Small Fruit Crop Germplasm Committee Vulnerability Statement - (April 2000)

The Small Fruit Crop Germplasm Committee Vulnerability Statement was assembled in four parts based on the major small fruit genera as follows:

I. Fragaria
Coordinators: James Hancock, Michigan State University; James Luby, University of Minnesota

II. Ribes
Coordinator: Kim Hummer, USDA-ARS National Clonal Germplasm Repository, Corvallis, Ore.

III. Rubus
Coordinators: Chad Finn, USDA-ARS, Corvallis, Ore.; Carlos Fear, Sweetbriar Development Inc., Watsonville, Cal.

IV. Vaccinium
Coordinators: Paul Lyrene, University of Florida, Gainesville, Fla.; Mark Ehlenfeldt, USDA-ARS, Chatsworth, N.J.

The CGC Chair was assigned overall responsibility for the assembly of the document and it is to the Chair that any questions or concerns should be directed. The coordinators responsibility was to draw on the experts within each genera to assemble their respective vulnerability statements. The formats for each genera varied considerably; the Ribes statement is all-inclusive and complete, whereas the Rubus and Fragaria statements are more concise statements that will hopefully be easily used by others dealing with germplasm issues in these genera. Hopefully, the next revision of this document will begin to apply some standardization. The coordinators began their work in the summer of 1999. The document in total was put to the Crop Germplasm Committee for approval by email and subsequently approved in Spring 2000. The document has subsequently been submitted to the USDA-ARS Plant Germplasm Office.

I. Fragaria

A. Needs for collection and preservation

A high priority should be given to rounding out the world collection of octoploid strawberries, since they represent an extensive array of diversity that can be directly incorporated into commercial cultivars. Fragaria chiloensis has been adequately collected from most of its native range, although more attention needs to be placed on its northern reaches in Alaska. In addition, a number of valuable land races of F. chiloensis still need to be collected in Chile, Peru and Colombia. Collections of F. virginiana are much more spotty than F. chiloensis, with the most important holes being in northwestern and northeastern Canada, the midwestern United States, and the southwestern United States below Colorado. Fragaria iturupensis also warrants much additional attention, as it has only been described at one location in Asia and has not been collected at all.

The collection of diploid, tetraploid and hexaploid Fragaria is of secondary importance to the octoploids. However, we need to get a better representation of the Asian diploids and tetraploids, as only a few clones of each is currently represented in the national germplasm collection, and these species will ultimately be the key to determining evolutionary relationships in the genus.

B. Needs for evaluation and enhancement A USDA funded effort is ongoing to determine how representative the national germplasm collection reflects the native diversity patterns of the octoploids, but there remains a critical need to screen the existing collections of octoploid clones for disease resistance. The diseases which deserve the most attention are anthracnose, angular leaf spot, verticillium wilt and botrytis (both crown and foliar), as they are particularly widespread problems. Emphasis also needs to be placed on finding new sources of day?neutrality and heat tolerance in F. virginiana, as our current day?neutral cultivars perform poorly when mid?summer temperatures exceed 28 C.

II. Ribes

A. Introduction

The genus Ribes L., the currants and gooseberries, includes more than 150 described species of shrubs which are native throughout Northern Europe, Asia, North America, and in mountainous areas of South America and northwest Africa (Brennan, 1996). Only about twelve of these species comprise the primary gene pool from which domesticated currants and gooseberries were developed.

Total world Ribes acreage was stable over the past several decades although the breakup of the former Soviet Union greatly increased fruit availability. Black currants, the major crop, are primarily grown for the juice market. They are also valued for production of jams, jellies, liqueurs, such as 'Creme de cassis' in France, for the conversion of white wines to rosé, and as flavorants and colorants for dairy products. Black currant juice has intense flavor, color, high ascorbic acid, and other antioxidant levels that are now becoming recognized for nutraceutical properties. Poland, the Russian Federation, United Kingdom, and the Scandinavian countries lead the world production of black currants.

Red currants are valued for fresh market and for the production of preserves and juice. The main red currant producers are Poland, Germany, Holland, Belgium, France, and Hungary. Gooseberries, which are eaten fresh or processed into pies and jams, are primarily grown in Poland, Germany, and Hungary (Brennan, 1996). Several species of currants have ornamental qualities for plant habit, flowering, or fall foliage.

