Codiaeum variegatum is a valuable ornamental plant with distinct bright yellowing and golden spots on dark green leaves, which resemble virus symptoms. To investigate the factors, especially viral agents, associated with the variegated leaf color of C. variegatum, we performed virome profiling of a single C. variegatum ‘Gold Dust’ leaf sample collected from Hainan, China, using ribosomal RNA-depleted total RNA sequencing on an Illumina NovaSeq 6000 platform. Two novel viruses, with two variants each, belonging to the family Closteroviridae, were detected and characterized: Croton golden spot-associated virus C variants 1 and 2 (CGSaVC-v1 and CGSaVC-v2) of the genus Crinivirus and Croton golden spot-associated virus A variants 1 and 2 (CGSaVA-v1 and CGSaVA-v2) of the genus Ampelovirus. Transmission electron microscopy showed long, flexuous, filamentous virus particles approximately 15 nm in diameter and 760 to 770 nm in length. Molecular screening of 97 variegated individual plant leaves showed a high prevalence of CGSaVA-v2 (90.7%), CGSaVA-v1 (75.3%), CGSaVC-v1 (70.1%), and CGSaVC-v2 (47.4%), while asymptomatic leaves near the meristem tip were mostly free of the target viruses. To our knowledge, this is the first study to demonstrate the significant association between closterovirids and the golden spots. The findings provide novel insights into the genetic diversity of the family Closteroviridae and inform future germplasm conservation and new cultivar development of C. variegatum.

Piper nigrum–Areca catechu intercropping mitigates soil problems related to continuous P. nigrum cropping, but the exact reason for this is not clear. In this study, the intercropping system increased P. nigrum’s single plant weight by 27.0–55.5% and unit yield per hectare by 5.1–33.5% in 2019–2022. Intercropping altered the metabolic profiles of root exudates from both species, with increases in flavonoids (epicatechin and 4′,5,6,7-Tetramethoxyflavone), alkaloids (litebamine), and amino acids (proline betaine, L-homocysteic acid and L-homocysteic acid). Intercropping further increased the abundance of dominant soil bacteria, including GAL15 (354.9%) and Bacteroidota (70.4%) in the P. nigrum rhizosphere, and Firmicutes (141.8%) and WPS2 (75.3%) in the A. catechu rhizosphere. In the intercropping system, the abundance of soil flavonoids, including tangeritin, trifolirhizin, and hexamethylquercetagetin, which participated in improving nutrient absorption and plant growth, increased by 106.4~356.0%, 28.9~45.5%, and 45.2~127.1%, respectively, during the whole growing period. Overall, intercropping with A. catechu promoted carbon input to the P. nigrum soil via root exudates. This increased the diversity of P. nigrum rhizosphere beneficial bacterial communities, as well as the amounts of nutrients and plant growth-promoting secondary metabolites. Together, these effects improved nutrient uptake and utilization, thereby driving the sustainable production of P. nigrum, and ultimately achieving higher yields.

Pathogens deploy various molecular mechanisms to overcome host defenses, among which glycoside hydrolases (GHs) play a critical role as virulence factors. Understanding the functional roles of these enzymes is essential for uncovering pathogen-host interactions and developing strategies for disease management. Fusarium wilt has occurred in the main Piper nigrum cultivation regions, which seriously affects the yield and quality of P. nigrum. Here, we identified and characterized FsGH28c, a GH28 family member in Fusarium solani. Its expression was significantly upregulated during the infection of black pepper (Piper nigrum) roots by F. solani cv. WN-1, indicating its potential role in pathogenicity. FsGH28c elicited cell death in Nicotiana benthamiana and modulated the expression of genes related to pathogenesis. FsGH28c exerts a positive influence on the pathogenicity of F. solani. The knockout of FsGH28c mutant strains markedly attenuated F. solani 's virulence in black pepper plants. The knockout mutant strains decrease the ability of F. solani to utilize carbon sources. The FsGH28c deletion did not affect mycelial growth on PDA but did impact spore development. We identified a U-box protein, PnPUB35, interacting with FsGH28c using yeast two-hybrid and bimolecular fluorescence complementation assays. PnPUB35 conferred enhanced resistance to F. solani in black pepper through positive regulation. These findings suggest that FsGH28c may function as a virulence factor by modulating host immune responses through its interaction with PnPUB35.

