|Bhardwaj, Harbans - Virginia State University|
Submitted to: International Legume Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: 6/23/2016
Publication Date: N/A
Interpretive Summary: Genetic diversity of 200 accessions of the tepary bean (Phaseolus acutifolius) was analyzed using different types of genetic markers. Targeted Region Amplified Polymorphic markers are designed to find traits associated with drought and heat tolerance. Amplified Fragment Length Polymorphic markers show random diversity. There was a significant correlation of both type of markers, indicating that both types actually determined random genetic variance. Drought tolerance was estimated using chloroplast fluorescence in plants under drought conditions. The collection was found to be very diverse, but none of the groupings found by the markers could be linked to fluorescence measurements. The groups identified, however, can be used by plant breeders to select diverse parents as sources of genes for drought tolerance to be transferred to common bean.
Technical Abstract: Tepary bean (Phaseolus acutifolius A. Gray), a truly Native American crop, is a short life-cycle annual desert legume indigenous to northwestern Mexico and the southwestern USA and is considered drought and heat tolerant. The Western Regional Plant Introduction Station currently maintains 211 accessions of tepary bean. Virginia State University Researchers have studied these extensively and separated some accessions to plant types based on morphology to a total of 222 accessions. Molecular genetic relationships among 222 accessions of the Phaseolus acutifolius A. Gray collection were assessed using Targeted Region Amplified Polymorphic (TRAP) markers designed from sequences of genes associated with heat and drought tolerance and random Amplified Fragment Length Polymprphic (AFLP) markers. Although TRAP markers attempt to analyze specific gene targets, they have been shown to produce random genetic differences among accessions analyzed. The correlation among the matrices produced by each marker was R = 0.81. Genetic relationships were compared to reactions to drought stress using measurements of variable fluorescence to maximum fluorescence (Fv/Fm). Cluster analysis using NTSys-pc and STRUCTURE of the combined marker set found 3 major groups and 7 sub-groups with an average Fst of 0.71, but there was no association of drought tolerance with any group. In fact, some plants separated by seed color within an accession tested as both drought tolerant and susceptible, though genetically similar at all marker loci tested. In other cases, plants separated by seed type clustered apart in different groups. Although the tepary bean has been used in interspecific crosses with common bean for heat tolerance and disease resistance, accessions have also been identified with prolific seed production, which could also increase yield in common bean.