Molecular Characterization of a Distinct Begomovirus Infecting Crassocephalum crepidioides in China

A Begomovirus isolate JH1 was obtained from Crassocephalum crepidioides showing yellow vein symptoms in Jinghong of Yunnan province, China. The complete sequence of Begomovirus DNA‐A‐like molecule of JH1 was determined to be 2745 nucleotides long. When compared with other begomoviruses, JH1 DNA‐A has the highest nucleotide sequence identity (86.4%) with that of Tobacco curly shoot virus. Comparisons of individual encoded proteins with other begomoviruses show that different parts of JH1 DNA‐A have different ancestors. The molecular data show that JH1 is a distinct Begomovirus species, for which the name Crassocephalum yellow vein virus is proposed.     

Molecular Characterization of a Distinct Begomovirus and its Associated Satellite DNA Molecule Infecting Sida acuta in China*

Three viral isolates Hn8, Hn40 and Hn41 were obtained from Sida acuta showing yellow mosaic symptom in the Hainan province, China. Comparison of partial DNA‐A sequences amplified with degenerate primers confirmed the existence of single type of Begomovirus. The complete nucleotide sequence of the DNA‐A‐like molecule of Hn8 was determined to be 2749 nucleotides, having a typical genetic organization of a Begomovirus. Hn8 DNA‐A had the highest sequence identity (78%) with that of Ageratum yellow vein China virus‐[G13] ( AJ558120 ), and had less sequence identity with other begomoviruses. Based on the above molecular data, Hn8 was thus considered as a new Begomovirus species, for which the name Sida yellow mosaic China virus (SiYMCNV) is proposed. Satellite DNA‐β molecules (Hn8‐β, Hn40‐β and Hn41‐β) were found to be associated with Hn8, Hn40 and Hn41 and their complete nucleotide sequences were determined. Sequence analysis showed that Hn8‐β, Hn40‐β and Hn41‐β shared more than 84% nucleotide sequence identity, and they were different from other characterized DNA‐β, sharing the highest nucleotide sequence identity (47.8%) with DNA‐β of Ageratum yellow vein virus.     

Molecular Characterization of a Strain of Squash Leaf Curl China Virus from the Philippines

The complete nucleotide sequence of infectious cloned DNA components (A and B) of the causal agent of squash leaf curl disease in the Philippines was determined. DNA‐A and DNA‐B comprise 2739 and 2705 nucleotides, respectively; the common region is 174 bases in length. Five ORFs were found in DNA‐A and two in DNA‐B. Partial dimeric clones containing DNA‐A and DNA‐B, constructed in a binary vector and transformed into Agrobacterium tumefaciens, induced systemic infection in agro‐inoculated pumpkin plants (Cucurbita moschata). The total DNA‐A sequence was most closely related to that of Squash leaf curl China virus (SLCCNV) (88% identity), although the existence of B component of SLCCNV has not been reported. The deduced coat protein was like that of SLCCNV (98% amino acid sequence identity) and the Philippines virus has low sequence identity to Squash leaf curl virus (SLCV) and Squash mild leaf curl virus (SMLCV) (63 and 64% total nucleotide sequence identities, respectively). From these results, we propose that the Philippines virus be designated Squash leaf curl China virus‐[Philippines] (SLCCNV‐[PH]).     

Association of a Distinct Begomovirus and a Betasatellite with Leaf Curl Symptoms in Pedilanthus tithymaloides

Pedilanthus tithymaloides (Redbird flower) is an ornamental shrub that occasionally exhibits leaf curl and enation symptoms in Pakistan. Symptoms were shown to be associated with a monopartite begomovirus and a betasatellite. The complete nucleotide sequence of the begomovirus was found to be 2764 nucleotides in length and have the highest nucleotide sequence identity to a begomovirus previously isolated from tomato (90.3% nucleotide sequence identity), followed by Radish leaf curl virus (86.3%). The complete betasatellite sequence was determined to be 1358 nucleotides in length and has the highest sequence identity (97%) with Tobacco leaf curl betasatellite . The analysis shows the begomovirus associated with leaf curl disease of Pedilanthus to be a distinct and previously unreported begomovirus for which the name Pedilanthus leaf curl virus (PedLCV) is proposed. This virus is one of an increasing number of monopartite begomoviruses shown to be associated with a betasatellite.     