Plant U-box genes play an important role in the regulation of plant hormone signal transduction, stress tolerance, and pathogen resistance; however, their functions in coffee (Coffea canephora L.) remain largely unexplored. In this study, we identified 47 CcPUB genes in the C. canephora L. genome, clustering them into nine groups via phylogenetic tree. The CcPUB genes were unevenly distributed across the 11 chromosomes of C. canephora L., with the majority (11) on chromosome 2 and none on chromosome 8. The cis-acting elements analysis showed that CcPUB genes were involved in abiotic and biotic stresses, phytohormone responsive, and plant growth and development. RNA-seq data revealed diverse expression patterns of CcPUB genes across leaves, stems, and fruits tissues. qRT-PCR analyses under dehydration, low temperature, SA, and Colletotrichum stresses showed significant up-regulation of CcPUB2, CcPUB24, CcPUB34, and CcPUB40 in leaves. Furthermore, subcellular localization showed CcPUB2 and CcPUB34 were located in the plasma membrane and nucleus, and CcPUB24 and CcPUB40 were located in the nucleus. This study provides valuable insights into the roles of PUB genes in stress responses and phytohormone signaling in C. canephora L., and provided basis for functional characterization of PUB genes in C. canephora L.

Fusarium wilt has occurred in the main Piper nigrum cultivation regions, which seriously affects the yield and quality of P. nigrum. To identify the pathogen of this disease, the diseased roots were collected from a demonstration base in Hainan Province. The pathogen was obtained by tissue isolation method and confirmed by pathogenicity test. Based on the morphological observation, sequence analyses of TEF1-α nuclear gene, Fusarium solani was identified as the pathogen causing P. nigrum Fusarium wilt and induced symptoms on inoculated plants, including chlorosis, necrotic spots, wilt, drying, and root rot. The experiments for the antifungal activity showed that all the 11 fungicides selected in this study showed certain inhibitory effects on the colony growth of F. solani, where 2% kasugamycin AS, 45% prochloraz EW, 25 g·L-1 fludioxonil SC and 430 g·L-1 tebuconazole SC exhibited relative higher inhibitory effects with EC50 as 0.065, 0.205, 0.395, and 0.483 mg·L-1 , respectively, and were selected to perform SEM analysis and test in seeds in vitro. The SEM analysis showed that kasugamycin, prochloraz, fludioxonil, and tebuconazole might have exerted their antifungal effect by damaging F. solani mycelia or microconidia. These preparations were applied as a seed coating of P. nigrum Reyin-1. The kasugamycin treatment was most effective in reducing the harmful impact of F. solani on the seed germination. These results presented herein provide useful guidance for the effective control of P. nigrum Fusarium wilt.

