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Genetic diversity of natural orchardgrass (Dactylis glomerata L.) populations in three regions in Europe.

Last L, Widmer F, Fjellstad W, Stoyanova S, Kölliker R - BMC Genet. (2013)

Bottom Line: The average expected heterozygosity (HE,C) ranged from 0.44 to 0.59 and was highest in the Norwegian region.Average genetic distances were low despite large geographic distances and ranged from D = 0.09 to 0.29 among populations.All three case study regions revealed high genetic variability of tetraploid D. glomerata within selected populations and numerous rare and localized alleles which were geographically unique.

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Affiliation: Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, Zurich 8046, Switzerland. roland.koelliker@agroscope.admin.ch.

ABSTRACT

Background: Dactylis glomerata (orchardgrass or cocksfoot) is a forage crop of agronomic importance comprising high phenotypic plasticity and variability. Although the genus Dactylis has been studied quite well within the past century, little is known about the genetic diversity and population patterns of natural populations from geographically distinct grassland regions in Europe. The objectives of this study were to test the ploidy level of 59 natural and semi-natural populations of D. glomerata, to investigate genetic diversity, differentiation patterns within and among the three geographic regions, and to evaluate selected populations for their value as genetic resources.

Results: Among 1861 plants from 20 Swiss, 20 Bulgarian and 19 Norwegian populations of D. glomerata, exclusively tetraploid individuals were identified based on 29 SSR markers. The average expected heterozygosity (HE,C) ranged from 0.44 to 0.59 and was highest in the Norwegian region. The total number of rare alleles was high, accounting for 59.9% of the amplified alleles. 80.82% of the investigated individuals could be assigned to their respective geographic region based on allele frequencies. Average genetic distances were low despite large geographic distances and ranged from D = 0.09 to 0.29 among populations.

Conclusions: All three case study regions revealed high genetic variability of tetraploid D. glomerata within selected populations and numerous rare and localized alleles which were geographically unique. The large, permanent grassland patches in Bulgaria provided a high genetic diversity, while fragmented, semi-natural grassland in the Norwegian region provided a high amount of rare, localized alleles, which have to be considered in conservation and breeding strategies. Therefore, the selected grassland populations investigated conserve a large pool of genetic resources and provide valuable sources for forage crop breeding programs.

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Average expected heterozygosity (HE,C) and the total number of rare alleles in populations of Dactylis glomerata. Boxplots of SSR data of 1861 individuals from 59 Dactylis glomerata populations, showing the median, 25% and 75% quartile (box) of (a) average expected heterozygosity values (HE,C) and (b) the total number of rare alleles (< 5% occurrence) per population for three European regions (Switzerland, Bulgaria and Norway). Boxes indicated with different letters are significantly different (P < 0.05) on the basis of pairwise comparison using Tukey’s honestly significant difference test.
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Figure 1: Average expected heterozygosity (HE,C) and the total number of rare alleles in populations of Dactylis glomerata. Boxplots of SSR data of 1861 individuals from 59 Dactylis glomerata populations, showing the median, 25% and 75% quartile (box) of (a) average expected heterozygosity values (HE,C) and (b) the total number of rare alleles (< 5% occurrence) per population for three European regions (Switzerland, Bulgaria and Norway). Boxes indicated with different letters are significantly different (P < 0.05) on the basis of pairwise comparison using Tukey’s honestly significant difference test.

Mentions: The maximum and mean number of alleles per locus across all loci was ≥ 3 for each sample. Consequently, at least one out of 29 loci per individual revealed 3 to 4 alleles per locus, which indicated tetraploidy of the corresponding individual (data not shown). Among 1861 D. glomerata plants, the 29 SSR primers detected 257 polymorphic alleles, varying in size from 73 to 260 bp (Table 2). The polymorphic information content (PIC) varied considerably, ranging from 0.12 to 0.88 (mean: 0.62 ± 0.18) (Table 2). The average expected heterozygosity (HE,C) across all loci was high in all regions, ranging from 0.44 to 0.59 (Table 1). The greatest variation in HE,C was detected in Bulgaria (Figure 1a). The mean HE,C was significantly higher in the Norwegian region (HE,C = 0.54) when compared to the Bulgarian region (HE,C = 0.52, P < 0.05). There was no significant difference between Switzerland (HE,C = 0.53) and the two other regions (Figure 1a). The total number of rare alleles (frequency < 5%) across all loci was 154 and covered 59.9% of all amplified allelic bands across all the three regions. 103 of the amplified alleles were classified as common with an occurrence larger than 5% and in more than two locations. Not all alleles were detectable in all of the regions. Two to seven unique alleles within one region were detected (Table 3).


