«A. Kolodinska Brantestam Faculty of Landscape Planning, Hordiculture and Agricultural Science Department of Crop Science Alnarp Doctoral thesis ...»
A Century of Breeding – is
Genetic Erosion a Reality?
Temporal Diversity Changes in Nordic and Baltic
A. Kolodinska Brantestam
Faculty of Landscape Planning, Hordiculture and Agricultural Science
Department of Crop Science
Swedish University of Agricultural Sciences
Acta Universitatis Agriculturae Sueciae
© 2005 Agnese Kolodinska Brantestam, Alnarp
Tryck: Repro, Alnarp 2005
Kolodinska Brantestam, A. 2004. A century of breeding – is genetic erosion a reality? Temporal diversity changes in Nordic and Baltic barley. Doctoral dissertation ISSN 1652-6880, ISBN 91-576-7029-3 Barley (Hordeum vulgare L. ssp. vulgare) is an important crop in the Nordic and Baltic countries, where it is mainly used for feed and malt. Commercial breeding of barley has been carried out in this region for more than a century, and landraces have been completely replaced by pure line cultivars. There is a concern that plant breeding might lead to a severe reduction of genetic diversity, so-called genetic erosion, since commercial breeding was initially based only on a few successful selections from landraces. The consequences of such erosion would affect plasticity of the crop, which might reduce its ability to adapt to future agriculture and consumption demands and increase the vulnerability to epidemics. The aim of this study was to evaluate the degree of putative genetic erosion and relationships in Nordic and Baltic barley material. A large collection representing landraces and cultivars from the end of the 19th century up to modern material were analysed by isozymes and DNA markers. In addition, field trials were performed in order to observe changes in the diversity of agronomic traits. General indications of a decrease in diversity were observed. A loss of less common alleles was found in molecular markers and a significant decrease of variability was detected for most agronomic traits. However, the molecular markers failed to prove significant diversity changes in the material as a whole. New alleles, not present in Nordic and Baltic landraces and old cultivars, were found in modern material.
Differences in the magnitude of diversity varied depending of country and region (North vs South) of origin and row type of the crop. Some of these diversity changes were also significant in the molecular makers, for example a significant decrease in material from the southern part of the region was observed. The two- rowed and six-rowed cultivars of this region were well differentiated not only by agronomic data, but also by DNA markers. They demonstrated differences at chromosome regions distant from the inflorescence determinating genes. While agronomical data separate modern material from landraces and old cultivars fairly well, DNA markers achieved this for most of the countries only when the material was analysed separately by country. The main conclusion of this study is that breeding in Nordic and Baltic countries has decreased diversity at some traits, but overall diversity of the crop has not changed significantly. However, the landraces and old cultivars of the region should still be considered as valuable diversity sources since some of the loci found there are not present in modern materials.
Keywords: genetic diversity, Hordeum vulgare, agronomic traits, molecular markers, barley breeding Author’s address: Agnese Kolodinska Brantestam, SLU Department of Crop
Science, Sundsvägen 14, P.O. Box 44, SE-230 53 Alnarp, Sweden. E-mail:
email@example.com Contents Introduction 4 Taxonomy, domestication and distribution 4 Barley in Northern Europe 6 Applications and adaptation requirements to regional conditions 6 Brief history of barley breeding in the region 7 The barley genome 11 Modern tools for barley breeding and their implications 12 Molecular maps and chromosome library 12 Quantitative trait loci and marker assisted selection 13 Genetic diversity and genetic erosion 14 Objectives 16 Diversity in Nordic and Baltic barley 17 Relationships 17 Genetic erosion? 20 Conclusions 22 References 23 Acknowledgements 30 Appendix Papers I-IV This thesis is based on the following papers, which will be referred to by their Roman
I. Kolodinska Brantestam, A., von Bothmer, R., Rashal, I. & Weibull, J. (2003) Changes in the genetic diversity of barley of Nordic and Baltic origin, studied by isozyme electrophoresis. Plant Genetic Resources Evaluation and Utilization 1, 143-149.
