The Key Roles of Seed Banks in Plant Biodiversity Management in New Zealand

Invited Address

The key roles of seed banks in plant biodiversity management in New Zealand

W.M. WILLIAMS Margot Forde Forage Germplasm Centre, AgResearch Grasslands, Private Bag 11008, Palmerston North, New Zealand [email protected]

Abstract species of seed plants (1,300 species of The New Zealand flora is a mixture of dicots, 470 monocots and 20 gymnosperms), indigenous and introduced species. The with a high degree of endemism (Allan indigenous species have a high intrinsic 1961; Moore & Edgar 1970; Webb et al. value while the introduced species include 1988; Edgar & Connor 2000). This native all of the crop and pasture plants upon which flora has both intrinsic and economic value the export-led economy depends. New and must be conserved because of its Zealand must maintain both of these botanical uniqueness, importance in land important sources of biodiversity in balance. stability and water quality and roles in Seed banks are useful tools for biodiversity providing the authentic New Zealand management. In New Zealand, a seed bank experience. The adventive flora is about the for indigenous species has been a very recent same size, consisting of approximately 1,420 initiative. By contrast, seed banks for dicots, 400 monocots and 30 gymnosperms introduced species have been established for (Healy & Edgar 1980; Webb et al. 1988; over 70 years. The reasons for this Edgar & Connor 2000; Heenan et al. 2008). discrepancy are discussed. For the economic In addition, there are over 30 000 introduced species, conserved genetic diversity is used plant species in New Zealand that have not to enhance productivity and the established self-sustaining populations (New environment. Large advances can be gained Zealand Plant Conservation Network 2005). from species that are not used as economic It is the adventive flora that supports the plants. The gene-pool of white clover has current New Zealand population of 4 million been expanded by the use of minor species people by providing food and fibre, $13 conserved as seeds in the Margot Forde billion of export earnings annually (New Germplasm Centre. Zealand Official Yearbook 2008) and a Keywords: Seed banks, biodiversity significant contribution to the domestic conservation, New Zealand flora economy, as reflected in its contribution to GDP. The role of introduced species in Status and sizes of introduced and native providing the unique tourist experience floras should not be under-estimated either, as The New Zealand flora consists of a mix of many of our landscapes are composed of indigenous and introduced plant species that mixtures of adventive and native occur mainly in separate ecosystems that are ecosystems. Because they are usually generally complementary, but can have managed separately, the tensions between tensions at the boundaries (Healy & Edgar indigenous and adventive ecosystems can 1980). The New Zealand indigenous flora is carry-over to the separate groups of people unique. There are approximately 1,800 who manage them for differing outcomes. 6 Agronomy Society of New Zealand Special Publication No. l3 / Grassland Research and Practice Series No. 14

One example is the importation and that these populations are likely to be conservation of introduced plants, which is genetically divergent. The conservationist often seen as undesirable by the ecological recognises that keeping the seeds of just one community but essential to the economy by of these populations will not do, because it is the agricultural community. The balance of important to use locally adapted (‘eco- this tension was altered when the sourced’) genetic material if a local plant government passed the Hazardous community has to be restored. There is Substances and New Organisms (HSNO) strong genetic evidence that knowledge of Act (1996) that effectively made importation place of origin is one of the strongest of new organisms difficult and expensive. indicators of genetic diversity available to This has placed plant importation largely on- us. Research using molecular markers on hold, and it may be several decades before ‘core collections’ (collections designed to the potentially serious negative economic represent the maximum amount of the effects are realised. Meanwhile, the genetic diversity of a species, but in a interactions between native and introduced limited number of accessions) revealed that species go on unaffected and we really need a collections with optimal eco-geographic to ask ourselves if any of the conservation representation usually show maximum issues around the native flora have been genetic diversity (Ghamkhar et al. 2007). altered by the legislation. We also need to recognise, as some of our most eminent The roles of seed banks in biodiversity botanists have (e.g., Healy & Edgar 1980) conservation and management that the New Zealand flora is a mixed one, Seed banks are an efficient way of with different elements that should and can conserving ex situ a huge amount of genetic be managed together and not separately. diversity in a single room. The advantages are that about 90% of seed plants have Biodiversity and ecosystems orthodox seeds (seeds that are amenable to Biodiversity is simply genetic diversity; but long-term storage under refrigeration at low genetic diversity is not simple. The temperatures), multiple collections can be ecosystem is one level of classification of conserved in a small space and database biodiversity. The ‘species’ is another level of systems enable the recording of multiple classification of biodiversity, and there are eco-geographic details on each seed various ways of defining species (e.g., population. Seeds from seed banks can be Rieseberg & Willis 2007). Within a species, used for both conservation and restoration of populations tend to be genetically differ- plant populations. Ideally, ex situ systems entiated among themselves by migration, serve only as back-ups to in situ mutation and selection. For natural and conservation systems, where biodiversity is naturalised populations, the terms ‘ecotype’ maintained in living ecosystems, e.g., in and ‘variety’ are used to designate national parks. However, idealism is not conspicuous inter-population diversity. sufficient and, in New Zealand, seed banks However, genetic diversity is not always are needed to play a significant part in conspicuous, and the designation of place of securing against environmental and origin is usually enough to suggest the biological threats that cannot be covered by likelihood of genetic diversity. For these, the in situ conservation, as outlined below. terms ‘provenance’, ‘collection’ and ‘accession’ are used to suggest differences Rationale for a New Zealand native plants between native/naturalised plant populations seed bank of the same species, say, in the Manawatu or A seed bank for endangered native plant on Banks Peninsular. The geneticist tells us species is a very recent initiative (2007)