Ribes production is negligible in North America because of white pine blister rust, Cronartium ribicola J. C. Fischer, a disease introduced from Asia, which kills susceptible five-needled white pines but does no great damage to Ribes. Ribes and Pinus L. subgenus Strobus are alternate hosts for this disease. Since the early 1900's, Ribes culture has been restricted in parts of the United States in an attempt to curtail white pine blister rust.

B. Ribes distribution and important species

Taxonomy

Ribes was originally placed in the Saxifragaceae (Engler and Prantl, 1891; Vetenant,1799), but more recent taxonomic treatments classify the genus in the family Grossulariaceae because of wholly inferior ovary, totally syncarpous gynoecium, and fleshy fruit (Cronquist, 1981; Lamarck and De Candolle, 1805; Sinnott, 1985).

Early classifications also recognized two genera, Ribes, and Grossularia (Berger, 1924; Coville and Britton, 1908; Komarov, 1971). Numerous infrageneric classifications are proposed for these two genera. Prevalent monographs recognize a single genus, Ribes (de Janczewski, 1907; Sinnott, 1985). Crossability between gooseberry and currant species supports the concept of a single genus (Keep, 1962). De Janczewski (1907) subdivided the genus into six subgenera: Coreosma, the black currants; Ribes (=Ribesia), the red currants; Grossularia, the gooseberries; Grossularioides, the spiny currants; Parilla, the Andean currants; Berisia, the European alpine currants

The centers of diversity for Coreosma, Ribes, and Berisia include Northern Europe, Scandinavia and the Russian Federation (Jennings et al., 1987); and for Grossularia in the Pacific Northwest of North America (Rehder, 1986). In addition several species of black currants with sessile yellow glands are native to South America.

Cytology and Evolution

The basic chromosome number of Ribes is x = 8 (Zielinski, 1953) and all species and cultivars are diploid. The chromosome complement and karyotype are highly uniform (Sinnott, 1985) and the chromosomes are 1.5 to 2.5 µm (Darlington, 1929). Mitotic and meiotic processes are also highly uniform (Zielinski, 1953).

The principal evolutionary pressure in the genus appears to be geographical adaptation (Sinnott, 1985). Messinger et al. (1999) examined subgeneric taxa of Ribes for restriction site variation in two cpDNA regions. While several infrageneric lineages were strongly supported, Grossularioides species were unexpectedly united with those from Grossularia. Coreosma species exhibited high divergence and were not monophyletic in the analysis. Messinger et al. (1999) consider two possible, not mutually exclusive, evolutionary scenarios for Ribes: 1) long periods of stasis is interrupted by sudden radiation of species; 2) gene flow due to hybridization as a force for diversification.

Endangered Species

The genus Ribes is fairly robust. Most species are broadly distributed and are not in danger of extinction. However, the World Conservation Monitoring Center 1997 Red List of Threatened plants (www.wcmc.org) includes 18 Ribes species. Ribes kolymense (Trautv.) Komarov ex Pojark is extinct from the former Soviet states; three American and one Sardinian species are endangered; six American are vulnerable; two from the Pacific Northwest, another Sardinian and a Chilean species are rare; three Russian species are indeterminate. Ribes ussuriense, one of the Russian species listed as indeterminate, contains the dominant gene, Cr, for immunity from white pine blister rust (Brennan, 1996). Genes from this species have allowed the cultivation of black currants in some of the white pine blister rust restricted zones of the United States.

The Endangered Species Act of the United States (Department of the Interior, Fish and Wildlife Service, 50 CFR Part 17) lists the Miccosukee gooseberry, R. echinellum (Cov.) Rehder. This spiny-fruited gooseberry species whose native habitat occurs along the shoreline of Lake Miccosukee near Monticello, Florida, and in limited locations in South Carolina and Georgia, is threatened by encroaching human development. Several accessions of this species are maintained ex situ at the National Clonal Germplasm Repository at Corvallis, Oregon. The Oregon National Heritage Program lists R. cereum var. colubrinum Hitchc. as rare, and R. divaricatum and R. klamathense (Cov.) Fedde as indeterminate.

