Paphiopedilum hirsutissimum (Lindl. ex Hook. f.) Stein is a rare and endangered plant in China with high ornamental value. In order to explore the genetic characteristics of wild P. hirsutissimum resources in Southwest China, and contribute to the protection and utilization of the wild resources, this study used SSR molecular marker to analyze the genetic diversity and population genetic structure of 190 P. hirsutissimum resources which collected from six populations in Guangxi, Yunnan and Guizhou provinces in Southwest China. In this study, the results showed that ten pairs of primers with good amplification effect were selected from 115 pairs of primers, and 50 alleles were detected by 10 pairs of SSR primers of 190 P. hirsutissimum. The average number of alleles (N_a) was five and the average number of effective alleles (N_e) was 2.4835. The average Shannon information index (I) was 0.8592. The average observed heterozygosity (H_o) was 0.4518 and the average expected heterozygosity (H_e) was 0.4387. The average polymorphic information content (PIC) was 0.3996 and the average Nei's expected heterozygosty (h) was 0.4370. In this six wild P. hirsutissimum populations, the number of alleles (N_a) was from 2.8000 to 4.3000. The number of effective alleles (N_e) was from 1.9655 to 2.4060. The observed heterozygosity (H_o) was from 0.3891 to 0.4839. The expected heterozygosity (H_e) was from 0.3795 to 0.4683. The Shannon information index (I) was from 0.6584 to 0.8369, and the Nei's expected heterozygosty (h) was from 0.3648 to 0.4382. In the six wild populations, the genetic diversity of Guangxi Yachang (GYC) and Guizhou Wanfeng Lake (QWF) populations was generally higher (h=0.4382, h=0.4276), while the genetic diversity of Guangxi Mulun (GML) population was relatively low (h=0.3648). Analysis of molecular variance (AMOVA) results showed that genetic variation mainly occurred among individuals within the population (94%), while genetic differentiation within populations was very small (6%). UPGMA cluster analysis based on genetic distance showed that the genetic distance of the six P. hirsutissimum populations was very small, there was no obvious group division and the genetic distance was not completely related to the geographical location. The results of Structure and principal coordinate analysis were consistent with those of UPGMA cluster analysis. Structure and principal coordinate analysis results showed that there was homogenization among the populations, and there was no obvious group division. In summary, the genetic diversity of Paphiopedilum hirsutissimum resources is relatively rich, which can provide a theoretical basis for the protection and utilization of wild P. hirsutissimum resources in Southwest China.

Corynespora leaf fall disease is one of the most severe leaf diseases in major rubber planting countries worldwide, which can cause serious yield and economic losses. The selection, creation, and utilization of resistant germplasms are the most effective prevention and control strategies for this disease. This study evaluated the disease resistance of 821 F₁ populations from three hybrid combinations Yunyan 277-5×IAN 873, RRIC103×Reyan 8-79, Yunyan 277-5×Reken 525 and identified the level of disease resistance. Based on the evaluation results of disease resistance, 32 candidate F₁ generation individual plants were selected from two hybrid combinations that conform to normal distribution. Using three divergent clusters of Corynespora cassiicola and two evaluation methods to identify the resistant candidate F₁ clone seedlings, five resistant germplasms were ultimately obtained by measuring the activity of defense enzymes and analyzing the expression characteristics of disease-related genes in five new resistant germplasms. Further investigation confirmed that the interaction relationship between five new resistant germplasms and multi host C. cassiicola during the infection process. This study provides excellent germplasm materials and a theoretical support for the early selection, cultivation, and utilization of resistant germplasms for the disease resistance of Corynespora leaf fall disease.

The specific transport routes of photosynthetic compounds affect the resource allocation of nutrients at different growth stages. The most important is to affect the quality of flowering and fruit, and promote the artificial cultivation and production of ornamental plants. In this study, Pleione formosana, an endangered species, was used as the material, carboxylfluorescein (CFDA) tracer and laser scanning confocal microscopy were used to study the assimilate transport directions in four different growth and development periods, namely, dormancy period, blossom period, vigorous growth period and half dry period to understand the function of source and reservoir of different organs in different periods. During the dormancy period, assimilates were introduced from mother pseudobulb to bulb plate and finally transported to bud for the growth and development of new bud. In the blossom period, the assimilates were transported irreversibly from the mother bulb to the flower organs to ensure the quantity and quality of flowering. In the vigorous growth period, the assimilates mainly supplied the growth of the leaf and new bulbils at the apex of the mother pseudobulb. In the half dry period, the two daughter pseudobulbs competed with each other for nutrients from the mother pseudobulb, while some assimilates were still used to satisfy the growth and development of apex bulbils. The results showed that pseudobulb, as a nutrient storage organ, played an important role in assimilate distribution and generation regeneration succession in four different periods. Its special function would provide reference for artificial cultivation and commercial production in the future.