The key roles of seed banks in plant biodiversity management in New Zealand (W.M. Williams) 7

taken by the New Zealand Plant Rationale for New Zealand introduced Conservation Network, with strong support species seed banks from the Department of Conservation Almost all of New Zealand’s biological (DoC). The need for such a facility had been economy is based on plant species that are recognised in the New Zealand Biodiversity native to other countries, and the most Strategy (Anon. 2000) in response to the fact suitable of these species are needed. This that 120 vascular species/subspecies are economy is highly vulnerable to multiple acutely threatened with extinction, 94 are existing and emerging threats from pests, chronically threatened and a further 496 are diseases and environmental changes, such as at some risk (de Lange et al. 2004). It was climate change. Progress in the development also noted that future environmental of new markets can also require new or changes, especially climate change, would different plants. These changes have exacerbate this problem. Although in situ previously required modification of, and will conservation programmes are already in the future require us to continually underway for some species, other species are modify, the economic plants that we grow. not covered. In addition, the in situ To be fully effective, plant breeders need to programmes are often not well documented be about 20 years ahead of these changes. and are also threatened by both Given our long distance from the sources of environmental and biological risks. most of the key plant species, it can be Recognising that 92% of New Zealand difficult to access new genetic diversity vascular plants are seed-bearing species and, quickly. Delays are exacerbated by the therefore, potentially amenable to long-term requirement under international agreements storage of dormant seed, it was sensible to to negotiate with countries of origin, by recommend a move toward development of biosecurity restrictions on arrival in New a seed bank. Based on the wider literature on Zealand and by the time needed to develop seed banks, e.g., Linington (2003), it was populations that are adapted to local anticipated that approximately 90% of conditions. For these reasons, each of the species would have orthodox seeds and so major biological plant industries (forest, be amenable to storage. Although there has field crops, vegetables, horticultural, crops, been little research on the storage pastures) has established collections of characteristics of New Zealand species (Hill genetic resources (Forde et al. 1985). One of 2004), the seed bank option nevertheless these is the Margot Forde Forage offered a potentially efficient solution. The Germplasm Centre, a seed bank established primary objective is not to bank the whole in the 1930s as a crucial collection of the flora, but to provide insurance support for world’s grassland genetic diversity. This the conservation of the most endangered diversity is immediately available to the species. This currently means about 50 pastoral industries and provides an insurance critically threatened species that have policy against future change. orthodox seeds. A possible secondary role of The Centre currently holds seeds of over the seed bank could be to store seeds 80,000 entries of about 2,000 plant species. harvested in good years for future restoration The collections have been developed and of populations. The seed bank was maintained for over 70 years. These have a established in August 2007 by the New monetary replacement value that is very high Zealand Plant Conservation Network, and is and cannot realistically be estimated. The hosted by the Margot Forde Forage collections are maintained and expanded Germplasm Centre, AgResearch Grasslands according to industry and research needs. Research Centre, Palmerston North and is Seeds are distributed for plant breeding and initially sponsored by MWH (NZ) Ltd. for genetic/genomic and other research

