actinidia kiwifruit hardy germplasm genebank gene bank genetics corvallis
Hardy Kiwifruit Genetic Resources - Actinidia Germplasm - Actinidia Genebank
by Kim E. Hummer, Research Leader/Curator
Classical Chinese texts describe how the "Monkey Peach" was collected in the mountains and brought down by the peasants to be sold in the markets. Fruit were not cultivated but were collected from the wild both in China and Japan. This practice continues today.
Actinidia species were first introduced to the west during the late 1800's, by E. H. Wilson, a Plant Explorer who worked for the U. S. Department of Plant Industry, forerunner of the Department of Agriculture. His collected Actinidia came primarily from Yichang, a town on the Yangtze River. These introductions gave rise to almost all of the commercial orchards of the large-fruited species, Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson. The first of these were established in the 1930's. The cultivation of this fruit continues to expand annually. Total world production is likely to exceed one million tons annually by the year 2000 (Ferguson et al., 1996) with the main producing countries being Italy, New Zealand, Chile, France, Japan, United States (California), Greece, Australia, and Spain. Kiwifruit is primarily produced for the fresh fruit market and processing is typically a way of using rejected fruit.
Recently interest has been expanding for the cultivation of the smaller-fruited hardy kiwifruit, which is the crop of interest here. As of 1999, about 85 acres of hardy kiwifruit have been established in commercial production in the Pacific Northwest of the United States (Strik, per. comm.). About two acres are under cultivation in Pennsylvania and two additional acres in New York. New Zealand has about 15 acres of hardy kiwifruit while Italy has just under five acres.
The genus Actinidia is placed in the Family Actinidiacea (Theales) and contains four sections with more than 60 species (Ferguson et al., 1996). These plants are perennial climbers which are native in high grasslands, low scrub and second growth forest, or in the main forests of China and Russia. Most species are functionally dioecious (Rizet, 1945) so that commercial orchards are planted in a regular pattern of female (fruiting) and interspersed male (pollenizer) plants.
Actinidia has oblong or spherical berries with a very large number of small seeds immersed in a fleshy pulp. The taxa are quite diverse in fruit characteristics. The fruit of A. deliciosa and A. chinensis Planch., the most economically important species, are the largest of the genus ranging from 78 to 140g (Ferguson et al., 1996). Fruit of Actinidia deliciosa is oblong and the skin is covered with long, stiff hairs that remain on ripe fruit. Fruit of Actinidia chinensis is a rounder and has softer hairs that are usually lost by harvest. Fruit of the hardy species are much smaller ranging from about 10 to 40 g.
Section Leiocarpae and Maculatae contain the ten species of hardy kiwifruit.
Section Leiocarpae Ploidy
The most economically important hardy kiwifruit A. arguta cultivars include: Ananasnaya, 74-49, Meader, Ken's Red, Geneva, and Issai. The important A. kolomikta cultivars include Krupnopladnaya (which means "large fruit" in Russian) and Pautske. Actinidia polygama, sometimes called the "Silver vine kiwi," has potential as an ornamental. The fruit of this species has an astringent, peppery flavor when ripe (Strik and Cahn, 1996)
Kiwifruit contain large numbers of very small chromosomes (Ferguson et al., 1996). The base chromosome number is 2n = 2x = 58. This large number possibly implies a polyploid origin for the genus. Most species are diploid, though tetraploids have been observed in A. arguta, A. callosa, A. polygama, A. rubricaulis,and A. valvata. Actinidia deliciosa appears to be exclusively hexaploid and A. arguta cv. Issai is hexaploid.
The U. S. Department of Agriculture, Agricultural Research Service, National Clonal Germplasm Repository at Corvallis, presently contain representatives of 5 species and 42 cultivars. Several botanical gardens in China, including Lushan, Wuhan, and Guilin, the Vavilov Far East Research Center in Vladivostok, Russia, and HortResearch Inc. in New Zealand, hold extensive germplasm collections.
Strik and Cahn (1996) describe the culture and management of growing kiwifruit. These plants are dioecious and about one male is required for every six to ten females in a commercial orchard. Self-fertile cultivars require no male pollinizer although fruit size may become larger with cross pollination. The vines require trellis and training. T-bar or pergola trellises are common commercial systems.
Yield for Actinidia arguta cultivars can range from 50 to 100 lb per plant. Hardy kiwifruit can be stored for only about two months under refrigerated conditions (4 C).
Actinidia kolomikta and A. polygama contain compounds similar to those found in catnip. In China, kiwivine leaves are reportedly fed to large cats as a sedative (Strik and Cahn, 1996).
Seed can be extracted from kiwifruit through the use of a blender and sieves.
Large quantities of seed can be extracted from the fruit pulp after several days in the presence of low concentrations of cellulases of pectinases. The seeds can be separated with a sieve and dried. The seeds are long-lived and can be stored dried at refrigerator temperatures. Long term viability of seeds under freezing or liquid nitrogen conditions is being researched.
Kiwifruit seed require a cool, moist period (stratification) for about one month at 4oC prior to germination. Gibberellic acid (2.5-5.0 g/L for 24) has improved fuzzy kiwifruit germination as a substitute for stratification (Lawes and Anderson, 1980). Seedlings must be transplanted in a well-drained medium because they are intolerant of waterlogging.
Actinidia cuttings root fairly readily from hardwood or softwood cuttings. Hormone dip increases rooting percentages. Semi-hardwood cuttings of fuzzy kiwifruit taken in August and treated with a 10 second dip in 3000 ppm Napthalene (ANA) solution produced plants that out yielded grafted plants of the same cultivar (Diaz Hernandez and Garcia Berrios, 1997)
Diaz Hernandez, M. B. and J. Garcia Berrios. 1997. Performance of kiwifruit plant material propagated by different methods. Acta Horticulturae 444: 155-169.
Ferguson, A. R., A. G. Seal, M. A. McNeilage, L. G. Fraser, C. F. Harvey, and R. A. Beatson. 1996. Kiwifruit. Chapter 5 pp. 371-417. In: J. Janick and J. N Moore (eds.) Fruit Breeding Vol II. Vine and Small Fruits. John Wiley & Sons, Inc. New York.
Lawes, G. S. and D. R. Anderson. 1980. Influence of temperature and gibberellic acid on kiwifruit (Actinidia chinensis) seed germination. New Zealand J. Exp. Agric. 8:277-280.
Rizet, G. 1945. Contribution a líetude biologique et cytologique de líActinidia chinensis. C. R. Seances Soc. Biol. Paris 139:140-142.
Strik, B., and H. Cahn. 1996. Growing Kiwifruit. EC 1464. Oregon State University. Corvallis.