Suwonll (Su11) group has been becoming dominant in recent years. For simplification of identifying method, random amplified polymorphic DNA (RAPD) was used to analyze polymorphisms and find specific DNA band of eight pathotypes in the group. Of the 190 random primers analyzed in total, 94 primers firmly showed amplification profiles. The results indicated that the genetic variations among types of Su11 were abundance. The specific DNA fragment of Su11-4 was found by amplifying with primer S1410 and those of Su11-14 were found by amplifying with S1412 and S1304. The specific DNA fragment obtained with S1304 was cloned and sequenced. Based on the sequencing, a primer pair was designed and the SCAR marker for Su11-14 was obtained. The results indicated that a molecular identification system for Puccinia striiformis f. sp. tritici races could be established by means of searching specific RAPD fragments of different races.

One disease on jujube fruit was reported in Shanxi Province in recent years. The typical symptom was brown spots formed on the top or shoulder of fruits. The suspected pathogen was isolated from diseased fruits. After pathogenicity tests in lab and field and re-isolation of the pathogen, the strain CN535 was determined to be responsible for the disease. CN535 colony on PAD was 69.2-73.5 mm in diameter, with concentric rings in light-gray and dark-green color in seven days. The conidia, (22.5-40.0) μm× (8.0-13.5) μm, were obclavate and obpyriform, ellipsoidal in form and formed singly or in short chains, with a conical or cylindrical beak and transverse, longitudinal or oblique septa; they were showing the typical morphology of the genus Alternaria. Its rDNA ITS sequence had 100% similarity with those of A. alternata, A. tenuissima, A. longipes, A. mali and A. citri searched in GenBank. The species specific fragments of 341 bp and 450 bp were amplified with two pairs of sensitive primers AAF₂/AAR3 and Aalt-F/Aalt-R. Based on the morphological characteristics and rDNA molecular analysis, the pathogen was finally identified as A. alternata (Fries) Keissler.

Valsa canker is one of the most destructive bark-rot diseases on trunk of apple tree in China. The aim of the research was to develop a simple but stable, efficient and easy method for disease evaluation in laboratory. Excised leaves, young shoots, fruits and twigs of ‘Fuji’ apple trees were inoculated with a virulent isolate 03-8 after making different wounds. The samples were kept at 25℃ in a saturated moisture box. No disease was found in uninoculated and/or unwounded samples, while lesions were occurred in treatments by wound inoculation. The type of wound affected the disease development greatly. Lesions developed much faster on upper side wound than lower side of the leave. No significant difference was observed between wounds pricking one time and ten times on upper side of the leave. Bigger lesions were formed on young shoots by pricking wound than leaf scar. There were significant differences (P<0.05) among wounds of pricking one time, ten times and removing partial peel on fruits. Also, the disease developed much faster on leaf, young shoot and fruit samples (1.5-2 days) than on the twigs (10 days). Furthermore, four different virulent isolates were used to test the reliability and stability of the method. The results showed that expanded leaves or young shoots were better materials than twigs and fruits because different lesions caused by the different isolates could be observed obviously in less than 3 days. Thus, the evaluation method for Valsa canker was suggested as follows:using detached expanded leave or young shoot as plant material in growing season, inoculating one pathogenic fungi disc on the upper side of leaf or surface of shoot after pricking one time with needle, keeping at 25℃ for 2 days in a satisfied moisture box, then measuring the lesion diameter. This me-thod could be used to assess materials in quantity at a short time, obtain good results from replication, screen resistant cultivar, test isolate virulence and chemical efficacy indoor.

The grapevines infected with leafroll viruses were inferior in vigour and stress resistance, poor fruit coloring, delayed maturity and lower sugar content. Eleven grapevine leafroll-associated viruses (GLRaVs) had been isolated from the infected grapevines so far. To improve detecting efficiency and decrease the cost, a multiplex RT-PCR based on single RT-PCR detection of GLRaVs was applied to detecting four grapevine leafroll-associated viruses (GLRaV-1, 3, 4, 5). In this paper, the mainly factors affecting RT-PCR reaction was studied. The results showed that concentration of template, primer or Taq DNA polymerase, annealing temperature and reaction cycles all had considerable influence on the system, and the influence of extension time or dNTP concentration wasn't significant. The sequence identity of GLRaV-1 was 96% compared with AF₁95822, GLRaV-3 was 99% with AJ748524, GLRaV-4 was 99% with EU746619, and GLRaV-5 was 95% with EU815935 in GenBank. The multiplex RT-PCR was proved simple, rapid and sensitive for detection of these 4 GLRaVs.

A multiplex RT-PCR (mRT-PCR) system was established for simultaneous detection on Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Tobacco mosaic virus (TMV), Squash mosaic virus (SqMV)and Cucumber mosaic virus (CMV)infected watermelon by using five sets of specific primers designed on the basis of conserved sequences of the 5 viruses. The concentrations of the primers, Mg²⁺, Taq DNA polymerase and dNTPs were examined and the PCR conditions including annealing temperature and amplification cycles were optimized. The results showed that expected fragments of 542 bp (ZYMV), 485 bp (WMV), 410 bp (TMV), 354 bp (SqMV) and 293 bp (CMV)were amplified and the mRT-PCR system was successfully established and the multiplex RT-PCR had been applied in practice, provided a simple, rapid and economic method for simultaneous detection of the five watermelon viruses.

