Analysis and comprehensive evaluation of fruit trait diversity of 72 Actinidia chinensis accessions in Yichang

Abstract:【Objective】Kiwifruit has high nutritional and economic values. Actinidia has 75 species or variants, most of which are found only in China. Actinidia chinensis (including A. chinensis var. chinensis and A. chinensis var. deliciosa) is currently the most important domesticated species, with more than one hundred cultivars. These cultivars are mostly from the wild resources. China’s abundant wild Actinidia resources have greatly contributed to the development of the world kiwifruit industry. Hayward, the most widely grown cultivar in the world, comes from the wild resources in Yichang, Hubei Province, and has spawned more than 20 related varieties. In recent years, there has been a lack of information about wild kiwifruit germplasm resources in Yichang. We collected in Yichang 72 wild A. chinensis. Through the study of trait diversity, excellent varieties can be screened.【Methods】The 72 wild A. chinensis fruits collected from Yichang, Hubei province were used as the materials. A total of 14 qualitative traits including fruit shape, fruit shoulder shape, head shape, beak shape, surface hairiness, calyx ring, sepals persistence, degree of lenticel protrusion, cross section shape of fruit center, flesh color, flesh center color, fruit flavor, degree of soft rot during storage were described. Fruit weight, longitudinal and transverse diameters, fruit shape index, soluble solid content and dry matter content were determined. Statistical software was used to analyze genetic diversity and carry out cluster analysis and principal component analysis based on quantitative traits, and comprehensive evaluation was conducted based on principal component score, and the excellent accessions was screened out according to ranking.【Results】The 72 wild A. chinensis fruits had abundant genetic variation in each trait. The genetic diversity index (H’) of the 14 qualitative traits ranged from 0.25 (flesh center color) to 1.36 (fruit shape), and the coefficient of variation (CV) ranged from 11.79% (flesh center color) to 71.15% (fruit shape). The genetic diversity index of the six quantitative traits ranged from 1.84 (fruit weight) to 2.02 (fruit shape index), and the coefficient of variation ranged from 14.68% (fruit diameter) to 42.22% (fruit weight). Cluster analysis divided the accessions into 4 groups at 15 Euclidean distance. Group Ⅰ consisted of 15 accessions, and the content of soluble solid and dry matter were significantly higher than those of the other groups, while the fruit diameter was significantly smaller than that of the other groups. The soluble solid and dry matter contents in group Ⅱ, which consisted of 29 accessions, were significantly lower than those of the other groups. Group Ⅲ was composed of 11 accessions and the fruit shape index in this group was significantly higher than in the other groups, and the longitudinal diameter of fruit was the largest. Group Ⅳ included 17 accessions and their single fruit weight and fruit transverse diameter were significantly higher than those in the other groups. The results of principal component analysis and comprehensive evaluation showed that the accumulative contribution rate of the first three principal components was 94.643%; the characteristic value of the first principal component was 2.704, and the contribution rate was 45.070%, which was mainly determined by the higher characteristic vector value of single fruit weight, fruit longitudinal diameter and fruit transverse diameter. The characteristic value of the second principal component was 1.587, and the contribution rate was 26.450%, which was mainly determined by the characteristic vector value of soluble solid content and dry matter content. The characteristic value of the third principal component was 1.387 and the contribution rate was 23.123% , which was mainly determined by the fruit shape index. The comprehensive scores of the accessions ranged from -1.72 to 2.17, and YC36, YC66, YC08, YC07, YC69, YC18, YC67 and YC68 had comprehensive scores greater than 1, which could be used as excellent wild breeding materials.【Conclusion】The 72 wild kiwifruit accessions in Yichang have high phenotypic diversity index, high coefficient of variation and rich genetic diversity. Eight of them with excellent comprehensive characters were screened for breeding of local varieties.