【Objective】To address the significant decline in papaya fruit quality and yield caused by postharvest anthracnose, this study aimed to isolate and screen high-quality antagonistic bacteria, evaluate their antifungal activity against Colletotrichum siamense, and preliminarily investigate their mechanisms of action against anthracnose.【Method】Rhizosphere soil samples were collected from diseased papaya plants in Zhanjiang City, Guangdong Province, to isolate and screen bacterial strains exhibiting strong antagonistic activity against C. siamense. Taxonomic identification of the target strain was performed through morphological observation, physiological and biochemical characterization, and phylogenetic analysis. The antagonistic activity of bacteria against C. siamense T3 and seven pathogens was assayed using the dual-culture plate method. Furthermore, the biocontrol efficacy of the antagonistic bacteria against anthracnose was validated through in vivo inoculation of papaya fruits and leaves.【Result】A biocontrol strain J28 with antagonistic activity against C. siamense T3 was successfully isolated. Morphological characteristics, physiological and biochemical properties, and phylogenetic analysis identified the strain J28 as Bacillus velezensis. The strain J28 was capable of hydrolyzing starch and litmus milk, liquefying gelatin and reducing nitrate. It could also utilize citrate, glucose, sucrose, and maltose, and exhibited catalase activity, as well as the ability to participate in the Methyl Red and Voges-Proskauer reactions. Strain J28 exhibited high salt tolerance, maintaining robust growth capability on LB plates containing 125 g/L NaCl. B. velezensis J28 significantly inhibited the mycelial growth of C. siamense T3 isolated from papaya, with an inhibition rate of 61.81%. Concurrently, strain J28 exhibited broad-spectrum antifungal activity, inhibiting the growth of C. gloeosporioides, Botryosphaeria dothidea, and five other pathogenic fungal species, with inhibition rates ranging from 60.28% to 70.94%. In addition, the fermentation broth of strain J28 inhibited the germination of C. siamense T3 by 65.89% at a concentration of 100%. In vivo inoculation experiments confirmed that B. velezensis J28 effectively inhibited C. siamense in both papaya fruits and leaves, achieving biocontrol efficacies of 72.35% and 93.33%, respectively.【Conclusion】In conclusion, strain J28 possesses broad-spectrum antifungal activity and exhibits significant biocontrol potential against papaya anthracnose. This research provides a theoretical basis and technical support for future exploration of salt-tolerant microbial resources and the development of broad-spectrum biological antifungal agents for plants.
【Objective】To clone the papaya eukaryotic translation initiation factor 4E gene (CpeIF4E), and analyze its expression pattern in response to papaya leaf distortion mosaic virus (PLDMV) infection, the subcellular localization of CpeIF4E protein, as well as the interaction and key interaction sites between CpeIF4E and PLDMV genome-linked protein (PLDMV-VPg). This study will provide a theoretical foundation for the application of CpeIF4E in disease-resistant molecular breeding of papaya.【Method】CpeIF4E and PLDMV-VPg genes were cloned from healthy and PLDMV-infected papaya leaves, respectively, and their coding sequences were identified. The subcellular localization vector CpeIF4E-GFP was constructed and transformed into rice protoplasts to determine the subcellular localization of CpeIF4E. The expression level of CpeIF4E under PLDMV infection was detected by realtime quantitative PCR (RT-qPCR). The interaction between CpeIF4E and PLDMV-VPg was verified using yeast twohybrid assay (Y2H), bimolecular fluorescence complementation (BiFC) assay, and luciferase complementation (LCI) assay. Based on natural variation sites of resistant eIF4E, site-directed mutagenesis of CpeIF4E at amino acid positions 73, 75, 82, 87, 114, and 117 was performed using overlap-extension PCR. Interaction assays were performed to identify the key residues for CpeIF4E and PLDMV-VPg interaction.【Result】The full-length CDS of CpeIF4E was 711 bp, encoding 236 amino acids containing an IF4E domain. The coding sequence of PLDMV-VPg was 561 bp, encoding 186 amino acids. CpeIF4E was localized in the cytoplasm and nucleus. The expression level of CpeIF4E peaked at 7 days post PLDMV inoculation. CpeIF4E physically interacted with PLDMV-VPg. Mutations at positions 73, 75, 82, and 114 completely abolished the interaction between CpeIF4E and PLDMV-VPg, whereas mutations at positions 87 and 117 did not affect the interaction.【Conclusion】CpeIF4E interacts with PLDMV-VPg, and the key interaction amino acid sites are positions 73, 75, 82, and 114. This study provides a clear theoretical basis and operable targets for creating novel PLDMV-resistant papaya germplasm through targeted modification of CpeIF4E via gene-editing technology.