C. Present germplasm activities

The U. S. national collection of currants and gooseberries, Ribes L., resides at the U.S. Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository, in Corvallis, Oregon. As of January 2000, this collection consists of 87 species and 803 available accessions (Table 1). Background and evaluation data are loaded to the Germplasm Resource Information Network, which can be obtained through a database search on the web at: www.ars-grin.gov/npgs. Images of flowers and fruit will be loaded to the GRIN system during 2000.

The species collection consists of seeds stored at -20 o C, with single clone representatives of specific seed lots maintained as plants in the field. Cultivars undergo pathogen-testing procedures. Pathogen-negative plants are maintained under screen to prevent re-infection by viruses. A core collection of 335 accessions has been designated to represent species diversity. For on-site back up, 66 accessions are preserved as in vitro cultures in short-term storage at 4 o C, and about half of these are backed-up at the National Seed Storage Laboratory, Ft. Collins, Colorado. Virus testing, in vitro culture, and cryogenic preservation will be performed on additional accessions as resources permit.

D. Status of crop vulnerability

Several diseases and pests challenge the culture of Ribes for fruit production. Key pests in Europe include black currant reversion virus and the black currant gall mite, Cecidophyopsis ribis Westw. Key pests in North America include white pine blister rust, Cronartium ribicola J. C. Fischer, and powdery mildew Sphaerotheca mors-uvae Schw. Additional pests include caneborers, aphids, sawflies, and others (Table 2). Breeders are looking to expand the range of production by producing plants that resist spring frosts, survive drought and heat, and are disease and insect resistant or immune.

In North America, 15 states have regulations prohibiting or restricting Ribes culture because of white pine blister rust. Ribes cultivation must work in consort with foresters to minimize the risk of increasing the incidence of white pine blister rust in North America.

E. Germplasm needs

Collections The U.S. Ribes collection lacks representation more than 67 species from around the world. Significant disease resistant European and Asian species are not in the collection (Table 3.) Ribes ussuriensis, the species with potentially the most economically important genes for North America, is not represented in the Repository collection. The collection is also missing major European cultivars of black, red and white currants, and large fruited gooseberries. Many heirloom cultivars are in the British, German, French, Scandinavian, Polish, Dutch, Belgian, and other Eastern European collections. A significant effort should be made to import these older cultivars into the United States and establish them in the National Ribes collection at Corvallis, Oregon. Any foreign Ribes plant must enter the United States through the National Quarantine Laboratory, Beltsville, Maryland. Import permits must be secured prior to requesting plant germplasm. Importation quotas have been instituted at Quarantine center so prior approval must be obtained. Ribes seed has no quarantine requirement.

Evaluation

The U. S. Ribes collection needs to be evaluated for resistance to the diseases and pests mentioned in Table 2. These evaluations should be made at locations where significant disease or pest pressure occurs. In terms of North American priorities: evaluation of white pine blister rust resistance should be first priority; mildew resistance second priority for diseases. For insect difficulties caneborer, sawfly, and aphid resistance evaluation should be made. A constant vigil should be made to avoid importation of black currant reversion virus or of black currant gall mite or gooseberry mites.

Enhancement

Several institutions throughout the United States and North America are enhancing breeding, or evaluating Ribes germplasm to a limited extent. These include: Cornell University, University of Maryland, University of Minnesota, University of Idaho, University of Guelph, and the USDA, ARS at Corvallis, Oregon. Ribes is a significant horticultural crop in Eastern Europe. Programs for breeding and enhancement exist in most of the Eastern European countries. Scotland, Poland, Germany, Belgium and New Zealand specialize in black currant breeding. France, Norway, Finland, Sweden, The Netherlands, and others breed for improvement of currants and gooseberries.

Preservation

Additional technical staff members are needed at the Repository for small fruit preservation. The number of accessions at the repository has doubled during the past 10 years. The number will double again over the next ten years. The Repository is in severe immediate need of an additional permanent technical assistant for the maintenance of small fruit germplasm as in vitro cultures and in cryogenics. In addition, a permanent technical assistant for small fruit virus-testing and screenhouse plant maintenance is needed. An additional $100,000 increase in base funds plus administrative approval to recruit two permanent federal technical support personnel for specifically for small fruit germplasm maintenance is requested.

