In order to explore the growth and branching genetic variation of Casuarina equisetifolia half-sib families at seedling stage, the annual seedlings of 40 half-sib C. equisetifolia families were used as the materials. Genetic analysis was carried out on seven traits: seedling height, ground diameter, dry weight, root shoot ratio, number of lateral branches, angle of lateral branch, and length of lateral branch. At the same time, cluster analysis and multi-trait comprehensive evaluation method were used to select excellent families. The results showed that the growth and branching traits of C. equisetifolia half-sib families at seedling stage varied widely, and the differences of the seven traits among families reached extremely significant level. The family heritability of the growth and branching traits ranged from 0.36 to 0.83, which were controlled by moderate or strong inheritance. Four excellent families, 3-265, 5-373, 1-266 and 2-343, were selected at a 10% selection rate. The real gains of seedling height, ground diameter, dry weight, number of lateral branches and length of lateral branches of the selected families was 21.14%, 19.10%, 41.83%, 19.97% and 18.88%, respectively. The genetic gains were 17.55%, 15.66%, 29.70%, 15.57% and 15.10%, respectively. The effect of selection work was remarkable. C. equisetifolia seedlings have great breeding potential among families. The excellent families selected in this study not only enrich the excellent germplasm resources of C. equisetifolia, but provide better germplasm materials for the subsequent genetic improvement and forest construction of C. equisetifolia.

Rubber tree is an important economic tree species. In order to explore the reasonable amount of fertilization in rubber plantations, field experiments with different nitrogen fertilizer dosages were set up to clarify the nitrogen transportion characteristics of rubber plantations after mid- and late-stage fertilization. Four treatments were set up: ① blank control (CK), no fertilization; ② conventional fertilization (C, total fertilization 2 kg/plant, early stage∶middle stage∶late stage=5∶3∶2); ③ reduced fertilization (J, total fertilization 1.6 kg/plant, early stage : mid dle stage∶late stage=5∶3∶2), and the reduction of fertilization is equivalent to a 20% reduction in conventional fertilization; ④ simultaneous fertilization (T, total fertilization 1.6 kg/plant, early stage∶middle stage∶late stage=3∶3∶2). The results showed that the characteristics of soil nitrogen transportion in rubber plantations with different fer tilization treatments were different, mainly vertical transportion, and horizontal transportion fluctuated significantly within 5 cm, and there was no obvious change with the increase of horizontal distance. The ammonium nitrogen in the mid-term fertilization mainly transported to 40-60 cm, while the ammonium nitrogen in the later fertilization mainly stayed at 0-20 cm. The trend of inorganic nitrogen was consistent with that of ammonium nitrogen, the main form of soil inorganic nitrogen under different fertilization treatments was ammonium nitrogen. The transportation ability of both ammonium and nitrate nitrogen was reduced and the transportation to deep soil was reduced in the late fertilization. Therefore, adjusting the amount and time of fertilization is beneficial to improving the utilization rate of nitrogen fertilizer in rubber plantations and reduce nitrogen loss.

