Abstract:Walnut (Juglans) species are economically important hardwood trees cultivated worldwide for both edible nuts and high-quality wood. Broad-scale assessments of species diversity, evolutionary history, and domestication are needed to improve walnut breeding. In this study, we sequenced 309 walnut accessions from around the world, including 55 Juglans relatives, 98 wild Persian walnuts (J. regia), 70 J. regia landraces, and 86 J. regia cultivars. The phylogenetic tree indicated that J. regia samples (section Dios… Show more
“…The local climate and environmental conditions in different cultivation areas have allowed for the diversification of different varieties adapt to specific agricultural ecosystems [ 38 , 39 , 40 ]. These genotypes, with particular bio-agronomic and organoleptic characteristics, constitute a significant reservoir of crop genetic diversity with good tolerance to abiotic and biotic stresses that can promote sustainable regional economic development [ 41 ]. Among these, the ‘Sorrento walnut’ is an indigenous Italian walnut originating from the Sorrento peninsula; today, it is cultivated throughout the Campania region (southern Italy), having become a mixture of heterogeneous genetic entities in terms of fruit size and yield, and marketed as ‘Sorrento walnut’ [ 42 ].…”
Walnut processing generates considerable quantities of by-products that could be reprocessed into value-added products that have food and non-food applications. In this context, the aim of this study is to characterize the ‘Sorrento’ and ‘Tulare’ walnut cultivars using the UPOV guidelines and analyze the chemical composition and antioxidant activity of their shells. Insight into the chemical composition of the different granulometric fractions of walnut shell, obtained by sieving, was obtained following ultrasound-assisted extraction by Ultra-High-Performance Liquid Chromatography–High-Resolution Mass Spectrometry (UHPLC-HRMS). The total phenolic, flavonoid, and tannin content and antiradical capacity, obtained by DPPH and ABTS assays, and the Fe(III) reducing power of the extracts were also evaluated. The UHPLC-HRMS analysis indicated the presence of thirty-two compounds ascribable to four major classes of specialized metabolites. Furthermore, the extraction efficiency of gallic acid, ellagic acid derivatives, as well as glansreginin A, increased with the decrease in shell matrix particle size in contrast to chlorogenic acids and flavonoid glycosides. This is the first study to highlight new knowledge on the chemical composition of walnut shells. The results obtained demonstrate the feasibility of recovering valuable bioactive components from agro-waste that may be further valorized.
“…The local climate and environmental conditions in different cultivation areas have allowed for the diversification of different varieties adapt to specific agricultural ecosystems [ 38 , 39 , 40 ]. These genotypes, with particular bio-agronomic and organoleptic characteristics, constitute a significant reservoir of crop genetic diversity with good tolerance to abiotic and biotic stresses that can promote sustainable regional economic development [ 41 ]. Among these, the ‘Sorrento walnut’ is an indigenous Italian walnut originating from the Sorrento peninsula; today, it is cultivated throughout the Campania region (southern Italy), having become a mixture of heterogeneous genetic entities in terms of fruit size and yield, and marketed as ‘Sorrento walnut’ [ 42 ].…”
Walnut processing generates considerable quantities of by-products that could be reprocessed into value-added products that have food and non-food applications. In this context, the aim of this study is to characterize the ‘Sorrento’ and ‘Tulare’ walnut cultivars using the UPOV guidelines and analyze the chemical composition and antioxidant activity of their shells. Insight into the chemical composition of the different granulometric fractions of walnut shell, obtained by sieving, was obtained following ultrasound-assisted extraction by Ultra-High-Performance Liquid Chromatography–High-Resolution Mass Spectrometry (UHPLC-HRMS). The total phenolic, flavonoid, and tannin content and antiradical capacity, obtained by DPPH and ABTS assays, and the Fe(III) reducing power of the extracts were also evaluated. The UHPLC-HRMS analysis indicated the presence of thirty-two compounds ascribable to four major classes of specialized metabolites. Furthermore, the extraction efficiency of gallic acid, ellagic acid derivatives, as well as glansreginin A, increased with the decrease in shell matrix particle size in contrast to chlorogenic acids and flavonoid glycosides. This is the first study to highlight new knowledge on the chemical composition of walnut shells. The results obtained demonstrate the feasibility of recovering valuable bioactive components from agro-waste that may be further valorized.
