为揭示柑橘黄龙病自然感染年序病情发生规律，以提高监测预警防控水平提供科学依据，笔者于2002—2015 年在天然隔离屏障良好的一个老龄果园开展柑橘黄龙病自然感染发病危害研究，在初入侵果园采取3 个重复样地定点定株发病扩散危害系统调查。坚持14 年试验结果表明：柑橘黄龙病自然感染发病力以自然感染发病4~5 年后为最强盛，其发病力可达年新发病率10%~15%，较其初发病力增强2~3 倍；其当年新发病率消长呈“M型”曲线变化规律：第1 自然感染发病显症高峰一般为初次入侵后的第5 年前后，峰期一般为2~3 年；第2 个自然感染发病显症高峰为初次入侵后的第9 年前后，峰期一般为1~3 年，两峰之间为高位波动变化动态。老龄果园黄龙病积年发病呈Logistic 曲线上行变化轨迹，其年序数值化变化模型为Q = 85.81441 EXP( 4.0063-0.5837N )(n=14，r=0.9941**)，其自然感染扩散大周期为15年（其中核心为害周期10 年左右）。运用这些变化规律，对提升老龄果园黄龙病监测预警防控具有十分重要的指导意义。

Plant immunity inducers represent a new and rapidly developing field in plant-protection research. In this paper, we discuss recent research on plant immunity inducers and their development and applications in China. Plant immunity inducers include plant immunity-inducing proteins, chitosan oligosaccharides, and microbial inducers. These compounds and microorganisms can trigger defense responses and confer disease resistance in plants. We also describe the mechanisms of plant immunity inducers and how they promote plant health. Furthermore, we summarize the current situation in plant immunity inducer development in China and the global marketplace. Finally, we also deeply analyze the development trends and application prospects of plant immunity inducers in environmental protection and food safety.

Citrus Huanglongbing (HLB), also known as greening, is a destructive disease caused by the fastidious, phloem-colonizing bacteria Candidatus Liberibacter spp.; 'Ca. Liberibacter asiaticus' (Las) is the most prevalent of the species causing HLB. The Asian citrus psyllid (ACP, Diaphorina citri) transmits Las. HLB is threatening citrus production worldwide, and there is no cure for infected trees. Management strategies targeting diseased trees at different stages of colonization by Las are needed for sustainable citrus production in HLB-endemic regions. We evaluated the effect of the combinations of plant defense elicitors, nitrogen (N) fertilizer, and compost on mildly diseased trees. We tested thermotherapy on severely diseased trees and assessed tree protectors to prevent feeding by ACP, thus preventing Las from being transmitted to new plantings that replaced HLB-moribund trees. After four applications over two consecutive growing seasons we found that the combination of compost, urea, and plant defense elicitors β-aminobutyric acid, plus ascorbic acid and potassium phosphite with or without salicylic acid, slowed down the progression of HLB and reduced disease severity by approximately 18%, compared with the untreated control. Our data showed no decline in fruit yield, indeed treatment resulted in a higher yield compared with the untreated control. Thermotherapy treatment (55°C for 2 min) exhibited a suppressive effect on growth of Las and progress of HLB in severely diseased trees for 2 to 3 months after treatment. The tree protectors prevented feeding by ACP, and therefore young replant trees remained healthy and free from infection by Las over the 2-year duration of the experiment. Taken together, these results may contribute to a basis for developing a targeted approach to control HLB based on stage of host colonization, application of plant defense elicitors, N fertilizer, compost, thermotherapy, and tree protectors. There is potential to implement these strategies in conjunction with other disease control measures to contribute to sustainable citrus production in HLB-endemic regions.

