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In order to better understand the changes in fruit quality and soluble sugar components in wild Actinidia eriantha at the soft ripening stage, this study explored the fruit quality indexes, soluble sugar components, sucrose metabolism-related enzyme activities and the expression of sucrose metabolism-related enzyme genes in wild A. eriantha germplasm resources. The results showed that the fruit quality of wild A. eriantha at the soft ripening stage was quite different, and the coefficient of variation of fructose content was the largest, followed by sucrose and glucose. Principal component analysis and systematic clustering analysis showed that the comprehensive performance of fruit quality indexes of M28 and M10 was the most prominent. The accumulation and composition of soluble sugar components in different wild A. eriantha varieties (lines) were not consistent. The activities of sucrose metabolism enzymes among wild A. eriantha varieties (lines) were different to some extent. The sucrose metabolism-related enzyme genes among wild A. eriantha germplasm resources had different expression patterns. The results will contribute to understanding the fruit quality changes and the mechanism of sugar metabolism in wild A. eriantha at the soft ripening stage, and lay a foundation for the protection and utilization of wild A. eriantha germplasm resources.

According to the investigation of wild Actinidia eriantha in Jiangxi province of China, we found that soluble solids content of fruit was lower than edible standard (14%). However, we found a high-sugar type A. eriantha line (code was ‘MM24’, test material) during investigative process at Nancheng county (E 116° 48′, N 26° 23′, 845 m). We sheared its scions to asexual reproduction in Fengxin County (rootstock was A. deliciosa ‘Miliang 1’ with 7 years old) and at the same time DUS (Distinctness, Uniformity and Stability) test was also carried out. There were uncontested differences between the two comparative genotypes according to the results of polyacrylamide gel electrophoresis, it can be judged as a new cultivar. In addition, there was great similarity on most important morphological and quality characteristics. While, there was difference on SSC, DM and TS between the two materials on ripen fruit, these indicators were much higher on test material than on control. The sugar degree assessment showed that the sugar degree of test material was strong and retention time was long. Further, no sucrose was found before DAF 135 d in test material and sucrose were significantly higher than in control only at DAF 165 d and DAF 175 d. The qRT-PCR results of sucrose-related genes showed that the relative expression levels of AcSPS1, AcSPS3, AcSPS5 and AcSUS5 genes were consistent with the sucrose accumulation trend, which was probably the main genes for the difference in sugar degree.

Jinyan (Actinidia eriantha × A. chinensis) is one of the gold-fleshed kiwifruit cultivars currently being promoted in south China. However, its fruit dry matter is usually less than 16%, which seriously affects fruit quality including taste and flavor. This causes a financial loss to growers: not only are the prices paid for the fruit low because of their bad reputation for quality, but some orchards have been removed. Improvement of fruit quality is essential. In this study, a method is described for squeezing and twisting flowering shoots before flowering and removing the distal vegetative parts of flowering shoots after fruit set. The effects on fruit quality were determined. The dry matter of fruit was increased by 6.6%. Fruit size also increased as did the chlorophyll a content and the chlorophyll:carotenoid ratio. The significantly increased fruit dry matter, resulting in significant increases in fruit soluble solids concentrations (P < 0.01), thereby possibly improving fruit taste. Fruit weight, fruit length, and carotenoid and ascorbic acid concentrations were significantly enhanced in comparison with controls (P < 0.01), increasing by 20%, 7%, 12%, and 19%, respectively. However, there was no significant difference in soluble sugar concentrations, titratable acid concentrations, and the reduced chlorophyll b concentrations. This research provides a practical method to increase fruit dry matter, and hence a way to allow fruit quality to reach commercial requirements for cultivars such as Jinyan, which under previous management systems had significant shortcomings in fruit flavor and taste.

To evaluate the domestication and cultivation value of wild Actinidia eriantha germplasm resources in the mountainous areas of southern China, 145 genotypes collected in the Magu Mountain Nature Re...

The chilling requirements of 35 kiwifruit genotypes in south China were evaluated. The number of hours at low temperature (0–7.2°C) required to break natural dormancy was determined. Results showed that the average chilling requirement of the 35 genotypes was 675 h. The chilling requirement of 89% of the genotypes ranged from 576 to 768 h. Overall, the chilling requirements of genotypes of Actinidia chinensis var. deliciosa were higher than those of Actinidia eriantha, which in turn were higher than those of A. chinensis var. chinensis. These results provide a basis for breeding and selection of kiwifruit cultivars suitable for cultivation in low-chill areas of south China.

