Molecular characterization of the hippeastrum chlorotic ringspot virus L segment and its protein.

Hippeastrum chlorotic ringspot virus (HCRV) is a novel tospovirus that was identified in Yunnan Province, China, in 2013. We have sequenced the HCRV L gene, which is 8909 nt long and encodes the RNA-dependent RNA polymerase (2873 amino acids, 330.8 kDa). The HCRV L protein shared highest similarity (89.4 %) with that of tomato yellow ring virus. The L protein contains a negative-sense RNA virus RNA-directed RNA polymerase motif and an endonuclease domain at the N-terminus. Combined with our previous reports of the S and M RNAs, the genome sequence of HCRV is now completed.

[Dynamics and combined injuries of main pest species in rice cropping zones of Yunnan, Southwest China].

A series of rice pest injuries (due to pathogens, insects, and weeds) were surveyed in 286 farmers' fields for major rice varieties of three rice cropping zones of Yunnan Province, Southwest China. The composition and dynamics of main pest species were analyzed, and the trend of rice pest succession in Yunnan was discussed based upon landmark publications. The results showed that the three rice cropping zones had different pest characteristics as regard to main species, dynamics and combined injuries. Sheath rot, bacterial leaf blight, rice stripe, leaf hoppers, armyworms and stem borers were serious in the japonica rice zone. Sheath blight and rice stripe were serious in the japonica-indica interlacing zone. Leaf blast, sheath blight, leaf folders and weeds above rice crop canopy were serious in the indica rice zone. False smut, plant hoppers and weeds below rice crop canopy were ubiquitous and serious in the three kinds of rice cropping zones. Many kinds of weed infestation emerged in the whole rice cropping seasons. Echinochloa crusgalli, Sagittaria pygmaea, Potamogeton distinctus and Spirodela polyrhiza were the main species of weeds in the rice cropping zones of Yunnan. Overall, levels of combined injuries due to pests in the japonica rice zone and the indica rice zone were higher than that in the japonica-indica interlacing zone. In terms of the trend of rice pest succession in Yunnan, injuries due to false smut, sheath blight and plant hoppers seemed to be in a worse tendency in all rice cropping zones of Yunnan, while dominants species of weeds in the paddy fields are shifting from the annual weeds to the perennial malignant weeds.

[Root growth characteristics and competitive effects of Ageratina adenophora and four functional type herbaceous plants].

A field experiment was conducted to explore the root competitive effects of Ageratina adenophora and Setaria sphacelata, S. yunnanensis, Eupatorium fortunei, Chenopodium serotinum in monoculture and mixture, and the relative competitive abilities were evaluated. The results showed that the root length, superficial area and volume of A. adenophora in mixture were lower than in monoculture, but those of S. sphacelata were higher in mixture than in monoculture. The biomass of A. adenophora in mixture decreased by 77.1% and that of S. sphacelata increased by 80.4% compared with those in monoculture. The relative yield and competitive balance index of S. sphacelata were significantly higher than those of A. adenophora, and the relative yield was about 1.0, suggesting that the underground competitive ability of S. sphacelata was higher than A. adenophora. The root morphology of S. yunnanensis in monoculture and mixture was higher than those of A. adenophora, but the root morphology of two species in mixture was lower than in monoculture. The biomass of A. adenophora and S. yunnanensis in mixture decreased by 45.3% and 22.8% compared with those in monoculture, respectively. Competition effect parameters showed that A. adenophora was a mutual antagonism with S. yunnanensis. The root morphology of E. fortunei and A. adenophora in mixture showed no significant difference compared with that in monoculture. The biomass of A. adenophora and E. fortunei was lower than that in monoculture, respectively. Competition effect parameters showed that A. adenophora was a superior competitor. In the mixture of A. adenophora and C. serotinum, the root morphology parameters and competitive ability of A. adenophora were superior to those of C. serotinum. Above all, S. sphacelata is a preference plant material to control the A. adenophorum invasion and recover biodiversity in A. adenophorum invasion fields.

Genetic diversity of the planthopper, Sogatella furcifera in the Greater Mekong Subregion detected by inter-simple sequence repeats (ISSR) markers.

The white backed planthopper, Sogatella furcifera (Hemiptera: Delphacidae), is a serious pest of rice in Asia. In the present study, inter-simple sequence repeat (ISSR) markers were employed to investigate the genetic diversity and differentiation of 47 populations sampled from 14 prefectures of the Greater Mekong Subregion. A total of 14 selected primers yielded 121 bright and discernible bands, with an average of 8.6 bands per primer. According to the hierarchical analysis of molecular variance (AMOVA), the genetic variation among geographic regions (79.84%) was higher than that of among populations within region (20.16%), and the FST value was 0.72, indicating a high level of genetic differentiation. Neighbor-Joining cluster analysis of the 47 populations showed two major clusters, one consisting of mostly southwestern Yunnan Province and Myanmar populations; and the other one consisting of southeastern and central of Yunnan Province plus Vietnam and Laos populations. No significant positive correlation was observed between genetic and geographic distances by Mantel test (r = 0.2230, p = 0.8448), indicating the role of geographic isolation did not shape the genetic structure of the sampled S. furcifera populations. This paper provides useful data for understanding and speculating the migration of S. furcifera and reveals available information to develop sustainable strategies for manage this long-range migratory pest.

[Analysis of the coding region for signal peptide-containing proteins in Pseudomonas syringae pv. tomato genome].

The completed 5 615 ORFs of chromosome sequence of Pseudomonas syringae pv. tomato were analyzed by SignalP 3.0. The result revealed that 679 ORFs consisted of putative secretary proteins with signal peptides. 107 ORFs of signal peptides have been named. The length of most signal peptides was different from 19 amino acids to 31 amino acids, and the most dominant one was 23 amino acids in length. The size of most ORFs varied between 101 ~ 400 amino acids. The frequency of particular amino acids in signal peptides by statistical approach was 48.54% for hydrophobic, 18.67% for uncharged, 24.54% for negative and 8.00% for positive amino acids. The most frequent amino acid was alanine, and the least was isoleucine. Three classes of signal peptides were found in the genome of P. syringae pv. tomato: 501 ORFs belong to secretary signal peptides, 36 ORFs belong to twin-arginine signal peptides, and 15 ORFs belong to lipoprotein signal peptides. Type IV pilin signal peptide and bacteriocins and pheronoes signal peptide was not found in the genome.