In order to find out the ratio of silicon and calcium fertilizer suitable for the cultivation of passion fruit in the low-heat valley area of Guizhou, this study took passion fruit Qinmi No. 9 as the test material. The experiment was conducted with 50 g of silicon fertilizer per plant before flowering, spraying calcium fertilizer about 10 days after flowering, spraying once every 15 days, spraying three times continuously, and the concentration of calcium fertilizer was 500 times, 1000 times and 1500 times. CK was used as the control group, which received no fertilizer application. The effects of different medium and micro fertilizers, as well as dosages, on the quality and related cell wall metabolism indexes of passion fruit were explored by applying silicon fertilizer to the soil and spraying calcium fertilizer during the flowering and fruiting periods. The aim was to screen for the best specialized silicon-calcium fertilizer formula. The aim is to provide a theoretical basis and practical guidance for improving the quality of passion fruit. The results showed that compared with the control, soil application of silicon fertilizer and spraying calcium fertilizer 1000 times combined application increased the single fruit weight, fruit hardness and fruit shape index of passion fruit. Additionally, they elevated the content of soluble solids (TSS) and vitamin C (Vc), while reducing the content of titratable acidity (TA). Furthermore, there was an increase in soluble sugar (SS) and soluble protein content (SP). Peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities were promoted. However, the activities of water-soluble pectin (WSP) content, cellulase (CX), polygalacturonase (PG), and pectin methylesterase (PME) decreased due to the increase in protopectin and cellulose in the peel, each index was significantly different from the control group. It shows that silicon-calcium fertilizer had the best effect on enhancing passion fruit quality and improving the mechanical strength, toughness and stability of peel. Compared to CK, the single fruit weight, fruit hardness, longitudinal diameter and transverse diameter increased by 11.15%, 27.18%, 6.23% and 3.29%, respectively. Moreover, the contents of TSS, Vc, SS and SP increased by 16.95%, 16.12%, 20.57% and 24.55%, respectively, while the content of TA decreased by 36.03%, and the activities of POD, SOD and CAT increased by 13.16%, 19.67% and 21.65%, respectively. The content of protopectin and cellulose in peel increased by 19.29% and 17.19%, respectively. Meanwhile, the content of WSP decreased by 10.63%, and the activities of CX, PG and PME decreased by 8.58%, 22.98% and 7.52%, respectively.

Pigeonpea is an important food and forage crop in the tropics. In order to dissect the physiological characteristics of pigeonpea under cold stress and its cold tolerance, eight seedlings of pigeonpea were tested and analyzed by 8 physiological indexes under 4 ℃ stress, and cold tolerance of pigeonpea were evaluated by subordinate function value method in this study. The results showed that with the prolongation explored to cold stress, REC, SS, MDA and Pro increased respectively, SOD and POD increased firstly and then decreased, and Chl showed a general trend of decline, and the variation of CAT activity was significant difference only in P₂ among the 8 accessions. The cold tolerance of the 8 accessions was in the order: Miandian>Danzhou>170306001>060302216>ICPL7086>Nan 02137>Guangxi>Qiongzhong. The content of Chl, SOD and POD activity were significantly correlated with cold tolerance of pigeonpea, which could be the reliable physiological indexes to evaluate the cold tolerance of pigeonpea.

Five shading levels (0, 30%, 50%, 70% and 90%) were set up to analyze the biomass distribution patterns, the differences in mineral element composition characteristics and nutrient accumulation of Ficus hirta Vahl (FH). The average plasticity index of the biomass indicators of FH was 0.81. The proportion of stem biomass was less affected by shading, while fruit biomass and its proportion were significantly affected. 90% shading level inhibited fruit production, while the 50% shading level exhibited the highest fruit biomass proportion. Shading increased nitrogen and potassium content in FH, while decreasing calcium and phosphorus. The calcium-to- phosphorus ratio ranged from 1.65 to 6.32, with lower ratios in fruits and higher ratios in leaves. Among trace elements, iron content was most affected by shading. 70% and 90% shading levels led to a more than 65% reduction in iron content compared to the control. The iron content was most affected by shading. Under shading, the crude protein content in FH leaves and fruits ranged from 13.91% to 16.82% and 12.22% to 16.46%, respectively. The average content of crude fiber in leaves and fruits was 13.73% and 17.33%, respectively. The ether extract content in FH fruit planted in the full light was the highest, at 13.30%. Shading significantly reduced the content of flavonoids in leaves, stems, and fruits of FH, but the polyphenol content in the leaves and fruits reached its highest under 30% shading rate. In conclusion, The production mainly based on seed harvesting for seedling breeding is not suitable for high shading cultivation. 50% shading level can be used to improve the fruiting rate. Shading altered the accumulation and composition ratio of nutrient in different plant parts. When used as feed material, environmental impact and nutrient ratio adjustments should be considered in FH cultivation. 30% shading rate is better for FH planting when using its leaves as materials for beverage production.