Pandanus amaryllifolius, also known as pandan, is a perennial herb, growing in Indonesia, China and the Maluku Islands (Wakte et al. 2009). It is the only plant with aromatic leaves in the Pandanaceae. It is widely used in food, medicine, cosmetics and other industries, and is also known as "Oriental Vanilla." Pandan is planted in Hainan province over 1,300 ha and is the main plant intercropped among the forest trees. From 2020, the leaf spot was surveyed for three years. Diseased leaves occurred on 30 to 80% of the surveyed plants, with an incidence of 70% and yield losses of 40%. The disease occured from mid-November to April and was most severe at low temperatures and humidity. Initial symptoms were pale green spots, that formed dark brown, nearly circular lesions. As the lesions expanded, their centers became greyish white, with yellow halos at the junction of the diseased and healthy tissue. When the humidity was high, there were small black spots scattered in the center of the lesion. Symptomatic leaf samples were collected from four different sites. The leaf surface was disinfested with 75% ethyl alcohol for 30 s and washed with sterile distilled water three times. Samples from the junction of diseased and healthy tissue (0.5 × 0.5 cm) were removed and placed on potato dextrose agar (PDA) medium containing 100 µg/mL of cefotaxime sodium and cultivated in a dark incubator at 28°C. After two days, hyphal tips from the edges of growing colonies were transferred to fresh PDA plates for further purification. Following Koch's postulates, colonies from strains were used as inoculum in pathogenicity tests. Colonies with 5 mm diameter were inoculated upside onto fresh and healthy pandan leaves via wounding method (pinpricked by sterilized needles) and non-wounding method. Sterilized PDA was used as control. All plants were setted three replicates and were incubated at 28℃ for 3 to 5 days. When symptoms on leaves similar to those in the field appeared, the fungus were reisolated The colonies formed on PDA were also consistent with the original isolate (Scandiani et al, 2003). After seven days, the colony covered the whole petri dish with white, petal-shaped growth with a slight concentric, annular bulge in the center, irregular edges, with black acervuli emerging at a later stage of colony growth. Conidia were fusiform, 18.1±1.6 × 6.4±0.3 μm, showing four septations and five cells, the middle three cells were brownish black to olivaceous, and the apical cell colorless with two to three filaments, 21.8±3.5 μm long. The caudate cell was colorless with one stalk 5.9±1.8 μm long (Zhang et al. 2021; Shu et al. 2020). According to the colony and conidia characteristics, the pathogen was initially identified as Pestalotiopsis spp. (Benjamin et al. 1961). To confirm the pathogen identity, we used the universal primers ITS1/ITS4, targeting primers EF1-728F/EF1-986R and Bt2a/Bt2b sequences (Tian et al. 2018). The sequences of the PCR products were deposited in NCBI GenBank with accession numbers OQ165166 (ITS), OQ352149 (TEF1-α) and OQ352150 (TUB2). BLAST results showed that the sequences of the ITS, TEF1-α and TUB2 genes shared 100% homology with the sequences of Pestalotiopsis clavispora. The maximum likelihood method was used in the phylogenetic analysis. The result showed that LSS112 was clustered with Pestalotiopsis clavispora with a support rate of 99%. Based on morphological and molecular characteristics, the pathogen was confirmed as Pestalotiopsis clavispora. To our knowledge, this is the first report of leaf spot of pandan caused by Pestalotiopsis clavispora in China. This research will be immediately helpful for the diagnosis and control the disease on pandan.

Black pepper (Piper nigrum L.) is an important tropical cash crop in China and suffers huge economic losses every year due to foot rot disease. In order to clarify the pathogen in black pepper main producing area and screen potential fungicides for disease control. Seven strains were isolated from Wanning City of Hainan Province and identified by morphological characteristics and ITS sequence specificity. The laboratory toxicities of 20 fungicides, registered for the control of oomycete diseases, were determined by the mycelial growth rate method. Results showed that all three strains isolated from black pepper foot rot disease samples, were Phytophthora capsici. Among the 20 tested oomycete fungicides, pyraclostrobin, fluazinam, thiram, dimethomorph, cyazofamid, and metalaxyl showed the highest activity in suppressing the mycelial growth of three P. capsici isolates (EC50<1 μg/mL), followed by oxine-copper, chlorothalonil, mancozeb, zineb, copper hydroxide (1 μg/mL300 μg/mL). This study would help further the understanding and management of tropical P. capsici diseases.

The fungal species in Colletotrichum genus are important pathogens of black pepper (Piper nigrum) to cause dieback of leaves and branches. The black pepper anthracnose has been observed frequently in Hainan, which is the main production area of black pepper in China. Thirty-six isolates from diseased leaves were collected through different fields located in six main production areas of Hainan. Twenty-three isolates were found related to black pepper anthracnose and were identified as Colletotrichum spp. through morphological characteristics and ITS information via BLAST search. All isolates collected in this study belonged to Colletotrichumgloeosporioides complex. Six genes including ITS, TUB2, CHS-1, ACT, GAPDH and ApMat were amplified and sequenced. C. siamense,C. fructicola, C. arecicola, and C. kahawae were identified as the main pathogens based on the multi- gene phylogenetic analysis and morphological characters. This is the first report of these four isolates associated with black pepper anthracnose in Hainan, China.

