Search Results (9)

In the past, the Silk Road was a vital trade route that spanned Eurasia, connecting East Asia to the Mediterranean Sea. The genus Prunus, belonging to the Rosaceae family and encompassing plums, peaches, apricots, cherries, and almonds, thrived as human travel along the Silk Road increased. The majority of fruits within this genus, whether wild or cultivated, are naturally sweet and easily preserved by drying for storage and transport. The interaction along the Silk Road between wild populations and diverse varieties of Prunus fruits led to the development of various hybrids. This article provides a summary of archaeological findings related to prominent Prunus fruits such as peaches, apricots, plums, cherries, and almonds, shedding light on their evolutionary history, genetic diversity, population structure, and historical dynamics crucial for species conservation. The origins of biodiversity may involve factors like migration of pre-adapted lineages, in situ variation, or the persistence of ancestral lineages. Furthermore, climate change is affecting spatial genetic patterns and potentially further threatening rare Prunus species. Evaluating the scope and composition of genetic diversity within germplasm collections is essential for enhancing plant breeding initiatives and preserving genetic resources in this changing context. From a molecular point of view, techniques such as genome-wide association studies (GWASs) and the identification of quantitative trait loci (QTLs) and genes responsible for phenotypic changes in cultivars and germplasm collections should be of great interest in these breeding programs, while genomic estimated breeding values (GEBVs) derived from genome-wide DNA polymorphism information can facilitate the selection of superior genotypes. Full article

Peach (Prunus persica), a significant economic fruit tree in the Rosaceae family, is extensively cultivated in temperate and subtropical regions due to its abundant genetic diversity, robust adaptability, and high nutritional value. Originating from China over 4000 years ago, peaches were introduced to Persia through the Silk Road during the Han Dynasty and gradually spread to India, Greece, Rome, Egypt, Europe, and America. Currently grown in more than 80 countries worldwide, the expansion of peach cultivation in Egypt is mainly due to the development and utilization of peach varieties with low chilling requirements. These varieties exhibit unique phenotypic characteristics such as early maturity, reduced need for winter cold temperatures, low water requirements, and high economic value. In this study, a systematic analysis was conducted on the genetic characteristics and kinship relationships of peaches with low chilling requirements in Egypt. We conducted a comprehensive evolutionary and Identity-by-Descent (IBD) analysis on over 300 peach core germplasm resources, including Egyptian cultivars with low chilling requirements, to investigate their origin and genetic characteristics. The evolutionary analysis revealed that ‘Bitter almond’ is closely related to China’s wild relative species Prunus tangutica Batal, while ‘Early grand’ shares one branch with Chinese ornamental peach cultivars, and ‘Nemaguard’ clusters with some ancient local varieties from China. The IBD analysis also indicated similar genetic backgrounds, suggesting a plausible origin from China. Similarly, the analysis suggested that ‘Swelling’ may have originated from the Czech Republic while ‘Met ghamr’ has connections to South Africa. ‘Desert red’, ‘Early swelling’, and ‘Florida prince’ are likely derived from Brazil. These findings provide valuable insights into the genetic characteristics of Egyptian peach cultivars. They offer a significant foundation for investigating the origin and spread of cultivated peaches worldwide and serve as a valuable genetic resource for breeding low chilling requirement cultivars, which is of considerable significance for the advancement of peach cultivation in Egypt. Full article

Parallel evolution usually occurs among related species with similar morphological characters in adaptation to particular environments. Four wild almond species (Prunus) sharing the character of dry mesocarp splitting are distributed in China, most of which occur in arid Northwestern China. In the present study, we aimed to clarify the phylogenetic relationship, evolutionary history, and environmental adaptation of these wild almond species based on genome-wide SNP data and chloroplast genomes. Chloroplast phylogeny showed P. pedunculata and P. tenella were clustered with wild cherry species (Prunus), while P. mongolica and P. tangutica were clustered with wild peach species (Prunus). Genomic phylogeny suggested P. tenella formed an independent clade. An ABC-RF approach showed P. pedunculata was merged with P. tenella and, then, diverged from the ancestor of P. mongolica and P. tangutica. P. tenella was split from other wild almond species at ca. 7.81 to 17.77 Ma. Genetic environment association analysis showed precipitation variables contributed the most to genetic variations between P. mongolica from an arid environment and P. tangutica from a humid environment. Finally, a total of 29 adaptive loci were successfully annotated, which were related to physiological processes in response to abiotic stresses. Inconsistent genomic and chloroplast phylogenetic positions of P. tenella suggested this species could have originated from historical hybridization among different clades of Prunus. Physiological mechanisms promoted P. mongolica in adapting to the arid environment in Northwestern China. Full article

