Feasibility of integration of molecular markers and morphological descriptors in a real case study of a plant variety protection system for soybean

Abstract

Use of molecular markers such as Random Amplified Polymorphic DNA (RAPD), Amplified Fragment Length Polymorphism (AFLP) and Simple Sequence Repeats (SSR) as descriptors to characterize and differentiate a set of 100 soybean varieties of commercial use in Argentina was taken as a leading case study for plant variety protection (PVP) purposes. Sixteen morphological traits were recorded to compare pedigree relationships among varieties with information derived from conventional descriptors and molecular markers. Analysis of 109 polymorphic loci confirmed the rather low genetic variability of commercial soybean germplasm. Still, genetic fingerprinting of the 100 varieties could be established. Calculated similarity indexes were dependent on the technique, ranging from 0.262 (SSR), 0.407 (RAPD), 0.400 (AFLP) and 0.574 (morphological traits).Dendrograms generated from morphological data matrix showed low value correlation with kinship coefficient matrix (r = 0.216). Still, they were suitable to identify and differentiate each of the 100 varieties analyzed; which was not possible with RAPD or AFLP markers using comparable numbers of polymorphic loci. SSR data showed the best fit to pedigree information (r = 0.353), while maintaining an association to morphologically based separation. Results suggest that the four techniques describe genetic variability in different and specific ways. A combination of SSR and morphological descriptors show the best compromise of regarding genetic relationships and the needs of clear classification for PVP and may help to establish minimum genetic distances for distinctness within PVP Office definition.