Tetramycin, a novel polyene agriculture antibiotic, has excellent antimicrobial activity against many plant pathogens. In this study, the antimicrobial activities of tetramycin and conventional antibiotics on eight common pathogens and their field control efficacies against four serious diseases in kiwifruit were investigated. The results show that 0.3% tetramycin aqueous solutions (AS) exhibited the superior antibacterial and antifungal activity against Pseudomonas syringae pv. actinidiae, Pseudomonas fulva, Agrobacterium tumefaciens, Botryosphaeriadothidea, Phomopsis sp., Alternaria tenuissima, Armillariella mellea and Phytophthora cactorum of kiwifruit pathogens with EC₅₀ values of 1.21, 1.24, 0.72, 0.14, 0.09, 0.16, 0.06 and 0.17 mg kg⁻¹, respectively. These EC₅₀ values of tetramycin were much higher than those of conventional kasugamycin, zhongshengmycin or polyoxin. Meanwhile, 0.3% tetramycin AS possessed the good field control efficacies for canker, soft rot, blossom blight and brown spot disease of kiwifruit with 74.45, 83.55, 84.74 and 89.62%. Moreover, 0.3% tetramycin AS application notably increased fruit resistance substances contents, activated fruit superoxide dismutase and polyphenoloxidase activities, as well as remarkably enhanced fruit growth, improved fruit quality and storability. This study highlights that tetramycin can be used as a preferred alternative to conventional antibiotics in kiwifruit production.

Almost all of a plant’s life activities involve electrochemical reactions. Plant electrical parameters respond quickly to environmental changes and are closely related to physiological activities. In this study, the theoretical intrinsic relationships between clamping force and leaf impedance (Z) or capacitive reactance (Xc) and capacitance (C) were revealed as 3-parameter exponential decay and linear models based on bioenergetics, respectively, for the first time. Leaf electrical characteristics including intrinsic impedance (IZ), capacitive reactance (IXc), capacitance (IC) and specific effective thickness (d) were successfully detected using the above-mentioned relationships and were used to manifest plant metabolic activity. The intracellular water-holding capacity (IWHC), water-use efficiency (IWUE), water-holding time (IWHT) and water transfer rate (WTR) of plant leaves were defined on the basis of IZ, IXc, IC and d, and applied to reflect the intracellular water metabolism. The results demonstrated that the leaves of Broussonetia papyrifera plants grown in agricultural soil had higher IC, d, IWHC, WTR, water content values and lower IZ, IXc values than those grown in moderately rocky desertified soil. The leaf IC, d, IWHC, WTR and water content values of herbaceous plants were higher than those of woody plants. Solanum tuberosum L. had higher leaf IC, d, IWHC and WTR values, but exhibited lower IZ, IXc, IWUE and IWHT values than Capsicum annuum L. This study highlighted that a plant’s electrical parameters based on bioenergetics clearly indicate its physiological process—e.g., the intracellular water metabolism.

Drought, low nutrition, and weeds have become the major limiting factors of young kiwifruit orchards. In this study, the effects of intercropping Vicia sativa L. on the moisture, microbe community, enzyme activity, and nutrients in rhizosphere soils of young kiwifruit plants and their growth were investigated. The results show that intercropping V. sativa could effectively enhance soil moisture by 1.39–1.47 folds compared with clean tillage. Moreover, intercropping V. sativa could significantly (p < 0.01) increase the microbial community, enzyme activity and nutrient of kiwifruit rhizosphere soils, and improve plant height, stem girth, leaf number, maximum leaf length, maximum leaf width, and chlorophyll content of young kiwifruit plants by 43.60%, 18.68%, 43.75%, 18.09%, 21.15%, and 67.57% compared to clean tillage, respectively. The moisture, microbial quantity, enzyme activity, and nutrients in rhizosphere soils of young kiwifruit plants exhibited good correlations with their plant height, stem girth, leaf number, maximum leaf length, maximum leaf width, and chlorophyll content. This study highlights that intercropping V. sativa in young kiwifruit orchard can be used as an effective, labor-saving, economical and sustainable practice to improve the moisture, microbial community, enzyme activity, and nutrient of soils, and enhance kiwifruit plant growth and control weeds.