The five independent countries of Central Asia, namely Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan, contain one of the richest areas in the world for the specific and intraspecific diversity of temperate fruit and nut tree species. Research was carried out via the collaboration of national research and education institutes with local community-based agencies and farmer communities. Raw data (2014 observations) for almond, apple, apricot, cherry plum, currant, grapevine, pear, pomegranate, and walnut were collected at the household (HH) level across the five countries: Uzbekistan, Kazakhstan, Tajikistan, Turkmenistan, and Kyrgyzstan. A set of models was used, including household variety richness as the dependent variable, to understand the influence of socio-ecological variables on the amount and distribution of crop varietal diversity in the farmers’ production systems. Four variables were included as explanatory variables of variety richness (fixed factors): ecoregion, ethno-linguistic group, management, and abiotic stress. The results show clear evidence that abiotic stress determines a higher richness of intra-specific diversity in the form of local varieties grown by farmers living in climatically unfavorable areas. The results for the studied ecoregions follow the same trend, with ecoregions with harsher conditions displaying a higher positive correlation with diversity. Mild environments such as the Central Asian riparian woodlands show an unexpectedly lower diversity than other harsher ecoregions. Ethno-linguistic groups also have an effect on the level of varietal diversity used, related to both historic nomadic practices and a culture of harvesting wild fruit and nuts in mountainous areas. The home garden management system hosts a higher diversity compared to larger production systems such as orchards. In Central Asia, encouraging the cultivation of local varieties of fruit and nut trees provides a key productive and resilient livelihood strategy for farmers living under the harsh environmental conditions of the region while providing a unique opportunity to conserve a genetic heritage of global importance. Full article

The almond [Prunus dulcis (Mill.) D.A. Webb] is normally self-sterile, requiring orchard placement of pollinizer cultivars and insect pollinators. Honeybees are the primary insect pollinators utilized, but climate change and the higher frequency of extreme weather events have reduced their availability to levels insufficient to meet the demands of current and anticipated almond acreage. The incorporation of self-fruitfulness may eliminate the need for both pollinizers and pollinators and allow the planting of single cultivar orchards that facilitate orchard management and reduce agrochemical inputs. Self-fruitfulness requires self-compatibility of self-pollen tube growth to fertilization, as well as a high level of consistent self-pollination or autogamy over the range of anticipated bloom environments. The Italian cultivar Tuono has been the sole source of self-compatibility for breeding programs world-wide, leading to high levels of inbreeding in current almond improvement programs. Both self-compatibility and autogamy have been successfully transferred to commercial almonds from cultivated peaches (Prunus persica L.), as well as wild peach and almond species. Self-compatibility was inherited as a novel major gene, but was also influenced by modifiers. Molecular markers developed for one species source often failed to function for other species’ sources. Autogamy was inherited as a quantitative trait. Breeding barriers were more severe in the early stages of trait introgression, but rapidly diminished by the second to third backcross. Increasing kernel size, which was similarly inherited as a quantitative trait, was a major regulator of the introgression rate. Self-fruitfulness, along with good commercial performance of tree and nut traits, was recovered from different species sources, including Prunus mira, Prunus webbii, P. persica, and the P. webbii-derived Italian cultivar Tuono. Differences in expression of self-fruitfulness were observed, particularly during field selection at the early growth stages. Introgression of self-fruitfulness from these diverse sources also enriched overall breeding germplasm, allowing the introduction of useful traits that are not accessible within traditional germplasm. Full article

