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Cymbidium goeringii is one of the important ornamental orchids, but its high-quality genome has not been previously published. Here, we report a chromosome-level genome of C. goeringii and report the gene family expansion, and contraction of the C. goeringii genome and the regulation mechanism of MADS-box genes in floral organ development. We constructed the pathways of carotenoids and anthocyanins that contribute to the different flower colors of C. goeringii and the metabolic pathways of the main components of flower fragrance. Moreover, we found the genes that regulate colourful leaves and analyzed the resistance genes involved in the adaptive evolution of C. goeringii. Our results provide valuable genomic resources for the improvement of orchids and other ornamental plants.

Bearded irises are horticulturally important worldwide. Molecular assessment of the germplasms is helpful for their scientific utilization. In this study, forty bearded iris cultivars derived from Iris × germanica L., I. variegata L., I. pumila L. and I. pallida Lam. were selected to characterize their genetic diversity and population structure using AFLP markers. 568 bands were generated, of which 479 (84.3%) were polymorphic. The genetic distances among accessions ranged from 0.20 to 1.09, with an average of 0.52. Six clusters could be obtained by cluster analysis, which was generally in accordance with the color performances of tepals. In PCoA analysis, the first two principal co–ordinates accounting for 17.49% and 13.75% of the total variation revealed closer relationships among I. × germanica, I. variegata and I. pallida, whereas I. pumila was further. Five sub-populations could be detected by structure analysis. The findings provide an insight into the germplasm innovation for bearded irises.

A better understanding of embryo development would provide insights into seed quality and subsequent germination events in the interspecific hybridization of Cymbidium faberi ‘Jiepeimei’ × C. sinense ‘Qijianheimo’. At the mature stage, 26.1% of the ovules were abnormal. Most of the hybrid embryos could develop normally. Abortions mainly occurred at the zygote (9.5%) and 2-4-celled embryo (15.1%) stages. No germination was observed at 90 and 105 days after pollination (DAP), when the embryo was at the early globular stage, with abundant organelles but no storage materials. During 110-130 DAP, the globular embryo was formed and the starch grains began to accumulate in plastids. The hybrid seeds collected at 120 DAP showed initiation of germination. Germination significantly increased at 135 DAP and was maximal at 150 DAP, during which period the hybrid embryos developed into the late globular stage. The storage materials, i.e. lipid and protein bodies, began to accumulate and the filamentary structures derived from suspensor cells still persisted. After the seeds matured (160 DAP), the germination percentage declined sharply. Safranin staining revealed that the outer seed coat was totally cuticularized and the inner seed coat appeared as a cuticle layer enclosing the embryo proper tightly, which may be the main factor inhibiting the subsequent germination of hybrid seeds. In conclusion, 150 DAP should be the opportune time for the in vitro germination of C. faberi ‘Jiepeimei’ × C. sinense ‘Qijianheimo’ hybrid seeds. Key words: C. faberi × C. sinense ; embryo development; in vitro ; interspecific hybridization; seed germination Received: September 1, 2015; Revised: September 24, 2015; Accepted: September 25, 2015; Published online: April 27, 2016