First Report of Fusarium avenaceum Causing Canker Disease on Kiwi Tree in China

In May 2021, canker symptoms were detected on ‘Xuxiang’ kiwi trees in southwestern Shaanxi (Hanzhong municipality; 107.27° E, 33.23° N) in China. Seven-year-old trees exhibited black necrotic lesions and cracked areas in the trunk (Figure 1). The symptoms were observed in approximately 10% of the trees in 6 orchards (31 ha in total). Application of commercial fungicides did not control the advancement of the pathogen, and infected trees were removed to control the spread. Three samples, approximately 1 cm2 in size, of symptomatic tissue were collected and surface sterilized in 2% NaOCl for 1 min, and washed with sterile ddH2O. Four isolates showing white mycelium with yellow pigmentation were obtained after 4 days of incubation on PDA, containing chloramphenicol (50 µg/mL), at 28 ºC. The pathogen was isolated from all collected samples. ITS, EF1-α, TUB2, RPB1 and RPB2 genes were amplified using ITS1/ITS4, EF1-728F/EF1-986R, T1/T22, RPB1-5F/RPB1-8R and RPB2-5F/RPB2-7cR (strain NJC06), or RPB2-c7F/RPB2-11aR (strains NJC07 and NJC08), primers, respectively. Two isolates shared the same sequences (strain NJC08). Obtained sequences were submitted to GenBank under accession numbers MZ669205 and OL347898-OL347899 (ITS), OL439731-OL439733 (EF1-α), OL439734-OL439736 (TUB2), OL439737-OL439739 (RPB1), and OL439740-OL439742 (RPB2). The sequences shared >99% (ITS; F. avenaceum CBS 128538, MH864972), >99% (EF1-α; F. avenaceum 55-2, MN473124), 100% (TUB2; F. avenaceum SICAUCC 18-0001, MK253102), >98% (RPB1; F. avenaceum NRRL 26911, MG282372), and >98% (RPB2; F. avenaceum SICAUCC 18-0001, MK396098; or F. avenaceum FRC R-09495, CQ915486) homology to multiple F. avenaceum strains. Molecular phylogenetic tree (Figure 2) was constructed using MEGA7 with Fusarium strains found causing rot in various hosts (Wang et al. 2015), and other fungal species, such as Cadophora nalorum, Diaporthe ambigua, D. australafricana, and Neofusicoccum parvum, which were reported to cause cordon dieback on kiwi tree in Chile (Diaz et al. 2021). Microscope observations after cultivation of all isolates on barley-honey-tryptone medium (Song et al. 2020) showed the presence of septate mycelium, fusiform microconidia (8-15 µm in length, containing between 0 and 3 septa; n = 77) and chlamydospores (n = 21), and agree with the morphology of F. avenaceum (Zhao et al. 2020). To confirm pathogenicity, a sterilized spatula was used to make wounds (3 mm diameter, 1 mm depth) on the trunk of 3-months-old ‘Xuxiang’ kiwi trees. Solutions containing 1 × 106 spores/mL (20 µL) of the isolates were injected in the wounds. Sterile ddH2O was used for the control experiment. Inoculated plants were maintained in a growth chamber at 28 °C and 80% relative humidity for 4 days. The pathogen was recovered from the canker lesions, which were similar to those observed in the orchards, and its identity was confirmed by sequence analysis. The pathogen only infected wounded trees, and probably invaded the orchards during the pruning in February 2021. F. avenaceum was reported to cause canker on almond tree (Stack et al. 2020), stem rot on Anthoxanthum aristatum and Polygonatum cyrtonema (Pieczul et al. 2018; Xu et al. 2019), and root rot on carrot, Coptis chinensis and wheat (Le Moullec-Rieu et al. 2020; Mei et al. 2020; Ozer et al. 2020). Recently, F. avenaceum was found causing fruit blotch in kiwi fruit in Anhui (China) (Zhao et al. 2020). Here, F. avenaceum was found causing canker disease in kiwi tree, demonstrating the host and tissue promiscuity of this pathogen. Kiwi is an important crop in China with nearly 1.5 million tons produced in 2019. This report will help to better understand the pathogens reducing kiwi production in China.