为获得优良生防木霉菌株,本研究以昆虫肠道为样本,从中分离鉴定木霉菌株,并以芒果炭疽病菌盘长孢状刺盘孢为靶标菌,通过对峙培养、挥发性物质和非挥发性物质筛选拮抗效果最优的木霉菌株,测定其孢子悬浮液对芒果炭疽病的室内防效研究.结果 显示,从105份昆虫肠道中共分离获得10株木霉,通过形态学特征和Tef1-Rpb2双基因联合建树,鉴定出长枝木霉、哈茨木霉和棘孢木霉各3株,加纳木霉1株;通过平板对峙培养显示加纳木霉HNDF-T-6对芒果炭疽病菌抑菌效果最好,其抑菌率为85.64％;其挥发性物质和非挥发性物质对菌丝生长抑制率分别为38.42％和44.01％.通过室内防效测定,经加纳木霉HNDF-T-6孢子悬浮液处理后的叶片病斑直径减少46.04％,表明该菌株对芒果炭疽病具有较好的生防潜能.

Viral diseases are one of the main categories of diseases that cause substantial yield losses in black pepper. Disease symptoms in black pepper are generally complex and are often caused by both known and undescribed viruses. To identify and clarify the etiology of viral diseases in black pepper in Hainan, China, we conducted high-throughput sequencing (HTS) by targeting purified double-stranded RNA (dsRNA) and ribosomal RNA depleted total RNA (rRNA-depleted totRNA). Analysis of the data revealed the presence of one known virus, piper yellow mottle virus (PYMoV), and three newly identified viruses: black pepper virus F (BPVF) in the genus Fabavirus, black pepper virus E (BPVE) in the genus Enamovirus, and black pepper virus B (BPVB) in the genus Badnavirus. The dominant viruses in P. nigrum sampled in Hainan are PYMoV, with an incidence of 100%, followed by BPVF (84%, 133 of 158) and BPVB (66%, 105 of 158). Mechanical inoculation of sap extracts from source plants containing PYMoV, BPVF, and BPVB gave negative results on both herbaceous and woody host plants 60 days postinoculation (dpi). BPVF and PYMoV were successfully transmitted to virus-free seedlings of black pepper through bark grafting, while BPVB was experimentally undetectable up to 150 dpi. Seed transmission experiments showed that no target viruses were present in all 59 germinated seedlings. This study provides information on diagnosis, prevalence, and transmission of black-pepper-associated viruses.

The viromic profile of Polyscias balfouriana cv. Marginata, a perennial woody and ornamental plant, was determined using ribosomal RNA-depleted total RNA (rRNA-depleted totRNA) sequencing. Five viruses (i.e., polyscias mosaic virus, PoMV; one potential novel rhabdovirus; and three novel viruses of Betaflexiviridae and Closteroviridae) were detected and prevalence-surveyed in Hainan province, China. The genomes of polyscias capillovirus 1 (PCaV-1) and polyscias citrivirus 1 (PCiV-1) of family Betaflexiviridae were completed, and the genomes of polyscias crinivirus 1 (PCrV-1) of Closteroviridae were nearly completed lacking the 5′ and 3′ termini. PCaV-1 shares 68% genome nucleotide (nt) identity and 66% replicase (Rep) amino acid (aa) identity with homologues in apple stem grooving virus (ASGV). PCiV-1 shares 65% genome nt identity and 64% Rep aa identity with homologs in citrus leaf blotch virus (CLBV). Meeting the species demarcation criteria, PCaV-1 and PCiV-1 were considered to be new species in genera Capillovirus and Citrivirus, respectively. PCrV-1 shares high genome nt identity (62%), heat shock protein 70-like protein (HSP70h) and RNA-dependent RNA polymerase (RdRp) aa identity (78–80%) with homologues in tomato chlorosis virus (ToCV). We tentatively consider PCrV-1 to be an unclassified member of the Crinivirus genus. PoMV, PCaV-1, PCiV-1, and PCrV-1 are the prevalent viruses with >73% occurrence in the Xinglong Tropical Botanical Garden, Hainan, China.