Huanglongbing (HLB) is currently the most economically devastating disease of citrus worldwide and no established cure is available. Defense inducing compounds are able to induce plant resistance effective against various pathogens. In this study the effects of various chemical inducers on HLB diseased citrus were evaluated in four groves (three with sweet orange and one with mandarin) in Florida (United States) for two to four consecutive growing seasons. Results have demonstrated that plant defense inducers including β-aminobutyric acid (BABA), 2,1,3-benzothiadiazole (BTH), and 2,6-dichloroisonicotinic acid (INA), individually or in combination, were effective in suppressing progress of HLB disease. Ascorbic acid (AA) and the nonmetabolizable glucose analog 2-deoxy-D-glucose (2-DDG) also exhibited positive control effects on HLB. After three or four applications for each season, the treatments AA (60 to 600 µM), BABA (0.2 to 1.0 mM), BTH (1.0 mM), INA (0.1 mM), 2-DDG (100 µM), BABA (1.0 mM) plus BTH (1.0 mM), BTH (1.0 mM) plus AA (600 µM), and BTH (1.0 mM) plus 2-DDG (100 µM) slowed down the population growth in planta of 'Candidatus Liberibacter asiaticus', the putative pathogen of HLB and reduced HLB disease severity by approximately 15 to 30% compared with the nontreated control, depending on the age and initial HLB severity of infected trees. These treatments also conferred positive effect on fruit yield and quality. Altogether, these findings indicate that plant defense inducers may be a useful strategy for the management of citrus HLB.

Citrus huanglongbing (HLB) or greening is a devastating bacterial disease that has destroyed millions of trees and is associated with phloem-residing 'Candidatus Liberibacter asiaticus' (Las) in Florida. In this study, we evaluated the spatiotemporal dynamics of oxytetracycline in planta and its control effect against HLB via trunk injection. Las-infected 'Hamlin' sweet orange trees on 'Swingle' citrumelo rootstock at the early stage of decline were treated with oxytetracycline hydrochloride (OTC) using trunk injection with varying number of injection ports. Spatiotemporal distribution of OTC and dynamics of Las populations were monitored by high-performance liquid chromatography method and qPCR assay, respectively. Uniform distribution of OTC throughout tree canopies and root system was achieved 2 days postinjection. High levels of OTC (>850 µg/kg) were maintained in leaf and root for at least 1 month and moderate OTC (>500 µg/kg) persisted for more than 9 months. Reduction of Las populations in root system and leaves of OTC-treated trees were over 95% and 99% (i.e., 1.76 and 2.19 log reduction) between 2 and 28 days postinjection. Conditions of trees receiving OTC treatment were improved, fruit yield was increased, and juice acidity was lowered than water-injected control even though their differences were not statistically significant during the test period. Our study demonstrated that trunk injection of OTC could be used as an effective measure for integrated management of citrus HLB.

黄龙病（Huanglongbing，HLB）会造成柑橘韧皮部坏死堵塞，导致光合同化物运输不畅，淀粉大量积累。在感染HLB的4年生Valencia夏橙病株上分别注入0.1和0.2 g · 株-1土霉素（Oxytetracycline，OTC），90 d后运用qPCR检测，病株中HLB病原菌（Candidatus Liberibacter asiaticus，Las）含量均明显降低，且0.2和0.1 g · 株-1 OTC处理的效果相当。I2/KI显色及LM 观测表明，0.2 g · 株-1 OTC处理后植株的淀粉含量从注射前的18.58 μg · mm-2减少至90 d 的5.24 μg · mm-2，而0.1 g · 株-1的处理90 d 仅降至11.88 μg · mm-2。高效液相色谱（HPLC）检测结果表明，注射后90 d内，试验用浓度0.2 g · 株-1 OTC在植株体内可降解至200 μg · kg-1以下。基因表达结果表明，注射0.2 g · 株-1 OTC后30 和90 d，淀粉合成及分解相关基因表达量均下降，其中淀粉合成相关基因AGPase表达量下降最显著，这与OTC注射后30 和90 d叶片内淀粉含量下降结果一致。

抗生素的不合理使用会导致细菌产生耐药性,寻找传统抗生素的潜在替代品成为当前研究重点。抗菌肽因其独特的抗菌机制,不易产生耐药性,且具有抗细菌、真菌、病毒、寄生虫和肿瘤细胞等广谱生物活性,在多个领域得到应用。本文介绍了抗菌肽的分类、作用机制以及在食品加工等领域的应用情况等,为抗菌肽的相关研究提供参考。