一品红试管苗移栽驯化期叶片的解剖结构变化

对一品红试管苗移栽驯化,同时研究了驯化过程中叶片结构的变化,结果表明,一品红在珍珠岩基质中成活率达98%,随着移栽时间的延长,表皮细胞增大,排列紧密;叶肉细胞间隙减小,栅栏组织细胞长度增加,主脉增厚,导管数目增加,保水,输水和抗逆能力增强。     

一品红花色素抗氧化性能的研究

从一品红红色苞片中提取花色素,并用自由基测定试剂盒测试了一品红花色素的体外抗氧化性能,并用碘量法测定了其抑制猪油氧化的效果,用TBARS法测定其对血浆脂蛋白氧化的抑制能力。结果表明:一品红花色素具有较强的清除超氧阴离子(O2.-)和羟自由基(.OH)的能力,清除效果优于同浓度的VC;其对猪油氧化的抑制效果和同浓度的VC相近,而对人血浆脂质过氧化的抑制效果显著高于VC。     

一品红苞片花色素的分离及初步鉴定

用紫外-可见光分光光度计、高效液相色谱（HPLC）和质谱（MS）技术对一品红（Euphorbia pulcherrima）红色苞片中的花色素提取液进行了初步鉴定.一品红花色素的甲醇溶液分别在270、340和520 nm处有3个吸收峰;在440 nm吸光度与可见光最大吸收波长520 nm吸光度的比值为0.29;花色素的甲醇溶液中加入AlCl3后发生红移,再加入HCl后发生蓝移;色素溶液在紫外光下无荧光;色素样品经液相色谱分离后在270 nm检测有5个比较明显的吸收峰;质谱中得到595、611、381、571和589等对应的分子离子峰;花色素酸解液高效液相色谱图谱和鼠李糖、葡萄糖的出峰时间一致.由这些结果可推断一品红花色素样品中主要含有5种组分：矢车菊花色素芸香苷、飞燕草花色素芸香苷、飞燕草花色素苯甲酰基葡糖苷、矢车菊花色素苯甲酰基葡糖苷和一种未知成分.     

一品红体细胞胚胎发生与植株再生

一品红不同部位愈伤组织诱导能力存在差异,嫩茎>幼花序>嫩叶。愈伤组织的长势主要受生长素的影响,细胞分裂素对愈伤组织生长有促进作用;但在含6-BA和NAA的培养基中诱导出的愈伤组织,其胚性明显强于单独用NAA诱导出的愈伤组织。液体悬浮培养是一品红体细胞胚胎高频发生的中间步骤。不同浓度BA对一品红体细胞胚的萌发率影响不大,萌发培养基中KNO₃含量加倍可提高萌发率。     

A Branch-inducing Phytoplasma in Euphorbia pulcherrima is Associated with Changes in Expression of Host Genes

Phytoplasma infection causes a desirable branching phenotype in the ornamental plant Euphorbia pulcherrima by releasing apical dominance . Four E. pulcherrima genes specifically regulated during phytoplasma infection were identified using a combination of differential display of cDNA-polymerase chain reaction (PCR) products and microarray analysis. According to BLAST searches the possible functions of identified genes included a histidine-containing phosphotransmitter, an α-expansin, a protein with similarity to the gibberellin-regulated GAST-1 and a protein with similarity to an Arabidopsis thaliana protein with unknown function.     

Molecular Evidence for the Association of Tomato leaf curl Gujarat virus with a Leaf Curl Disease of Phaseolus vulgaris L.

A leaf curl disease with symptoms typical of begomoviruses was observed in bean (Phaseolus vulgaris) at the Main Research Farm of the Indian Institute of Pulses Research, Kanpur, India. Infected plants had severe distortion of leaves and the plants were unproductive. PCR indicated the involvement of French bean leaf curl virus (JQ866297), a recently described Begomovirus, and Tomato leaf curl Gujarat virus (ToLCGV). The full‐length genome of ToLCGV associated with leaf curl disease of bean was 2757 nucleotides long and had maximum identity (97–98%) with seven isolates of ToLCGV (AY234383, AF449999, EU573714, GQ994098, AY190290, FR819708, AF413671) and is designated as Tomato leaf curl Gujarat virus‐(IN:Knp:Bean:2013) (KF440686). To the best of our knowledge, this is the first record of ToLCGV infecting a leguminous host, P. vulgaris.     

