticas, biológicas y químicas para el manejo del cultivo se deben evaluar constantemente para maximizar el rendimiento y la calidad de grano. En este trabajo, se evaluó el comportamiento agronómico y la interacción genotipo x ambiente de ocho híbridos de maíz sembrados en cuatro fechas de siembra y tres años de cultivo con base el análisis de la interacción de efectos principales aditivos y multiplicativos (AMMI) y el modelo genotipo, genotipo x ambiente (GGA) Biplot; así como en el análisis de sendero secuencial (ASS). El análisis AMMI para rendimiento de grano indicó diferencias significativas (p≤ 0.01) entre híbridos y ambientes de prueba. El análisis de componentes principales indicó que los dos primeros componentes (CP) contribuyeron con 76% de la varianza total (PC1= 20 y PC2= 56%); el análisis GGE biplot indicó que DK-697 fue el híbrido con mayor rendimiento y mayor estabilidad. El gráfico biplot mostró que los vectores estuvieron más alejados del centro para el año 2006A, 2006B, 2006C y 2007A (mayores interacción y capacidad de discriminación de genotipos), mientras que los vectores más cercanos fueron 2008B y 2008C (menor interacción). Entre híbridos, los más alejados del origen (menos estables) fueron H-437 y G-8222; el más cercano al origen y más estable fue DK-697. El análisis ASS detectó colinealidad moderada para todas las características evaluadas, con efectos fuertes del número de mazorcas sanas (Valor de Inflación de la Varianza o VIF= -1.41) y peso de mazorca (VIF= -1.19). Las variables con mayor asociación al rendimiento de grano fueron peso de mazorca, altura de planta, relación de altura de planta/mazorca y número de mazorcas sanas que explicaron 86% de la variación.