Resource evaluation and novel germplasm mining of Actinidia eriantha

Fruit of Actinidia eriantha are well known for their high nutrient content, especially for their high ascorbic acid (AsA) content. This paper reviews the literature on the origin and distribution, physiological and palynological evaluation, molecular research, and selection and breeding of A. eriantha germplasm resources in China, which will be helpful to its rational development and utilization. There are large abundant wild germplasm resources in China, the distribution area and altitude range of the A. eriantha have been revised: it is mainly distributed in the Yangtze River basin, the Yunnan-Guizhou plateau and the Sichuan basin, at altitudes 200−2000 m. The range of AsA in mature leaves and young fruit is 30−379 mg/100 g fresh weight and 741−2127 mg/100 g fresh weight, respectively. In general, AsA is highest in young fruit and decreases gradually during subsequent growth and development. Some genes related to AsA metabolism have been cloned from A. eriantha, for example, GalUR, GME, GMP, GPP and cAPX. The content of total phenolics, 466.06–1112.6 mg/100 g fresh weight, of A. eriantha fruit is significantly higher than that of A. chinensis var. chinensis and A. chinensis var. deliciosa. Gallic acid is the most abundant phenolic, 109.13–620.55 mg/100 g fresh weight. The main sugar components during fruit development are fructose, glucose and sucrose and the main organic acid components are quinic acid, citric acid and malic acid. There is rich genetic diversity among the different male genotypes of A. eriantha, especially in flower color and pollen characteristics. There are three types of pollen surface ornamentation: brain-like, irregular ripple and warty. Simple sequence repeats techniques (SSR) can effectively distinguish genotypes of A. eriantha, and using this technique, eight SSR markers were found to be associated with soluble sugar content, titratable acid content, chlorophyll content, dry matter and soluble solids content, and five excellent SSR markers were associated with leaf and fruit AsA content. Transformation of A. eriantha allows it to be a potential species for functional genomics studies in Actinidia. Several excellent A. eriantha female and male cultivars (selections) with special or superior characteristics have been introduced, at present, most new cultivars were selected from wild A. eriantha germplasm. These excellent selections could supply possible commercial cultivars for industry, and also can be used for novel breeding through inter- and intra-hybridization.