Recommendations

Literature cited

Berger, A. 1924. A taxonomic review of currants and gooseberries. Bull. New York State Agric. Exp. Sta. 109.
Brennan, R. M. 1996. Currants and Gooseberries. Chapter 3 pp. 191-295 in: J. Janick and J. N. Moore (eds.) Fruit Breeding, Vol. II Vine and Small Fruit Crops. John Wiley & Sons. Inc. N.Y.
Coville, F. V. and Britton, N. L. 1908. Grossulariaceae. N. Am. Fl. 22:193-225.
Cronquist, A. 1981. An integrated system of classification of flowering plants. Columbia Univ. Press, New York.
Darlington, C. D. 1929. A comparative study of the chromosome complement in Ribes. Genetica 11:267-269.
Engler, A. and Prantl, K. 1891. Ribesioideae. Naturl. Pflanzenfam. 3:97-142.
Hamat, L., A. Porpaczy, D. G. Himelrick, and G. J. Galletta. 1989. Currant and Gooseberry Management. Chapt. 6, pp. 245-272. In: G. J. Galletta and D. G. Himelrick, (eds.) Small Fruit Crop Management. Prentice Hall. New Jersey.
Janczewski, E. de. 1907. Monograph of the currants Ribes L. (in French). Mem. Soc. Phys. Hist. Nat. Geneve. 35: 199-517.
Jennings, D. L., Anderson, M. M., Brennan, R. M. 1987. Raspberry and blackcurrant breeding. p. 135-147. In: A. J. Abbot and R. K. Atkin (eds.). Improving vegetatively propagated crops. Academic Press, London.
Keep, E. 1962. Interspecific hybridization in Ribes. Genetica 33:1-23.
Komarov, V. L. (ed.). 1971. Flora of the [former] USSR Vol. IX p. 175-208. In: Ribesioideae Engl. (Translated from the Russian by the Israel Program for Scientific Translation, Jerusalem). Keter, London.
Lamarck, J. B., and De Candolle, A. P. 1805. Flore Francaise. Desray, Paris.
Messinger, W., A. Liston, and K. Hummer. 1998. Ribes phylogeny as indicated by restriction-site polymorphisms of PCR-amplified chloroplast DNA. Plant Systematics and Evolution. In Press.
Rehder, A. 1954. Manual of cultivated trees and shrubs. 2nd ed. Macmillan: New York.
Sinnott, Q. P. 1985. A revision of Ribes L. subg. Grossularia (Mill.) per. Sect. Grossularia (Mill.) Nutt. (Grossulariaceae) in North America. Rhodora 87:189-286.
Tuinyla, V. and A. Lukosevicius. 1996. Pomology of Lithuania. Lithuanian Science and Encyclopedia Publisher; Vilnius Lietuva, Lithuania.
Vetenant,1799. Tableau du regne vegetal. J. Drisonnier, Paris.
Zielinski, Q. B. 1953. Chromosome numbers and meiotic studies in Ribes. Bot. Gaz. 114:265-274.

Threatened status

Diseases

Viruses

Insects

Mites

Nematodes

III. Rubus

A. Overview

With several exceptions, Rubus is in need of systematic collection and evaluation. Red, black and purple raspberries and blackberries are the most important commercial crops derived from this genus in North America and worldwide. However, wherever Rubus is found there is usually a local species that is important as a berry crop; for example, Mora (Rubus glaucus) of Andean South America, Rubus crataegifolius of northeastern Asia, and the arctic raspberries (R. stellatus, R. arcticus, R. stellarcticus and R. chamaemorus) of Scandinavia. The only known systematic collection and evaluation for horticultural purposes in the United States of Rubus in modern times has been the Rubus, particularly R. ursinus, of western North America. However, large collections of Rubus were made by L.H. Bailey and assembled in New York in the first half of the 1900's; these collections are largely gone, other than in herbariums.