为筛选黄翅绢野螟(Diaphania caesalis)逆境胁迫下稳定表达的内参基因,使该虫抗逆基因的定量表达分析标准化.本研究根据黄翅绢野螟成虫转录组注释结果,利用qPCR技术分析了9个分别编码ACT、β-TUB、GAPDH、G6PDH、RPS3a、RPL13a、EF1α、EIF4A、/3-ACT的候选内参基因在温度及药剂胁迫下mRNA的表达水平,并通过geNorm、NormFinder、BestKeeper和RefFinder软件(算法)分析各基因的稳定性.结果表明:温度胁迫下,geNorm分析表明ACT和RPS3a为表达最稳定的基因,NormFinder和BestKeeper分析结果表明GAPDH和EIF4a的表达最稳定.药剂胁迫下,geNorm和NormFinder分析结果均表明EIF4a和ACT为最稳定的内参基因,而BestKeeper分析结果表明GAPDH和RPS3a为最稳定内参基因.全样品条件下,geNorm和NormFinder分析结果相似,表明EF1α和EIF4a为最稳定的内参基因,BestKeeper表明GAPDH和RPL13a为最稳定的内参基因.根据geNorm软件成对变异值Vn/Vn+1＜0.15的原则,确定3种条件下对靶标基因表达进行标准化时需引入的内参基因的数目均为2个.利用在线分析软件RefFinder综合评价上述3个分析结果,最终确定温度胁迫下最合适的内参基因为EIF4A和GAPDH,药剂胁迫下最适内参基因为ACT和EIF4A,全样品下最适内参基因为EF1α和EIF4A.本研究结果为利用qPCR技术分析黄翅绢野螟温敏及抗药性相关基因表达差异提供了稳定的内参基因,进而为基因的功能分析奠定了基础.

The coffee white stem borer, Xylotrechus quadripes Chevrolat (Coleoptera: Cerambycidae), is a major destructive pest of Coffea arabica L. (Gentianales: Rubiaceae), widely planted in many Asian countries, including China. Quantitative real-time polymerase chain reaction (qRT-PCR) is a common method for quantitative analysis of gene transcription levels. To obtain accurate and reliable qRT-PCR results, it is necessary to select suitable reference genes to different experimental conditions for normalizing the target gene expression. However, the stability of the expression of reference genes in X. quadripes has rarely been studied. In this study, the expression stability of nine candidate reference genes were investigated under biotic and abiotic conditions for use in qRT-PCR's normalization. By integrating the results of four algorithms of NormFinder, BestKeeper, geNorm, and RefFinder, the optimal reference gene combinations in different experimental conditions were performed as follows: RPL10a and EIF3D were the optimal reference genes for developmental stage samples, EIF4E, RPL10a, and RPS27a for tissue samples, V-ATP and EF1α for the sex samples, EIF3D and V-ATP for temperature treatment, RPS27a and RPL10a for insecticide stress, and RPL10a, RPS27a, and EF1α for all the samples. This study will help to obtain the stable internal reference genes under biotic and abiotic conditions and lay the foundation for in-depth functional research of target genes or genomics on olfactory molecular mechanisms, temperature adaptability, and insecticide resistance in X. quadripes.

生防菌株Bacillus velezensis Z对胡椒瘟病等多种植物病害具有良好的生防效果;全基因组测序能够为其分子机理研究和开发应用提供信息基础.本研究开展该菌株全基因组测序,并进行比较基因组学和抑菌次生代谢产物合成基因簇预测研究.结果表明:B.velezensis Z菌株的基因组中含有1条4054780 bp大小的环形染色体DNA和1个17122 bp大小的环形质粒,总基因组的GC含量为46.24％,共编码基因4173个;包含27个rRNA,86个tRNA基因,34个sRNA;含有串联重复序列179个,其中13个微卫星DNA,138个小卫星DNA;通过比较基因组学分析,结果发现该菌株与贝莱斯芽孢杆菌模式菌株FZB42同源性极高,与枯草芽孢杆菌模式菌株168之间具有一定的遗传距离;同时发现B.velezensis Z基因组中共编码次生代谢产物合成基因簇13个,其中8个与表面活性素(surfactin)、泛革素(fengycin)、溶杆菌素(bacilysin)、macrolactin H、bacillaene、difficidin、plantazolicin、amylocyclicin等已知基因簇完全相似或高度相似,其他5个基因簇皆功能未知.总之,本研究揭示了B.velezensis Z的全基因组遗传信息,明确其与贝莱斯芽孢杆菌和枯草芽孢杆菌的比较基因组学关系,预测了抑菌产物合成编码基因簇,为该生防菌株及其抑菌产物的机理研究和开发应用奠定基础.