Mutagenesis breeding is a fast and effective breeding method, which has special important significance for the improvement of ornamental plant varieties. Orchids have important ornamental, medicinal, edible and/or cultural value, and broad market prospects. Studies have shown that mutagenesis causes the character changes including plant type, leaf character, flower number, flower size, flower type, flower color, flowering time, ornamental period, insect resistance, disease resistance, stress resistance in orchids, and to date, at least 930 mutants and 16 new orchid cultivars have been generated. This paper reviews the achievements of mutagenesis breeding research in orchids, clarifies current situation and factors affecting the effect of orchid mutation breeding, summaries mutation mechanism of orchids, and finds the methods to further improve the efficiency and effect of orchid mutation breeding. It would provide references for creating new varieties of orchids by better utilizing mutation breeding technology and further clarifying the mutation mechanism of orchids.

In order to deepen the understanding of the tolerance of Excoecaria cochinchinensis, Nerium oleander and Fagraea ceilanica to intermittent flooding and high concentration of ammonia nitrogen, an intermittent flooding cultivation experiment was conducted with six aqueous solutions of ammonia nitrogen concentration (0, 0.5, 7.5, 14.5, 21.5, 28.5 mg/L). After 90 days of continuous test, the morphological and physiological indexes of the three plants were determined, aimed to provide theoretical references for the application of the three plants in rain garden, subsurface flow wetland, intermittent flooded green space and other environments. The results showed that: (1) Compared with the soil culture control, under intermittent flooding, all three plants showed adaptive changes in enhancing oxygen delivery to the roots, such as enlarged stem base lenticels and adventitious root formation, and significantly promoted the height growth of N. oleander. However, the growth rate of E. cochinchinensis and F. ceilanica was slowed down due to the influence of flooding; (2) Under the interaction of intermittent flooding and ammonia nitrogen, the plant height of N. oleander increased with the increase of ammonia nitrogen concentration, while the plant height growth of E. cochinchinensis and F. ceilanica was significantly inhibited after the ammonia nitrogen reaching 14.5 mg/L, and when the ammonia nitrogen was 21.5 mg/L, the leaves of E. cochinchinensis appeared symptoms such as reduced leaf area and green loss; (3) Intermittent flooding had no significant effect on the activities of antioxidant enzymes and the contents of chlorophyll, malondialdehyde (MDA), free proline (Pro) and soluble protein (SP) of the three plants. On the 60th days, the activities of antioxidant enzymes, free proline and soluble protein of the three plants fluctuated to some extent, but on the 90th day, each index had little difference compared with soil culture; (4) Under the interaction of intermittent flooding and ammonia nitrogen, on the 90th day, N. oleander could recover to the normal level even when the ammonia nitrogen was 28.5 mg/L. After the ammonia nitrogen was 14.5 mg/L, E. cochinchinensis and F. ceilanica tended to produce more antioxidant enzymes, MDA and free proline, less soluble protein, with obvious physiological disorders. It could be seen that N. oleander showed active morphological adaptation and strong resistance in the aqueous solution with ammonia nitrogen concentration of 0-28.5 mg/L, and could grow in a certain length of time and intermittent flooding environment. Although E. cochinchinensis and F. ceilanica also showed strong adaptability, the tolerance to ammonia nitrogen was weaker than that of N. oleander, and they only grew well in the range of 0-14.5 mg/L ammonia nitrogen concentration aqueous solution. Therefore, the three plants could be used in the intermittent flooded green space, and N. oleander has strong adaptability to high concentration ammonia nitrogen water environment.

Phalaenopsis has a rich variety of flower colors, a long-lasting flowering period, a unique flower type, and high ornamental value. It is considered the most popular and commercially valuable orchid in the market. The axillary buds at the base of each leaf of Phalaenopsis orchid can form pedicels, but most of the axillary buds are in a dormant state during the flowering period. Studying the germination law of latent axillary buds can help improving the proportion of multiple flower stalks in Phalaenopsis, and has good application prospects. The main environmental factors (temperature, plant hormones, light environment, nutrient accumulation, etc) affecting the germination of Phalaenopsis bud and the regulatory methods to promote flower bud germination will be reviewed, in order to provide a reference for the application of regulating more flower bud germination in Phalaenopsis industry in the future.

