Abstract
Landraces represent valuable genetic resources for breeding programmes to produce high-yielding varieties adapted to stressful environmental conditions. Although the common bean (Phaseolus vulgaris L.) is an economically important food legume for direct human consumption worldwide, common bean production in Croatia is based almost exclusively on landraces and there is no common bean breeding program. Information on phaseolin type and results of population structure and genetic diversity obtained by analysis of SSR and SNP markers, in combination with the morphological characterization of 174 accessions of 10 common bean landraces (morphotypes), enabled thorough classification of accessions. The accessions were classified into phaseolin type H1 (“S”) of Mesoamerican origin and phaseolin types H2 (“H” or “C”) and H3 (“T”) of Andean origin. By applying distance- and model-based clustering methods to SSR markers, the accessions were classified into two clusters at K = 2 separating the accessions according to the centres of origin, while at K = 3, the accessions of Andean origin were further classified into two clusters of accessions that differed in phaseolin type (H2 and H3). Using SNP markers, model-based analysis of population structure was performed, the results of which were consistent with those of SSR markers. In addition, 122 accessions were assigned to 14 newly formed true-type morphogenetic groups derived from three different domestication events: (1) Mesoamerican (H1A) (“Biser”, “Kukuruzar”, “Tetovac”, “Trešnjevac”), (2) Andean—indeterminate type (H2B1) (“Dan noć”, “Sivi”, “Puter”, ”Sivi prošarani”, “Trešnjevac”) and (3) Andean—determinate type (H3B2) (“Bijeli”, “Dan noć”, “Puter”, “Trešnjevac”, “Zelenčec”). The rest of the accessions could represent putative hybrids between morphogenetic groups. The differences between the true-type groups of accessions were further analysed based on nine quantitative traits, and the subsets of traits that best distinguish among centres of origin (A: Mesoamerican, B: Andean) and genetic groups (H1A, H2B1, H3B2) were proposed.
Highlights
IntroductionLandraces are characterized by specific adaptation to the environmental conditions of the area of cultivation [1,2] and can provide sources of genetic diversity for abiotic and biotic stress resistance by preserving valuable alleles and gene combinations [3,4,5]
Analysis of genetic diversity using SSR markers shows that Croatian common bean landraces have a high degree of genetic diversity with 135 alleles detected in 174 accessions with an average of 5.192 alleles per locus
After analysis of the genetic structure using both SSRs and SNPs and phaseolin type, the accessions were almost completely grouped into two main groups, Mesoamerican (A) and Andean (B), and further analysis separated the Andean into two subgroups (B1 and B2)
Summary
Landraces are characterized by specific adaptation to the environmental conditions of the area of cultivation [1,2] and can provide sources of genetic diversity for abiotic and biotic stress resistance by preserving valuable alleles and gene combinations [3,4,5]. As they are genetically diverse and phenotypically variable, landraces can be used in breeding programs to produce new high-yielding commercial cultivars adapted to specific agricultural production ecosystems and resistant to climate change [6,7,8]. Common bean (Phaseolus vulgaris L.) is an economically significant vegetable crop and food legume for direct human consumption worldwide [11,12] and its global production is estimated at more than 55 million tons in 2018
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