通过室内选择性试验研究了茶角盲蝽(Helopeltis theivora Waterhouse)对26份可可种质果实的取食偏好性,以具有相对抗性差异的2-7和STS-17种质为材料,采用HS-SPME/GC-MS鉴定分析上述2份特异种质果实挥发物的组分和含量,并利用"Y"型嗅觉仪测定了该虫对2份特异种质及其挥发物的行为反应.结果表明:室内选择性试验显示2-7种质表现出对茶角盲蝽相对易感,STS-17、BGL44-64和15-9种质表现出对该虫的相对抗性,其中STS-17果实上的取食斑数量最少."Y"型选择试验显示茶角盲蝽对2-7种质的选择性显著高于STS-17,对STS-17和空白对照无选择性差异,进一步验证了二者的特异性.2-7和STS-17种质果实中共检测出6类18种挥发物,但二者挥发物组分与含量差异较大,二者共有成分为1-己醇、反-α-香柠檬烯和六甲基环三硅氧烷.茶角盲蝽对不同浓度的挥发物有不同趋性,β-石竹烯表现为在高浓度(100 mg/mL)下驱避、中浓度(10 mg/mL)下引诱、低浓度(1 mg/mL)下无影响;六甲基环三硅氧烷则在低浓度下有引诱作用;而丁酸顺式-3-己烯酯和八甲基环四硅氧烷在高浓度下驱避、其余浓度下无影响.综合分析认为,STS-17为茶角盲蝽相对抗性种质,2-7为相对易感种质,挥发物成分在茶角盲蝽寄主选择行为中具有导向作用.

[目的]黄翅绢野螟Diaphania caesalis是热带木本粮食作物菠萝蜜Artocarpus heterophyllus的重要钻蛀性害虫,对热区快速发展的菠萝蜜产业威胁巨大.本研究旨在明确该虫的生物学特性及田间发生规律,为准确预测和高效治理该虫提供理论基础.[方法]在室内温度26 ±1℃、相对湿度70％±5％、光周期14L:10D条件下,以菠萝蜜叶片为食料,观察黄翅绢野螟各龄期形态特征、发育历期及繁殖能力,并在田间网室中观察该虫年生活史;通过室内选择和非选择试验,研究该虫的寄主多样性;2018年1-12月通过田间系统调查,分析该虫在海南省琼中县的种群动态规律.[结果]黄翅绢野螟卵、幼虫、预蛹、蛹和成虫的发育历期分别为4.58±0.50,21.00±1.36,2.50±0.51, 10.20±0.53和12.31±3.16d,平均世代历期为50.50±3.54 d.各龄期主要形态特征为:卵椭圆形,表面具网纹;幼虫体黄褐色,化蛹前变白色,蜕裂线呈倒“Y”形;蛹红褐色,足和翅芽长至第5腹节;成虫体麦黄色,前翅有瓜子状和塔状黄斑.雌蛾可多次产卵,单雌产卵量为147.25±84.24粒.幼虫偏好取食菠萝蜜、榴莲蜜Artocarpus champeden和面包果Artocarpus altilis 3种植物.室内和网室观察结果表明,黄翅绢野螟在海南一年发生8代.2018年1-12月田间调查结果表明,从3月开始种群数量明显增加,至7月始终保持相对稳定的水平;7月中下旬至9月为种群高峰期;10月后种群开始回落,至次年2月种群保持在较低的水平.[结论]黄翅绢野螟能以菠萝蜜叶片为食料完成继代繁殖,属寡食性;7-9月是该虫在海南的种群高峰期(第5代),因此精准防控的关键时期为上代(第4代)成虫期,即7-8月.