Plant phospholipase A (PLA) is a key enzyme in cell membrane phospholipid metabolism. It can catalyze the cleavage of multiple functional groups on phospholipids to generate signaling molecules, which are involved in regulating plant growth and development as well as environmental and biological stresses. PLA possesses important research value. In this study, the effects of various factors such as substrate concentration, reaction temperature, pH of buffer solution, buffer solution volume, and reaction time on catalytic activities of banana PLA for phospholipid hydrolysis were investigated, so as to optimize PLA activity assay method. According to the optimal assay conditions, the change of banana PLA activity under anthracnose stress was further studied. The results showed that the optimal conditions for the determination of banana PLA activity by acid-base titration method were as follows: pH 9, reaction temperature 55 ℃, substrate concentration 4 g/L, 15 mL substrate, 3 mL crude enzyme extract, the ratio of extraction buffer volume to peel weight (mL/g) 3, and reaction time 7 h. According to the optimal conditions, the PLA activity of banana peel tissue under anthracnose stress was determined. It was found that the degree of disease in peel tissue was positively correlated with PLA activity, indicating that PLA activity increased with the deepening of disease. This suggested that the level of PLA activity was probably related to fruit resistance. As disease degree deepened, PLA activity increased, membrane phospholipids degraded, and cell membrane integrity disrupted, leading to fruit decay. In this article, a convenient and feasible method for the determination of banana PLA activity was established, which laid a foundation for further study of the catalytic mechanism of banana phospholipase A.

Banana is an important economic crop in the subtropical region of China. The occurrence of banana Fusarium wilt has seriously hindered the development of banana industry in recent years. Biological control has attracted attention because of its green environmental protection and durable disease resistance. It’s very important to get the efficient biocontrol strains with different inhibition mechanisms on banana Fusarium wilt. In this study, four different types of biocontrol strains against banana Fusarium wilt which were obtained in the laboratory in the early stage were mutated by ultraviolet-nitrite compound mutagenesis, with the highest antimicrobial activity increased by 186.24% and the highest control effect increased by 46.54%. The disease prevention mechanism of the four mutants obtained was preliminarily investigated. The results showed that the strain Ba62v had the highest inhibition rate on the colony growth of Fusarium oxysporum f. sp. cubense (Foc), and could also induce the activity of SOD enzyme in banana seedlings. The strain Blz02v could promote the growth of banana seedlings and induce the activities of POD and SOD of banana seedlings. The strain Bc11v had the highest inhibition rate on the spore germination of Foc, and could induce the activities of PPO, CAT and SOD in banana seedlings. The strain Pt05v had the highest inhibition rate on the sporulation of Foc, and could induce the activities of POD, PPO and SOD in banana seedlings. The main action mechanisms of the four biocontrol mutants on Foc and hosts are different, and there is a potential for biocontrol of compound synergism, which would provide an important strain resource for the development and utilization of the disease-resistant compound fungicides in the future, and has a good application prospect.

Shanlan upland rice (Oryza sativa L.) is an unique variety in Hainan, with excellent taste quality traits and rich nutrition. At the same time, it also has excellent stress resistance, such as disease resistance, drought resistance and heat resistance. However, thus far, the resistance of Shanlan upland rice to herbivores remains largely unknown. Thus, in this study, using TN1 and RHT as susceptible and resistant control varieties, respectively, the resistance of three Shanlan upland rice varieties, Shanlanchaihongmi, Shanlanjianshanlannuo and Shanlanyingmigaochan to BPH was evaluated, and their resistance mechanisms were analyzed. The results showed that at the seedling stage, the variety of Shanlanjianshannuo showed resistant to Nuaparvata lugens, brown planthopper BPH, whereas the other two varieties were susceptible to BPH. At the tillering stage, the resistance of the three rice cultivars to BPH was all significantly higher than that of TN1. The mechanism studies revealed that the thickness of the thick-walled tissue in the outer leaf sheaths and the level of cell wall components including lignin, pectin, cellulose and hemicellulose were significantly higher in the three Shanlan upland rice cultivars and the insect-resistant control cultivar RHT than the insect-susceptible control cultivar TN1. Moreover, the basal and BPH-induced levels of JA, JA-Ile, ABA and SA in the three Shanlan upland rice cultivars were significantly higher than those in TN1, and the content of ABA in Shanlanjianshanlannuo plants was the highest in all of the tested varieties. The results demonstrated that the thickness of the thick-walled tissue of the outer leaf sheaths of Shanlan upland rice and the rapid and strong responses of JA, ABA and SA signaling pathways to BPH infestation might be the major reasons why the BPH resistance is stronger in Shanlan upland rice cultivars than TN1.

This research aimed to identify a pathogenic fungus of the brown spot disease in the leaves of Cycas and screen for its chemical control agents, which provides a theoretical basis for the protection of Cycas. The pathogenic fungus was isolated from the lesion spots in some Cycas leaves. The pathogenicity of the fungus was confirmed by isolating and purifying the infected leaf tissues and reintroduced to the healthy leaves of Cycas diannanensis following Koch’s postulates. Morphological identification of the pathogenic fungus was conducted. To further confirm the identification, a phylogenetic tree was constructed using eight gene sequences: SSU, LSU, GAPDH, tef1, rpb2, Alt, OPA10-2 and ITS. Effective chemical control agents were screened from seven chemical agents by inhibition assay in vitro. Phylogenetic analyses showed that this pathogen was Alternaria burnsii. Among the tested chemical agents, the most effective inhibition was fluoxastrobin, which displayed 73.48% inhibition rate at a concentration of 0.67 mg/L.