II. Kolodinska Brantestam, A., von Bothmer, R., Dayteg, C., Rashal, I., Tuvesson, S. & Weibull, J. (2004) Inter simple sequence repeat analysis of genetic diversity and relationships in cultivated barley of Nordic and Baltic region. Hereditas 141, 186-192.
III. Kolodinska Brantestam, A., von Bothmer, R., Dayteg, C., Rashal, I., Tuvesson, S. & Weibull, J. Genetic diversity changes and relationships in spring barley germplasm of Nordic and Baltic areas as shown by SSR markers (Submited).
IV. Kolodinska Brantestam, A., von Bothmer, R., Gullord, M., Rashal, I., & Weibull, J. Changes in variation of agronomic traits of Nordic and Baltic spring barley bred during the 20th century (Manuscript).
Taxonomy, domestication and distribution Barley is the fourth largest cereal crop in the world (FAO, 2004). It is globally grown in a wide range of habitats reaching to higher altitudes and latitudes and deeper into semi-arid areas than those of most other crops (Graner et al., 2003).
Cultivated barley Hordeum vulgare L. ssp. vulgare, belongs to the genus Hordeum, tribe Triticeae, family Poaceae. Besides H. vulgare there are another 31 species in this genus (Bothmer et al., 1995). The progenitor of cultivated barley is H. vulgare ssp. spontaneum – wild barley which has no crossing barriers to the crop (Asfaw & Bothmer, 1990). According to the genepool concept of Harlan and de Wet (1971) H. vulgare ssp. spontaneum belongs to the primary barley genepool. All other Hordeum species, except H. bulbosum (secondary genepool) belong to the tertiary genepool (Fig. 1). H. bulbosum shares the basic H genome with cultivated barley, but crosses with some difficulty to the crop (Bothmer et al., 2003).
Fig. 1. Genepools in cultivated barley (Hordeum vulgare L. ssp. vulgare) (Bothmer et al., 2003).
Clear evidence of early barley domestication and cultivation dates back approximately 10 000 years in the area of the Fertile Crescent (Zohary & Hopf, 1993; Harlan, 1995), which geographically corresponds to a region extending from Israel and Jordan, through Syria, Lebanon and southern Turkey, into Iraq and Iran (Fig. 2). One of the most important traits of domestication was probably nonbrittleness of rachis, which is of benefit for efficient harvesting without loss of grains (Bothmer et al., 2003). The two recessive genes brt1 and brt2, each responsible 4 for non-brittle rachis, arose through natural mutation and were later selected for during domestication (Takahashi, 1987).
Fig. 2. The Fertile Crescent, the area of early domestication of cultivated barley (H. vulgare L. ssp. vulgare) in the Middle East, distribution of the wild progenitor of barley (H. vulgare L. ssp. spontaneum) (within solid line) and approximate time, year before present (BP) for cultivated barley to reach different areas (Bothmer et al., 2003).
The major types of cultivated barley, based on combinations of hulled versus naked kernels and spike type, i.e. two-rowed versus six-rowed ears (Fig. 3), appeared during the early phases of plant cultivation in the Old World (Zohary & Hopf, 1993).
The ‘naked kernel’ and ‘six-rowed’ types were also spontaneous mutations. Sixrowed barley originated from at least two independent mutations at the vrs1 locus (Tanno et al., 2002). This type comprised some 90% of cereal crop production in ancient Mesopotamia (Harlan, 1970) and played a major role during later and more far-reaching expansions of agriculture (Fischbeck, 2002; Tanno et al., 2002).
Only the six-rowed ear type reached Northern Europe during the third and fourth
Barley in Northern Europe Applications and adaptation requirements to regional conditions Barley is one of the most important crops in northern Europe. Here it was historically used as one of the major food sources for humans. It also became the major source of malt needed by the brewing guilds that were formed in Europe during medieval times, from which modern malting and brewing industries later developed. Cultivation of barley for feed is a more recent development, but despite that most of the barley produced nowadays is used for this purpose. This fact relates to the decreasing importance of barley in food production (Fischbeck, 2002). Today in the Nordic and Baltic countries, the crop is used mainly for the feed and malt. In Denmark, for example, the need for feed barley is related to the pig-based meat export industry. In the south (Denmark, Lithuania, southern Sweden) two-rowed types of barley are mainly grown, and these types are generally preferred by the malting industry (Trolle, 1957; Persson, 1997;
Fischbeck, 2002). In the northern part of the region, early maturing, six-rowed types are more common (Ortiz et al., 2002).
