Diversity in Barley (Hordeum vulgare)

By Elsevier Science

Genetic diversity is one of the main resources sustaining human life. Food security largely depends on the availability and utilization of this diversity, which is of strategic importance for countries and companies. Conservation and utilization of biodiversity is thus currently an urgent area of global debate and concern.

Barley is a major crop in the world used for food, feed and malt, and with a wide religious and ethnic importance. The crop was domesticated in Neolithic time in SW Asia and spread rapidly under cultivation to new areas. Nowadays it is one of the most widespread and widely adapted crops grown under contrasting edaphic conditions. Adaptations to new environments, different agricultural practices and selection for different uses have further added to the complex diversity pattern.

Is it at all possible to give a complete picture of the diversity in a crop or wild species? Are we, by adding new technologies, only revealing parts of the diversity? Do different sets of data show similar or conflicting pictures of genetic diversity? Will the large genome size reduce the role of barley as a model organism in these current sequencing days? Or, are there still major reasons to continue to work with this beautiful crop?

The aim of this book is to cover the complex issue of diversification in time and space in a single crop: barley. Leading scientists from various fields describe the entire variation pattern in different sets of characters and an attempt is made for a synthesis to a holistic picture. The book proposes ways to use the achievements of diversity studies in future research and breeding programmes.

• Language: English
• Publisher: Elsevier Science
• Release date: Jul 3, 2003
• ISBN: 9780080530475

Book preview

barley

Section I - Introduction

Chapter 1

Barley diversity – an introduction

Roland von Bothmera, Kazuhiro Satob, Helmut Knupfferc and Theo van Hintumd,     aDepartment of Crop Science, Swedish University of Agricultural Sciences, Box 44, SE-230 53 Alnarp, Sweden; bBarley Germplasm Center, Research Institute for Bioresources, Okayama University, Kurashiki, 710-0046, Japan; cInstitute of Plant Genetics and Crop Plant Research (IPK), D-06466 Gatersleben, Germany; dPlant Research International B.V., Centre for Genetic Resources, The Netherlands (CGN), PO Box 16, NL-6700 AA Wageningen, The Netherlands

Biodiversity – a matter of global concern

Genetic diversity is one of the main resources sustaining human life on this planet. Without it, crops would not be able to adapt to changing biotic and abiotic conditions, they would soon disappear and leave us hungry. Food security largely depends on the availability and utilisation of this diversity, and there are very large economical interests at stake both in the food and the non-food sectors. It is a combination of these elements, which makes genetic diversity a commodity of strategic importance for countries and companies. However, due to the activities of man over the last few centuries, plant and animal species are dying out at a rate which has increased 1000-fold (Soulé, 1991). Plant populations are vanishing or becoming impoverished with regard to their genetic variation, the factor which would ensure their long-term survival and a necessary prerequisite for evolutionary changes.

The importance of conservation and utilisation of biodiversity has been widely recognised in recent years, and genetic resources have become a major issue of global concern and a driving force for political decisions. The issues of extinction, genetic erosion and possibilities for long-term conservation were the topics of the world conference in Rio de Janeiro in 1992 and the Convention of Biodiversity (CBD) which, since 1993, has been ratified by 180 countries (CBD, 2001). At one time, genetic diversity was considered to be a common heritage of mankind, but that is no longer the case since the Rio convention states national ownership over the native biodiversity. All countries are, however, interdependent with regard to the access to, and utilization of plant genetic resources. The particular issues concerning access to, utilisation and benefit sharing of the exploitation of plant and animal genetic resources are still unsolved problems. Therefore, a multinational agreement is urgently needed in order to secure increased efforts for conservation as well as for utilisation of plant genetic resources to broaden the genetic basis for breeding material.

The Rio declaration led to intensified activities of the FAO Commission on Genetic Resources, with for example, the initiative to report on the Current State of the World (SW; FAO, 1996a) based on information from individual countries. The Global Plan of Action (GPA) and the Leipzig Declaration (1996) stressed the issues of conservation and utilisation even further (FAO, 1996b). Based on the SW report, we now have a fairly good view of the general problems and status in the world, but the detailed knowledge of variation patterns, status of conservation of individual crops are far from being satisfactorily reviewed.

Genetic diversity also plays an important role in scientific research. To understand properly how plants grow and multiply, how populations develop and how species evolve, we need to improve our knowledge of distribution and function of genetic diversity. Since barley is one of the major crops in the world, it is natural that this interesting species is the focus of a book on diversity.