Root exudates are one of the important sources of plant autotoxic substances. Studies have shown that phthalic acid is a well known allelopathic autotoxic substance, and it is also one of the substances with higher content in rubber tree root exudates. In order to explore whether phthalic acid has an autotoxic effect on rubber tree, the effects of different concentrations (0.05, 0.50, 1.00, 2.00 mmol/L) of phthalic acid solutions on the seed germination and seedling growth of rubber tree RRIM600 were investigated. Phthalic acid delayed the initial germination time of rubber tree seeds, and reduced the germination rate, germination speed and uniformity of seeds germination. Compared with the control, the germination rate, germination index, germination speed, and uniformity of seeds germination of 2.00 mmol/L phthalic acid trestment decreased by 23.60%, 42.75%, 37.18%, 58.69%. All concentrations of phthalic acid treatment inhibited the growth of shoot length, diameter of shoot base, root diameter, and reduced the seedling biomass accumulation. In the concentration range of 0.05-2.00 mmol/L, the shoot length, diameter of shoot base, root diameter, shoot weight and root weight reduced by 12.91% to 40.70%, 20.05% to 21.59%, 7.89% to 34.13%, 16.18% to 26.47%, 20.00% to 36.00%. The content of soluble sugar, proline and malondialdehyde (MDA) increased gradually with the increase of phthalic acid concentration, along with the degree of cell membrane lipid peroxidation gradually increased. The pigment content and catalase (CAT) activity of rubber tree seedlings increased first and then decreased with the increase of phthalic acid treatment concentration, while peroxidase (POD) and superoxide dismutase (SOD) activities decreased with the increase of phthalic acid treatment concentration. 0.05 mmol/L phthalic acid promoted the accumulation of chlorophyll b in seedlings, decreased the content of chlorophyll a, increased the activity of CAT, reduced POD and SOD activity. When the concentration reached 0.50 mmol, the content of chlorophyll a, total amount of chlorophyll, and carotenoid accumulated to the maximum, and decreased the activities of POD and SOD, at 2.00 mmol/L, the activities of POD and SOD continued to decrease. In conclusion, phthalic acid delayed the initial germination time of rubber tree RRIM600 seeds, decreased the seed germination rate and germination rate, led to the disorder of the physiological function of rubber tree seedlings, and inhibited the growth and development. The results could provide basic data support for the evaluation of the autotoxicity of phthalic acid on rubber trees.

Cassava (Manihot esculenta Crantz) is an important food and bioenergy crop globally. One of the most significant methods for germplasm development and variety selection is hybridization. However, a series of problems including difficulty in seed germination hinder severely the development of new cultivars. Thus, in present study, seed dormancy characteristics as well as dormancy breaking methods were investigated with freshly harvested natural hybrid seeds of SC124. The cassava seeds are oval and contain a seed coat, endosperm and embryo according to the observation of anatomy and scanning electron microscopy. The outer epidermis is smooth and contains epidermal layer, spongy parenchma and densely arranged palisade parenchma from outside to the inside. The seed coat and seed caruncle slow down the water absorption of cassava seeds, while the primary reason for inducing seed dormancy is the mechanical hindrance of seed coat and the existence of the inhibitor, which could be classified as physiological dormancy. Treatments by scarified seed micropyle, removing seed coat and scarified seed micropyle + two alternating cycles of moist cold temperature (0 ℃) for 2 h followed by moist warm temperature (30 ℃) for 2 h could effectively break seed dormancy and improve seed germination percentage. Treatment by scarified seed micropyle was the most effective methods, which promoted seed germination from 2% to 88% and germination rate was also the fastest. The optimum temperature for germination of cassava seeds was 35 ℃, and the germination percentage and germination index was 88% and 36.6, respectively. The research could provide scientific basis for understanding seed structure, seed dormancy characteristics and the best broken method for cassava seeds in production practice, and also provide a theoretical reference for the expression of excellent traits of cassava hybrid offspring.

