Genetic diversity in the Durango race population complex of common bean >Phaseolus vulgaris L.

Abstract

Durango is an important center of genetic diversity and domestication of common bean (Phaseolus vulgaris L.). Several commercial classes of common bean were originated from the Durango Race Population Complex and show tolerance to water stress. The objective of this work was to determine the genetic diversity of the common bean Durango Race Population Complex. Seeds were randomly collected from individual plants in native populations and intermediate forms in La Ferrería, Dgo., México. Twenty-six common bean collections were used [wild (11), intermediate or regressive forms (7), landrace varieties (4) and improved cultivars (4)] and an accession of Phaseolus coccineus L., was also used as a reference. The seeds were sown under field conditions on July 10^th, 2023, in Durango, Mex., to perform morpho-agronomic and molecular characterization. Forty-eight morpho-agronomic traits were recorded, and amplification profiles were obtained with four pairs of ISTR (Inverse Sequence Tagged Repeat) molecular marker primers. The data generated were analyzed with descriptive statistics, principal component analysis (PCA) and cluster analysis (UPGMA - Unweighted Pairwise Clustering with Arithmetic Averages, Jaccard). The computer programs R (2023.12.0+369), GelAnalyzer (23.1) and PAST4- 4.15 were used. The PCA of morpho-agronomic traits showed a low proportion of variance explained by each principal component (PC). The PC 1 showed that the highest level of variance explanation was related to seed size and pod width. The cluster analysis revealed the most pronounced difference between P. coccineus and all the common bean accessions. The native common bean group (IIa) was divided into two sub-groups, one included the bayo (beige), brown and black bean accessions (IIa₁); the other (IIa₂), the small bayo (beige) and flor de mayo seeded accessions. The other group (IIb) consisted of two sub-groups, one with pinto bean varieties (IIb₁), as well as intermediate forms of flor de mayo with large seeds. The morpho-agronomic traits allowed discrimination of the landrace varieties, improved cultivars and flor de mayo (pink) regressive forms. Another sub-group (IIb₂) included two landrace varieties, known as Pinto Burro and Borroso, considered as interracial recombinants. The ISTR molecular markers produced 69 polymorphic bands and the B8/F9 primer combination registered the highest polymorphism level (86%). The cluster analysis generated by using four ITSR combinations showed clear separation of the common bean evaluated germplasm. The group I included native germplasm with two sub-groups and the Borroso variety, considered as a genetic recombinant. The group II included landrace and improved common bean germplasm, with two sub-groups, one (IIa) with a marked separation for a common bean collection with small bayo grains (LF 2), landrace varieties of the Jalisco race (Negro San Luis) and intermediate forms resulting from genetic recombination between races. Another clade included landrace and improved varieties of the Durango Race (Bayo Madero and Pinto Saltillo) and intermediate (regressive forms), with medium-large brown, black and flor de mayo seeds. The sub-group IIb included only P. coccineus. The use of morpho-agronomic attributes and molecular genetic markers allowed the evaluation of the genetic diversity present in the Durango Race Population Complex of common bean. Native populations and intermediate forms of common bean from Durango can be discriminated by morphometric traits and molecular markers, according to their genetic and geographic origin.