Undifferentiated In Vitro Cultured Actinidia deliciosa as Cell Factory for the Production of Quercetin Glycosides

Land plants produce a vast arsenal of specialized metabolites and many of them display interesting bioactivities in humans. Recently, flavonol quercetin gained great attention in the light of the COVID-19 pandemic because, in addition to the anti-inflammatory, antiviral and anti-cancer activity already described, it emerged as possible inhibitor of 3CLpro, the major protease of SARS-CoV-2 virus. Plant cell and tissue culture (PCTC) is an attractive platform for the biotechnological production of plant metabolites. This technology allows a large amount of water and agricultural land to be saved and, being free of contaminants in the process, it is suitable for scaling up the production in bioreactors. In a project aimed to generate and screen in vitro plant cells for the production of valuable specialized metabolites for commercial production, we generated various cell lines from Actinidia deliciosa (kiwi fruit tree) and Actinidia chinensis (gold kiwi fruit tree), that were able to produce relevant amounts of quercetin derivatives, mainly quercetin glycosides. Three cell lines from A. deliciosa were characterized by targeted and untargeted metabolomics. In standard growing conditions, they produce and accumulate up to 13.26 mg/100 g fresh weight (419.76 mg/100 g dry weight) of quercetin derivatives. To address future industrial applications, these cell lines should be entered into an acceleration program to further increase the amount of these metabolites by optimizing the culture conditions and elicitation.

Influence of Different Types of Polysaccharide-Based Coatings on the Storage Stability of Fresh-Cut Kiwi Fruit: Assessing the Physicochemical, Antioxidant and Phytochemical Properties

The present study focuses on studying the influence of various edible biopolymer coatings at several concentrations on physicochemical, antioxidant and lipid peroxidation activity levels of biopolymer-coated fresh-cut kiwi slices stored at room temperature (relative humidity: 90%). Kiwi slices were coated by dipping in xanthan gum (0.1, 0.2, 0.3% w/v), alginate (1, 2, 3% w/v) and chitosan (0.25, 0.50, 0.75% w/v) solutions for 2 min. Kiwi fruit slices without any treatment were designated as the control. Compared to the control, all coated samples retained higher ascorbic acid, titratable acidity, total phenolic component and antioxidant capacity levels. However, xanthan-gum-coated slices retained significantly higher amounts of total phenolics in comparison to alginate- and chitosan-coated slices (p ≤ 0.05). HPLC analysis showed the presence of neochlorogenic acid, chlorogenic acid, ellagic acid and epicatechin. The results suggest that the xanthan gum can be utilized to enhance the shelf life of fresh-cut kiwi slices without compromising quality.

Effect of Oxygen and Carbon Dioxide Concentration on the Quality of Minikiwi Fruits after Storage

The rapid increase in the production of hardy kiwi fruit (A. arguta) since the beginning of the 21st century has required the development of new cultivation technologies and postharvest handling procedures in order to extend the supply and transport of the fruit to distant markets. Fruit storage focuses on the inhibition of ripening processes regulated by ethylene activity or respiration. Both of these are effectively regulated by appropriate concentrations of O2 and CO2 in the atmosphere surrounding the fruit. In this study, the effect of the concentration of both gases in the cold room on the physico-chemical indices of fruit quality, i.e., mass loss, firmness, soluble solids and monosaccharides content, titratable acidity and acid content, and color of the peel was evaluated. Studies have shown that high CO2 concentrations inhibit ripening processes more effectively than low O2 concentrations. Softening of berries as well as an increase in soluble solid contents was recorded during the first 4 weeks of storage in the fruit. However, the increase in monosaccharides was fairly stable throughout the study period. The increase in soluble solids content as well as the loss of acidity were more strongly determined by CO2 than O2, although the acid content in a 10% CO2 atmosphere did not change. Additionally, the fruits were greener after storage in 10% CO2, but the weakness was skin dulling and darkening. The results indicate that the use of high CO2 concentrations (5–10%) effectively inhibits ripening processes in fruit. After 12 weeks of storage, the fruit was still not suitable for direct consumption, which suggests that the storage period can be extended further.

Current Phytochemical and Pharmacological Outlook of Actinidia deliciosa (Kiwi Fruit)

: Worldwide health and therapeutic practices seek to amalgamate alternative medications with evidence-based medicine for an improved understanding of metabolic progression and its influences on the human body. Actinidia deliciosa, also known as “Kiwi fruit”, is a dioecious plant that is native to China and distributed widely across the Asian continent. Commercial planting of kiwifruit was started in the early 20th century when it reached New Zealand from China. In recent times, Kiwi fruit has gained a major demand due to its high content of vitamin C. Kiwi fruit also contains dietary fiber, iron, carotenoids and is a rich source of antioxidants. These may aid in lowering blood pressure, improve wound healing, blood glucose control and improve bowel health. Vitamin C, choline, lutein, and zeaxanthin are antioxidants that assist in the removal of free radicals from the body and may prevent the body from various diseases and inflammations. Herein, we state the health benefits found in diverse compounds from Actinidia deliciosa, highlighting the source, morphology, chemical constituent, cultivation, production, traditional uses, nutritional value, health benefits, toxicity studies, clinical trials, and pharmacological activities while highlighting side effects associated with kiwifruit. This review provides a bird’s eye insight mainly on the morphological, phytochemical, and pharmacological activity, which could be beneficial in making use of technological and scientific advances. This plant can be used as a current medical adjuvant for its potential. The complete plant must be broadly investigated for further future perspective.