A field experiment was conducted to investigate the effects of different fertilization and irrigation rates on plant growth, nutrient uptake, yield and fruit quality of MD-2 pineapple. The goal was to deal with the seasonal drought in the main producing areas of pineapple, and determine the appropriate rates of fertilization and irrigation for high-yield and high-quality pineapple variety growth, which can increase the yield and efficiency. MD-2 pineapple was subjected to a field plot experiment with eight treatments: (1) CK (no fertilization and no irrigation), (2) F₁W₀ (no irrigation with conventional fertilization), (3) F₁W₁ (fertigation with 50%-60% of field capacity), (4) F₂W₁ (25% reduction in fertilizer application with 50%-60% of field capacity), (5) F₃W₁ (50% reduction in fertilizer application with 50%-60% of field capacity), (6) F₁W₂ (fertigation with 30%-40% of field capacity), (7) F₂W₂ (the amount of fertilizer was reduced by 25%, 30%-40% of field capacity), and (8) F₃W₂ (the amount of fertilizer was reduced by 50%, 30%-40% of field capacity). The results showed that the total number of leaves, root, stem, leaf, stalk, fruit and plant dry biomass accumulations, and plant N, P, K accumulations of MD-2 pineapple of F₁W₁ treatment were significantly higher than those of CK. Compared with F₁W₀, F₁W₁ treatment significantly increased the plant height, stem height, stem diameter, D leaf length, D leaf width, peduncle diameter, and stem, leaf, peduncle, fruit and plant dry biomass accumulations, and N and K accumulations of plant. The transverse diameter, vertical diameter, fruit weight and fruit yield of MD-2 pineapple of F₁W₁ treatment were significantly higher than those of CK and F₁W₀. And the fruit yield of F₁W₁ was 117.46% higher than CK and 99.40% higher than F₁W₀, while there was no difference between F₁W₀ and CK. The fertilizer contribution rate and agricultural efficiency of each fertigation treatment were significantly higher than those of F₁W₀. The contents of vitamin C and titratable acid of F₁W₀ were the highest, but the sugar-acid ratio was the lowest. Under the same irrigation level, there were no significant differences in growth, dry biomass accumulation and fruit quality of MD-2 pineapple among different fertilization levels. The yield of F₁W₁ treatment was the highest, which had no significant difference with that of F₃W₁ treatment. The irrigation water productivity of F₃W₁ treatment was equivalent to that of all treatments with low irrigation level. Under the same fertilization level, the soluble sugar content and sugar-acid ratio of treatments with high irrigation rate were significantly higher than those of treatments with low irrigation rate. Considering the growth situation, yield and quality of MD-2 pineapple, irrigation water productivity and fertilizer contribution rate, F₃W₁ treatment was the optimal combination of fertilization and irrigation, which was beneficial to realize high yield, quality and efficiency of MD-2 pineapple.

Chili pepper (Capsicum annuum) is an important vegetable and condiment, but the current cropping pattern makes its continuous cropping obstacles increasingly prominent. Most studies show that reasonable rotation is an effective method and means to solve the continuous cropping obstacles of chili pepper. Industrial hemp (Cannabis sativa) is an ideal rotation plant, but the effect of industrial hemp rotation on alleviating the continuous cropping obstacle of chili pepper is not clear. In order to explore the effect of industrial hemp-chili pepper rotation on the growth and physiology of chili pepper, this study took the industrial hemp variety Yunma 1 and two local chili pepper varieties Taiyanghong and Yangjiaola as the materials in the agronomic experiment greenhouse of Yunnan University from 2018 to 2019. Pot experiments were carried out on chili pepper continuous cropping and industrial hemp-chili pepper rotation, respectively. The morphological growth and physiological and biochemical indexes of chili pepper after industrial hemp rotation were comparatively analyzed, and the effect of industrial hemp rotation on the growth and physiology of chili pepper in the later season was preliminarily explored. The results showed that the main physiological and biochemical indexes of chili pepper in the rotation group and the continuous cropping group had the same trend. However, compared with the chili pepper continuous cropping, the chlorophyll content of the two chili pepper varieties increased to a certain extent at 40, 50, 60 and 100 days after seedling thinning, while the activities of antioxidant enzymes (SOD and POD) and root activity also increased correspondingly, especially in the harvest period (100 days after seedling thinning) in the industrial hemp-chili pepper rotation. After the industrial hemp rotation, the net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i) and transpiration rate (T_r) of the leaves of the two pepper varieties were significantly increased at 40, 50 and 60 days after seedling thinning, resulting in a significant increase in plant height, stem diameter, shoot dry weight and root shoot ratio at harvest stage. Compared with the chili pepper continuous cropping, the plant height of Yangjiaola and Taiyanghong increased by 20.65% and 16.85%, the stem diameter increased by 16.32% and 19.94%, the aboveground dry weight increased by 15.39% and 27.50%, and the root shoot ratio increased by 33.26% and 25.47% in the industrial hemp-chili pepper rotation, respectively. In conclusion, the industrial hemp rotation enhanced the physiological activity of late season chili pepper and better maintained the normal growth and development of chili pepper. The results have a guiding significance for the selection of reasonable planting mode of chili pepper in the future.

