Gerald J. Seiler and Devon L. Doney
USDA-ARS, Northern Crop Science Laboratory, Fargo,ND
Since cultivated sugarbeet has a very narrow genetic base, utilization of the wild species has the potential of broadening the genetic base and providing a valuable source of genes for increasing genetic resistance to insect and disease pests. The initial step in genetic conservation is the assemblage of wild species from their native habitats. Collection and exploration for sugarbeet represents one of the most difficult and challenging phases in the process of conserving genetic diversity in wild sugarbeet germplasm.
The collection of wild sugarbeet has received increased attention in recent years because natural habitats are continually being destroyed. The center of origin of the genus Beta is the Mediterranean region. Wild sugarbeet species are found along the coastal areas of all Mediterranean and North Atlantic European countries. Collection expeditions by the UDSA-ARS over the past five years has centered on the Mediterranean and North Atlantic areas in an effort to preserve the wild species that are being depleted in that region. Explorations were undertaken to southern Italy, Sardinia, and Corsica in 1985, and England, Wales and Ireland in 1987. The USDA-ARS Beta explorations have been coordinated with the International Board for Plant Genetic Resources (IBPGR) efforts and were supported by the Sugarbeet Crop Advisory Committee (CAC), and the International Beta Genetics Resources Network. However, very few accessions of wild beets were available from the Northern European area. A cooperative exploration between the USDA-ARS and Institute National de la Recherche Agronomique (INRA, France), Maribo Seed(Denmark), and SES Seed (Belgium) was undertaken during August and September of 1989 to collect wild sugarbeet germplasm, mainly Beta vulgaris ssp. maritima (sea beet) which inhabits the coastal areas of France, Channel Islands (Guernsey and Jersey), Denmark, and Belgium.
Populations of B. vulgaris ssp. maritima were sampled at 20 to 40 kilometers intervals, or where ever there was a definite geographic barrier separating populations. The exploration began at the Gulf of Lion (Ligurian Sea), the Mediterranean side of France and progressed along the entire Atlantic coast of France, Channel Islands (Guernsey and Jersey), the major islands of Denmark, and along the Atlantic Coast of Belgium.
A total of 2992 individual plants were sampled from 123 populations in France, 154 individual plants from 5 populations in Jersey, 101 individual plants from 3 populations in Guernsey, 305 individual plants from 19 populations in Denmark, and 57 individual plants from 3 populations in Belgium. Site characterization data was recorded which included elevation, population area, population size (approximate number of plants), population uniformity, plant type (erect or prostrate), soil type and specific habitats where the populations occurred. Notes were also taken on the diseases present, monogermness of seed and male sterility. Ten to 40 individual plants were sampled at each population location. Seeds from each sampled plant from a location were bulked and considered a population accession. Information from the collection trip will be entered into the Germplasm Resources Information System (GRIN) and seed accessions collected will be given a permanent plant introduction (PI) number. The Beta collection will be deposited at the National Plant Germplasm System (NPGS), North Central Regional Plant Introduction Station (NC-7) at Ames, Iowa&042. A portion of the bulked seed will be deposited at the National Seed Storage Laboratory, Fort Collins, CO for long term storage. Another portion of the bulked seed will be increased under controlled isolation through a Cooperative Agreement at Logan, UT. The resultant seed increases will be deposited at NC-7 as part of the Beta working collection and made available for further testing and evaluation. Evaluation will be conducted in coordination with the Sugarbeet CAC. French INRA has agreed to cooperate by evaluating the French collection to complement efforts in the U.S.
Wild sugarbeet populations along the Mediterranean coast of France appear to be typical of the Mediterranean sea beet. Populations were scattered and the largest was found along the southwest side of the Gulf. Most sea beets appeared to be annual with some tending toward perennial, and varied from prostrate and spreading to erect plant types. Plants generally had small anceolate leaves which were usually thick with a waxy surface.
Beta vulgaris ssp. macrocarpa (a wild annual beet with large seed) was found inland at Nerac, one of the major seed production areas of France. The populations appeared to be mixed, segregating for wild and cultivated types with large cultivated type leaves, large multigerm seeds, pigmentation in petioles and stems and even some roots. The populations appeared to be restricted to garden areas with heavy clay soils where cultivated beet were previously grown, but were not found in the surrounding seed production fields.
Along the Atlantic coast of France, sea beet was found as far south as St. Jean-de-Luz. Populations were sparsely scattered in limestone boulders and large well distributed populations were not found until we reached the Arcachon estuary. Here we found sea beet in old oyster shell dumping grounds near old boat docks.Plants were especially vigorous in these areas.
Sea beet populations were found all along the Atlantic coast of France to the Belgium border. Populations were usually found at sea level (sometimes they were covered at high tide) or a few meters above sea level, but rarely far from the beach areas of saline water. They occupy areas where there is barely adequate soil to grow and sometimes grow in cracks of rocks and sea walls. They were seldom found in sandy soil because of the shifting nature of that environment. As the name implies, sea beet was rarely found inland and never in fresh water. It was often found in estuaries where the sea meets a river where the water was saline, and often brackish. Sea beet also survives along canals and in fence rows. The island of Ile d'Oleron, Ile de Re, and Isle de Noirmoutier off the coast of France were also sampled. Sea beet populations were abundant on the Islands, and found in typical habitats where they are found on the mainland.
