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.

Abundant germplasm resources are the basis for mango variety breeding and industrial development. For better protection and utilization of mango germplasm resources, the TP-M13-SSR marker developed by our team previously were used to analyze the genetic diversity and construct molecular ID of 145 mango germplasms containing local cultivars, bred varieties and wild relative species, which stored in the nursery of Guangxi Innovation Base of mango germplasm resources conservation. The results showed that the average number of observed alleles for the 12 primer pairs was 3.2838, the average observed heterozygosity (H_o) was 0.5858, the average expected heterozygosity (H_e) was 0.6725, the average Shannon index (I) was 1.3383, and the average Nei's gene diversity index (N_a) was 0.6702. The polymorphism information content (PIC) of the 12 primer pairs ranged from 0.5036 to 0.7827, with an average value of 0.6396. All the primers were highly polymorphic sites. The result suggested that TP-M13-SSR primer could provide data support for genetic diversity analysis of mango. The genetic similarity coefficient of 145 materrials varied from 0.5676 to 1.000, with an average of 0.7417. The genetic similarity coefficient between Irwin and Indian No. 1 was 1.000. The minimum genetic similarity coefficient was 0.5676, between M. persiciformis 20-2 and Dadouxiang mango, M. persiciformis 20-2 and Shuoshuai mango, Jinhuang mango and Guire 10-1 mango. All the 145 mango germplasms were divided into two groups when the genetic similarity coefficient was 0.7060. Group I contained 108 mango species and 20 M. persiciformis species, accounting for 88.90% of the total number of germplasms. Group Ⅱ contained 17 specimens, all of which were M. persiciformis species. Group I could be further divided into five subgroups when the genetic similarity coefficient was 0.7330, among which subgroups I-1 and I-3 were the most abundant, accounting for 91.92% of all mango germplasms. The results of UPGMA clustering analysis showed that M. persiciformis were not clustered strictly according to the species relationship, and the overall clustering result of mango germplasms was basically consistent with its geographical origin. All the 145 materials were amplified by 12 pairs of SSR fluorescent primers to obtain the fingerprint map, and the molecular ID was obtained by the assignment of numbers and letters combination. Each pair of primers could distinguish 12.4 germplasms on average, and the identification rate was significantly higher than that of previous studies, indicating that TP-M13-SSR had more advantageous than denaturing polyacrylamide gel electrophoresis in mango germplasm identification. This study would provide scientific basis for the collection and utilization of germplasm resources and variety breeding of mango. It is also proposed for molecular identification of bred varieties, which is of great significance to the development of mango industry for providing methods for molecular identification and intellectual property of bred varieties.

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.

Eight germplasm resources of Camellia sect. Chrysantha from Daweishan Mountain of Yunnan province were studied to provide scientific basis and research materials for the exploitation and utilization of Camellia plants. In this study, the leaf length and width of 13 cultivars of Camellia sect. Chrysantha were evaluated by direct observation of leaf phenotype, using five known germplasm resources as the control and mature leaves as the test materials, the content of six mineral elements (Cu, Zn, Fe, Mn, Ca, Mg) was determined by the wet ashing method, the contents of four functional components (tea polyphenols, total polysaccharides, total saponins and total flavonoids) were determined by the UV photometer method, the relationship between them and germplasm resources of Camellia sect. Chrysantha was analyzed by the cluster analysis. The results showed that the leaf shape of 13 Camellia sect. Chrysantha could be divided into two types: elliptic and oblong, and there were great differences in leaf area, leaf color and leaf serration. The highest and lowest content of Cu, Zn, Fe, Mn, Ca and Mg in leaves was 2.1, 1.9, 4.3, 6.6, 1.4 and 1.8 times, respectively. The content of total saponins, tea polyphenols, polysaccharides and flavonoids was 10.9, 5.8, 5.0 and 2.0 times, respectively. The correlation analysis showed that tea polyphenols had a significant negative correlation with leaf length/leaf width, a significant positive correlation with leaf color and leaf quality, and a significant negative correlation with leaf length/leaf width and zinc, there were significant positive correlations between leaf color and manganese, villi and copper. The results of cluster analysis showed that the 13 germplasm resources could be divided into 5 groups when the distance coefficient was 4.5, group I (including ‘Honghe 1’ Camellia sect. Chrysantha, JHC-2, JHC-3, JHC-4) and Group IV (including ordinary Camellia sect. Chrysantha, JHC-8, Camellia pubipetala Wan et Huang) contained relatively high contents of the constituents, JHC-2 and JHC-8 may have higher medicinal and health-care functions, but the mineral element contents and contents were generally higher, so the later development and utilization value was higher. The results of this study would be useful for further studies on the accumulation mechanism of important functional components in Camellia sect. Chrysantha, it would also provide theoretical basis for breeding new varieties of Camellia and further development and utilization of Camellia group plants in the future.

