Tree Genetics & Genomes最新文献

The quantitative nature of wood production poses a challenge for breeders. The complex interaction of genotypes with environments (G×E) makes cultivars recommendation difficult. Our objective was to model the G×E interaction using environmental covariates and map the adaptability of commercial Eucalyptus clones based on a geographic information system (GIS) across important plantation regions in Brazil. To achieve this, a productivity dataset with 13,483 stands of six commercial clones was utilized. The effects of geography, soil and climate covariates on clone yield were modeled using partial least squares regression, with data from WorldClim and SoilGrids databases. Using the models for each clone, yield maps were generated at a spatial resolution of approximately 5 km². Then, cultivar recommendation was made through a pixel-by-pixel comparison of predicted yield values among the clones. The covariates that most affected the performance of the clones were annual rainfall, rainfall of the driest month, rainfall of the driest quarter, maximum temperature of the hottest month and average temperature of the wettest quarter. Thus, G×E modeling based on environmental covariates combined with GIS enables a large increase in the resolution of cultivar recommendations by mapping the adaptability of genotypes in each site.

Genomic selection (GS) is increasingly used in tree breeding because of the possibility to hasten breeding cycles, increase selection intensity or facilitate multi-trait selection, and to obtain less biased estimates of quantitative genetic parameters such as heritability. However, tree breeders are aiming to obtain accurate estimates of such parameters and breeding values while optimizing sampling and genotyping costs. We conducted a metadata analysis of results from 28 GS studies totalling 115 study-traits. We found that heritability estimates obtained using DNA marker-based information for a variety of traits and species were not significantly related to variation in the total number of markers ranging from about 1500 to 116 000, nor by the marker density, ranging from about 1 to 60 markers/centimorgan, nor by the status number of the breeding populations ranging from about 10 to 620, nor by the size of the training set ranging from 236 to 2458. However, the predictive accuracy of breeding values was generally higher when the status number of the breeding population was smaller, which was expected given the higher level of relatedness in small breeding populations, and the increased ability of a given number of markers to trace the long-range linkage disequilibrium in such conditions. According to expectations, the predictive accuracy also increased with the size of the training set used to build marker-based models. Genotyping arrays with a few to many thousand markers exist for several tree species and with the actual costs, GS could thus be efficiently implemented in many more tree breeding programs, delivering less biased genetic parameters and more accurate estimates of breeding values.

Pear scab is a major disease of pear worldwide and is caused by two distinct species that are aligned with different commercial Pyrus species: Venturia pirina with European pear (P. communis) and V. nashicola with Asian pear species P. pyrifolia, P. ussuriensis and P. X bretschneideri. As these host-pathogen systems are mutually exclusive, interspecific pear breeding provides an avenue for breeding new scab-resistant cultivars. Here we describe the genetic mapping of resistance to V. nashicola in a pear progeny between interspecific pear selection P019R045T042 and ‘Shinko’ (P. pyrifolia) consisting of 274 seedlings, which was phenotyped twice with V. nashicola inoculum prepared from scab-infected leaves collected from trees of susceptible ‘Niitaka’ (P. pyrifolia). A set of 613 polymorphic DNA markers were selected from the apple and pear Illumina Infinium^® II 9K single nucleotide polymorphism array and genotyping-by-sequencing for the creation of the parental genetic maps with JoinMap v4.1. Using the Interval Mapping module in MapQTL v6.0 software, two significant quantitative trait loci were detected in P019R045T042: one on linkage group (LG) 7 and another on LG10, which we name Rvn5 and Rvn6, respectively. Both Rvn5 and Rvn6 displayed weak additive effects for pear scab (V. nashicola) resistance when both loci worked together in this family. They will contribute to more strong resistance based on gene pyramiding through marker-assisted selections for the introduction of non-host resistance into both Asian and European pears through interspecific hybridization.

Forests help to reduce global warming by capturing and storing atmospheric carbon. Understanding the genetics of keystone species at a population level is vital for the management and sustainable utilization of forest genetic resources. A comprehensive population genetics study was carried out on Rubroshorea curtisii, an important widespread hill dipterocarp species in Peninsular Malaysia. A total of 41 populations across its distribution range in Peninsular Malaysia were collected to elucidate the genetic diversity and ultimately provide management guidelines for this species. The population samples were analysed using 10 polymorphic microsatellite loci and sequenced with three chloroplast DNA (cpDNA) regions. A total of 145 alleles were derived from the microsatellite loci, and 21 haplotypes were identified based on 1,113 bp of concatenated cpDNA sequences. The populations showed moderately high genetic diversity (mean H_E = 0.627 for microsatellite gene diversity and H_T = 0.574 for average haplotype diversity) but low genetic differentiation (F_ST = 0.036). Using Bayesian clustering, the studied populations can be divided into two groups, one of which shows further substructuring. Further sub-structuring in Cluster 1 led to sub-clustering of 1a and 1b. Bottleneck analysis did not detect any recent bottleneck events. Based on our findings, priority areas for in situ and ex situ conservation and minimum population size are recommended for the sustainable utilization of R. curtisii.