Kiwifruit has a high commercial value and is especially rich in vitamin C. Successful fruit set in kiwifruit depends on several reproductive processes including pollen germination and pollen tube growth. In this study, we investigated impacts of heat stress temperatures (27, 30, 33 and 36 °C) on pollen germination and pollen tube growth of 25 wild genotypes of Actinidia eriantha. Before heat stress application, pollens were stored at −20 °C for 6 months. The results showed great variation among genotypes in each treatment. Eight genotypes showed no significant change in the reduction of germination percentage. Some genotypes gave unsteady response in tube growth. MH22, MH30 and MH58 were evaluated as more tolerant genotypes. In contrast, MH48 and MH67 were the two most sensitive genotypes. The research of heat stress impact on pollen germination and pollen tube growth will be helpful for breeding new varieties and the identified tolerant genotypes can be used in future breeding programmes.

We examined the influence of storage time on germinability and tube growth of freeze stored pollens collected from 25 wild male plants in Actinidia eriantha variety. Pollens were stored in freezer at - 20°C for six months and one year periods to determine changing at germinability in time. In vitro germination was conducted in certain cultural medium defined for Actinidia genus. The results showed that the germination percentages and tube lengths of genotypes decreased at the end of storage period. MH22, MH45, MH47, MH56, MH67, MH70, MH71, MH72, MH74, MH55 and MH61 genotypes were evaluated as vigor genotypes, because they maintained their viability and germination capability displaying statistically insignificant decreasing although their tube lengths significantly decreased except MH67. This investigation provided to determine some robust wild male germplasm resources in A. eriantha in point of durability of pollens against long term conservation for using at future pollination and breeding programs.

Plantlets were regenerated from leaf explants of Actinidia eriantha Benth. cv White (kiwifruit). The best medium for adventitious shoot formation from leaf blade strips was Murashige-Skoog (MS) medium with 0.1 mg L−1 NAA and 2.0 mg L−1 BA. The frequency of shoot regeneration (%) was dependent on the size and the part of the leaf from which the explant was taken. The highest frequency of shoot regeneration was 7.30±2.61 shoots per explant, for explants taken from within 0–3 cm of the leaf blade base, near a vein and not on the leaf edge. When using petiole-derived explants, a maximum frequency of adventitious shoot regeneration of 79.17% with 6.54±2.31 shoots per explant was obtained using 0.1 mg L−1 NAA and 2.0 mg L−1 ZT in MS medium. The highest rate of rooting obtained was 96.67% when using 1/2 MS medium containing 0.6 mg L−1 IBA and 93.75% when using wet moss without IBA. This is the first report to study the effect of explants taken from different parts of the leaf blade on shoot regeneration...

We report the release of a new, large-fruited kiwifruit cultivar, ‘White’, selected from Actinidia eriantha. Fruit of ‘White’ had a mean fruit weight of 94 g, and a maximum fruit weight of 132 g at harvest in Zhejiang, China. The mean fruit weight is c. 2–4 times that of wild A. eriantha fruit found in Zhejiang and nearly 4 times that of ‘Bidan’, the only other registered A. eriantha cultivar. The fruit are oblong and the peelable skin is covered with dense white hair. The flesh of ripe fruit is green and has good eating quality but little juice. The soluble solids concentration was 14.7%, total sugar 9%, total acid 1.24%, and vitamin C 628.37 mg/100 g fresh weight. Its harvest season is during the last 10 days of October in the south of Zhejiang province, which is c. 2 weeks later than A. deliciosa ‘Bruno’ in the same area. It is sometimes referred to as the “banana kiwifruit” because the skin is easy to peel. This new cultivar has been registered in China (PVR No. CNA20050673.0).

Actinidia eriantha Benth. usually flowers in late spring on shoots that develop from buds initiated during the previous growing season. Documented here is the occurrence of secondary floral shoots in summer on both male and female vines. Those summer shoots were produced by “new” buds initiated during the current growing season. A series of sequential shoot tip removals, to force the most distal developing buds, showed that those secondary floral shoots could be induced when the primary shoots were tipped as early as late November (late spring).