Isolation and characterization of antagonistic bacteria against bacterial leaf spot of Euphorbia pulcherrima

Aims: To investigate the inhibition potential of leaf‐associated bacteria against the pathogen of bacterial leaf spot of Euphorbia pulcherrima. Methods and Results: Seven out of 200 bacterial strains were effective antagonists by in vitro screening and the two strains PAB241 and PAB242 significantly reduced the disease incidence and severity as foliar treatments of E. pulcherrima. The two effective strains, PAB241 and PAB242, were both identified as Bacillus amyloliquefaciens by a polyphasic approach including phenotypic feature, carbon source utilization profile, fatty acid methyl esters and analysis of 16S rRNA gene sequence. In addition, the suspensions of B. amyloliquefaciens PAB241 and PAB242 showed antibacterial activities against the pathogen of bacterial leaf spot of E. pulcherrima under different treatments. Conclusions: The leaf‐associated bacteria, B. amyloliquefaciens PAB241 and PAB242, markedly inhibited the growth of X. axonopodis pv. poinsettiicola under different treatments and protected E. pulcherrima from pathogen infection in growth chamber conditions. Significance and Impact of the Study: This is the first study that showed B. amyloliquefaciens from plant leaves was a potential bactericide against bacterial leaf spot of E. pulcherrima.     

Identification and Molecular Characterization of a New Geminivirus Betasatellite Infecting Malvastrum coromandelianum in China

The complete nucleotide sequence of a satellite molecule associated with Malvastrum leaf curl Guangdong virus (MLCuGdV) infecting M. coromandelianum plants exhibiting leaf curl symptoms in a suburb of Guangzhou, Guangdong Province of China, is described and analysed. The molecule has typical features of betasatellites, containing a single ORF in the complementary‐sense strand, an A‐rich region, the satellite‐conserved region and a stem–loop structure. Compared with the geminivirus betasatellites in GenBank database, this molecule shows the highest nucleotide sequence identity of 71.9% with Tomato leaf curl Philippine betasatellite isolate Laguna1 (ToLCPB, AB307732). Phylogenetic analysis indicates that it is more related to isolate Laguna 1 and Laguna 2 of ToLCPB. According to the proposed species demarcation threshold of betasatellites (78% nucleotide identity), it is a novel betasatellite species, for which we propose the name Malvastrum leaf curl Guangdong betasatellite (MLCuGdB).     

Molecular Characterization of a Strain of Squash leaf curl China Virus from North India

A Begomovirus causing yellow vein mosaic disease of pumpkin (Cucurbita maxima L.) was characterized at molecular level by cloning and sequence analysis of its complete DNA‐A genome. The DNA‐A of the isolate contains 2758 nucleotides which encode six open reading frames (ORFs): AV1 and AV2 in the virion‐sense and AC1, AC2, AC3 and AC4 in the complementary‐sense. Based on the highest (96%) sequence identities and close phylogenetic relationships with Squash leaf curl China virus species, the Begomovirus was identified as strain of Squash leaf curl China virus. The presence of DNA‐B genome of the virus strain was also detected by dot blot hybridization test using DNA‐B specific probe.     

Begomovirus and Associated Satellite Components Infecting Cluster Bean (Cyamopsis tetragonoloba) in Pakistan

Cluster bean (Cyamopsis tetragonoloba) is a legume that is grown widely on the Indian subcontinent. Leaf curl symptoms of cluster bean plants collected in the Punjab, Pakistan, were shown to be associated with the begomovirus Papaya leaf curl virus; the first time this virus has been identified infecting cluster bean in Pakistan. The virus was shown to be associated with Tomato leaf curl betasatellite. Additionally, some cluster bean plants were shown to also harbour Cotton leaf curl Multan alphasatellite. The significance of these findings is discussed.     

