Molecular Characterization of Kiwifruit (Actinidia) Cultivars and Selections Using SSR Markers

ADDITIONAL INDEX WORDS. DNA fi ngerprinting, genetic diversity, cultivar identifi cation, A. chinensis, A. deliciosa ABSTRACT. Forty-eight kiwifruit cultivars and selections, representing more than 90% of total world kiwifruit production, were investigated using nine SSR markers to establish genetic identities, and evaluate genetic diversity and relatedness. These nine SSRs were polymorphic and a total of 213 alleles were detected, resulting in a mean number of 23.7 alleles per locus, ranging from nine to 38 alleles. One hundred and thirty-three alleles were found to be common to both A. chinensis and A. deliciosa, while 33 and 36 were specifi c to A. chinensis and A. deliciosa, respectively. In addition, 34 alleles were specifi c to one single genotype and provided a set of valuable alleles for cultivar identifi cation. A single SSR locus UDK 96-414 could differentiate all 48 genotypes except two presumable clones. Mean number of alleles per locus (A), percentage of polymorphic loci (P), and direct count heterozygosity (Ho) assessed for each genotype over all loci revealed considerable differences among these 48 genotypes. On average, A = 2.6, P = 89.4% and Ho = 0.546 were found in A. chinensis cultivars, while A = 3.5, P = 97.0% and Ho = 0.671 in A. deliciosa cultivars. Consensus fi ngerprint profi ling using SSR markers is a useful and reliable method for establishing genetic identities of kiwifruit cultivars and selections. It also improves evaluation effectiveness of genetic diversity and relatedness compared to RAPD markers. Commercial kiwifruit production is based on two Actinidia species, A. deliciosa C.F. Liang et A.R. Ferguson and A. chinen- sis Planch. The genus Actinidia Lindl. comprises 66 species and about 118 taxa with a remarkably wide natural range extending from the tropics (latitude 00 ) to cold temperate regions (500 N). All these species occur naturally in China except four species that are native to neighboring countries: A. strigosa Hook & Thoms. in Nepal, A. petelotii Diels in Vietnam, A. hypoleuca Nakai and A. rufa (Sieb. et Zucc.) Planch ex Miq. in Japan (Huang et al., 2000). Since the fi rst seed introduction of A. deliciosa was made from China into New Zealand in 1904, the economic potential of kiwifruit has been extensively exploited (Ferguson and Bollard 1990). Currently, the international kiwifruit industry has achieved more than 100,000 hectares with annual production of one million tons (Huang and Ferguson, 2001). China has a long history of local consumption of the Actin- idia as fresh fruits and Chinese herbal medicines for centuries (Cui, 1993). The successful development of kiwifruit industries, fi rst in New Zealand and then in other countries, has stimulated Chinaʼs interest in the potential of native Actinidia species for commercial production. A government organized nationwide selection program was initiated in China in 1977. This program had two missions: 1) to conduct a national germplasm survey and inventory of natural resources of Actinidia; 2) to select genotypes superior to the 'Haywardʼ cultivar developed in New Zealand, the single cultivar planted worldwide during the 1970s. As a result, more than 1400 genotypes were selected from wild populations of A. chinensis, A. deliciosa, and A. arguta. Most of