Importance of barley

Barley has a long history as a domesticated crop, as one of the first to be adopted for cultivation. Migration of people together with their seed crops led to a major diversification and adaptation to new areas, and the crop is now virtually found worldwide. Conscious selection of desired genotypes by farmers at an early stage, together with natural selection, increased the diversity and created the rich genepool source of variation found today in local varieties. These landraces also formed the basic material for modem plant breeding, which started some 150 years ago. The development of new technology and methods increased the genetic diversity even further and turned barley into the universal, highly diverse crop it is today.

The importance of the crop cannot be overestimated. Today it is cultivated on a total area of 55 million hectares (USDA-FAS, 2001), and is grown and used in fertile as well as in marginal areas under extreme conditions, including at altitudes up to 4,500 m in the Himalayas, in seasonally flooded areas in SE Asia, and in arid regions of the Mediterranean. Barley thus shows a very wide spectrum of adaptation. Over the centuries, barley has been planted for many different purposes. It was initially used as source of human food and animal feed. As a human staple food it has persisted until today in large regions in the mountainous areas of Central Asia, in southwest Asia and northern Africa including Ethiopia, where barley is still used for bread, porridge and tsamba (flour of roasted barley with black tea and yak butter). Its importance as an animal feed has increased over the years and barley is now one of the most important feed crops in temperate areas. Early on in the history of agriculture, man invented the processes of malting and brewing. For example, barley beer was one of the most important drinks in ancient Egypt. The processes have been refined and beer produced from pure malt as well as good malting barley varieties are currently in demand all over the world. Not to mention other beverages based on distillation, such as whisky and barley water (Central Asia) for which the special flavour and malting characteristics of barley are utilised. Special uses are the characteristic barley tea of Japan and Korea, pearled barley for mixing with rice in SE Asia, and barley grass as a functional food. Moreover, due to its specific characteristics, barley has also received attention in religious ceremonies or other rituals since ancient times.

One of the aims of this book is to review the present state of knowledge on diversity in a particular crop of global importance – barley. Over the last century, barley has been the subject of a great deal of scientific work, but, so far, no collective attempt has been made to produce a general review of the diversity of this important crop. Such a survey will eventually identify gaps in our current knowledge or in existing germplasm collections. It is our intention that this book will initiate further exploration and research.

Barley has the advantage, apart from being an important agricultural crop for food and feed, that it has also been used virtually worldwide as a model species for biological research. It is a diploid species with a low chromosome number (2n=14) possessing large chromosomes, and hence, a large genome. Over many decades, starting as early as in the 1930s, it has been the target of intense research on mutagenesis, mutagens, and mutants, particularly in Japan, Sweden and the USA (cf. Lundqvist, 1992). Pioneering works in the USA, Sweden and Germany have been dedicated to cytogenetics and chromosomal rearrangements, thus creating a fundamental knowledge of chromosomal structures (Hagberg et al., 1961; Hagberg, 1986). Other fields of importance have been the basic work on morphological and adaptational differentiation mainly by Russian scientists (Sinskaya, 1969; Trofimovskaya, 1972; Lukyanova et al., 1990), and on principles of evolution and domestication (cf. Zohary and Hopf, 1993; Bothmer et al., 1995). Barley has also been a target organism for more practical approaches such as conservation and gene-banking (cf. Hintum and Visser, 1995), creation of core collections (cf. Hintum and Haalman, 1994; Knüpffer and Hintum, 1995), and plant breeding methodology for self-pollinating crops (Sunesson, 1963). Over the last decade, a great number of studies have been directed at research on molecular markers and genetic diversity for conservation and utilisation.

This book makes one thing very clear: there is a large diversity in barley, but there is possibly an even larger diversity in barley research. These two levels of diversity provide an excellent starting point for a book.

Components of the book

This book describes various aspects of the genetic diversity found in barley. It starts with a section on the origin of the current diversity. Chapters 2 and 3 put the genus Hordeum, its various species and macro-geographical groups into a genetic and historical context. They also explain how the current genetic diversity was shaped in nature and by man. The evolutionary and the domestication processes are described together with the early migration of the crop, and the results of breeding efforts in ancient as well as in modem times.