钙肥对B型烟粉虱发育、存活及取食为害的影响

以清水为对照,研究了施用钙肥后一品红植株对B型烟粉虱发育、存活和取食为害的影响.结果表明:在温度(26±1)℃、相对湿度60％～80％条件下,钙肥处理的一品红植株上的B型烟粉虱在发育历期上与对照存在显著差异,卵期明显缩短,各龄若虫期延长,从卵到成虫的发育时间为20.18 d,而对照为18.72 d;但钙肥处理对B型烟粉虱各虫态的存活率无显著影响.B型烟粉虱的取食为害诱导了一品红叶片叶绿素荧光参数的变化,显著降低了叶片的光合作用能力,其中光化学效率(Fv/Fm)、光化学淬灭系数(qp)、光能利用效率(α)、最大光合速率(rETRmax)以及对光的耐受能力(Ik)显著降低,而非光化学淬灭系数(NPQ)显著增加.钙肥处理一品红受害叶片的光抑制参数(β)、rETRmax和Ik水平与对照相当.通过指甲油印迹法观察叶片下表皮细胞的形态结构发现,钙肥能有效增强叶片对B型烟粉虱为害损失的补偿.     

Tomato yellow leaf curl virus and Tomato leaf curl Taiwan virus Invade South-east Coast of China

An epidemic outbreak of severe yellow leaf curl disease was reported in field grown tomato within Zhejiang Province of China in the autumn–winter cropping season of 2006. A molecular diagnostic survey was carried out based on comparisons of partial and complete viral DNA sequences. Comparison of partial DNA‐A sequences amplified with degenerate primers specific for begomoviruses confirmed the presence of two types of begomoviruses. The complete DNA sequences of five isolates, corresponding to the two types, were determined. Sequence comparisons and phylogenetic analysis revealed that they correspond to two previously identified begomoviruses, Tomato yellow leaf curl virus and Tomato leaf curl Taiwan virus. The satellite DNAβ molecule was not detected in these samples by either PCR or Southern blot hybridization analysis. There has been no previous report of geminivirus disease incidence in Zhejiang Province, indicating that the introduction of these two tomato infecting geminiviruses into the agro‐ecological zone of South‐eastern China is a fairly recent event. The implications for disease control are discussed.     

Mixed Infection of Two Begomoviruses in Malvastrum coromandelianum in Fujian, China

Virus isolates were obtained from three Malvastrum coromandelianum plants showing vein thickening symptoms in Fujian Province, China. A fragment of approximately 500 bp was amplified from all the samples by PCR using the special degenerate primer pair PA/PB for begomoviruses. Sequence differences among the partial DNA-A fragments revealed that all three samples contained two virus isolates. Isolate I and isolate II share the highest nucleotide sequence identity (98–99%), respectively, with Malvastrum leaf curl Guangdong virus (MLCuGdV) and Ageratum yellow vein virus (AYVV). The complete nucleotide sequences of Fs1 and Fs2 isolates representing each virus were determined to be 2741 and 2756 nucleotides, respectively. Alignment and phylogenetic analysis showed that the complete DNA-A sequences of Fs1 and Fs2 were most closely to those of MLCuGdV (AM503104) and AYVV (AB100305), with 90.4% and 93.3% nucleotide sequence identity, respectively. Fs1 and Fs2 are considered therefore to be isolates of MLCuGdV and AYVV, respectively. This is the first report of AYVV in M. coromandelianum.     

Tomato Yellow Leaf Curl Virus Infection in a Monocotyledonous Weed (Eleusine indica)

Tomato yellow leaf curl virus (TYLCV) is one of the most important plant viruses belonging to the genus Begomovirus of the family Geminiviridae. To identify natural weed hosts that could act as reservoirs of TYLCV, 100 samples were collected at a TYLCV-affected tomato farm in Iksan from 2013 to 2014. The sample weeds were identified as belonging to 40 species from 18 families. TYLCV was detected in 57 samples belonging to 28 species through polymerase chain reaction using root samples including five species (Eleusine indica, Digitaria ciliaris, Echinochloa crus-galli, Panicum dichotomiflorum, and Setaria faberi) from the family Poaceae. Whitefly Bemisia tabaci-mediated TYLCV transmission from TYLCV-infected E. indica plants to healthy tomatoes was confirmed, and inoculated tomatoes showed typical symptoms, such as leaf curling and yellowing. In addition, TYLCV was detected in leaf and root samples of E. indica plants inoculated by both whitefly-mediated transmission using TYLCV-viruliferous whitefly and agro-inoculation using a TYLCV infectious clone. The majority of mastreviruses infect monocotyledonous plants, but there have also been reports of mastreviruses that can infect dicotyledonous plants, such as the chickpea chlorotic dwarf virus. No exception was reported among begomoviruses known as infecting dicots only. This is the first report of TYLCV as a member of the genus Begomovirus infecting monocotyledonous plants.