To preserve biodiversity and maintain ecosystem services provided by trees in the course of climate change, it is essential to consider challenging tree species, which are less studied primarily due to a lack of investment compared to commercial species. Species of the genus Quercus present an interesting case because of their economic and ecological importance, and their syngameon biology. As a model for exploring ecological diversification, and with recent advances in forest genomics, knowledge, data, and genomic resources for oak have accumulated and are summarized in this review to foster oaks as potential candidate species for future reforestation programs in Canadian natural, peri-urban, and urban ecosystems. We summarize the state of current genomic research in oak and the accompanying opportunities genomics can provide to achieve the potential of oak silviculture in Canada. Further, we highlight the socio-economic benefits of planting oaks and genomic tools for the development of a traceability system along the value chain. Finally, we discuss some of the remaining challenges to successfully integrate oaks into different forest management programs. In light of their increased drought resistance, oak species exhibit a strong potential as viable choices for future forests, resilient agricultural landscapes, and urban areas. By leveraging the progress made in oak genomics and the new applications that have been developed for commercial species, we can foster the successful management of oak genetic resources for the production of suitable seedlings, thereby aiding Canada in its ambitious pursuit of planting two billion trees to combat climate change.

Macadamia (Macadamia integrifolia, and M. tetraphylla) production has increased rapidly in China over the past two decades. However, our understanding of the genetic diversity and genomic background of available macadamia germplasm resources remains limited. Here, we conducted whole genome resequencing of 208 macadamia accessions in a macadamia germplasm from China. In all, 1,110.83 Gb of clean reads and 458,205,696 single nucleotide polymorphisms (SNPs) were identified, including 5,470,885 high-quality SNPs. The overall genetic diversity of 208 macadamia accessions showed nucleotide diversity (Pi), expected heterozygosity (He), and observed heterozygosity (Ho) values of 1.716 × 10^–3, 0.270, and 0.202, respectively. Australian germplasm generally possessed the highest genetic diversity, followed by Chinese germplasm, with macadamia germplasm resources introduced from the United States exhibiting the lowest genetic diversity. Furthermore, both phylogenetic and PCA analyses consistently clustered American accessions together. Genetic structure analysis divided the 208 accessions into nine groups, with moderate to high genetic differentiation found between different groups. These findings and genomic resources obtained from this study will be crucial for the strategic utilization of macadamia germplasm and will significantly contribute to future genome-wide associate studies.

The actin (ACT) family genes are essential for plant growth and development. However, the evolution and function of the ACT family within the Rosaceae species, particularly in pear, remain poorly understood. Here, we identified 41 ACT genes across five Rosaceae species based on phylogenetic and structural features that can be categorized into two primary groups: subfamily I (reproductive) and II (vegetative). Evolutionary analysis suggests that purifying selection played a crucial role in the evolution of the ACT family in Rosaceae, and whole genome duplication (WGD) and dispersed duplication led to the expansion of ACT genes. The pear genome contains twelve ACT genes, which can be classified into two groups based on their phylogeny and expression patterns: reproductive (PbrACT1-5) and vegetative (PbrACT6-12), further validating the reliability of the ACT family classification in Rosaceae. Expression analysis of twelve PbrACT genes across various pear tissues indicated that five genes from subfamily I (PbrACT1-5) were predominantly expressed in pollen tubes, with PbrACT1 exhibiting the highest level of expression. Knockdown of PbrACT1 expression in pear pollen tubes significantly diminished F-actin levels, triggered F-actin depolymerization, and resulted in pollen tube growth inhibition, indicating that PbrACT1 is essential for the formation of the microfilament skeleton during pear pollen tube growth. Overall, this study offers significant insights into the evolution and function of ACT genes in Rosaceae and enhances our understanding of PbrACT in microfilament formation in pear pollen tubes.

Self-compatibility (SC) in a naturally self-incompatible fruit tree species is an incredibly interesting trait for breeding objectives and a valuable tool to investigate the mechanism of the gametophytic self-incompatibility system. We focused on an apple (Malus × domestica Borkh.), in which studies on the SC remain largely unexplored because of a lack of spontaneous and/or induced self-compatible mutants, and performed gamma-ray mutagenesis and succeeded in producing several pollen-part self-compatible mutants. We revealed that SC in the mutants was not caused by a dysfunctional pollen S factor in either of the S-haplotypes but presumably by a translocation of an S-haplotype to a non-homologous chromosome, which allowed the mutants to produce S-heteroallelic pollen grains that overcome self-incompatibility through the competitive interaction between the two different S-factors in the pollen grain. The results from our study demonstrate that duplication of the pollen-S in a pollen grain causes the breakdown of the pollen function in Malus, like Pyrus of Rosaceae and Solanaceae, but not in the mutation of the pollen-S itself, like Prunus. The mutants and our finding will be useful for apple breeding programs.

Abstract

Syagrus coronata (Mart.) Becc. belongs to the Arecaceae family. It is a species native to Brazil of ecological, social, and economic importance. To date, there are few mitochondrial genomes in Arecaceae (Cocos nucifera and Phoenix dactylifera L.), and studies of the mitochondrial genome are essential to understand the evolution of the Arecaceae family. This study reports and compares the newly sequenced genome of S. coronata. Single-end and paired-end reads were used to obtain de novo contigs. The mitochondrial contigs were selected using C. nucifera as a reference and were merged using mate paired-end reads. The mitochondrial genome showed 642,817 bp, circular structure, containing 73 predicted functional genes, including four ribosomal RNA (rRNA) genes, 27 transfer RNA (tRNA) genes, and 42 coding protein genes. Large chloroplast genomic fragments were identified in the mitochondrial genome, and large DNA repetitive fragments were into intergenic space regions. Arecaceae mitochondrial genomes showed partial similarities in size, genome structure, and gene content. However, they exhibited numerous rearrangements. In summary, (1) we sequenced the mitochondrial genome of S. coronata and compared with other mitogenomes of Arecaceae. (2) Genomic rearrangements and gene transfer have been identified from the chloroplast genome to the mitochondrial genome. (3) The mitochondrial genome of Arecareae showed similarities in size, structure, and gene content. (4) The expansion of intergenic space size occurs due to the insertion of genes originating from the nucleus.