游动孢子是胡椒瘟病最主要的侵染源,其产量受环境条件影响,但是具体影响关系尚不明确.本研究利用胡椒瘟病菌孢子囊诱导技术,逐个分析光照、温度、湿度、pH等单一环境因素变化对胡椒瘟病菌游动孢子产量的影响.结果 表明:光照强度在200～20000 lx时胡椒瘟病菌均可产孢,在5000 lx时产孢量最高(1.28×106个/mL),分别是2000和10000 lx的6.89倍和12.40倍;温度在20～30℃时,产孢量均能达到5.82×105个/mL以上,在25℃时产孢量最高;相对湿度在50％～99％时,产孢量均能达到2.27×105个/mL以上,其中相对湿度较低的条件下(50％和65％)游动孢子产量显著高于其他湿度条件;环境pH在6.0～8.0时,产孢量较高,pH 7.0时最高.综上所述,4种环境因素均对胡椒瘟病菌游动孢子产量具有显著影响,最适宜产孢的环境条件为光照强度5000 lx、温度25℃、相对湿度65％、pH 7.0.本研究为后续致病相关研究及田间病害防控奠定基础.

孢子囊的产生和发育过程是研究胡椒瘟病菌（Phytophthora capsici）及其病害防控的重要基础。本研究分析不同诱导条件下胡椒瘟病菌孢子囊的产生情况,并通过光学显微镜和共聚焦显微镜观察孢子囊及其内部游动孢子的发育过程。结果发现:（1）3种诱导方法均能诱导出大量孢子囊,其中在V8-A平板上光照和抹伤双重诱导法获得的孢子囊数量最多,其次是在V8-A平板上光照诱导法,获得孢子囊数量最少的是V8液体光照诱导法,但仅差异最大的2个处理间达到显著水平;（2）显微镜观察发现,孢子囊由气生菌丝顶端逐步膨大形成,初始为近球形逐渐发育成倒洋梨形,孢子囊成熟后从顶端排出大量游动孢子,偶尔可见孢子囊顶端直接发育出芽管;（3）共聚焦显微镜观察发现,首先孢子囊内部原生质体被膜结构隔裂成大约数十个独立小格,然后在每个格子中积累数倍于细胞核的DNA,最后每份细胞核DNA发育成一个游动孢子。本研究从微观角度揭示P.capsici孢子囊发育外观及内部的形态特征,为胡椒瘟病菌后续致病机制研究和胡椒瘟病田间防控提供技术基础。

为研究硬枝黄蝉Allemanda nerii olia Hook.乙醇提取物的抑菌活性,本研究采用减压柱层析、薄层色谱等对其乙醇提取物的抑菌成分进行了初步分离,以胡椒瘟病菌Ph ytophthora capsici为供试病原菌,测定了不同馏分对胡椒瘟病菌的抑菌活性.结果 表明,石油醚萃取组分(AN-LS1)、氯仿萃取组分(AN-LS2)、乙酸乙酯萃取组分(AN-LS3)对胡椒瘟病菌均具有一定抑菌活性,抑制率分别为69.59％、66.73％和15.10％.对3种萃取组分采用活性跟踪分离,发现馏分AN-LS1-05、AN-LS1-06、AN-LS2-03、AN-LS2-04、AN-LS2-05、AN-LS3-02、AN-LS3-03对胡椒瘟病菌抑制率达到了100％,馏分AN-LS2-06、AN-LS2-07和AN-LS3-04抑制率达到了80％.对各馏分进一步分离最终得到AN-LS1-05-04、AN-LS1-07-07、AN-LS2-04-04、AN-LS2-06-05-06、AN-LS3-04-06等16个化合物,其化学结构有待进一步鉴定.

芽孢杆菌(Bacillus sp.)产生的脂肽类化合物具有广谱生防效果.针对广谱生防菌株B.subtilis VD18R19,采用酸沉淀法提取发酵液中的脂肽类化合物,并通过MALDI-TOF/TOF-MS进行鉴定,田间生防试验分析该菌株及其脂肽类化合物对胡椒花叶病的生防效果.结果 表明B.subtilis VD18R19发酵液中可以提取到脂肽类化合物,粗提物和提取物的平均产量分别为5.92、3.13 g/L;质谱结果发现,提取物中主要含表面活性素(Surfactin)和大侧柏素(Plipastatin)2种脂肽类化合物;田间试验表明,生防菌VD18R19及其脂肽类化合物均能有效防控胡椒花叶病,防效分别达79.49％和87.18％;且2处理均能促进胡椒冠幅和果枝生长,尤其生防菌VD18R19的促生效果达显著水平.说明B.subtilis VD18R19及其脂肽类化合物在防控胡椒花叶病上具有良好的应用潜力.