8 Agronomy Society of New Zealand Special Publication No. l3 / Grassland Research and Practice Series No. 14

projects. Unique and valuable samples are The contrasting roles of the New Zealand identified and, where necessary, seeds are seed banks replenished. Seed imports are managed Seed banks can be used for a range of under permits from the Environmental Risk purposes, including the following: Management Authority (ERMA) and MAF 1. ‘species bank’ – to conserve species Biosecurity. (generally back-up to in situ measures); Where possible, research on the genetic 2. ‘population bank’ – to conserve genetic diversity of the collections is carried out and diversity within species (this sometimes used to optimise the seed replenishment includes population restoration); programme as well as to identify potentially 3. ‘genome bank’ or ‘gene-pool bank’ – to valuable new genes for industry use. conserve sets of related species that may be Diversity in pasture species is essential. able to share genomes in a single gene-pool; Although ryegrass and white clover appear 4. ‘breeding bank’ – to conserve selected to predominate, there are many different families of interbreeding genotypes or genetic populations contributing to a very 5. ‘gene bank’ – to conserve genetic stocks large amount of variation in these species. resulting from individual gene differences. The best grass species or variety for a In the current New Zealand context, the new northern dairy farm is not the best for a endangered species seed bank and the older southern sheep farm. The current best grass introduced species seed bank have very for that southern sheep farm will not the best contrasting roles. The endangered species be one in five years time because the bank is both a species bank and a population pastoral environment is constantly changing bank. It serves to conserve species that – the climate, farming systems and pests otherwise might be lost. It also stores seeds change. New pasture plants are constantly of regional populations so that regional needed and that is why we need the seeds diversity is conserved and restoration of here in New Zealand – now. local populations can be achieved in future. Some visionary scientists began this seed By contrast, the introduced species seed collection about 70 years ago. It is a crucial bank serves all of the purposes listed above. collection of genetic diversity – and an It is designed to provide the country with insurance policy against future change. It access to the maximum amount of genetic enables the New Zealand pastoral industries diversity of key species for economic use. to respond to anticipated changes needed in Included among its key roles are the storage the feed-base and prepare for the future. In a of seeds of so-called ‘minor species’, of study commissioned by MAF Policy, breeding families and also genetic stocks. Lancashire (2006) calculated that, in the last 30 years, overseas germplasm imported Importance of minor species through the Centre has contributed over The number of plant species sown in New $700 million annually to the approximately Zealand pastures is fewer than 40. In fact, $14 billion annual revenue from pastoral only three species, perennial and Italian agriculture. International collections can also ryegrasses and their hybrids, and white benefit the countries of origin, because seed clover dominate the seed production samples are generally shared with those statistics, with the remainder less used. As countries. Parallel values can be placed on mentioned above, the germplasm centre the genetic resource collections of the other stores seeds of nearly 2,000 different New Zealand biological sectors, although grassland species. What is the strategic value these are not entirely seed-based. of storing over 1,900 species that are apparently unused? The primary reason is that such species can be of very high value.

The key roles of seed banks in plant biodiversity management in New Zealand (W.M. Williams) 9

