Actinidia latifolia, with the highest vitamin C content in its genus, is a unique wild relative of kiwifruit that could be important for genetic breeding research. Climate change significantly influences the distribution range of wild plants. Accurately assessing the potential distribution of wild kiwifruit and its response to climate change is crucial for the effective protection and sustainable utilization of its germplasm resources. In this study, we utilized the optimized MaxEnt model to predict the potential habitats of A. latifolia in China, employing the jackknife test to assess the importance of environmental variables in our modeling process. The results showed that annual precipitation (Bio12) and temperature annual range (Bio7) emerged as the most influential environmental variables affecting the distribution of this kiwifruit wild relative. As radiative forcing and time increase, the potential habitats of A. latifolia in China are projected to shrink southward, thereby exacerbating habitat fragmentation. This research offers significant scientific references for the investigation, protection, cultivation, and application of wild relatives of the kiwifruit.
Understanding genetic diversity and structure in natural populations and their suitable habitat response to environmental changes is critical for the protection and utilization of germplasm resources. We evaluated the genetic diversity and structure of 24 A. chinensis populations using simple sequence repeat (SSR) molecular markers. The potential suitable distribution of tetraploid A. chinensis estimated under the current climate and predicted for the future climate was generated with ecological niche modeling (ENM). The results indicated that the polyploid populations of A.chinensis have high levels of genetic diversity and that there are distinct eastern and western genetic clusters. The population structure of A. chinensis can be explained by an isolation-by-distance model. The results also revealed that potentially suitable areas of tetraploids will likely be gradually lost and the habitat will likely be increasingly fragmented in the future. This study provides an extensive overview of tetraploid A. chinensis across its distribution range, contributing to a better understanding of its germplasm resources. These results can also provide the scientific basis for the protection and sustainable utilization of kiwifruit wild resources.
Anthocyanin is the main component of pigment in red-fleshed kiwifruit. 'Jinhongguan' is a new cultivar of Actinidia arguta with red peel and flesh after harvest. However, the specific types of anthocyanin in the 'Jinhongguan' fruit and its biosynthesis pathways remain largely unknown. Here, the total anthocyanin content in the fruit color conversion process was determined. The results showed that total anthocyanin content increased with the deepening color of the peel and flesh. To identify the genes related to anthocyanin biosynthesis and the types of anthocyanins in the 'Jinhongguan' fruit, a combined analysis of transcriptome and anthocyanin-targeted metabolome was carried out. A total of 5751 common differentially expressed genes (DEGs) at different stages of peel and flesh were identified, of which 2767 were common up-DEGs and 2976 were common down-DEGs. KEGG and GO enrichment analyses showed that the common up-DEGs were significantly enriched in anthocyanin synthesis-related pathways, suggesting some up-DEGs are involved in anthocyanin biosynthesis. In total, 29 metabolites were detected in the flesh by anthocyanin-targeted metabolome. Among these, nine were differential accumulation metabolites (DAMs) in comparison to red flesh vs green flesh. Six DAMs were up-regulated, with five of them were cyanidins. The content of cyanidin-3-O-galactoside was much higher than that of other DAMs, making it the main pigment in 'Jinhongguan'. Moreover, a total of 36 anthocyanin synthesis-related structural genes, 27 MYB transcription factors (TFs), 37 bHLH TFs and 9 WDR TFs were screened from the common DEGs. Correlation analysis of transcriptome and metabolome revealed that 9 structural genes, 6 MYB TFs, 6 bHLH TFs and 1 WDR TF were significantly associated with cyanidin-3-O-galactoside. Further, qRT-PCR analysis demonstrated that structural genes (AaPAL3, Aa4CL3, AaCHS2/3/8/9/11, AaDFR1/2, AaANR1, UFGT3a and UFGT6b) and TFs (MYB108, bHLH30, bHLH94-1 and WD43) play important roles in cyanidin biosynthesis. Overall, this study identified cyanidin-3-O-galactoside as the main anthocyanin type and revealed key candidate genes of red coloration of post-harvest fruit in Actinidia arguta. These findings provided new insights into the color formation mechanism of post-harvest fruit and offered a theoretical basis for color regulation in kiwifruit.
Kiwifruit belonging to the Actinidiaceae family is a perennial, dioecious vine called ‘the king of fruits’ due to its considerably nutritious and sweet characteristics. A. chinensis complex, including two main groups, A. chinensis var. chinensis and A. chinensis var. deliciosa, is a major component of Actinidia due to their huge economic value and the high degree of development and utilization. Wild resources are widely distributed in China, but are under serious threat due to extreme environments and destroyed habitats. Thus, it is of great significance for the conservation of kiwifruit resources and the sustainable development of the kiwifruit industry to evaluate the genetic diversity of existing genetic resources and to systematically construct a core collection of the A. chinensis complex. In this study, 40 high polymorphism microsatellites markers were used to investigate all accessions from the A. chinensis complex. A total of 888 alleles were marked with 22.2 alleles in each locus. The expected heterozygosity was 0.846, the observed heterozygosity was 0.622, the polymorphism information content was 0.835, and the Shannon information index was 2.369. Among these loci, the observed heterozygosity of 38 loci was lower than expected. The inbreeding coefficient was 0.257, which indicates that frequent hybridization occurred between close relatives. Analyses of molecular variance showed that genetic variations mainly came from the population. Finally, a core collection containing 93 accessions was constructed. The bank not only perfectly represented the genetic diversity of the original population, but also had excellent potential for development and utilization. Our research provides a crucial reference for the future conservation, germplasm identification, and genetic breeding of kiwifruit.
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