Pleurotus giganteus is a kind of rare edible fungus newly developed in China. It has typical high temperature resistance and plays an important role in the development of edible fungus industry in tropics. With the large-scale cultivation of P. giganteus in tropics, two strains with different fruiting temperature types were selected, which are suitable for cultivation in hot season and cold season respectively, and can effectively ensure the annual supply of the local P. giganteus market. In order to fully understand the nutritional needs and suitable culture conditions of P. giganteus mycelia, the screened high-temperature strain (PG46) and med-temperature strain (PG79) of P. giganteus were used as the materials to compare and analyze the biological characteristics and liquid fermentation conditions with single factor and orthogonal experimental methods, and the dynamic changes of mycelia growth in liquid fermentation were further studied. The experimental data were analyzed by SPSS 26 software. The experiment results of biological characteristics showed that in the single factor experiment, the growth conditions of PG46 and PG79 were basically the same, the optimal carbon source was maltose, the optimal nitrogen sources were yeast extract powder and peptone, the optimal pH was 7, and the optimal temperature was 25-28 ℃. However, the mycelia of PG79 began to suffer from heat stress at 30 ℃, and the colony morphology became irregular. The orthogonal experiment proofed the single factor results, and the impact order of each factor on the mycelia growth of P. giganteus was: nitrogen source > pH > temperature > carbon source. The experimental results of liquid fermentation showed that on the basis of biological characteristics, when the rotating speed was 150 r/min, the liquid volume was 120 mL, and the inoculation amount was 12%, it was more suitable for the mycelia growth of P. giganteus. The mycelial growth of PG46 and PG79 showed a dynamic pattern of "logarithmic growth", and the highest mycelia biomass was obtained at 15 d (0.95 g) and 13 d (1.09 g) respectively. The mycelia biomass of PG79 was always higher than that of PG46, which was consistent with the difference in growth rate between them (PG79>PG46). The study could provide references for the large-scale cultivation of P. giganteus strains with different temperature types, the optimization of heat stress conditions, cross breeding, and the further study of the phenotype and genotype of P. giganteus.

Phosphorus is an indispensable element in the process of plant growth and development, but it is mostly in the form of ineffective bound phosphorus in the field. The microorganisms in soil can convert the ineffective phosphorus into free effective phosphorus, and fully improve the utilization rate of phosphorus. In this study, a phosphate-solubilizing fungus XZY3PSF was isolated and purified from the corn rhizosphere soil using the phosphorus-solubilized halo method, and the strain was identified. The activity of the strain to dissolve 2.5-20.0 g/L tricalcium phosphate and the phosphate solubilization ability of 10-10⁵ spores/mL to tricalcium phosphate in 1-25 d were analyzed. The mineralization ability of 2.5 g/L and 5.0 g/L calcium phytate was evaluated, and the interaction between it and Bacillus amyloliquefaciens and the pathogen of banana Fusarium wilt disease was evaluated. Based on the morphological characteristics combined with ITS and β-tubulin gene sequences, the strain XZY3PSF was identified as Talaromyces purpureogenus. The highest content of available phosphorus dissolved by phosphate-solubilizing strain under different concentrations of tricalcium phosphate was between 500 and 570 mg/L. The content of available phosphorus in the medium decreased with the prolongation of culture time. The decreasing range of the available phosphorus content in the tricalcium phosphate medium was weakened. On the 25th day, the available phosphorus content in the 15.0 and 20.0 g/L tricalcium phosphate medium was significantly higher than that of the other concentrations. With the increase of the spore concentration in the medium, higher peak value of the available phosphorus content in the culture medium appeared, and its decreasing range expanded with the increase of the spore concentration. During the test period, with the extension of culture time, the mineralization ability of XZY3PSF to calcium phytate was stronger. XZY3PSF and Bacillus X5 had antagonistic effects on the pathogen of banan Fusarium wilt, but the phosphate solubilizing fungus and Bacillus spp. also antagonized each other. The research results would lay a foundation for the development of microbial fertilizers composed of phosphorus-solubilizing fungi and antagonistic bacteria. At the same time, the mineralization of XZY3PSF on calcium phytate would provide a basic theoretical basis for subsequent studies on whether it can degrade organophosphorus pesticides.