“…Many studies have demonstrated that genetic diversity in species is influenced by multiple factors, including gene flow (Feliciano et al, 2022;Su, Richardson, et al, 2017), selection (Luo et al, 2022;Niu et al, 2019), evolutionary history (Guerra-Garcia et al, 2022;Roy et al, 2017), and the level of inbreeding (Dicks et al, 2023). For example, Feliciano et al (2022) found low population genetic diversity associated with restricted gene flow in the endemic and endangered species Portulaca hatschbachii in Brazil.…”
Whether ex situ populations constructed in the limited nursery resources of botanical gardens can preserve enough genetic diversity of endangered plants in the wild remains uncertain. Here, a case study was conducted with Camellia tunghinensis, which is one of the species with the lowest natural distribution area in the sect. Chrysantha (golden camellia) of the family Theaceae. We investigated the genetic diversity and population structure of 229 samples from wild and ex situ populations using genotyping by sequencing (GBS). Core germplasm was constructed from these samples. The results showed that wild C. tunghinensis exhibited high genetic diversity, with observed heterozygosity of 0.257–0.293 and expected heterozygosity of 0.247–0.262. Compared with wild populations, the genetic diversity of ex situ populations established by transplanting wild seedlings was close to or even higher. However, the genetic diversity of those established by seed or cuttings of a few superior trees was lower. The Admixture analysis revealed that the structure of the ex situ populations derived from seeds and cuttings was relatively simple compared with the ex situ populations derived from transplanted wild seedlings and wild populations. These results suggested that direct transplanting of wild seedlings was more conducive to preserving the genetic diversity of endangered plants in the wild. In addition, wild populations demonstrated a small differentiation (mean FST = 0.044) among themselves, possibly due to long‐term and frequent gene flow between the wild populations. In contrast, moderate differentiation (mean FST > 0.05) was detected among ex situ populations and between ex situ and wild populations. This may be the combined result of the absence of gene flow pathways and strong selection pressure in various ex situ environments. Finally, 77 core germplasms were extracted from 229, likely representing the genetic diversity of C. tunghinensis. This study provides future strategies for the ex situ conservation and management of the golden camellia species and other rare and endangered plants.
“…Juglans regia (2n = 32, Persian walnut), being wind-pollinated and monoecious, is an important woody oil tree cultivated worldwide, naturally distributed in Eurasia and even southeastern Europe [ 20 , 21 , 22 ]. J. sigillata (iron walnut) is the most closely related to Persian walnut, which grows in the southwest of China [ 23 , 24 , 25 ].…”
Section: Introductionmentioning
confidence: 99%
“…J. sigillata (iron walnut) is the most closely related to Persian walnut, which grows in the southwest of China [ 23 , 24 , 25 ]. The kernels of Persian walnut and iron walnut are rich in nutrition and high in fatty acid content [ 20 , 21 , 22 , 23 , 24 , 25 ]. Persian walnut is the most important species in Juglans , which is distributed and cultivated widely across the world [ 21 , 22 ].…”
Section: Introductionmentioning
confidence: 99%
“…The kernels of Persian walnut and iron walnut are rich in nutrition and high in fatty acid content [ 20 , 21 , 22 , 23 , 24 , 25 ]. Persian walnut is the most important species in Juglans , which is distributed and cultivated widely across the world [ 21 , 22 ]. Persian walnuts and iron walnuts are also used as timber tree species for their high-quality wood [ 20 , 21 , 23 ].…”
Cold stress impacts woody tree growth and perennial production, especially when the temperature rapidly changes in late spring. To address this issue, we conducted the genome-wide identification of two important transcription factors (TFs), CBF (C-repeat binding factors) and ICE (inducers of CBF expression), in three walnut (Juglans) genomes. Although the CBF and ICE gene families have been identified in many crops, very little systematic analysis of these genes has been carried out in J. regia and J. sigillata. In this study, we identified a total of 16 CBF and 12 ICE genes in three Juglans genomes using bioinformatics analysis. Both CBF and ICE had conserved domains, motifs, and gene structures, which suggests that these two TFs were evolutionarily conserved. Most ICE genes are located at both ends of the chromosomes. The promoter cis-regulatory elements of CBF and ICE genes are largely involved in light and phytohormone responses. Based on 36 RNA sequencing of leaves from four walnut cultivars (‘Zijing’, ‘Lvling’, ‘Hongren’, and ‘Liao1’) under three temperature conditions (8 °C, 22 °C, and 5 °C) conditions in late spring, we found that the ICE genes were expressed more highly than CBFs. Both CBF and ICE proteins interacted with cold-related proteins, and many putative miRNAs had interactions with these two TFs. These results determined that CBF1 and ICE1 play important roles in the tolerance of walnut leaves to rapid temperature changes. Our results provide a useful resource on the function of the CBF and ICE genes related to cold tolerance in walnuts.
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