B. Germplasm needs as delineated by regions/species
The following are needs for collection expressed by the Small Fruit CGC.

Rubus idaeus var. strigosus (North America)/ R. idaeus var. idaeus (Eurasia) from throughout its range. These two groups of R. idaeus, form the underpinning of the red raspberry industry. They are distributed throughout northern temperate regions with some notable, southern remnant populations. While extensive, but haphazard collections representing North America have recently been assembled by Agriculture and Agri-Foods Canada in British Columbia, this species is not well represented from throughout its North American and Eurasian distribution. What sampling has been done has lead to the identification of valuable sources of Phytophthora root rot resistance. There is special interest in collecting this species from the extremes (wettest, driest, coldest and hottest) of its range.

Rubus idaeus var idaeus (Eurasia) from the former Soviet Union. This is a critical, pressing need. The large Russian collection of R. idaeus is in danger of being lost because of the current economic situation in the former Soviet Union. While some of this material may be well characterized, it is only available in Russian, so the information is not readily available to breeders worldwide.

Rubus occidentalis. The black raspberry industry, concentrated in Oregon, is entirely reliant on wild selections and turn of the 20th century developed cultivars. There is very little variability present within the cultivars that have been developed and it is difficult to tell one from another. This industry has a strong need for more disease resistant cultivars. No known systematic collection or evaluation has taken place in this species, which is native to the mid-Atlantic states and west into the Midwest.

Blackberry Rubus sp. from the eastern U.S. When North America was settled and opened to agriculture, intercrossing among somewhat distinct species was greatly accelerated creating a huge interbreeding hybrid population in Eastern North America. However, there are still types, at least on the edges of the range that are isolated either physically or temporally form other blackberry taxa.

A. Species in the sections Alleghenienses and Arguti (e.g. R. argutus, R. allegheniensis). While the cultivars are most often tetraploid, the species are usually diploid. While several breeding programs in the Eastern U.S. have utilized this germplasm this century the predominant breeding efforts (Univ. of Arkansas and USDA-Carbondale/Beltsville) have relied on a very small germplasm base. A systematic collection that might help clarify the taxonomy of these species and serve as a genetic base for further breeding is highly desirable.

B. Other eastern U.S. species. Rubus canadensis, R. hispidus, and R. setosus are three northern or northeastern species that are primarily diploid,. Unfortunately, R. hispidus and R. setosus tend to have small fruit and are adapted to low pH soils. Rubus flagellaris and the entire section Flagellares are a complex mix of polyploids. While the range of R. flagellaris does not extend as far north as the first three species mentioned, there are representatives of that section that are found in USDA hardiness zone 3 in northern Minnesota, New England and Canada. Rubus cuneifolius appears to be tolerant of saline conditions and in limited enhancement efforts has proven to be a source of excellent flavors and fruit size. These various blackberry species offer tremendous adaptation for blackberries adapted to the extreme northern and southern environments of North America. The northern adapted blackberry species (e.g. R. canadensis, R. flagellaris) has been used very little, if at all in breeding, have not been systematically collected, and could provide excellent northern/winter adaptation for blackberry. Similarly, the southern adapted species (e.g. R. trivialis), from which at least two cultivars have been developed, need to be better, collected and characterized.

Asian Rubus sp. The major center of diversity for Rubus appears to be in this area; China alone is reported to have over 250 species. Systematic collections were made by M. Thompson et al., in China's Guizhou Province, and in northeast China, in trips supported by the USDA. These collections are being evaluated and potentially valuable germplasm incorporated into advanced breeding material. However, very little other collecting has been done in China, India and the other Asian countries and the reality is that very little is even known about most of the species in this region. This is even more true with the Rubus sp. native to the islands of the South Pacific. Rubus parvifolius has proven to be a valuable germplasm resource in breeding southern adapted red raspberries, this species in particular needs to be systematically collected in Asia including Japan.

Western Europe blackberries. This region represents a center of diversity for Rubus. However, as with Asia and eastern North America, very little is known outside of western Europe about the huge diversity present there and about Rubus taxonomy in this region. In much of this region, human agriculture has led to the interbreeding of many species leading to a mix that is difficult to separate or characterize taxonomically. Weber's biosystematic treatment may make sense, but it is written in German and is not widely accessible. While Nybom, Edees, Newton and Holub have all contributed to some understanding of these blackberries, there is no cohesive, compiled, and available treatment of this group.