Genetic diversity of natural orchardgrass (Dactylis glomerata L.) populations in three regions in Europe.

Last L, Widmer F, Fjellstad W, Stoyanova S, Kölliker R - BMC Genet. (2013)

Average expected heterozygosity (HE,C) and the total number of rare alleles in populations of Dactylis glomerata. Boxplots of SSR data of 1861 individuals from 59 Dactylis glomerata populations, showing the median, 25% and 75% quartile (box) of (a) average expected heterozygosity values (HE,C) and (b) the total number of rare alleles (< 5% occurrence) per population for three European regions (Switzerland, Bulgaria and Norway). Boxes indicated with different letters are significantly different (P < 0.05) on the basis of pairwise comparison using Tukey’s honestly significant difference test.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231346&req=5

Figure 1: Average expected heterozygosity (HE,C) and the total number of rare alleles in populations of Dactylis glomerata. Boxplots of SSR data of 1861 individuals from 59 Dactylis glomerata populations, showing the median, 25% and 75% quartile (box) of (a) average expected heterozygosity values (HE,C) and (b) the total number of rare alleles (< 5% occurrence) per population for three European regions (Switzerland, Bulgaria and Norway). Boxes indicated with different letters are significantly different (P < 0.05) on the basis of pairwise comparison using Tukey’s honestly significant difference test.
Mentions: The maximum and mean number of alleles per locus across all loci was ≥ 3 for each sample. Consequently, at least one out of 29 loci per individual revealed 3 to 4 alleles per locus, which indicated tetraploidy of the corresponding individual (data not shown). Among 1861 D. glomerata plants, the 29 SSR primers detected 257 polymorphic alleles, varying in size from 73 to 260 bp (Table 2). The polymorphic information content (PIC) varied considerably, ranging from 0.12 to 0.88 (mean: 0.62 ± 0.18) (Table 2). The average expected heterozygosity (HE,C) across all loci was high in all regions, ranging from 0.44 to 0.59 (Table 1). The greatest variation in HE,C was detected in Bulgaria (Figure 1a). The mean HE,C was significantly higher in the Norwegian region (HE,C = 0.54) when compared to the Bulgarian region (HE,C = 0.52, P < 0.05). There was no significant difference between Switzerland (HE,C = 0.53) and the two other regions (Figure 1a). The total number of rare alleles (frequency < 5%) across all loci was 154 and covered 59.9% of all amplified allelic bands across all the three regions. 103 of the amplified alleles were classified as common with an occurrence larger than 5% and in more than two locations. Not all alleles were detectable in all of the regions. Two to seven unique alleles within one region were detected (Table 3).

Bottom Line: The average expected heterozygosity (HE,C) ranged from 0.44 to 0.59 and was highest in the Norwegian region.Average genetic distances were low despite large geographic distances and ranged from D = 0.09 to 0.29 among populations.All three case study regions revealed high genetic variability of tetraploid D. glomerata within selected populations and numerous rare and localized alleles which were geographically unique.

View Article: PubMed Central - HTML - PubMed

Affiliation: Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, Zurich 8046, Switzerland. roland.koelliker@agroscope.admin.ch.

ABSTRACT

Background: Dactylis glomerata (orchardgrass or cocksfoot) is a forage crop of agronomic importance comprising high phenotypic plasticity and variability. Although the genus Dactylis has been studied quite well within the past century, little is known about the genetic diversity and population patterns of natural populations from geographically distinct grassland regions in Europe. The objectives of this study were to test the ploidy level of 59 natural and semi-natural populations of D. glomerata, to investigate genetic diversity, differentiation patterns within and among the three geographic regions, and to evaluate selected populations for their value as genetic resources.

Results: Among 1861 plants from 20 Swiss, 20 Bulgarian and 19 Norwegian populations of D. glomerata, exclusively tetraploid individuals were identified based on 29 SSR markers. The average expected heterozygosity (HE,C) ranged from 0.44 to 0.59 and was highest in the Norwegian region. The total number of rare alleles was high, accounting for 59.9% of the amplified alleles. 80.82% of the investigated individuals could be assigned to their respective geographic region based on allele frequencies. Average genetic distances were low despite large geographic distances and ranged from D = 0.09 to 0.29 among populations.

Conclusions: All three case study regions revealed high genetic variability of tetraploid D. glomerata within selected populations and numerous rare and localized alleles which were geographically unique. The large, permanent grassland patches in Bulgaria provided a high genetic diversity, while fragmented, semi-natural grassland in the Norwegian region provided a high amount of rare, localized alleles, which have to be considered in conservation and breeding strategies. Therefore, the selected grassland populations investigated conserve a large pool of genetic resources and provide valuable sources for forage crop breeding programs.

Show MeSH
Related in: MedlinePlus