There was considerable variation in the populations of sea beet from the Bordeaux region of France. Populations were segregating for pigmentation in leaves, stems, and seeds. Populations appeared to have larger seeds than those found further north. Also monogerm plants were found in several populations and some plants appeared to be male sterile. Seed set was variable in some populations, indicating problems with self sterility. Populations were segregating for prostrate and erect plant types, and appeared to be strong perennials.
The Brittany coast of France is more rocky (granite) and hilly with poorer soils than the southwest coast, but is typically wet and humid, however this year was very dry. An interesting population was found growing in sandy soil in and around large Cyprus trees near the bay of Ile Besnard. This population was located on a piece of land connecting the Ile to the bay. This was one of the few populations found inland from the sea and in sandy soil. It contained some monogerm plants and one with clustered flower stalks. The wild sea beets found in Brittany varied considerably from population to population varying from prostrate(usually close to water) to more erect in area above the beach. They also varied in pigmentation of petioles, leaves and seeds, and in plant and leaf size. Leaves appeared in many cases to be less succulent and not as waxy on the surface as was seen in the more southern areas. Sea beet plants here also appeared to be strong perennials.
One population of sea beet from Jersey Island had some characteristics similar to the Mediterranean sea beet i.e. thick succulent leaves and small leaf size, but was perennial. Most other populations appeared to be typical of what was seen on the mainland and were found in typical habitats on the south and west sides of the Island. Populations found on Guernsey Island, which has less tourism, appeared to be typical of what was seen on Jersey Island and the mainland.
The coastal areas of Normandy ranged from sandy beaches in the south, which are not typical sea beet habitat, to pebble beaches further north. Populations found in the southern area were few and scattered and appeared to have low seed set, a problem probably due to self sterility. Plants with monogerm seed were also found. One of the largest populations of sea beet found on the exploration was located near Veulettes along an estuary of the Durdent River. This population had been there for 30 years according to local information and had been about four times larger before construction of beach homes and a new road. Plants were very tall, mostly erect with good seed set, and were segregating for seed size. There appeared to be a higher frequency of male sterile plants in several populations north of Dieppe.
Collection efforts for sea beet in Denmark concentrated on the eastern islands, especially Sjaelland, Samso, Fyn, Aero, Langeland, and Lolland. Even though the earliest recorded observation of sea beet in Denmark was 200 years ago on the island of Aero, the oldest and largest populations were in the northern islands. The island of Samso contained some of the best populations. Large populations were also found on the northwest side of Sjaelland and the north ends of Fyn, Langeland, and Lolland. Most populations had prostrate plants at flowering, with few plants exhibiting an erect flower stalk, and some vigorous plants. All populations exhibited the thick leaf characteristic of the North Atlantic sea beet. Some populations appeared to have moderate to strong monogerm seed characteristic. Some populations had poor seed set suggesting varying levels of self sterility.
The Belgium coast is short, sandy and highly industrialized. The sandy soil is not the typical habitat where sea beet is usually found, but in Belgium this is where the 3 populations collected were found. One population was segregating for growth habit and leaf thickness and appeared to have been out crossed with cultivated beet at some time.
Varying degrees of disease infection were observed during the exploration. The most frequently observed disease was Cercospora, which did not ever appear to totally kill a plant or significantly reduce leaf area. Powdery mildew was the second most frequently observed disease with some populations showing a severe attack and destroying older leaves. Powdery mildew was present on plants from Jersey and Guernsey Islands, while Cercospora was present only on Guernsey Island. What appeared to be beet yellow virus was observed only a couple of times. Two populations of sea beet had what appeared to be rust. Most populations showed varying degrees of disease infection within a population. No disease symptoms were observed on the limited number of populations of wild beets collected in Denmark and Belgium.
Beta vulgaris ssp. maritima is considered one of the most valuable wild Beta species since it readily crosses with cultivated sugarbeet and is considered by many as the progenitor of modern beet(sugar, garden, fodder, leaf. etc). It has survived for several hundred years in diverse habitats and under adverse environmental conditions and has potential characteristics for agronomically improving cultivated sugarbeet. Beta vulgaris ssp. maritima has already provided disease resistance genes for Cercospora leaf spot, Erwina root rot, powdery mildew, Rhizomania, and beet cyst nematode and has the genetic potential of providing additional genes for disease resistance.
The accessions of B. vulgaria ssp. maritima from the present exploration combined with the other recent explorations make the USDA-ARS collection of sea beet the most complete in the world. This collection is a tremendous genetic reserve and resource that will only be realized through the systematic evaluation of the accessions. This resource is available to plant breeders throughout the world for incorporation into their breeding programs. A copy of the detailed report of the exploration can be obtained from the authors.
*The Beta collection was transferred to the Western Regional Plant Introduction Center at Pullman Washington in 1994.