Genetic Relationships and Fingerprinting of Rapeseed Cultivars by AFLP: Consequences for Varietal Registration

Abstract

At present, registration and protection of rapeseed (Brassica napus L.) cultivars relies on a small number of morphological traits. As the number of cultivars increases, the ability to distinguish them on the basis of these traits becomes more difficult. New descriptors like molecular markers are required to maintain the efficiency of registration testing. The objectives of this study were to (i) evaluate the discrimination power of 17 amplified fragment length polymorphism (AFLP) primer combinations tested on a collection of 83 spring and winter rapeseed cultivars, (ii) assess the structure of the genetic diversity revealed by AFLPs, and (iii) compare three genetic distance estimators (Jaccard, Sokal, and Michener and Sokal and Michener weighted by the PIC). A total of 324 polymorphic markers were scored, with an average of 19.1 markers per primer combination. The use of only two primer combinations was sufficient to identify uniquely all the cultivars. The analysis of the genetic structure of the diversity by cluster and principal component analyses and AMOVAs (analyses of molecular variance) clearly delineated three significant factors: the cultivar type (winter or spring), the country of origin (France or Germany), and the breeding company. The three measures of genetic distance were highly correlated (P < 0.001, r = 0.96–0.98) and led to similar groupings. AFLPs were shown to be a powerful method for identifying cultivars and analyzing the genetic structure of the diversity in rapeseed.

Repeated Polyploidy Drove Different Levels of Crossover Suppression between Homoeologous Chromosomes inBrassica napusAllohaploids

“…Molecular analyses confirmed that these three groups represent distinct gene pools (Song et al, 1988;Diers and Osborn, 1994). Our selection of oilseed accessions included both winter and spring types, which were shown to be differentiated gene pools (Diers and Osborn, 1994;Lombard et al, 2000;Hasan et al, 2006) and accessions from broad geographic origins, which was shown to correlate with the patterns of genetic diversity in this germplasm (Diers and Osborn, 1994;Chen et al, 2008). Most of the cultivars (22 out of 29) were represented by a single genetically homogeneous line, which was obtained after several generations of selfing (Table 1).…”

“…Our worldwide sample encompassed three main B. napus gene pools (ssp oleifera, ssp rapifera, and ssp pabularia), included both winter and spring oilseed types (Diers and Osborn, 1994;Lombard et al, 2000;Hasan et al, 2006), and thus represented a major part of B. napus genetic diversity. Although phenotyping other B. napus accessions could provide supplementary information, the dichotomy of meiotic behaviors found here certainly highlights the overall variation present in this species, which contains germplasm of shared recent common ancestry (Prakash and Hinata, 1980;Allender and King, 2010).…”

Comparison of Isozyme, RAPD and AFLP Markers in Genetic Similarity Assessment of CMS Ogura F1 Hybrids of Winter Oilseed Rape (Brassica Napus L.) Parental Lines

“…Genetic similarity estimates can differ due to differences in the number of marker observations and in the character of polymorphic markers. Generally, the percentage of polymorphic DNA bands is smaller for AFLP and yet this technique is more efficient than RAPD and isozymes for analyzing genetic divergence, thanks to the large number of polymorphic DNA fragments per assay unit (Lombard et al, 2000;Simoniuc et al, 2002). Our study confirmed this: the RAPD method generated 61.0% polymorphic DNA fragments, and the AFLP method only 34.5% (Tabs.…”

CARACTERISATION VARIETALE Les marqueurs moléculaires : un nouvel outil pour l’inscription et la protection variétale ?

“…L'application d'un modèle linéaire liant chaque variable phénotypique quantitative à des marqueurs moléculaires a permis d'économiser la mise au champ d'un tiers de la collection de référence, sans risque d'erreur significatif, dans une étude réalisée sur les 145 lignées de maïs présentées précédemment [5]. Pour plus de sécurité, dans les simulations réalisées par Nuel et al, seules les fausses distinctions ont été autorisées (dès qu'une lignée de référence avait une distance prédite avec la lignée candidate inférieure à la borne supérieure, elle était implantée à ses côtés).…”