The present study revealed the effects of chemical fertilizer reduction patterns on growth, cane yield and fertilizer utilization rate of sugarcane, in order to provide a theoretical basis for the application of mulched drip fertigation and find out the best pattern to reduce fertilizer in sugarcane. Seven different treatments were conducted: no fertilization (CK₀), conventional fertilization (CK₁), mulched drip irrigation + conventional fertilization (CK₂), mulched drip fertigation T₁₀₀ (fertilizer amount equated with CK₁) and T₈₀, T₇₀, T₆₀ (20%, 30% and 40% reduction of fertilizer amount of T₁₀₀). Main agronomic characters, cane yield, sucrose content, sugar yield, economic benefit and nutrient utilization rate of sugarcane were measured in the seven different treatments. The results showed that compared with CK₁, the millable stalk number in CK₂ increased significantly, the tillering rate, plant height, millable stalk number and stalk formation rate in T₁₀₀ were all improved significantly, the effective stalk number and stalk formation rate in T₈₀ and T₇₀ were improved significantly. Compared with CK₁, the cane yield in CK₂, T₁₀₀, T₈₀ and T₇₀ increased significantly by 13.64%, 32.20%, 27.00% and 20.18%, respectively. In the different drip fertigation treatments, there was no significant differences for cane yield between T₁₀₀ and T₈₀, but the cane yield for T₇₀ and T₆₀ decreased significantly in contrast to T₁₀₀. There was no significant difference in sugar content among the different drip fertigation treatments. The change trend of sugar yield and cane yield among the treatments was consistent. Sugar yield in T₁₀₀ and T₈₀ was higher than that in other treatments, and there was no significant difference between that in T₁₀₀ and T₈₀. Compared with CK₁, the net benefit in T₁₀₀ and T₈₀ increased significantly by 4534.4 yuan/hm² and 3953.8 yuan/hm², respectively. The net benefit in T₇₀ and T₆₀ decreased significantly compared with T₁₀₀, and the net benefit in T₆₀ was even 2350 yuan/hm² lower than that in CK₁. The fertilizer utilization rate of all drip fertigation treatments was significantly higher than that of CK₁, and the average utilization rates of nitrogen, phosphorus and potassium fertilizers in T₈₀ were the highest in all the treatments, reached 48.36%, 27.70% and 68.95%, respectively, which was 28.42, 17.95 and 30.71 percentage points higher than that of CK₁, respectively. Overall, in the middle fertility of laterite soil, the application of mulched drip fertigation pattern for T₈₀ could obtain ideal cane yield and benefit.

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.

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.

HSP90 is a key component in maintaining intracellular homeostasis, and it controls multiple cellular processes by regulating the maturation, stability, activity and turnover of its substrates. Rubber tree (Hevea brasiliensis Müll. Arg.) is an important source for the production of natural rubber, which has thousands of industrial uses and a high socioeconomic value. Using PCR technique, an HSP90 family member gene, named HbHSP90.6 gene (GenBank accession number: OP375588), was cloned from rubber tree variety Reyan73397 latex, and the sequence analysis showed that its coding region (CDS) was 2112 bp. Physicochemical analysis showed that its relative molecular weight was 80 774.85 Da, isoelectric point was 5.04, instability coefficient was 38.98, and total average hydrophilicity was -0.610, presumably HbHSP90.6 protein is a stable hydrophilic protein. The results of conserved structural domain analysis and multiple sequence alignment showed that HbHSP90.6 contained a structural domain of PTZ00272 and a highly conserved MEEVD motif, which is a member of the HSP90 family. Phylogenetic analysis showed that HbHSP90.6 clustered with Arabidopsis AtHSP90.1 (NM_124642.4) and rice OsHsp90-1 (LOC_Os04g01740) with 92.34% and 86.44% homology, respectively. Tissue expression analysis showed that the gene expression of HbHSP90.6 gene in latex was significantly higher than that in root, flower, branche, stem and leaf, and the expression of HbHSP90.6 gene in latex reached 283-fold relative to flowers, presumably the HbHSP90.6 gene may be involved in intracellular transport of latex tubes and regulation of latex metabolism. Mechanical wounding treatment in latex significantly upregulated the expression of HbHSP90.6 gene by 19 fold compared to the pretreatment pair, and it is hypothesized that HbHSP90.6 gene is involved in mechanical wounding regulated physiological and metabolic activity responses in rubber trees. The expression of HbHSP90.6 gene reached the highest level at 6 h of treatment with the phytohormones ethephon, jasmonic acid and 3-Indoleacetic acid, which were 45 fold, 17 fold and 6 fold higher than before treatment, respectively. The expression of HbHSP90.6 gene was significantly upregulated at 12 h after brassinosteroids treatment, reaching 50 fold of the pretreatment expression, presumably the HbHSP90.6 gene is involved in phytohormone mediated transcriptional regulation. Subcellular localization was performed by constructing a 35S::HbHSP90.6::GFP fusion expression vector, and the results showed that the HbHSP90.6 gene was localized in the cytoplasm and nucleus, which was consistent with the predicted results of subcellular localization. The results of this study would provide a thorough basis for elucidating the molecular mechanisms of HbHSP90.6 gene in plant hormone signaling-regulated stress and latex metabolism in rubber trees.

