Biodiversity in Ethiopian linseed (Linum usitatissimum L.): molecular characterization of landraces and some wild species

Genet Resour Crop Evol https://doi.org/10.1007/s10722-018-0636-3 RESEARCH ARTICLE Biodiversity in Ethiopian linseed (Linum usitatissimum L.): molecular characterization of landraces and some wild species Worku Negash Mhiret . J. S. Heslop-Harrison Received: 6 January 2018 / Accepted: 26 March 2018 Ó The Author(s) 2018 Abstract Molecular characterization of germplasm is important for sustainable exploitation of crops. DNA diversity was measured using inter-retrotransposon-amplified-polymorphism and inter-simple-sequence-repeat markers in 203 Ethiopian landraces and reference varieties of linseed (flax, Linum usitatissimum) and wild Linum species. Molecular diversity was high (PIC, 0.16; GD, 0.19) compared to other reports from the species. Genotyping separated reference from landrace accessions, and clustered landrace accessions from different altitudes and geographical regions. Collections showed evidence for recent introduction of varieties in some regions. The phylogeny supported L. bienne Mill. as the progenitor of domesticated L. usitatissimum. Markers developed here will be useful for genetic mapping and selection of breeding lines. The results show the range of characters that can be exploited in breeding lines Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10722-018-0636-3) contains supplementary material, which is available to authorized users. W. N. Mhiret (&) Department of Biology, University of Gondar, Gondar, Ethiopia e-mail: ; J. S. Heslop-Harrison Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK appropriate for smallholder and commercial farmers in Ethiopia, producing a sustainable, secure, highvalue crop meeting agricultural, economic and cultural needs. Keywords Biodiversity  Ethiopia  Linseed  L. usitatissimum  Landraces  L. bienne  Altitude  Region  Diversity Introduction Knowledge about the extent and distribution of genetic diversity in crop plants is important for any breeding program (Rahman et al. 2016; Khan et al. 2007). Linum usitatissimum L. is a multipurpose crop grown in many environments for fibre, food, industrial, feed and potentially pharmaceutical uses. The bast or phloem fibres have outstanding mechanical properties (Fernández 2016) with strength and flexibility. Fibre orientation and ratio of fibre length-todiameter are important characters (Sliseris et al. 2016). Linseed oil has high a-linolenic acid (an omega-3 fatty acid) content (Schardt 2005) and seeds are used whole or crushed in foods. The hardening oil is used for varnishes, linoleum, putty and for leather preparation. It is in local medicines as demulcent, emollient and laxative, and is taken orally in bronchial infection and diarrhoea (Gul et al. 2016). Cellulosic and lignified material remaining after extraction of fibre or oil is 123 Genet Resour Crop Evol used for manufacture of paper and straw board, and for animal feed or bedding. As a food, linseed is eaten with wot (a stew) particularly in the north Ethiopia and used to make a beverage of fasting days. Linseed is one of the oldest cultivated plants and was an important commercial crop before the invention of petroleum and extensive use of cotton (McHughen 1990). Because of the diverse uses and sustainability, there is renewed interest in its cultivation. Additional information on the genetic basis of variation is required to enable modern breeding exploiting the biodiversity in the species and its wild relatives (McKenzie et al. 2008; Kurt and Evans 1998). In Ethiopia, a Vavilovian centre of crop diversity (Zohary and Hopf 2000) and a major part of the Horn of Africa endemism hot-spot (Harrison and Noss 2017), linseed is valued for food and is also exported. We have assessed the morphological variation in the highly diverse Ethiopian germplasm (Worku et al. 2015), which is grown over a wide topical and subtropical environments from 3 to 15°N and from 1200 to 3500 ma.s.l. Ethiopia has several agro-ecological zones (Hurni 1998) and other crops such as durum wheat (Mengistu 2016); enset (Ensete ventricosum (Welw.) Cheesm.) (Olango et al. 2015); tef (Eragrostis tef (Zucc.)) Trotter (Bedane et al. 2015; Ayalew et al. 2015); coffee (Tadele et al. 2014); sesame (Gebremichael and Parzies 2011); and barley (Muhe and Assefa 2011) have many landraces shown to have high genetic diversity in Ethiopia. DNA-based molecular markers have advanced genetic studies in the last three decades. Reports from different authors (Uysal et al. 2010; Cloutier et al. 2009; Fu et al. 2002; Wiesnerova and Wiesner 2004) showed that RAPDs, AFLPs, SSRs and ISSRs have low diversity in linseed germplasm, although Pali et al. (2015) reported higher variation within 48 Indian accessions. Oil seed cultivars have been considered to have more genetic diversity than fibre cultivars (Fu et al. 2002). As might be expected from genetic bottlenecks during selection, diversity is higher among wild species, and within cultivated germplasm it decreases from landraces to breeding lines and then to cultivars (Smykal et al. 2011; Habibollahi 2015). The wide variation in chromosome number found in the genus Linum (2n = 16 up to 84) indicates that hybridization and polyploidy have played a role in its evolution (Bolsheva et al. 2015). To contribute to a better understanding of the genetic diversity and 123 species relationships in this genus, Bolsheva et al. (2015) recommended comparative studies of karyotypes, and the development of suitable molecular markers will complement this approach. A high proportion of the linseed genome is composed of repetitive DNA sequences with motifs present in tens to millions of copies (Cullis 2005). Primers amplifying DNA between SSRs (inter simple sequence repeat, ISSR), retroelements (inter retroelement amplified polymorphisms, IRAP) or SSRs and retroelements (retrotransposon-microsatellite amplification polymorphism, REMAP) have proved to be valuable as informative and polymorphic markers (Kalendar and Schulman 2006; Teo et al. 2005; Alsayied et al. 2015). Both SSR (evolving by slippage replication or recombination) and retroelements (amplifying through an RNA intermediate and reinserting in the genome) can evolve rapidly and hence show polymorphisms in germplasm with little diversity. Different markers reveal different classes of variation (Powell et al. 1996), and evolve at different rates, so a primer useful in distinguishing varieties of a crop may be too polymorphic to be of use in wild germplasm of the same species. Saeidi et al. (2006, 2008) analysed a collection of wild Aegilops tauschii Coss. germplasm from Iran, finding that SSR markers developed for use in the D genome (derived from Ae. tauschii) of wheat cultivars were very highly polymorphic. Thus, while useful in the cultivated hexaploid, the SSR markers gave little information about relationships in the wild species because of their fast evolutionary rate comp (...truncated)