The diversity can be measured or assessed by a number of different methods, each showing a specific pattern, and it may often be difficult to compare sets of data obtained by different techniques. How can we compare the importance of a molecular marker study with a study of disease resistance or yield? The section includes detailed descriptions of various aspects of barley diversity. It starts with a, nowadays, rather unusual way of looking at the morphological and adaptational diversity in barley. Using the ecogeographical differentiation of the crop as a starting point, the resulting morphological peculiarities of the locally adapted material are described in the Vavilovian tradition (Chapter 4). Chapter 5 describes natural and induced mutations, which have received particular attention by the molecular geneticists, as a number of induced mutations allow physiological processes to be unravelled. The cytogenetic diversity pattern includes the variation found in chromosomal rearrangements, such as translocations, deletions, trisomics, heterochromatic regions, all of which have been thoroughly studied in barley over many years (Chapter 6). A wealth of new and interesting techniques for surveying the diversity have been developed over the last few decades, including biochemical and molecular markers, and numerous studies have contributed to our knowledge of the genetic variation patterns (Chapter 7). The diversity in response to stress is dealt with in two chapters, one on biotic and one on abiotic stress (Chapters 8 and 9, respectively). The first is a comprehensive survey of diseases and pests, and the genetic diversity to resist them. Chapter 9 lists abiotic stresses and the mechanisms and genetic background found in barley to adapt to, or tolerate them. The section is concluded by a discussion on quality characters and particularly the QTL variation in barley, what is known and what can be expected to be found (Chapter 10).

After describing the genetic diversity, another section will look at how genetic diversity can be utilised. It starts with a visionary chapter, a source of ideas about how information on genetic diversity in barley can be efficiently gathered, and how a holistic multivariate approach could result in new information on genotypes hidden behind complex phenotypes, viz. the new area of bioinformatics (Chapter 11). Barley is one of the most frequently collected crops, and barley accessions are widely distributed in genebanks. Chapter 12 sheds some new light on the diversity conserved and how to identify gaps and redundancies in existing collections. In the last part of the section, one chapter (13) is devoted to the International Barley Core Collection (BCC), a research tool which summarises the genetic diversity in barley in an accessible, optimised collection of barley lines, landraces and wild species in a growing base of knowledge about the material.

The concluding chapter presents a view on barley diversity, discusses various issues arising from the information presented in the book, composes the various chapters and searches for consensus and discrepancies.

Conventions

A few conventions have been used throughout the book. Most of them are of a typographical and editorial nature, such as the style of references and the way names of cultivars are written. Other matters are less trivial.

For reasons of convenience an attempt was made to use a single taxonomic classification system consistently throughout the book (cf. Bothmer et al., 1995). This implies that, for example, the closest wild ancestor of cultivated barley is referred to as Hordeum vulgare L. ssp. spontaneum (C. Koch) Thell., or simply ssp. spontaneum, and all cultivated barleys as H. vulgare ssp. vulgare.

The nomenclature for designating barley genes and mutations has been a matter of intense discussion and disagreement over the years; several suggestions for gene designations have been proposed. At the 7th International Barley Genetics Symposium (IBGS) in Saskatoon, Canada in 1996, a consensus was reached where each gene is symbolised by a three-letter code. This system was proposed by Lundqvist et al. (1996), and their publication includes a detailed description of all known genes in barley. This system has been adopted and followed in the book.

Just like the gene symbols, the genomic constitution and designation of barley (Hordeum vulgare) and its wild allies in the genus Hordeum has been a matter of controversy over the years. Likewise at the 7th IBGS in 1996, a decision was taken that barley (H. vulgare s. lat.) and its secondary genepool relative (H. bulbosum) contain the genome named H, and the major part of other Hordeum species have the genome I, or still imperfectly known genomes, named Xa and Xy, respectively (Bothmer et al., 1995; Linde-Laursen et al., 1997). At the same meeting, the numbering sequence of the barley chromosomes was changed (1H-7H) to be congruent with the numbering system in wheat to which the barley chromosomes are homoeologous (Linde-Laursen et al., 1997). These recommendations are followed throughout this book.

Whenever possible, genebank accession numbers are given of material described. These numbers can usually be recognised via a preceding letter code, such as CI for the material in the USDA collections, HOR for the material in the collection of the genebank of IPK, Gatersleben, or K for material in the collection of the Vavilov Institute, St. Petersburg. This material is, in principle, available for interested scientists and breeders.

Closing remarks

What image do we form if we cannot see the elephant, but only touch it? Will the descriptions of one person feeling the leg conflict with those of another person feeling the ear or the tusk or the trunk? This book is written in an attempt to create as complete a picture of the elephant as possible, by bringing together the descriptions of all aspects observed.