The sugar transporter SWEET (sugars will eventually be exported transporter) family has sugar transportation activity for glucose, fructose or sucrose, which is involved in the phloem loading and unloading of photosynthetic product, as well as physiological processes such as flower, fruit and seed development in higher plant. To explore the physiological functions of CitSWEET15 (Cs7g02970) during fruit development and ripening of sweet orange, gene cloning, expression patterns, subcellular localization and sucrose transport activity were performed in the study. The ORF (open reading frame) of CitSWEET15 gene was 918 bp, which encoded 305 amino acids, and possessed seven transmembrane domains. The theoretical isoelectric point of CitSWEET15 was 6.29, and the relative molecular weight was 34.15 kDa. Phylogenetic analysis suggested that CitSWEET15 together with AtSWEET15, VvSWEET15, LcSWEET15 and PuSWEET15 were orthologous genes, and belonged to the SWEET III clade. Sequence alignment showed that nucleotide and amino acid sequence identities of CitSWEET15 with those of Clementine mandarin, Mangshan wild mandarin, Kumquat, Pomelo, Citrus ichangensis Swingle and Citron were 98.69%-99.9% and 97.38%-100%, respectively. CitSWEET15 and the mentioned Citrus SWEET15 members were completely consistent with four sucrose recognition sites and three sucrose transport activity sites of AtSWEET13, which suggested that all CitSWEET15 and Citrus SWEET15 members may have sucrose transport activity. Quantitative real-time PCR analysis demonstrated that the expression of CitSWEET15 was high in the seed and fruit pulp of sweet orange, the expression level of CitSWEET15 in fruit pulp was low at 80-140 days after flowering, then significantly up-regulated as fruit development, and reached the highest at 230 days after flowering. CitSWEET15 was fused with green fluorescent protein at the C-terminus, and then transiently expressed in Arabidopsis mesophyll protoplasts. The subcellular localization analysis suggested the fluorescence signal was distributed around the outer edge of protoplast, indicating that CitSWEET15 was located in the plasma membrane. By heterologous expression in Saccharomyces cerevisiae W303a (W303-1A) strain and incubation in the sucrose analogue Esculin, the fluorescence intensity was detected to test the sucrose transportation activity of CitSWEET15 and AtSWEET10 (At5g50790, positive control). The fluorescent intensity of yeast cells expressing CitSWEET15, as similar as AtSWEET10, was significantly higher than vector control, indicating that CitSWEET15 had sucrose transportation activity. In conclusion, CitSWEET15 is highly conserved in Citrus species, functions as a plasma membrane sucrose transporter, and involves in apoplastic sucrose transport during fruit ripening of sweet orange. The results would provide a basis for understanding the soluble sugar accumulation in sweet orange fruit, and a candidate gene for improving fruit flavor and quality.

Peroxidase (POD) is a ubiquitous and highly active enzyme in plants, which plays an important role in plant growth and development and stress response. There are few reports on the analysis of POD family genes and the response to salt stress. In this study, 94 POD family members were identified in luffa genome by bioinformatics methods. They had similar gene structure, most of them contained 3-4 exons. The number of coding amino acids were ranged from 89 to 688, with an average of 309. The pI of the protein was between 4.58 and 10.34. 57 of them were basic amino acids. 82 members were hydrophilic proteins. POD family members were unevenly distributed on 13 chromosomes of luffa, of which chromosome 7 was the most (20) and chromosome 12 was the least (1). Phylogenetic analysis divided the POD family members into 8 subfamilies. The analysis of the collinearity of POD family genes with Arabidopsis showed that there were 12 pairs of collinearity genes between the two species, and the POD family genes in luffa had expanded. Protein conserved domain analysis showed that POD family members all contained plant peroxidases conserved domains and had similar conserved bases. The gene promoter contained a large number of plant hormone response elements such as abscisic acid, gibberellin, auxin, ethylene, salicylic acid, methyl jasmonate, and stress response cis elements such as low temperature, hypoxia, light, drought defense and stress response, indicating that it may be induced by abiotic stress. The analysis of cis acting elements in the promoter showed that the promoter contained a large number of phytohormone (abscisic acid, gibberellin, auxin, ethylene, salicylic acid, methyl jasmonate) response elements and stress (low temperature, low oxygen, light, drought, defense and stress response) response cis elements. When luffa seedlings were stressed by 200 and 500 mmol/L NaCl, the POD activity increased, and the gene expression of 56 POD family members increased significantly. Through expression trend analysis, two significant enrichment trends were obtained, including 35 genes that were significantly up-regulated under salt stress, indicating that the genes may participate in the response to salt stress. This study is the first time to identify the members of the POD family of luffa at the genomic level, and analyzed the physical properties and expression under salt stress. The results of this study would lay a theoretical foundation for exploring the biological functions of POD family members in luffa.