Ring nematodes are obligate ectoparasites on cultivated and wild herbaceous and woody plants, inhabiting many types of soil, but particularly sandy soils. This study explored the morphometrical and molecular diversity of ring nematodes resembling Criconema annuliferum in 222 soil samples from fruit crops in Spain, including almond, apricot, peach and plum, as well as populations from cultivated and wild olives, and common yew. Ring nematodes of the genus Criconema were detected in 12 samples from under Prunus spp. (5.5%), showing a low to moderate nematode soil densities in several localities from southeastern and northeastern Spain. The soil population densities of Criconema associated with Prunus spp. ranged from 1 nematode/500 cm³ of soil in apricot at Sástago (Zaragoza province) to 7950 and 42,491 nematodes/500 cm³ of soil in peach at Ricla and Calasparra (Murcia province), respectively. The integrative taxonomical analyses reveal the presence of two cryptic species identified using females, males (when available), and juveniles with detailed morphology, morphometry, and molecular markers (D2-D3, ITS, 18S, and COI), described herein as Criconema paraannuliferum sp. nov. and Criconema plesioannuliferum sp. nov. All molecular markers from each species were obtained from the same individuals, and these individuals were also used for morphological and morphometric analyses. Criconema paraannuliferum sp. nov. was found in a high soil density in two peach fields (7950 and 42,491 nematodes/500 cm³ of soil) showing the possibility of being pathogenic in some circumstances. Full article

Xylella fastidiosa (Xf) is a vascular plant pathogen native to the Americas. In 2013, it was first reported in Europe, implicated in a massive die-off of olive trees in Apulia, Italy. This finding prompted mandatory surveys across Europe, successively revealing that the bacterium was already established in some distant areas of the western Mediterranean. To date, the Balearic Islands (Spain) hold the major known genetic diversity of Xf in Europe. Since October 2016, four sequence types (ST) belonging to the subspecies fastidiosa (ST1), multiplex (ST7, ST81), and pauca (ST80) have been identified infecting 28 host species, including grapevines, almond, olive, and fig trees. ST1 causes Pierce’s disease (PD) and together with ST81 are responsible for almond leaf scorch disease (ALSD) in California, from where they were introduced into Mallorca in around 1993, very likely via infected almond scions brought for grafting. To date, almond leaf scorch disease affects over 81% of almond trees and Pierce’s disease is widespread in vineyards across Mallorca, although producing on average little economic impact. In this perspective, we present and analyze a large Xf-hosts database accumulated over four years of field surveys, laboratory sample analyses, and research to understand the underlying causes of Xf emergence and spread among crops and wild plants in the Balearic Islands. The impact of Xf on the landscape is discussed. Full article

Prunus species are important crops in temperate regions. In these regions, drought periods are predicted to occur more frequently due to climate change. In this sense, to reduce the impact of climate warming, obtaining new tolerant/resistant cultivars and rootstocks is a mandatory goal in Prunus breeding. Therefore, the current study assembled three Prunus species including almond, (P. dulcis Mill D.A. Webb), apricot (P. armeniaca L.) and peach (P. persica L.) to model the temporal effects of drought. A hybrid peach × almond and a wild almond-relative species Prunus webbii were also included in the study. Physiological traits associated with photosynthetic activity, leaf water status, and chlorophyll content were assessed under three watering treatments. Results showed that effects of time, genotype, and treatment interact significantly in all traits. In addition, results confirmed that P. webbii have a greater tolerance to drought than commercial rootstocks. However, “Real Fino” apricot showed the fastest recovery after re-irrigation while being one of the most affected cultivars. In addition, from the better response to these watering treatments by the almond genotypes, two different trends were observed after re-irrigation treatment that clearly differentiate the response of the almond cultivar “Garrigue” from the rest of Prunus genotypes. A better characterization of the short-term drought response in Prunus, an accurate and more efficient evaluation of the genotype effect was obtained from the use of mixed models considering appropriate variance–covariance structures. Although the advantages of these approaches are rarely used in Prunus breeding, these methodologies should be undertaken in the future by breeders to increase efficiency in developing new breeding materials. Full article

In order to improve the effectiveness of breeding practices for Prunus rootstocks, it is essential to obtain new resistance resources, especially with regard to drought. In this study, a collection of field-grown Prunus genotypes, both wild-relative species and cultivated hybrid rootstocks, were subjected to leaf ash and carbon isotope discrimination (Δ¹³C) analyses, which are strongly correlated to water use efficiency (WUE). Almond and peach wild relative species showed the lowest Δ¹³C ratios, and therefore, the highest WUE in comparison with hybrid genotypes. In addition, drought-related cis-regulatory elements (CREs) were identified in the promoter regions of the effector gene PpDhn2, and the transcription factor gene DREB2B, two genes involved in drought-response signaling pathways. The phylogenetic analysis of these regions revealed variability in the promoter region sequences of both genes. This finding provides evidence of genetic diversity between the peach- and almond-relative individuals. The results presented here can be used to select Prunus genotypes with the best drought resistance potential for breeding. Full article