Abstract
BackgroundLolium perenne L. is the most important forage grass species in temperate regions. It is also considered as a sustainable source of biomass for energy production. However, improvement in biomass yield has been limited by comparison with other major crops. More efficient utilisation of genetic resources and improved breeding schemes are required to advance L. perenne breeding. In an attempt to elucidate the extent of genetic diversity in L. perenne, 1384 DArT, 182 SNP and 48 SSR markers were applied to 297 accessions (Set I) contributed by three German breeding companies and the IPK Genebank. Due to the heterogeneous nature of Lolium accessions, bulk samples were used. Apart from germplasm set I, additional set II and set III was used to determine the reproducibility of marker system and judge the feasibility of bulk strategy in this study.ResultsBy assessing different bulk sizes, 24 individuals per sample were shown to be a representative number of plants to discriminate different accessions. Among the 297 accessions, all marker types revealed a high polymorphism rate; 1.99, 2.00 and 8.19 alleles, were obtained per locus on average using DArTs, SNPs and SSRs, respectively. The Jaccard distance for DArT markers ranged from 0.00 to 0.73, the Modified Roger’s distance (MRD) for SNP markers ranged from 0.03 to 0.52, and for SSR markers from 0.26 to 0.76. Gene diversity for dominant DArT and co-dominant SNP and SSR markers was found to be 0.26, 0.32 and 0.45, respectively. DArT markers showed the highest consistency and reproducibility.ConclusionThe resulting data were evaluated using a number of different classification methods, but none of the methods showed a clear differentiation into distinct genetic pools. With regard to hybrid breeding, this will possibly impede substantial progress towards increased biomass yields of L. perenne by utilising heterosis.
Highlights
Lolium perenne L. is the most important forage grass species in temperate regions
Genetic diversity within the germplasm set I A total of 342 bulk samples were genotyped using Diversity Array Technology (DArT), Single Nucleotide Polymorphism (SNP) and Single Sequence Repeat (SSR) markers, the corresponding genetic distances were calculated for all samples and Nei’s gene diversity was estimated for SSR markers were applied to accessions (Set I) using various categories
Hu et al [18] observed a gene diversity of 0.28 within 75 L. perenne accessions collected from 27 countries and four continents using dominant Inter-Simple Sequence Repeat (ISSR) markers, which is similar to what we found for dominant DArT markers
Summary
Lolium perenne L. is the most important forage grass species in temperate regions. It is considered as a sustainable source of biomass for energy production. Improvement in biomass yield has been limited by comparison with other major crops. More efficient utilisation of genetic resources and improved breeding schemes are required to advance L. perenne breeding. Lolium, which shares evolutionary lineage with economically important cereal crops like rice (Oryza sativa), wheat (Triticum aestivum) and barley (Hordeum vulgare) [1], is generally considered the major forage grass genus in temperate regions like Northwest and Central Europe, Australia, New Zealand, parts of Japan, South Africa and South America [2]. To advance the yield improvement, more efficient utilisation of plant genetic resources is required. Polymorphic molecular markers could provide reliable characterisation of germplasm resources [12] and offer possibilities to identify germplasm structure or even heterotic patterns [13]
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