This study aimed to identify the pathogen which causes Areca catechu Linnaeus leaf spot and study its biological characteristics. The pathogen was isolated and purified from disease samples by the tissue isolation method, and the pathogenicity of the strain was tested. Combined with morphological characteristics and multi gene (ITS-TUB-TEF) joint analysis, a phylogenetic tree was constructed to identify the pathogen, and to study its biological characteristics under different culture conditions. Leaf spot of A. catechu was caused by Neopestalotiopsis sonneratae. The hyphal growed the fastest on CA medium and the aerial hyphal was the most developed on MEA medium. The optimum temperature for both hyphal growth and spore germination was 28 ℃. 24 h illumination was most favorable for the hyphal growth. Hyphal growed the best at pH 5, and the optimum pH for spore germination was 6. The study would provide a theoretical basis for the control of the leaf spot on A. catechu.

Cassava is an important food crop and economic crop in the world. Tetranychus urticae is one of the important alien invasive pests and one of the four major cassava pests in China. Breeding and utilization of mite resistant varieties is an important means to realize green integrated pest control. The exploitation and utilization of secondary metabolites with mite resistance function and their regulation genes can effectively breed mite resistant varieties in crops. Flavonoid play an important role in plant defense against phytophagous pests, however, there is little knowledge about the function of flavonoid pathway genes in cassava resistance to mite. Based on this, this study used mite-resistant and mite-susceptible cassava cultivars were used to analyze the flavonoid pathway genes related to plant insect resistance and to analyze the difference of gene expression after mites fed for 1 d and 4 d, respectively. The results showed that, compared with before those mites fed, the relative expression of CHS, PGT1, F3H, FLS, LAR, C3'H and CYP93B_16 genes in the cassava cultivars of BREAD, SC9 and BAR900 showed a trend of first decreasing (1 d) and then increasing (4 d) to the levels before the mites feed (0 d), while the relative expression of the above genes in the mites-resistant cassava cultivars C1115, SC9 and Myanmar showed a trend of first significantly increasing (1 d) and then decreasing (4 d). However, they were all significantly higher than those of the levels before the mites feed (0 d). Further comparison of the differences in the expression of the flavonoids synthesis pathway gene in the mites-resistant and sensitive tapioca cultivars before and after mites was infested, it was found that after the pest of the two-spotted spider mites was harmed for 1 d, the expression of CHS, PGT1, FLS and C3'H in the mites-resistant cassava cultivars was significantly higher than that in the sensitive mites cassava varieties. Correlation analysis showed that the expression of the four genes was significantly and positively correlated with cassava mite resistance. Before mites (0 d) and 4 days after mites infestation, the expression of the above genes in mites-resistant cassava varieties was generally higher than that of the tapioca cultivars. The results speculated that mite-resistant cassava cultivar could activate flavonoid pathways to defend T. urticae infestation. This study would lay a theoretical foundation for further elucidating the molecular mechanism of cassava resistance to mite, and for breeding and creating mite-resistant cassava cultivars.