Diacylglycerol kinase (DGK) is a lipid kinase that phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Based on converting one important signaling molecule (DAG) to another (PA), DGK plays an important role in plant responses to abiotic stress, including waterlogging stress. However, no studies have been reported on the characterization of the DGK gene family in the waterlogging-tolerant kiwifruit germplasm Actinidia valvata Dunn. In this study, we identified 18 AvDGK genes in the A. valvata genome. The phylogenetic analysis showed that AvDGKs can be classified into three clusters, and members within the same cluster have similar domain distributions, exon-intron structures, and conserved motif compositions. The chromosome localization analysis revealed that all AvDGK genes are located across 18 different chromosomes. There were 29 duplicated gene pairs in A. valvata and all had undergone purifying selection during evolution. The promoter cis-element analysis revealed that the cis-elements within AvDGK genes are associated with multiple functions, including phytohormone signal transduction, stress responses, and plant growth and development. The expression pattern analyses indicated that AvDGKs play important roles in fruit development and plant responses to waterlogging stress. The AvDGK gene family in the tetraploid A. valvata genome might promote PA synthesis and subsequent signal transduction both under short- and long-term waterlogging stresses. These results provide information regarding the structural characteristics and potential function of AvDGK genes within A. valvata and lay a fundamental basis for further research into breeding to enhance the kiwifruit’s tolerance to waterlogging stress.

The genetic diversity of 52 kiwifruit wild germplasms, which were collected by the kiwifruit germplasm nursery of the Guangxi Institute of Botany, was studied using start-codon-targeted (SCoT) molecular markers. The objective was to understand the genetic relationships of the 52 kiwifruit wild germplasms. The results showed that a total of 113 bands were amplified from 52 wild kiwifruit germplasms using 10 primers (9–17 bands per primer, 11.3 on average), of which 103 (91.15%) were polymorphic bands (10.3 bands per primer). The genetic identity of the 52 wild kiwifruit germplasms was in the range of 0.405–1.000, with an average of 0.709. The genetic distance was 0.000–0.904, with an average of 0.355. At the threshold of 0.650, the germplasms were clustered into three clusters. The genetic distances between Guilin and Fushekuoye and between Jinhua and Liangye were both the smallest (0.000), meaning they had a similarity of 100%, as indicated by the SCoT molecular markers. In conclusion, the genetic relationships at the molecular level (genetic distance) were clustered preferentially according to the place of origin instead of by morphological classification, geographical distribution, or ploidy. The genetic relationships between wild kiwifruit germplasms were partially verified through disease resistance analysis.

Kiwifruit (Actinidia spp.) is a globally important economic fruit with high nutritional value. Fruit peelability, defined as the mechanical ease of separating the peel from the fruit flesh, is a critical quality trait influencing consumer experience and market competitiveness and has emerged as a critical breeding target in fruit crop improvement programs. The present review systematically synthesized existing studies on kiwifruit peelability, and focused on its evolutionary trajectory, genotypic divergence, quantitative evaluation, possible underlying mechanisms, and artificial manipulation strategies. Kiwifruit peelability research has advanced from early exploratory studies in New Zealand (2010s) to systematic investigations in China (2020s), with milestones including the development of evaluation metrics and the identification of genetic resources. Genotypic variation exists among kiwifruit genera. Several Actinidia eriantha accessions and the novel Actinidia longicarpa cultivar ‘Guifei’ exhibit superior peelability, whereas most commercial Actinidia chinensis and Actinidia deliciosa cultivars exhibit poor peelability. Quantitative evaluation highlights the need for standardized metrics, with “skin-flesh adhesion force” and “peel toughness” proposed as robust, instrument-quantifiable indicators to minimize operational variability. Mechanistically, peelability is speculated to be governed by cell wall polysaccharide metabolism and phytohormone signaling networks. Pectin degradation and differential distribution during fruit development form critical “peeling zones”, whereas ethylene, abscisic acid, and indoleacetic acid may regulate cell wall remodeling and softening, collectively influencing skin-flesh adhesion. Owing to the scarcity of easy-to-peel kiwifruit cultivars, artificial manipulation methods, including manual peeling benchmarking, lye treatment, and thermal peeling, can be employed to further optimize kiwifruit peelability. Currently, shortcomings include incomplete genotype-phenotype characterization, limited availability of easy-peeling germplasms, and a fragmented understanding of the underlying mechanisms. Future research should focus on methodological innovation, germplasm development, and the elucidation of relevant mechanisms.

Diacylglycerol kinase (DGK) is a lipid kinase that phosphorylates diacylglycerol (DAG) to generate phosphatidic acid (PA). Based on converting one important signaling molecule (DAG) to another (PA), DGK plays an important role in plant responses to abiotic stress including waterlogging stress. However, no studies have been reported on the characterization of the DGK gene family in the waterlogging-tolerant kiwifruit germplasm, Actinidia valvata Dunn. Here, we identified 18 AvDGK genes in the A. valvata genome. The phylogenetic analysis showed that AvDGKs can be classified into three clusters, and members within the same cluster have similar domain distribution, exon-intron structures and conserved motif compositions. Chromosome localization analysis revealed that all the AvDGK genes are located across 18 different chromosomes. There were 29 duplicated gene pairs in kiwifruit and all had undergone purifying selection during evolution. Promoter cis-element analysis revealed that the cis-elements within AvDGK genes are associated with multiple functions, including phytohormone signal transduction, stress response, and plant growth and development. The expression pattern analyses indicated that AvDGK play an important role in the fruit development and plant response to waterlogging stress. AvDGKs gene family in the tetraploid A. valvata genome might promote PA synthesis and subsequent signal transduction both under short-term and long-term waterlogging stress. These results provide information regarding the structural characteristics and potential function of DGK genes within kiwifruit and lay a fundamental basis for further research into breeding for enhancing the kiwifruit’s tolerance to waterlogging stress.