Chinese Cymbidium are prized for their ornamental beauty, ecological significance, and economic value. However, genomic resources crucial for breeding studies within this genus remain scarce, which has hindered the identification of key genes controlling economically important traits and posed challenges for conservation efforts. We performed a comprehensive identification of whole-genome simple sequence repeats (SSRs) and single-nucleotide polymorphism (SNP) markers using the restriction-site associated DNA sequencing (RADseq) on C. goeringii and C. faberi. A total of 49,640 SSR loci were identified across both species, with an average density of 12.7 SSRs/Mb. Among these, 17,637 SSRs were common to both C. goeringii and C. faber, while 17,676 and 14,329 SSRs were uniquely identified in C. goeringii and C. faberi, respectively. Additionally, we identified 405,416 SNPs and 26,870 InDels, with average densities of 105.2/Mb and 6.5/Mb. Furthermore, we validated two SSRs (located at Chr01:78857480-78860461 and Chr01:93382182-93384869) and developed an efficient method for identifying hybrids among the progeny resulting from crosses between C. goeringii and C. faberi. We also validated two SNP markers that showed a close association with the petal and lip length using Sanger sequencing. Our findings revealed that the Chr01_99657375 SNP achieved 73% predictive accuracy for identifying long-petal/lip phenotypes. The results are expected to greatly benefit marker-assisted breeding efforts in Cymbidium orchids and lay a solid foundation for the molecular breeding process of improving flower shape traits in orchid plants.

The Coelogyne s.l. is one of the emblematic genera of the Asian orchids, with high horticultural and medicinal values. However, the phylogenetic relationships of the genus inferred from previous studies based on a limited number of DNA markers remain ambiguous. In this study, we newly sequenced and assembled the complete plastomes of seven Coelogyne species: C. bulleyia, C. fimbriata, C. flaccida, C. prolifera, C. tricallosa, C. uncata, and an unknown taxa, Coelogyne sp. The plastomes of Coelogyne exhibited a typical quadripartite structure, varying in length between 157,476 bp and 160,096 bp, accompanied by a GC content spanning from 37.3% to 37.5%. A total of 132 genes were annotated for each plastome, including 86 protein-coding genes, eight rRNA genes, and 38 tRNA genes. Among these, 19 genes underwent duplication within the inverted repeat (IR) regions, and 18 genes exhibited the presence of introns. Additionally, we detected 54 to 69 simple sequence repeats (SSRs) and 30 to 49 long repeats. In terms of codon usage frequency, leucine (Leu) emerged with the highest frequency, while cysteine (Cys) exhibited the lowest occurrence. Furthermore, eight hypervariable regions (atpB-rbcL, psbK-psbI, rps8-rpl14, rps16-trnQ^UUG, psaC-ndhE, ndhF-rpl32, psbB-psbT, and ycf1) were identified. Phylogenetic analyses using complete plastomes and protein-coding genes indicated that Coelogyne s.l. was monophyletic. Moreover, the results robustly supported the division of Coelogyne s.l. into five clades. This study provides a comprehensive analysis of the structural variation and phylogenetic analysis of the Coelogyne s.l. based on plastome data. The findings offer significant insights into the plastid genomic characteristics and the phylogenetic relationships of Coelogyne s.l., contributing to a deeper understanding of its evolutionary history.

Citrus is a highly important global fruit crop that faces significant challenges from citrus Huanglongbing (HLB). The nucleotide binding site leucine-rich repeat (NBS-LRR) gene family plays a central role in plant immunity. However, comprehensive studies on the function of NBS-LRR genes in HLB resistance or tolerance remain limited. In this study, we identified 278 NBS-LRR genes from Citrus clementina. These genes exhibit 7 domain architectures. Physicochemical analyses revealed significant subfamily divergence in length (91-2101 aa), molecular weight (10.57-237.18 kDa), and isoelectric point (pI, 4.61–9.35). Over 82% of proteins localize to the nucleus/cytoplasm, indicating roles in signal transduction and transcriptional regulation. NBS-LRR genes cluster non-randomly among chromosomes, forming tandem repeats on chromosomes 3, 5, and 7. Phylogenetic analysis grouped the NBS-LRR family into 5 clades. Conserved domain analysis identified 10 motifs; Motif 1 and 2 are highly conserved, potentially involved in pathogen recognition. Promoter analysis detected 36 cis-acting elements linked to diverse processes (e.g., hormone/stress response). Synteny analysis revealed 9 genes are orthologous genes of Arabidopsis thaliana. Crucially, transcriptome data showed that significantly higher NBS-LRR expression in Huanglongbing-infected plants, pinpointing candidate gene Ciclev10018143m.1. This study provides a foundation for citrus disease resistance breeding and candidate genes for functional validation.