The book is a tribute to all scientists who created the basis of current knowledge of barley, naming only the two legendary scientists N.I. Vavilov (Loskutov, 1999) of the former Soviet Union and Henry Harlan (Harlan and Martini, 1936; Harlan, 1957) of the USA. Both have made fundamental contributions to the knowledge of genetic diversity in barley through their life-long compassion for collecting barley germplasm around the world. The editors would, in particular, like to dedicate this book to the memory of the nestor of barley genetic research, namely the late Professor R. Takahashi of Japan.

Finally, the editors wish to stress not only the important prosaic utilisation of the crop as a food, feed or malt or the exciting scientific development but also the beauty of the barley plant. What can be more beautiful than an individual, vigorous barley plant with its long and delicate awns or a whole heading field moving in the wind.

Acknowledgements

A publication aimed to review genetic diversity comprising contributions by various authors must by necessity be as diverse in thoughts and ways of presentation as reflected by the different authors. This diversity contributes to an added value to the publication. We are most grateful to authors of the different chapters for taking their tasks seriously, which has resulted in valuable, interesting and comprehensive contributions.

A publication will not be successful without a positive, patient and promoting publisher. We acknowledge Elsevier Science for being encouraging and cooperative during the process of development of the book. Thanks are due particularly to Ms. Brenda Völlers for skilful corrections of all manuscripts.

The International Barley Genetics Symposium, being the platform and providing the network for joint barley research and international collaboration, has been an important forum of great value for the finalisation of this book.

The Nilsson-Ehle Foundation, Lund, Sweden, is gratefully acknowledged for providing grants for the publication of colour illustrations.

The process of completion of this book has been promoted by our respective organizations providing working facilities and other support for the editors, and therefore we wish to acknowledge:

Department of Crop Science, The Swedish University of Agricultural Sciences, Alnarp, Sweden

Centre for Genetic Resources The Netherlands (CGN), part of Plant Research International, Wageningen, The Netherlands

Genebank Department, Institute of Plant Genetics and Crop Plant Research (IPK), Gatersleben, Germany

Barley Germplasm Centre, Research Institute for Bioresources, Okayama University, Kurashiki, Japan

References

Bothmer, R. von, Jacobsen, N., Baden, C., Jørgensen, R.B., Linde-Laursen, I., An ecogeographical study of the genus Hordeum, 2nd e. Systematic and Ecogeographic Studies on Crop Genepools, 7. IPGRI: Rome, 1995.

info January 2001 CBD, Convention on Biological Diversity, 2001. http://www.biodiv.org/Index.html.

510 p FAO. FAO State of the World’s Plant Genetic Resources for Food and Agriculture. Food and Agriculture Organization of the United Nations, 1996.

63 p FAO. Global Plan of Action for the Conservation and Sustainable Utilization of Plant Genetic Resources for Food and Agriculture and the Leipzig Declaration. Food and Agriculture Organization of the United Nations: Rome, 1996.

Hagberg, A., Barley as a model crop. Barley Genetics V. Proc. 5th Int. Barley Genet. Symp. Okayama, Japan, 1986:823–831.

Hagberg, A., Ramage, T., Burnhman, C. A summary of translocation studies in barley. Crop Sci. 1961;1:277–279.

Harlan, H.V. One Man’s Life with Barley. Exposition Press: New York, 1957.

Harlan, H.V., Martini, M.L. Problems and Results in Barley Breeding. U.S. Dept. Agric. Yearbook of Agriculture, 1936.

Hintum, Th.J.L. van, Haalman, D. Pedigree analysis for composing a core collection of modern cultivars, with examples from barley (Hordeum vulgare s. lat). Theor. Appl. Genet. 1994;88:70–74.

Hintum, Th.J.L. van, Visser, D.L. Duplication within and between germplasm collections. II. Duplication in four European barley collections. Genet. Res. Crop Evol. 1995;42:135–145.

Knüpffer, H., van Hintum, Th.J.L. The Barley Core Collection—an international effort. In: Hodgkin T., Brown A.H.D., van Hintum Th.J.L., Morales E.A.V., eds. Core Collections of Plant Genetic Resources. UK: John Wiley and Sons; 1995:171–178.

Linde-Laursen, I., Heslop Harrison, J.S., Shepherd, K.W., Taketa, S. The barley genome and its relationship with the wheat genomes. A survey with an internationally agreed recommendation for barley chromosom nomenclature. Hereditas. 1997;126:1–16.

part 2 Lukyanova, M.V., Trofimovskaya, A.Ya., Gudkova, G.N., Terentyeva, I.A., Yarosh, N.P. [(in Russian)] Flora of cultivated plants, vol. 2. Agropromizdat: Barley. Leningrad, 1990.