Papaya (Carica papaya L.) plants exhibit three sex types, as female, male, and hermaphrodite. However, the segregation distortion caused by non-homozygous hermaphrodite plants has long hindered the achievement of the "all-hermaphrodite" commercial breeding goal. This review systematically traces the major breakthroughs in research on papaya sex differentiation, from classical genetics to molecular genomics. We summarize the sex types, floral morphology, and the classical single-gene triallelic hypothesis, and elaborate on the construction of physical maps of sex chromosomes, the delineation of sex determination regions, and the identification of key determining genes CpYYL (the YY/YhYh-lethality gene) and CpMp (the long male peduncle control gene), which together revealed the intrinsic links between sex chromosome evolution and dioecy. We also expound that the large-scale population genomic resequencing has overturned the traditional single-origin hypothesis and, for the first time, reported the multiple independent origins of hermaphrodites, specifically, HSY1 and HSY3 independently originating from wild males MSY1 and MSY3, respectively, which reshaping our understanding of papaya sex chromosome evolutionary history. Furthermore, this review discusses sex reversal, hormonal regulation, epigenetic regulation, the current applications and prospects of molecular marker-assisted breeding, and transgenic and gene-editing technologies for sex control in papaya. We address existing challenges and highlight future key research directions, and aim to ultimately achieve the goal of "all-hermaphrodite" commercial breeding in papaya through genetic engineering approaches.
【Objective】This study investigated the regulatory effects of reduced nitrogen application combined with organic fertilizer on soil physicochemical properties, fruit quality and yield in Weinan apple orchards, so as to provide theoretical and practical references for formulating cost-saving, high-efficiency, high-quality and high-yield fertilization schemes.【Method】Taking apple orchards of Weinan as the research object, five treatments were set up: conventional nitrogen application (CK), 25% nitrogen reduction with common urea plus organic fertilizer (T1), 25% nitrogen reduction with controlled-release urea plus organic fertilizer (T2), 45% nitrogen reduction with common urea plus organic fertilizer (T3), and 45% nitrogen reduction with controlled-release urea plus organic fertilizer (T4). Indicators including soil nitrogen content and forms, as well as fruit appearance, nutritional quality and yield were determined.【Result】Compared with CK, treatment T2 significantly increased the contents of ammonium nitrogen and total nitrogen in the 0-30 cm topsoil by 12.89%-23.67% and 18.69%-27.83%, respectively, and significantly decreased nitrate nitrogen content by 14.27%-22.08%. In 30-60 cm subsoil, the contents of ammonium nitrogen and total nitrogen under T2 were significantly increased by 10.24%-21.81% and 16.29%-25.97%, respectively, while nitrate nitrogen content was significantly decreased by 10.86%-18.75%. Compared with CK, treatment T2 significantly increased single fruit weight, fruit firmness, soluble sugar content and vitamin C content by 42.94%, 22.96%, 22.50% and 37.83%, respectively. Treatment T2 exhibited the optimal performance in soil physicochemical properties, fruit quality and yield, which was significantly superior to other treatments; treatment T1 ranked second and was significantly better than CK, T3 and T4; treatments T3 and T4 showed the lowest performance, with no significant difference observed between them. Correlation analysis and principal component analysis revealed that fruit quality and yield indicators were significantly or extremely significantly positively correlated with soil organic matter and total nitrogen contents, and significantly or extremely significantly negatively correlated with soil bulk density. Soil organic matter and total nitrogen contents were identified as the core regulatory factors governing fruit quality and yield.【Conclusion】The fertilization mode of 25% nitrogen reduction combined with controlled-release urea and organic fertilizer achieves the best synergistic improvement effect on orchard soil fertility, apple yield and fruit quality.
【Objective】This study aims to investigate the effects of different drying methods on the volatile components and quality markers of cinnamon (Cinnamomum cassia), thereby providing a basis for optimizing and standardizing the primary processing and drying procedures in cinnamon-producing regions.【Method】Four drying treatments (air-drying, hot-air drying at 30℃, hot-air drying at 60℃ and vacuum freeze-drying) were set up.Volatile components were analyzed qualitatively and semi quantitatively by simultaneous distillation extraction and gas chromatography-mass spectrometry (GC-MS). Orthogonal partial least-squares discriminant analysis (OPLS-DA) and cluster heatmap visualization were applied to screen for differential volatile components among the four drying treatments. Liquid chromatography-mass spectrometry (LC-MS) combined with external standard calibration method was used to determine the effects of four drying treatments on the contents of three quality markers—cinnamaldehyde, cinnamyl alcohol, and coumarin.【Result】A total of 76 volatile components were identified from four dried cinnamon samples, which belonged to 14 chemical classes, including alkenes, enols, and aldehydes. There were 57 components in the four drying treatments, mainly alkenes and enols, and only 7 volatile components were significantly different between the groups. Based on an OPLS-DA model (R2X = 0.761, R2Y = 0.826, Q2 = 0.452), 12 differential volatile components were screened out using the criteria of VIP > 1 and P < 0.05. Cluster heatmap analysis indicated that air-drying provided the best retention of aromatic constituents such as eucalyptol and decanal; hot-air drying at 60℃ yielded a chemical profile most similar to that of air-dryingwhile also elevating the levels of compounds like 1-phenyl-1, 2-propanedione; and hot-air drying at 30℃ enriched thermally inducedmetabolites such as ligustrazine. Quantitative LC-MS analysis revealed that, compared with airdrying, all other three drying treatments resulted in a highly significant decrease in cinnamyl alcohol content (P < 0.001); cinnamaldehyde decreased significantly only in the vacuum freeze-drying group (P < 0.05); while coumarin content was not significantly affected by any drying method.【Conclusion】Hot-air drying at 60℃ can be prioritized for optimization in largescale production, while hot-air drying at 30℃ favors the accumulation of specific components. Air-drying preserves cinnamyl alcohol best, but it is limited by long drying cycles and a high risk of mold. In practical applications, the appropriate drying method can be selected according to the target components of interest.