The flavonoid quercetin is one of the main active ingredients in Chinese medicinal herb, Euphorbia maculata. At present, there are few reports on quercetin biosynthesis gene, and real-time quantitative PCR (RT-qPCR) is one of the common methods in gene research. But it is a prerequisite for relative quantitative RT-qPCR to have suitable reference genes. In order to obtain a suitable reference gene, this experiment was based on the results of transcriptome sequencing, EmSE, EmUBC, EmGDI1, EmLSM12, EmGBP, EmSYP22, EmTRI1, EmRSZ21, EmRPL7 and EmUBQ obtained by our research group in the early stage were selected as candidate reference genes. RT-qPCR was used to detect the expression of the candidate reference genes in roots, stems, leaves and fruits of E. maculata during vegetative and reproduction stages. The expression stability of the candidate genes was analyzed using geNorm, NormFinder and BestKeeper software. The results of different software were integrated and ranked by the geometric mean method. The ranking was in the order EmGDI1>EmUBQ>EmSE>EmUBC>EmLSM12=EmGBP>EmTRI1>EmSYP22>EmRSZ21=EmRPL7. EmC4H, a key enzyme gene in quercetin biosynthesis, was analyzed using EmGDI1 as the reference gene. The difference of EmC4H expression in different tissues at different stages was consistent with the trend of transcriptome sequencing. The reference gene EmGDI1 developed in this study could be used as a suitable reference gene for tissue-specific expression studies of different stages of E. maculata.

The molecular mechanism of the formation of flower diversity is still unclear. In this study, the transcriptome and microRNA sequencing of Dendrobium officinale and D. loddigesii flower organs were performed, and the miRNA-mRNA network and target protein interaction network were constructed by cytoscape and compared at the molecular level. The results of transcriptome studies showed that mRNAs related to flower development had MADS-box AP3 gene, hormone genes, etc. The miRNA-mRNA network analysis showed that the differentially expressed miRNAs and mRNAs were involved in the differential formation of floral pattern, and miR5179 and its target genes AP3, miR160 and their target genes ARFs, miR164 and its target genes NAC021, miR159 and the target genes GAM1, bdi-miR159 and the target genes CKX9, miR167b-3p and the target genes ANT may be involved in floral pattern formation, and the above miRNA was upregulated in D. officinale. The protein interaction pathway showed that two kinds of dendrobium had the key gene of AP3, D. loddigesii lacked four genes: CUL1, TIR1, TIR1A and RBS; there weret wo differentially expressed ARFs genes in the auxin response interaction pathway of two Dendrobium, and D. loddigesii lacked one ARFI gene; D. loddigesii flora specifically possessed the protein interaction pathway of auxin signal transduction target genes constituted by the NAC021 gene. Differential expression of miRNAs/mRNAs in D. officinale and D. loddigesii and protein interaction of target genes may be the main mechanisms leading to the difference between the two Dendrobium flower types.

In this study, the effects of different concentration and ratio of growth regulators on seed germination, rapid propagation and in vitro flowering of Mengzia foliosa were studied. The results showed that the seeds had strong activity and high germination rate at 105 days after artificial self-pollination, and 1/2MS+0.6 mg/L NAA+1.0 mg/L 6-BA medium was more suitable for seed germination. Meanwhile, 2.0 mL/L 6-BA without NAA was more suitable for cluster bud proliferation; and 1/2MS+1.0 mL/L NAA+30 g/L potato homogenate medium was the best for rooting and hardening-off. In addition, 1.0 mg/L 6-BA+0.5 mg/L NAA+1.0 mg/L PP₃₃₃ medium had the highest flowering rate. Our results not only contribute to the conservation and sustainable use of the species, but also provide important materials and technical support for wild population restoration and reconstruction.

Black pepper (Piper nigrum L.) is a world-famous spice crop, known as ‘the king of spice’. The establishment of tissue culture and regeneration technology of black pepper has important application value in improving the efficiency of seedling breeding and industrial development. Here, we investigated the effects of explant sterilization, callus induction, and embryo differentiation in somatic cell regeneration systematically in black pepper, and established the tissue culture technology using the elite cultivar ‘Reyin-1’ as the material. The results showed that episperm micropylar tissues could be employed as the explants. The ripe fruits were first sterilized with 75% alcohol for 45 s, and then peeled seeds were sterilized for 45 s in 75% alcohol, followed by 6-10 min of soaking in 0.1% mercuric chloride. The episperm was removed from the plantlet after two weeks culture in darkness, which was used as the explant for somatic embryogenesis. The callus was induced from episperm micropylar tissues within two-month subculture. The optimal culture medium for callus induction and embryogenic callus differentiation was MS+1.5% sucrose+0.80 mg/L 2,4-D+1.200 mg/L KT, and the callus induction rate was 88.14 %, and differentiation rate of embryogenic callus was about 58.18%. The embryo callus were transplanted on somatic embryo induction medium. Somatic embryos were induced on the medium MS+1.5% sucrose+0.40 mg/L 2,4-D+0.600 mg/L KT, with a induction rate of 13.33%. After two months of rooted culture, tissue culture plantlets were obtained, and the optimal medium for rooting culture was 1/2MS+1.5% sucrose+0.25% activated carbon. In conclusion, the study provided a combine method of alcohol and mercuric chloride for explants sterilization, identified that micropylar tissues of the episperm was the best explants for somatic embryogenesis in black pepper. The medium and culture conditions of callus induction, embryo differentiation, rooting culture during somatic embryogenesis were further explored in black pepper. The results would lay a foundation for high-efficiency tissue culture seedling and transgenic breeding in black pepper.