C. Germplasm needs as delineated by traits

Shifting gears from regions that need to be collected, there are specific needs that cannot currently be met with available germplasm. Any collections that might meet the following needs are highly desired.

1. Disease resistance, particularly for:

a. Phytophthora root rot (Phytophthora fragariae var. rubi) in raspberry
b. Raspberry bushy dwarf virus (RBDV) in raspberry
c. Blackberry rosette (Cercosporella rubi)

2. Pest resistance, particularly for:

a. Amphorophora agathonica and A. idaei; particularly new biotypes that overcome previous resistance
b. Raspberry beetle (Byturus sp.), particularly in Europe, and sap beetles (Glischrochilus sp.)
c. Caneborers (Agrilus ruficollis and Oberea bimaculata) in eastern North America

3. Environmental stress tolerance, particularly:

a. tolerance to hot, humid, climates particularly in raspberries
b. tolerance to drought
c. tolerance to high ultraviolet light intensity, particularly in raspberries
d. tolerance to cold winter environments particularly in blackberries

4. New sources of primocane fruiting characteristic in raspberry and blackberry.

5. Adaptation to low-chill environments for all Rubus.

IV. Vaccinium

A. Germplasm collection needs

Vaccinium is a genus in the heath family that includes a wide diversity of useful and potentially-useful berry-producing plants. The genus has an almost worldwide distribution, and includes the important crops, blueberry, cranberry, and lingonberry. The first two of these have their most important wild gene sources in eastern North America. Western North America is home to a group of species in Vaccinium section Myrtillus, some of which are highly prized as wild berries and are gathered and sold as "huckleberries". Both Hawaii and Alaska have their own indigenous Vaccinium species, and the tropical highlands of both the New and Old World have a wide diversity of indigenous Vaccinium species.

Most Vaccinium species are long-lived woody shrubs. Most are cross-pollinated by insects, are partially to highly self-incompatible, and suffer much from inbreeding when self pollinated. Populations are highly variable within species for many traits, and preservation of just a few specimen plants per species does little to preserve the total diversity in the species. Some of the variability within species has great horticultural significance. For example, within diploid V. corymbosum (even when narrowly defined as by Wendel H. Camp), selections from the area just north of Lake Okeechobee in south Florida are evergreen and have no chilling requirement whereas those from New Jersey are deciduous with a very high chilling requirement. Thus, a large collection is needed just to preserve representatives of the diversity within this one species. A similar situation prevails with many of the other species.

A major challenge with preserving Vaccinium germplasm is knowing how to deal with the hundreds of little-known species native to the tropical highlands. Many of these have potential value in ornamental plantings or in fruit production, but the security of the germplasm has been assessed for only a few species. More on-site botanical studies are critically needed to provide information, and broad-based seed collections should be made to safeguard genetic resources in these species until they are better understood.

Cultivated blueberries originated from species in section Cyanococcus, which is native to eastern North America. The three principal cultivated species in this group are lowbush blueberry, based on V. angustifolium; highbush blueberry, based on V. corymbosum; and rabbiteye blueberry, based on V. ashei. Of these, the lowbush germplasm is the most secure, since the cultivated crop is harvested from thousands upon thousands of diverse individual clones that were brought into cultivation by applying cultural procedures to native stands.

The highbush blueberry is widespread on moist, organic soils from central Michigan to Lake Okeechobee in the south Florida peninsula. Both diploid and tetraploid races occur. The diploid, evergreen race in south Florida is represented sparsely or not at all in the germplasm collection, and is highly endangered due to land pressures from farming and urbanization. A large seed collection should be obtained from this population for long-term storage. Tetraploid races of V. corymbosum closely related to the type that was domesticated in New Jersey during the first decades of the 20th century as "highbush blueberry" extend from north Florida to central Michigan. Many of the best populations are rapidly being eliminated or degraded by urbanization, farming, or modern forest management practices. Large, diverse seed populations collected from the strongest bushes having the largest berries should be made from each area of the range.

