Genetic diversity of Hordeum species assessed by

Random Amplified Polymorphic DNA markers

 

A.-L. Lainé, J. Le Gouis & N. Bahrman

 

INRA, Laboratoire de Génétique et d’Amélioration des Plantes,

Domaine de Brunehaut, F-80200 Estrées-Mons, France, laine@mons.inra.fr

 

The genus Hordeum contains more than 30 species with a large natural area (Bothmer et al., 1995). Species are annual or perennial and the ploidy level ranges from 2x, 4x to 6x with basic chromosome number x = 7. Using morphological characters Bothmer et al. (1995) classified Hordeum species in four sections Anisolepis, Critesion, Hordeum and Stenostachys. Botanical characters well defined the grouping of species in a same genus Hordeum, but the classification within Hordeum with genetic markers remains subject to controversy (Marillia and Scoles, 1996 and the references therein). Geographical distribution is also not always correlated with morphological classification. The aim of this study was to assess genetic diversity with molecular markers and investigate phylogenetic relationships in genus Hordeum.

Seeds from 42 species or subspecies of Hordeum and 4 varieties of cultivated barley (Table 1) were germinated in Petri dishes for seven days. Thirty eight of the genotypes used in this study were kindly provided by Professor Roland von Bothmer. Five young seedlings were bulked for DNA extraction. PCR amplification was carried out using a Genius thermocycler (Techne, Cambridge, UK). RAPD reactions were realized with 10-base primers (AA19, AC09, G11, H14, I04, L04 and O19, Operon Technologies Inc., Alameda, USA) according to Bahrman et al. (1999). Variable bands were scored and statistical analyses were performed on a binary matrix using correspondence analysis. First, genetic distances between all pairs of taxa and then, mean dissimilarity indices in intra- and inter-section levels were computed (Bahrman et al. 1994).

A total of 77 variable bands were scored over all genotypes. High similarity levels were found between H.euclaston and H. flexuosum (0.97), between all cultivated varieties (0.89), between all pairs of H. bulbosum (0.85) and between H.vulgare ssp spontaneum and H. vulgare ssp vulgare (0.80). In general intra-section distances were smaller than inter-section ones. But, as indicated below, in two cases it was found to be at the same level :

 

                                                                       1          2          3          4

                                   1- Anisolepis               0.36

                                   2- Critesion                 0.43     0.30

                                   3- Hordeum                 0.48     0.49     0.40

                                   4- Stenostachys           0.39     0.37     0.46     0.36

 

All the distances between Hordeum sections were significatively important, this may be because Hordeum species have a large distribution in Eurasian region. It is important to note that intra Critesion distance was smaller than the other ones. This is probably due to the distribution of these species in North and South America. All the inter-specific distances were larger than intra-section ones. Correspondence analysis showed two main groups (Fig. 1). These two groups contained Hordeum species from American and Eurasian continents respectively, except H. secalinum, H. capense, H. bogdanii, H. brevisubulatum, H. roshevitzii, H. marinum  which were misclassified.

Up to now, we gathered only partial data about inter-specific distances with this limited set of RAPD markers. This study will be continued using microsatellites loci and in the future we hope to bring more information about the Hordeum phylogeny.

 

References

Bahrman N., Zivy M., Damerval C. & Baradat Ph. (1994) Organisation of the variability of abundant proteins in seven geographical origins of maritime pine (Pinus pinaster Ait.). Theor. Appl. Genet. 88: 407-411.

Bahrman N., Le Gouis J., Hariri D., Guilbaud L. & Jestin L. (1999) Genetic diversity of old French six-rowed winter barley varieties assessed with molecular, biochemical and morphological markers and its relation to BaMMV resistance. Heredity 83: 568-574.

Bothmer R. von, Jacobsen N., Baden C., Jorgensen R.B. & Linde-Laursen I. (1995) An ecogeographical study of the genus Hordeum. International Plant Genetic Resources Institute, Rome.

Marillia E. F. & Scoles G. J. (1996) The use of RAPD markers in Hordeum phylogeny. Genome 39: 646-654.

 

 

 

 

 

 

 

Figure 1 – Correspondence analysis with 77 polymorphic RAPD bands, for abbreviation see Table 1.

Table 1. Plant material and their belonging to one of the four Hordeum sections.

Section	Species or subspecies	Abbreviation	Distribution
Anisolepis	H. chilense	chi	South America
	H. cordobense	cor	South America
	H. euclaston	euc	South America
	H. flexuosum	fle	South America
	H. intercedens	int	North America
	H. muticum	mut	South America
	H. pusillum	pus	North America
	H. stenostachys	ste	South America
Critesion	H. arizonicum	ari	North America
	H. comosum	com	South America
	H. jubatum	jub	North America, Asia
	H. lechleri	lec	South America
	H. procerum	pro	South America
	H. pubiflorum	pub	South America
Hordeum	H.bulbosum	bul	Eurasia, North Africa
	H.bulbosum	bul	Eurasia, North Africa
	H.bulbosum	bul	Eurasia, North Africa
	H.bulbosum	bul	Eurasia, North Africa
	H. murinum ssp glaucum	mgl	Eurasia, North Africa
	H. murinum ssp leporinum	mle	Eurasia, North Africa
	H. murinum ssp murinum	mmu	Eurasia, North Africa
	H. vulgare ssp spontaneum	vsp	Eurasia, North Africa
	H. vulgare ssp vulgare	vvu
	Plaisant	pla
	Express	exp
	Shannon	sha
	Proctor	prt
Stenostachys	H. bogdanii	bog	Asia
	H. brachyantherum ssp brachyantherum	bbr	North America
	H. brachyantherum ssp californicum	bca	North America
	H. brevisubulatum ssp brevisubulatum	bre	Asia
	H. capense	cap	South Africa
	H. depressum	dep	North America
	H. erectifolium	ere	South America
	H. guatemalense	gua	Central America
	H. marinum ssp marinum	mma	Eurasia, North Africa
	H. marinum ssp gussoneanum	mgu	Eurasia, North Africa
	H. parodii	par	South America
	H. patagonicum ssp magellanicum	pma	South America
	H. patagonicum ssp mustersii	pmu	South America
	H. patagonicum ssp patagonicum	ppa	South America
	H. patagonicum ssp santacrucense	psa	South America
	H. patagonicum ssp setifolium	pse	South America
	H. roshevitzii	ros	Asia
	H. secalinum	sec	Europe
	H.tetraploïdum	tet	South America