A Core Set of Snap Bean Genotypes Established by Phenotyping a Large Panel Collected in Europe

Abstract

Snap beans are a group of bean cultivars grown for their edible immature pods. The objective of this work was to characterize the diversity of pod phenotypes in a snap bean panel (SBP), comprising 311 lines collected in Europe, and establish a core set (Core-SBP) with the maximum diversity of pod phenotypes. Phenotyping of the SBP was carried out over two seasons based on 14 quantitative pod dimension traits along with three qualitative traits: pod color, seed coat color, and growth habit. Phenotypes were grouped into 54 classes using a hierarchical method, and a Core-SBP with one line per phenotype class was established. A further field-based evaluation of the Core-SBP revealed higher diversity index values than those obtained for the SBP. The Core-SBP was also genotyped using 24 breeder-friendly DNA markers tagging 21 genomic regions previously associated with pod trait control. Significant marker-trait associations were found for 11 of the 21 analyzed regions as well as the locus fin. The established Core-SBP was a first attempt to classify snap bean cultivars based on pod morphology and constituted a valuable source of characteristics for future breeding programs and genetic analysis.

Keywords: Phaseolus vulgaris L.; QTL validation; core collections; diversity; genotyping; phenotyping; pod traits.

Figure 1

Biplots showing the results of the Hierarchical Clustering on Principal Components analysis from 14 evaluated quantitative pod traits (PLP, PLA, PLW, PL, PLC, PL/PLC, PSP, PSA, PSW, PSH, PSH/PSW, PSC, NSP, Seed weigh; see Table S2) in the Snap Bean Panel. Ellipses representing the clusters were drawn considering a confidence interval > 0.8.

Figure 2

Immature pod phenotype of the 54 lines included in the Core-SBP. Pods were scanned at 300 dpi.