Lundqvist, U. Mutation research in barley. PhD thesis at The Swedish University of Agricultural Sciences. 1992.

188 p Loskutov, I.G. Vavilov and his Institute. A history of world collection of plant genetic resources in Russia. Rome: IPGRI; 1999.

(In Russian) Sinskaya, E.N. Historical geography of the cultivated flora. Leningrad: Kolos; 1969.

Soulé, M.E. Conservation: tactics for a constant crisis. Science. 1991;253:744–750.

Sunesson, C.A., Breeding techniques-composite crosses and hybrid barley. Barley Genetics I. Proc. 1st Int. Barley Genet. Symp. Wageningen, The Netherlands, 1963:303–309.

(In Russian) Trofimovskaya, A.Ya. Barley (evolution, classification, breeding). Leningrad: Kolos; 1972.

info January 2001 USDA-FAS, United States Department of Agriculture-Foreign Agricultural Service, 2001. http://www.fas.usda.gov/.

Zohary, D., Hopf, M. Domestication of Plants in the Old World. Oxford Science Publications, 1993.

Uncited References

Lundqvist, U., Franckowiak, J.D., Konishi, T. New and revised descriptions of barley genes. Barley Genet. Newsl. 1996;26:22–516.

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Bothmer, R. von, K. Sato, H. Knüpffer and Th. van Hintum, 2003. Barley diversity – an introduction. In: R. von Bothmer, Th. van Hintum, H. Knüpffer and K. Sato (eds), Diversity in Barley (Hordeum vulgare), pp. 3-8. Elsevier Science B.V., Amsterdam, The Netherlands.

Section II - Origin of Barley Diversity

Chapter 2

The domestication of cultivated barley

Roland von Bothmera, Kazuhiro Satob, Takao Komatsudac, Shozo Yasudab and Gerhard Fischbeckd,     aDepartment of Crop Science, Swedish University of Agricultural Sciences, Box 44, SE-230 53 Alnarp, Sweden; bBarley Germplasm Center, Research Institute for Bioresources, Okayama University, Kurashiki, 710-0046, Japan; cNational Institute of Agrobiological Sciences, Kannondai, Tsukuba, 305-8602, Japan; dDepartment of Agronomy and Plant Breeding, D-85350 Freising-Weihenstephan, Germany

Taxonomic position of barley

Together with wheat (Triticum aestivum L.), rye (Secale cereale L.), and several important forages, like Russian wildrye (Psathyrostachys fragilis (Boiss.) Nevski) and crested wheatgrass (Agropyron cristatum (L.) Gaertn.), barley belongs to the tribe (tribus) Triticeae. This tribe represents a highly successful evolutionary branch in the grass family (Poaceae) and comprises a vast number of species and genera. The numerous wild species are thus potential gene sources for cereal breeding. The Triticeae comprises very complex modes of speciation, including polyploidy, interspecific and intergeneric hybridizations, which have resulted in a reticulate pattern of relationships. There are still major disagreements among taxonomists especially with regard to generic delimitations. No comprehensive systematic review of Triticeae has been presented in recent years (cf. Löve, 1984).

The tribe is distributed worldwide in all major temperate areas and is even present in the subtropics. Because of the large distribution area and the fact that diversity centres are confined to remote areas, which have not yet been fully explored botanically, there is still much basic taxonomic research to be done on species in the Triticeae. There is even a considerable uncertainty as to the number of species in the tribe, ranging from ca. 325 (Dewey, 1984) to ca. 500 (Löve, 1984).

Triticeae is considered to be monophyletic and is a good example of a plant group with a high degree of biological diversity including, for example, several genomes, various degrees of polyploidy, versatility in life forms, reproductive and dispersal patterns (Dewey, 1984).

The genus Hordeum and the genepools of barley

Barley, Hordeum vulgare L., is placed in Hordeum, which is a moderately sized genus with ca. 32 species and altogether ca. 45 taxa (Table. 2.1; cf. Bothmer et al., 1995, for review and references). All species in Hordeum have a similar set of diagnostic, morphological characters, particularly with three, one-flowered spikelets at each rachis node, called a triplet. The two lateral florets are pedunculate, or sessile and may be sterile (as in two-rowed barley) or fertile (as in six-rowed barley). The glumes are setaceous or flattened and placed on the adaxial side of (and not surrounding) the spikelet.

Table 2.1

Taxa in the genus Hordeum, their distribution, chromosome numbers and life forms.