Citrus is one of the most important fruits in China, and its post-harvest occurrence of citrus green mold is a serious threat to the quality and safety of citrus, and also causes mycotoxin contamination in the fruit. A strain of Streptomyces sp. R₂A-15 with good antagonistic effect on the pathogen of citrus green mold was isolated from the root soil of red orange plants in the red orange orchard of Jiuzhoujiang, Lianjiang, Zhanjiang city, Guangdong province. The optimization of the fermentation conditions and stability analysis of the bacterial inhibition activity were studied to provide reference for the preparation and application of the biocontrol agent of citrus green mold. In this study, Penicillium digitatum was used as the target fungus, and the fermentation broth was used as the inhibitory activity according to the size of the diameter of the inhibition zone by paper diffusion method. The fermentation medium of strain R₂A-15 was optimized using one-way and cross-combination tests, and the fermentation conditions were optimized by response surface analysis to improve the inhibitory activity of the fermentation broth, and the stability of the fermentation broth was investigated under different acid-base, temperature and ultraviolet light conditions. The optimum carbon source for the fermentation medium of the strain was cornmeal and the optimum nitrogen source was acid-hydrolyzed casein in the one-way and cross-combination tests. Based on response surface analysis, it was concluded that cornmeal and fermentation time had a significant effect on the bacteriostatic activity of the fermentation broth. The optimal fermentation medium for maximum inhibitory activity of the fermentation broth, as determined by validation tests, was 12.09 g of cornmeal, 4.00 g of acid-hydrolyzed casein, 2.00 g of calcium carbonate, 2.00 g of magnesium sulfate, 2.00 g of dipotassium hydrogen phosphate, 1.00 g of sodium chloride, and 1 L of distilled water. The optimal fermentation conditions were: initial fermentation pH 7.0, fermentation time 37.50 h, fermentation temperature 34 ℃, inoculum volume 3%, and shake flask filling volume 100 mL/250 mL. The bacteriostatic activity of the fermentation broth of the strains increased by 39% after optimization. The overall bacteriostatic activity of the fermentation broth of the strain could be maintained at a relatively stable and high activity level after treatment with different temperatures and ultraviolet light conditions, but the bacteriostatic activity of the fermentation broth decreased under strong acid and alkali. The results indicate that Streptomyces sp. R₂A-15 has a good and stable inhibitory effect on the citrus green mold pathogen, and has a good prospect for practical application, which lays a foundation for the later scale fermentation as well as the development of bacterial agents.

Yunyan 774 is a newly bred rubber tree cultivar in Yunnan, the research on its latex composition and properties is of great significance for its popularization and application. The changes of non-rubber components and colloidal properties, molecular weight and distribution of Yunyan 774 concentrated natural latex during storage, as well as the differences of crosslinking density, physical and mechanical properties, aging properties and latex particle size and distribution after 90 days of storage were measured and analyzed. The experimental results showed that the total solid content and ash content of Yunyan 774 remained unchanged after 90 days of storage, and the dry rubber content decreased by 1.1%, which was related to the reaction of some non-adhesive substances to form substances that could not be precipitated by adding acid. The content of volatile matter decreased slightly, but the content of acetone soluble content, water soluble content and nitrogen increased in different degrees. The content of advanced fatty acids of Yunyan 774 increased with the extension of storage time, and the ammonium soap with protective effect was generated, which played a role in improving the mechanical stability in the early stage. The thermal stability decreased gradually, and the viscosity decreased first and then was basically constant. The increase of volatile fatty acid content was not conducive to the preservation of latex. The physical mechanical properties and aging properties of Yunyan 774 latex vulcanized rubber film were better than those of the mixed strain. Compared with the mixed strain, the molecular weight distribution of Yunyan 774 was wider, the molecular weight was slightly lower, and the particle size was not different.

In order to obtain the structural mechanical property parameters of rubber bark and solve the problem that there is no reliable reference for accurate detection of rubber depth and accurate control of skin loss thickness in the research and development of mechanized rubber picking equipment, a test device for nonlinear mechanical property measurement of rubber bark based on PLC was designed to realize automatic continuous detection and data collection of rubber bark mechanical properties with high precision and low loss measurement of bark thickness. The mechanical properties of bark of 15-, 20- and 25-year-old rubber trees of Reyan 7-33-97 and PR107 were studied, and the mathematical model of piercing force with piercing depth was established. The experimental results showed that the performance of the device was stable, and the piercing force curves of different strains and different ages were similar, showing a high-low-high trend, and were highly correlated with the layered characteristics of the bark structure. Under the same age, the piercing force of two strains of Reyan 7-33-97 and PR107 was not significantly different, and the piercing force of older trees of the same strain was greater than that of younger trees. The maximum piercing force reached 48.5 N. The test device meets the requirement of detecting structural mechanical parameters of rubber bark and provides theoretical basis for the research and development of mechanized rubber harvesting equipment.