First, they can be potentially useful in their Examples of the potential value of minor own right, especially as environmental species changes occur. For example, we need think So-called minor species are often the wild only about climate warming to realise that relatives of important crop plants. They subtropical grasses may soon be very useful constitute the secondary and tertiary gene components of New Zealand pastures (Crush pools of these crops (Harlan & de Wet & Rowarth 2007). The Margot Forde Forage 1971). Examples of their use in enhancing Germplasm Centre has over 1,000 the gene-pools of cereals and legumes have accessions of about 150 species of tropical been reviewed by Dwivedi et al. (2008). and subtropical species stored ready for There are some excellent New Zealand future use (Williams 1996). Another examples in barley breeding, where the wild potential value of unused species could be barley species Hordeum bulbosum has been for the development of new functions for used to transfer multiple disease resistances future farm systems, e.g., carbon to cultivated barley (Pickering & Johnstone sequestration, mitigation of nutrient run-off. 2005). Another wild relative, H. vulgare ssp. Although, in New Zealand, the numbers of spontaneum, is also a source of disease newly domesticated agricultural species are resistances and drought tolerance. Similar low, the international research community is principles are currently being used to expand continually adding new species. For the gene-pool of white clover. In this work, example, Bituminaria bituminosa var. molecular phylogenetics has proved to be albomarginata from the Canary Islands is extremely valuable in determining the most being developed as a new perennial pasture likely closest relatives of white clover plant in Western Australia for areas with (Ellison et al. 2006). A group of 10 clover annual rainfall as low as 250 mm (Real species and subspecies from Europe and 2008). Second, so-called minor species may Eurasia has been identified as ‘the white contribute to the gene-pools of already clover species complex’. These are all established species. It is in this area that species that, on the basis of sequence minor species can play major roles in analyses of nuclear DNA (internally advancing genetic improvement of transcribed spacer region of the 45S agricultural plant species. ribosomal repeats) and chloroplast DNA (the trnL intron) are closely related and, indeed, appear to have evolved as a species lineage (Table 1). Every one of these taxa has been crossed with at least one other in the species

Table 1 The ‘white clover species complex - Trifolium species and traits that can contribute to the gene-pool of white clover through wide hybridisation. Species Potentially useful traits T. ambiguum Rhizomes, deep roots, drought tolerance, pest resistances T. uniflorum Drought tolerance T. occidentale Drought, salt tolerance T. nigrescens Seed production, pest resistance, heat tolerance T. isthmocarpum Salt, water-logging tolerance T. thalii Rapid establishment, cold tolerance T. pallescens Cold tolerance

10 Agronomy Society of New Zealand Special Publication No. l3 / Grassland Research and Practice Series No. 14

complex, indicating the potential for using manuscript by Drs. Marty Faville and Mike interspecific hybridisation to transfer traits Dodd. from species to species within the group (Williams et al. 2006). The primary gene- References pool (the natural intra-specific genetic Allan, H.H. 1961. Flora of New Zealand. variation) of white clover lacks many Volume I Indigenous Tracheophyta. potentially useful traits that are carried by Psilopsida, Lycopsida, Filicopsida, other species in the complex (Table 1). Gymnospermae, Dicotyledones. These include deep roots, rhizomes, drought Government Printer, Wellington, and heat tolerance, virus and nematode New Zealand. 1085 pp. resistances, salinity and water-logging Anon. 2000. The New Zealand Biodiversity tolerance. The transfer of these traits by Strategy. Prepared by the conventional hybridisation into the white Department of Conservation and clover gene-pool will ensure that new Ministry for the Environment with clovers can be bred that will be able to assistance from other government withstand climate change and other agencies, Wellington, New Zealand. environmental pressures. In fact, the 142 pp. potential gains can be much greater even Crush, J.R.; Rowarth J.S. 2007. The role of than this. Minor species frequently carry C4 grasses in New Zealand pastoral extremely useful genes that are masked, but systems. New Zealand Journal of which can contribute large genetic gains Agricultural Research 50: 125-137. when transferred into the major species de Lange, P.J.; Norton, D.A.; Heenan, P.B.; (Tanksley & McCouch 1997). It is likely Courtney, S.P.; Molloy, B.P.J.; Ogle, that this will occur when white clover is C.C.; Rance, B.D.; Johnson, P.N.; crossed with its wild relatives. This is an Hitchmough, R. 2004. Threatened example of not only how molecular and uncommon plants of New techniques are enabling future plant breeding Zealand. New Zealand Journal of to be more efficient, but also of how Botany 42: 45-76. apparently minor species tucked away in Dwivedi, S.L.; Upadhyaya, H.D.; Stalker, seed banks can contribute potentially very H.T.; Blair, M.W.; Bertioli, D.J.; usefully to the future economy. Nielan, S.; Ortiz, R. 2008. Enhancing crop gene pools with beneficial traits Conclusions using wild relatives. Plant Breeding Seed banks play vital roles in ensuring the Reviews 30: 179-230. future of New Zealand’s biodiversity. They Edgar, E.; Connor, H.E. 2000. Flora of New provide the necessary protection for Zealand. Volume V. Grasses. Manaaki indigenous seed plant biodiversity as well as Whenua Press, Lincoln, New Zealand. continuing access to the overseas 650 pp. biodiversity required for economic Ellison, N.E.; Liston, A.; Steiner, J.J.; development of the biological export Williams, W.M.; Taylor, N.L. 2006. economy. Molecular phylogenetics of the clover genus (Trifolium – Leguminosae). Acknowledgements Molecular Phylogenetics and The author is grateful to all members of the Evolution 39: 688-705. Genetic Diversity Team at AgResearch Forde M.B.; Burdon, R.D.; Dawes, S.N.; Grasslands who work to maintain and Dunbier, M.W.; Given, D.R.; Park, research the New Zealand flora. Very G.N. 1985. Report of the ad hoc helpful comments were made on the Committee on Conservation of Plant

