Genetic Diversity and Population Structure in a World Collection of Brassica napus Accessions with Emphasis on South Korea, Japan, and Pakistan

Abstract

1537 ReseaRch B raSSica napuS is an amphidiploid species formed from multiple independent fusion events between ancestors of Brassica rapa L. (AA; 2n = 20) and Brassica oleracea L. (CC; 2n = 18) (U, 1935). The diploid Brassica species most likely originated from a hexaploid ancestor (Parkin et al., 2005). Exchange of DNA segments between the A and C genome is rare and no major chromosomal rearrangements have occurred since the fusion of the two progenitor genomes (Howell et al., 2008;Parkin and Lydiate, 1997). A recent study based on comparative analysis of chloroplast haplotypes indicate that B. rapa is likely the maternal ancestor of B. napus rather than B. oleracea as previously thought (Allender and King, 2010). The B. napus gene pool can be subdivided into biannual vegetable, rutabaga, or swede subspecies [rapifera Metzg. including the variety napobrassica) and annual oilseed or fodder subspecies (napus or subspecies oleifera (DC) Metzg.], which include economically important crops primarily used for vegetable oil, leafy and root vegetables, fodder and to a lesser extent for industrial oil and biodiesel (McNaughton, 1995). It is believed that B. napus is a relatively ABSTRACT Information on genetic diversity and population structure is needed for continued improvement in Brassica napus L. A total of 169 B. napus lines, collected between 1970 and 2000 in Australia,

Genetic Diversity in Indigenous Landraces of Brassica napus based on Morphological and Biochemical Characteristics using Multivariate Techniques

“…24843, 24860, 24909, 24895, 24844, 24877, 24884, 24898 and Pakola Silique length ≥7 24847, 24848, 24892, 24890, 24888, 24877, 24874, 24873, 24870 and Pakola Seed per silique ≥28 24844, 24845, 24851, 24854, 24855, 24856, 24859, 24885, 24888 and 24892 Seed yield per plant ≥80 24866, 24868, 24882, 24889, 24896, 24883, 24880, 24870 and 24859 1000-ssed weight ≥4 24843, 24846, 24849, 24850, 24864, 24868, 24869, 24876, 24877, 24891, 24898 and Pakola Oil content ≥50 24850, 24852, 24857, 24871, 24893, 24882, 24897 and Shiralee Protein content ≥27 24843, 24851, 24874, 24880, 24884, 24888, 24908 and 24872 Oleic Acid ≥50 24844, 24849, 24854, 24861, 24868, 24870, 24881, 24890, 24891, 24907, 24908, Pakola and Shiralee Clusters (genotypes from those clusters) can only be related to geographical origin if their natural habitats differ so that the selective pressure forced populations to adapt in different directions. A total of 169 B. napus L. lines were genotyped with 84 SSR markers, and Nei's unbiased genetic diversity and Shannon's information index showed that genetic diversity was highest among lines from Europe followed by South Korea, Japan, China and Pakistan while lines from Australia and Canada had the lowest diversity (Gyawali et al, 2013;Jankulovska et al, 2014). In present studies, principal component analysis of B. napus L. accessions revealed grouping relationship differently, and indirectly supported cluster analysis.…”

“…The separation of genotypes based on PC1 and PC2 revealed that the populations were distributed in all the directions, which clearly recognized the diversification in indigenous landraces of B. napus L. Previous data based on first and second five PCs with > 1 contributed 73.30% and 64.45% of the genetic variability, respectively among various accessions of B. juncea L. (Ali et al, 2015). Past researchers have made divergence studies of morphological and seed attributes using principal component and cluster analyses in Brassica species (Takahata and Hinata, 1986), B. napus L. (Bus et al, 2011;Gyawali et al, 2013), Indian mustard (Dias et al, 1993;Rabbani et al, 1998b), Ethiopian mustard (Alemayehu and Becker, 2002;Genet et al, 2005;Warwick et al, 2006), and white head cabbage (Balkaya et al, 2005). However, the present two methods i.e., cluster and principal component analyses were found more appropriate and can better dig out the relationship between the genotypes of assorted origins.…”

Association mapping of seed quality traits in Brassica napus L. using GWAS and candidate QTL approaches

“…The subdivision observed in the association panel details further the diversity found in winter oilseed rape germplasm. Previous studies of this kind were conducted using diversity sets that include spring oilseed rape germplasm which hinder the ability to further dissect the winter-type germplasm (Hasan et al 2006;Ecke et al 2010;Bus et al 2011;Gyawali et al 2013). In this respect, the current study increases our understanding of the genetic composition of wintertype oilseed rape and expands on previous work in this field.…”

“…The F ST value (Online resource 1, Table S5b), a measurement of the genetic differentiation between subpopulations, suggested a weak population structure where the individuals in both subpopulations share a high number of alleles. Different studies using worldwide oilseed rape collections (Bus et al 2011;Gyawali et al 2013) have reported low F ST values among subpopulations (0.176 and 0.09, respectively) differentiated principally for growth habit. For a winter oilseed rape population characterized by Bus et al (2011), however, a low intra-population F ST value was observed (0.087).…”

Cytogenetic and Molecular Characterization of B-Genome Introgression Lines ofBrassica napusL.

“…Due to its relatively recent origin, probably as an agricultural hybrid, it has low allelic diversity as compared to that of its progenitors. Genetic studies based on DNA polymorphisms show a narrow genetic base (Diers et al 1996; Lombard et al 2000; Cartea et al 2005; Zhou et al 2006; Chen et al 2008; Wang et al 2009; Gyawali et al 2013) with germplasm tending to cluster by growth habit (Qian et al 2006; Zhou et al 2006; Chen et al 2008) or geographic origin (Hu et al 2007). The inherent problem of low genetic diversity in B. napus has been further intensified by aggressive plant breeding efforts toward improving oil quality and facilitating adaptation to restricted photoperiod and temperature regimes.…”