The rabbiteye blueberry, V. ashei, is a vigorous, rhizomatous, tall-growing hexaploid species native only in restricted areas along rivers in the southeastern U.S. It is probable that two of the three genomes in V. ashei derive from V. corymbosum, but what species provided the third genome and exactly how the hexaploid population formed are still unsolved mysteries. There are two major races of this species: one in west Florida and adjacent counties in Alabama, the other in southeast Georgia, centered around the Okefenokee Swamp, and adjacent areas of Florida and South Carolina. Although not in immediate danger of extinction, populations of both V. ashei races have diminished greatly in the past 30 years as a result of farming, forestry, and urbanization. Large, diverse seed populations should be made for both of these races.

A number of other Vaccinium section Cyanococcus species have been important in breeding improved rabbiteye and highbush varieties. Two hexaploids, V. amoenum and V. constablaei will be important to rabbiteye and highbush breeders of the future. Vaccinium constablaei is native only to the high mountain balds in the Appalachian mountains and is a source of cold hardiness. Large, diverse seed populations should be collected and preserved for this species. Vaccinium darrowii, a diploid, lowbush, evergreen species native to the Florida peninsula has been crossed with V. corymbosum to develop "southern highbush" blueberry cultivars that can be grown in subtropical areas to produce fruit in April and May in the northern hemisphere and in October and November in the southern. V darrowii on the Lake Wales Ridge at the southern end of its range is highly endangered. The Ocala National Forest farther north in the peninsula is an important reservoir of this valuable species, and the management of this forest should take into account the preservation both of V. darrowii and of diploid forms of V. corymbosum, both of which will be important in breeding subtropical highbush blueberries in the future. Vaccinium darrowii has possible uses in northern climates for improving V. corymbosum fruit quality.

Two other important indigenous Vaccinium species in the eastern U.S., V. arboreum and V. elliottii, are still widespread and abundant. Any long-range conservation strategy should include a plan to encourage the use of seedling plants of these attractive native species in home and institutional landscaping in the areas where they are native.

In the cranberry group (Vaccinium section Oxycoccus), the USDA National Clonal Germplasm Repository species holdings include 123 accessions of V. macrocarpon (large-fruited cranberry), 3 accessions of V. microcarpon (small-fruited cranberry), and 41 accessions of V. oxycoccus (2x/4x wild cranberry). Vaccinium microcarpon and V. oxycoccus are under-represented at present. Vaccinium macrocarpon is better represented. Areas deserving further collection of V. macrocarpon include southern Canada, Michigan, Minnesota, and West Virginia. The entire area should be re-sampled to obtain broad-based seed collections. Areas deserving further collection for V. oxycoccus include Alaska and the region south of Hudson Bay. For V. oxycoccus special consideration should be given to areas which have previously been determined to harbor 2x genotypes (most V. oxycoccus are 4x). The 2x types are particularly valuable for the possibilities of introgression into cultivated V. macrocarpon, which is also diploid. V. oxycoccus also exists in Scandinavia and Europe, and further collections should be made in these areas. Because of the Federal Wetlands Act, there is probably less threat to native cranberry sites than there is to native sites of other species. Guidelines should be made for collection to optimize genetic diversity in the final preserved accessions. Appropriate sampling strategies should be developed for sampling multiple locations in a region, sampling different individuals within a site, and in final compositing of seed from a site.

The lingonberry (V. vitis-idaea), also known as cowberry, partridgeberry, and mountain cranberry, is closely related to the cranberry, and the berries taste relatively alike. The plants are perennial, evergreen, dwarf shrubs and are widely distributed in north-temperate, boreal, and subarctic regions. The native range of the lingonberry includes areas in Alaska, Scandinavia and other parts of northern Europe and Asia. Lingonberry diversity has been studied at the Swedish University of Agriculture at Balsgard. Lingonberry cultivars have been developed in Sweden, Germany, and in Wisconsin. Wild lingonberry populations are variable in nearly all important horticultural traits. Large, diverse seed collections should be made from each geographical area within the range to provide seed for longterm storage and to supply short-term requests.

