Introgression of genomic components from Chinese Brassica rapa contributes to widening the genetic diversity in rapeseed (B. napus L.), with emphasis on the evolution of Chinese rapeseed

Abstract

In spite of its short history of being an oil crop in China, the Chinese semi-winter rapeseed (Brassica napus L., 2n = 38, AACC) has been improved rapidly by intentional introgression of genomic components from Chinese B. rapa (2n = 20, AA). As a result, the Chinese semi-winter rapeseed has diversified genetically from the spring and winter rapeseed grown in the other regions such as Europe and North America. The objectives of this study were to investigate the roles of the introgression of the genomic components from the Chinese B. rapa in widening the genetic diversity of rapeseed and to verify the role of this introgression in the evolution of the Chinese rapeseed. Ten lines of the new type of rapeseed, which were produced by introgression of Chinese B. rapa to Chinese normal rapeseed, were compared for genetic diversity using amplified fragment length polymorphism (AFLP) with three groups of 35 lines of the normal rapeseed, including 9 semi-winter rapeseed lines from China, 9 winter rapeseed lines from Europe and 17 spring rapeseed lines from Northern Europe, Canada and Australia. Analysis of 799 polymorphic fragments revealed that within the groups, the new type rapeseed had the highest genetic diversity, followed by the semi-winter normal rapeseed from China. Spring and winter rapeseed had the lowest genetic diversity. Among the groups, the new type rapeseed group had the largest average genetic distance to the other three groups. Principal component analysis and cluster analysis, however, could not separate the new type rapeseed group from Chinese normal rapeseed group. Our data suggested that the introgression of Chinese B. rapa could significantly diversify the genetic basis of the rapeseed and play an important role in the evolution of Chinese rapeseed. The use of new genetic variation for the exploitation of heterosis in Brassica hybrid breeding is discussed.

Genetic investigation of the origination of allopolyploid with virtually synthesized lines: Application to the C subgenome of Brassica napus

“…However, traditional plantbreeding processes threaten the genetic base on which breeding depends, because new varieties are usually derived from crosses among genetically-related modern varieties, and primitive ancestors, which are genetically more variable, but less productive, are excluded (Tanksley and McCouch, 1997). These ancestors are important sources for crop improvement because they can provide beneficial alleles or genes (Xiao et al, 1996;Fridman et al, 2004;He et al, 2006), and widen the genetic base (Seyis et al, 2003;Reif et al, 2005;Qian et al, 2006).…”

“…In this study, natural accessions of rapeseed from three divergent gene pools (Diers and Osborn, 1994;Becker et al, 1995;Qian et al, 2006) clustered together when compared with virtual rapeseed lines and parental species in principal component analysis. This indicates that the amount of variation in natural rapeseed is small compared with that in the parental species, and that there is great potential to widen the genetic base of natural rapeseed by using the parental species.…”

“…A total of 25 accessions from 10 wild types and 14 accessions from 7 cultivated types of the B. oleracea cytodeme, on the basis of the classification proposed by Snogerup et al (1990), were collected from the Centre for Genetic Resources (CGN; Wageningen, The Netherlands), the Institute of Plant Genetics and Crop Plant Research (IPK; Gatersleben, Germany), the Universidad Politécnica de Madrid (UPM; Madrid, Spain), the University of California (UC; Davis, CA, USA) and Southwest University (SWU; China). Four accessions of B. rapa that represented genetic variants from two centres of origin of B. rapa (East Asia and Europe) and six accessions of B. napus that represented natural variants of rapeseed (two European winter, two Chinese semi-winter and two European spring rapeseed) were selected on the basis of studies of the evolution of B. rapa (Gó mez-Campo and Qian et al, 2003;Zhao et al, 2005) and analyses of genetic diversity in natural rapeseed (Diers and Osborn, 1994;Becker et al, 1995;Qian et al, 2006). A total of 156 virtual lines of rapeseed were developed from the 39 accessions of the B. oleracea cytodeme and from the 4 accessions of the B. rapa as described below.…”

“…Hence, no information about the progenitors of rapeseed can be gained from wild rapeseed. (2) The frequent introgression of B. rapa into B. napus in breeding programs has led to substantial amounts of variation in the A subgenome of modern rapeseed (Qian et al, 2006). Hence, it is difficult to distinguish the genetic contributions of the B. rapa progenitor from genetic material that has been introduced more recently.…”

Broadening the genetic base of Abyssinian mustard (Brassica carinata A. Braun) through introgression of genes from related allotetraploid species

“…Nuclear genes for desirable agronomic traits have been incorporated from related sources exploiting non-homologous recombination following sexual/somatic hybridization like earliness to oil rape leading to release of cultivars like 'Norin 16' and 'Asahi-Natane' in Japan (Namai et al, 1980). Development of 10 lines of new type of rapeseed through introgression of genes from Chinese B. rapa to Chinese normal rapeseed (B. napus) (Qian et al, 2006) thereby revealing that Chinese B. rapa could significantly diversify the genetic basis of the rapeseed and play an important role in the evolution of Chinese rapeseed.…”