The key roles of seed banks in plant biodiversity management in New Zealand (W.M. Williams) 11

Genetic Resources in New Zealand. Gramineae. Government Printer, Proceedings of the Royal Society of Wellington, New Zealand. 354 pp. New Zealand for 1985 113: 117-133. New Zealand Official Yearbook 2008. In: Ghamkhar, K.; Snowball, R.; Bennett, S.J. Exports 2007. pp. 459-466. 2007. Ecogeographical studies Statistics NZ, David Bateman, identify diversity and potential gaps Auckland, New Zealand. in the largest germplasm collection New Zealand Plant Conservation Network. of bladder clover (Trifolium 2005. Naturalised plants. Retrieved 8 spumosum L.). Australian Journal of October, 2008 from Agricultural Research 58: 728-738. http://www.nzpcn.org.nz/exotic_plant_li Harlan, J.R.; de Wet, J.M.J. 1971. Toward a fe_and_weeds/index.asp rational classification of cultivated Pickering, R.; Johnstone, P.A. 2005 Recent plants. Taxon 20: 509-517. progress in barley improvement Healy, A.J.; Edgar, E. 1980. Flora of New using wild species of Hordeum. Zealand. Volume III. Adventive Cytogenetic and Genome Research Cyperaceous, Petalous & Spathaceous 109: 344-349. Monocotyledons. Government Printer, Real, D. 2008. Summer feed production Wellington, New Zealand. 220 pp. from perennials. Retrieved 8 Heenan, P.B.; de Lange, P.J.; Cameron, October, 2008 from E.K.; Parris, B.S. 2008. Checklist of http://www.futurefarmcrc.com.au/ dicotyledons, gymnosperms, and documents/summerfeedpotentialfro pteridophytes naturalised or casual in mperennials.pdf New Zealand: additional records Rieseberg, L.H.; Willis, J.H. 2007. Plant 2004-06. New Zealand Journal of speciation. Science 317: 910-914. Botany 46: 257-283. Tanksley, S.D.; McCouch S.R. 1997. Seed Hill, M. 2004. Propagation by seed. pp. 168- banks and molecular maps: 178. In: Making use of New unlocking genetic potential from the Zealand’s plants. Going Native. Eds. wild. Science 277: 1063-1066. Spellerberg, I; Given, D. Canterbury Webb, C.J.; Sykes, W.R.; Garnock-Jones, University Press, Christchurch, New P.J. 1988. Flora of New Zealand. Zealand. Vol. IV. Naturalised Pteridophytes, Lancashire J.A. 2006. The importance of Gymnosperms, Dicotyledons. Botany exotic germplasm to the NZ Division, DSIR, Christchurch, New livestock industry. pp. 1034-1041 In: Zealand. 1365 pp. Proceedings of the 13th Australasian Williams, W.M. 1996. Genetic resources of Plant Breeding Conference. temperate native and low-input Linington, S.H. 2003. The design of seed grasses in New Zealand and banks. pp. 591-636. In: Seed Australian collections. New Zealand conservation: turning science into Journal of Agricultural Research 39: practice. Eds. Smith, R.D.; Dickie, 513-526. J.B.; Linington, S.H.; Pritchard, Willliams, W.M.; Verry. I.M.; Ellison, N.E. H.W.; Probert, R.J. Royal Botanic 2006. A phylogenetic approach to Gardens, Kew, London, United germplasm use in clover breeding. Kingdom. pp. 966-971. In: Proceedings of the Moore, L.B.; Edgar E. 1970. Flora of New 13th Australasian Plant Breeding Zealand. Vol. II. Indigenous Conference. tracheophyta. Monocotyledons except