B. Germplasm preservation

Vaccinium germplasm can be preserved in situ by acquiring, managing, or preserving the natural areas in which they are growing. This could be done in conjunction with State and National forests and wilderness areas, private organizations such as The Nature Conservancy, and with private landholders. Because so much Vaccinium germplasm is indigenous to the United States, cooperative programs to manage Vaccinium germplasm in situ should be made a model for how indigenous germplasm could be managed in other countries.

In collections, Vaccinium germplasm can be preserved either as seed material or as clones. For preserving large amounts of genetic diversity far into the future, seed preservation is by far the most effective and inexpensive. During the next 50 to 100 years, breeders will probably still have much Vaccinium germplasm available to them directly from the forest. Beyond 100 years, however, germplasm banks may be the only source for some species. Thus, strategies to preserve a vast wealth of germplasm far into the future should be given priority over storage of a few hundred particular horticultural clones for the next 100 years. Vaccinium seeds are very small and longlived if stored properly. If properly collected and stored, a particular population, for example, diploid, lowchill, evergreen V. corymbosum from the south Florida peninsula, could be collected as a highly diverse seed population and stored at low cost. Every 50 years, a 1-acre isolated field planting containing 5,000 or more plants could produce open-pollinated seed to renew this seed population with little loss of diversity for a cost of about $20,000. If two populations of this type were renewed each year on a 50-year cycle, 100 highly diverse populations could be maintained in perpetuity for only $40,000 per year plus seed storage costs. This would be far more useful to future breeders than maintaining a few hundred genotypes of each species as clones. Examples of populations that could be saved in this way by seed storage and renewal might be: Population 1: Diploid, evergreen, highbush clones from the southern end of the species range in the Florida peninsula; Population 2: Tetraploid, deciduous to semi-deciduous highbush blueberries from cypress swamps in north Florida (the southern limits of the tetraploid V. corymbosum range); Population 3: Large-fruited, vigorous highbush blueberries from sandy-organic soils from southeast Georgia to southeastern North Carolina; Population 4: the best highbush blueberries from the swamps of southern New Jersey, representing the type that contributed most heavily to the founding populations used to start the USDA highbush breeding program from 1900 to 1920; Population 5: Coldhardy highbush blueberry from the northern extremes of the range in Michigan. It would probably require no more than 10 such populations to preserve a working capital of germplasm of the commercially most important blueberry species in the world. Other populations could be devoted to conserving highbush relatives such as V. elliottii, V. constablaei, V. ashei, V. amoenum, V. myrsinites, V. darrowii, V. tenellum, etc. A total of 100 populations would preserve most of the species of principal current concern. A committee of blueberry breeders and population geneticists should be appointed to design the collection strategy and define the populations.

Clonal collections should also be maintained, but these should not be the primary focus of the Vaccinium germplasm preservation program.

C. Utilization and Enhancement.

There are several reasons for preserving genetic diversity. Species can be saved which may someday be studied to better understand evolution, ecology, and other aspects of the natural world. Diverse populations can later be examined as sources of drugs or other valuable products. Species can serve as sources of genes, which, through genetic engineering, may someday be useful by transfer to crops such as corn, wheat, rice, and soya. Some of the still-undomesticated Vaccinium species have potential to make new domesticated crops in the future. Wild relatives of blueberries, cranberries, and lingonberries will be needed in the future to develop better cultivars of these three crops.

Germplasm enhancement is best accomplished as an integral part of a breeding program whose end product is a finished cultivar that can be grown by farmers in a particular production area. In utilizing a germplasm source for a desirable trait such as resistance to Phytophthora root rot, cold-hardiness, low chilling, improved fruit qualities etc., the breeder needs to have a wide range of gene sources from which to choose because they must consider the other traits that will come along with the desired trait when the gene source is crossed into the elite gene pool from which cultivars are being developed. Screening and cataloging large germplasm collections to find clones that most strongly exemplify this or that virtue, without regard for their other features, is not particularly useful to the breeder. Although breeding programs may or may not be active at present for some of the taxonomic groups, failure to preserve sufficient diversity will preclude any future development of these potentially valuable crop plants.