In this region the northern limit for barley cultivation extends to high latitudes.
Because of warm currents that heat up the waters of the North Atlantic, the annual isotherm of +4 ºC is located further north than in other parts of the world (Fig. 4).
This is why arable land extends up to 67 ºN latitude in Finland (Mukula & Rantanen, 1987) and 70 ºN in Norway (Fageria et al., 1997).
Fig. 4. Temperature climate around 60 °N latitude for the annual isotherm +4 °C (Kalliola, 1951, cit Lomakka, 1958).
800000 600000 400000 200000 0 1920 1924 1928 1932 1936 1940 1944 1948 1952 1956 1960 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 2004
Fig. 5. Annual harvest area (ha) for barley in the Nordic and Baltic countries over 85 years of cultivation (Paatela, 1953; Statistiska Centralbyrån, 1959, 1970;
Danmarks statistik, 1968; Statistical Office of Estonia, 1991; FAO 2004, Official Agricultural Statistics Finland, http://www.ssb.no; http://www.stat.ee;
A brief history of barley breeding in the region An increase in crop yield per hectare has been a typical trend in Nordic and Baltic agriculture over the past century (Fig. 6). For example, in Sweden during the period 1886-1995 the yield increased 200-300% (Persson, 1997). Sub-surface drainage and mechanization have greatly increased both the efficiency and speed of soil cultivation, so that spring sowing can be accomplished earlier than before.
20000 10000 0 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
Fig. 6. Annual yield of barley in the Nordic and Baltic countries over 85 years of cultivation (Statistiska Centralbyrån, 1959, 1970; Yllö, 1962; Danmarks statistik, 1968;
Statistical Office of Estonia, 1991; FAO 2004, http://www.ssb.no; http://www.stat.ee;
When commercial barley breeding in the Nordic and Baltic countries began (end of 19th and early 20th century) (Kivi, 1963; Gaiĸe, 1992; Persson, 1997), the initial breeding material and new cultivars were selected from local landraces or introductions of foreign selections. Only a few landraces from the major-growing regions were successfully exploited for the selection of superior genotypes in Europe at that time. These were ‘Binder’, ‘Hanna’, ‘Hannchen’ and ‘Kneifel’ from Moravia; ‘Bavaria’ and ‘Danubia’ from Bavaria; ‘Gull’ and ‘Schonen’ from southern Sweden; and ‘Archer’ and ‘Plumage’ from England (Fischbeck, 1992).
However, in Norway and Finland breeders also used some locally adapted barley landraces (‘Bjørneby’, ‘Jaerbygg’ etc.) to improve earliness in their material.
Other adaptation traits, for example, resistance to soil acidity in the Finnish cultivar ‘Pirkka’ and the Swedish ‘Vega’ (Aikasalo, 1988) probably came from the local landraces in their pedigree. At the end of the 1920s and beginning of the 1930s, the first cultivars obtained through combination breeding were released in this area (Trolle, 1957; Gaike, 1992; Persson, 1997). Later, new cultivars were bred mainly through successive cycles of crosses between established pure lines (Fischbeck, 1992). During these periods of barley breeding, lines could be classified according to their origin from different landraces and/or the contributions from main ancestors (Melchinger et al., 1994) (Fig. 7). From the beginning of 1970, crossings became more complicated (Fig. 8).
During the 1960s and 1970s, the mutation breeding technique was applied and resulted in some new resistance genes, e.g. the Mlo-resistance (Helms Jørgensen,
Fig. 7. Pedigree of the Danish cultivar ‘Maja’ (1927) and the Finnish cultivar ‘Louhi’ (1934).
Landraces are rich sources of disease resistance, especially those from the centre of origin in the Fertile Crescent and regions where barley cultivation started early, e.g. Ethiopia and North Africa (Jana & Bailey, 1995; Yitbarek et al., 1998;