In this study, the co–application of chitosan and tetramycin against kiwifruit soft rot and its effects on the disease resistance, growth, quality and aroma of kiwifruit were investigated. The results show that chitosan could effectively enhance tetramycin against soft rot of kiwifruit with the field control efficacy of 85.33% for spraying chitosan 100 time + 0.3% tetramycin AS 5000–time dilution liquid, which was higher than 80.99% for 0.3% tetramycin AS 5000–time dilution liquid and significantly (p < 0.01) higher than 40.66% for chitosan 100–time dilution liquid. Chitosan could significantly (p < 0.05) improve the promoting effects of tetramycin on total phenolics, total flavonoids, SOD activity of kiwifruit compared to tetramycin during storage for 0–28 days and enhance the disease resistance of kiwifruit. Moreover, the co–application of chitosan and tetramycin was more effective than tetramycin or chitosan alone in enhancing fruit growth, improving fruit quality and increasing fruit aroma. This study highlights that chitosan can be used as an adjuvant to enhance tetramycin against soft rot of kiwifruit and promote tetramycin’s improvement for the single fruit volume and weight, vitamin C, soluble sugar, soluble solid, dry matter, soluble protein, titratable acidity and aroma of kiwifruit.

The continuous cropping obstacle has become the key factor that seriously restricts the growth, yield, and quality of Pinellia ternata. In this study, the effects of chitosan on the growth, photosynthesis, resistance, yield, and quality of the continuous cropping of P. ternata were investigated by two field spraying methods. The results indicate that continuous cropping significantly (p < 0.05) raised the inverted seedling rate of P. ternata and inhibited its growth, yield, and quality. Spraying of 0.5~1.0% chitosan effectively increased the leaf area and plant height of continuous P. ternata, and reduced its inverted seedling rate. Meanwhile, 0.5~1.0% chitosan spraying could notably increase its photosynthetic rate (Pn), intercellular carbon dioxide concentration (Ci), stomatal conductance (Gs), and transpiration rate (Tr), and decrease its soluble sugar, proline (Pro), and malonaldehyde (MDA) contents, as well as promoting its superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. Additionally, 0.5~1.0% chitosan spraying could also effectively enhance its yield and quality. This finding highlights that chitosan can be proposed as an alternative and practicable mitigator for alleviating the continuous cropping obstacle of P. ternata.

Powdery mildew is the most serious fungal disease of Rosa roxburghii in Guizhou Province, China. In this study, the control role of chitosan-assisted pyraclostrobin against powdery mildew of R. roxburghii and its influences on the resistance, photosynthesis, yield, quality and amino acids of R. roxburghii were evaluated. The results indicate that the foliar application of 30% pyraclostrobin suspension concentrate (SC) 100 mg L⁻¹ + chitosan 500 mg L⁻¹ displayed a superior control potential against powdery mildew, with a control efficacy of 89.30% and 94.58% after 7 d and 14 d of spraying, respectively, which significantly (p < 0.01) exceeded those of 30% pyraclostrobin SC 150 mg L⁻¹, 30% pyraclostrobin SC 100 mg L⁻¹, and chitosan 500 mg L⁻¹. Simultaneously, their co-application could effectively enhance their effect on the resistance and photosynthesis of R. roxburghii leaves compared to their application alone. Meanwhile, their co-application could also more effectively enhance the yield, quality, and amino acids of R. roxburghii fruits compared to their application alone. This work highlights that chitosan can be applied as an effective adjuvant to promote the efficacy of low-dosage pyraclostrobin against powdery mildew in R. roxburghii and improve its resistance, photosynthesis, yield, quality, and amino acids.