To elucidate the function of fliExoo gene encoding a putative flagellar base body protein in Xanthomonas oryzae pv. oryzae (Xoo), the gene deletion mutant △fliExoo was generated by the Gm^R marker exchange from the wild-type strain PXO99^A. Non-flagellum, cell precipitation in the culture and significantly attenuated motility on 0.3% semi-solid medium were observed in △fliExoo compared to those of PXO99^A. While there were no apparent alterations in bacterial growth and activity of cellulase in vitro, significant decreases in extracellular polysaccharide (EPS) production and biofilm formation were found in △fliExoo. The pathogenicity on rice (Oryza sativa L cv. Nipponbare) and induction of hypersensitive response (HR) on tobacco (Nicotiana tabacum L.) were attenuated in △fliExoo. △fliExoo-C, the complementation strain restored the phenotypes of the mutant △fliExoo partially or completely. As a result, the fliExoo mutation not only influenced on flagellar motility, but also virulence-related phenotypes in Xoo.

The genome of the isolate of Banana bunchy top virus (BBTV) from Haikou was cloned and sequenced by the polymerase chain reaction (PCR) with total DNA from banana pseudostem and leaf showing typical BBTV symptom as template. The isolate originated from banana (Musa sp.) was designated BBTV-Haikou. The sequence analysis indicated that six full-length segments were 1 106, 1 040, 1 058, 1 040, 1 013 and 1 082 nt, respectively. All the segments contained an intergenic region and an open reading frame (ORF) except the segment 1, which had a small ORF in the main ORF. In the intergenic region (IR), there were a stem-loop common region (CR-SL) and a major common region (CR-M), which shared 91.55% and 88.45% identity, respectively. Comparison of the viral sequence from different country showed that DNA1 sequence was more conservative than other components, but DNA2 sequence mutation rate was higher than others, sharing homologies of 93.08% and 75.67%, respectively. Nucleotide sequence analysis between DNA1 of the isolate and that of the Asian group, Pacific group of BBTV and the two isolates of ABTV (Abacá bunchy top virus)showed that DNA1 of BBTV-Haikou shared 93.1%-99.1%, 89.6%-90.7% and 76.2%-77.4% nucleotide sequence identity, also 93.4%~100% and 85.7% deduced amino acids identity in BBTV and ABTV, respectively. According to the Karan's method of classification, the BBTV-Haikou isolate was belonged to the Asian group.

Mega, one of the European wheat cultivar, possessed effective resistance to the dominant races (CYR30, CYR31, CYR32, Su-4 and Su-14) of Puccinia striiformis f. sp. tritici in China at seeding stage. To identify and map new stripe rust resistance genes, seedlings of the parents, F₁, F₂, BC₁ progeny derived from a cross between resistant cultivar Mega and susceptible cultivar Mingxian169 were tested with the race CYR30 of P. striiformis f. sp. tritici in greenhouse. Simple sequence repeat (SSR) techniques were used to develop molecular markers linked to the resistance gene in wheat cultivar Mega. 237 pairs of wheat SSR primers were used to test the two parents, as well as resistant and susceptible bulks. Subsequently, 2 SSR markers were employed for genotyping the F₂ population. The results indicated that the stripe rust resistance in cultivar Mega was conferred by a single dominant gene, temporarily designated as YrMe, located closely to the chromosome 5BL and flanked by two SSR markers Barc232 and Wmc640, with the genetic distances of 3.7 cM and 8.6 cM, respectively. The research provided theoretical basis to wheat breeding in the use of Mega.

Using specific primers designed according to the cloned genome sequence of Potato virus Y^N (PVY^N), 400 bp cDNA fragments were amplified from 3' end of HC-Pro, CI, NIb and CP genes, respectively. The four cDNA fragments were inserted into binary vector pRCHS contained a intron derived from Chalcone synthase to construct the antisense vectors pRCHS-HC-Pro, pRCHS-CI, pRCHS-NIb and pRCHS-CP, containing intron splicing hpRNA (ihpRNA), respectively. Recombinant binary vectors were introduced into Tobacco NC89 mediated by Agrobacterium tumefaciens and transgenic plants were obtained. The virus resistance tests indicated that the proportion of PVY-resistant transgenic tobaccos with pRCHS-HC-Pro, pRCHS-CI, pRCHS-NIb and pRCHS-CP was 55.34%, 73.69%, 61.54% and 84.21%, respectively. Northern blot revealed an inverse correlation between transgenic transcript accumulation and virus resistance, and siRNA was detected in the presence of disease-resistant plants. It demonstrated that the resistance was RNA mediated.

The endophytic bacteria strain P1 was isolated from healthy potato tubers collected in potato bacterial ring rot field. Antagonistic tests showed that P1 strongly restricted growth of the pathogenic bacterium, Clavibacter michiganense subsp. sepedonicum. Strain P1 was preliminarily identified as Bacillus sp. based on the morphological, physiological and biochemical characteristics and then as B. megatherium by further contrast analysis of 16S rDNA sequence. The antibacterial substances extracted from P1 cultures were proven as crude protein, which were not sensitive to UV and showed the strongest activity at pH 7.0. The inhibitory activity of the crude protein decreased significantly when the temperature was higher than 80℃. Greenhouse tests indicated that strain P1 had a significant role in biocontrol against potato bacterial ring rot with the efficiency of 53.4% and in the promotion of seedling height, stem thickness, potato weight and the rate of commodity tubers.

The mechanism of biological control of Phytophthora blight by treatment with mangrove endophy-tic bacterium RS261 was studied. Tagged by the resistance to rifampicin (300 μg/mL), the strain RS261 could colonize many plants, such as capsicum, tomato, eggplant, et al. An obvious promotion on pepper growth occurred after watering roots with strain RS261. The metabolites of strain RS261 showed strong inhibitory activity against mycelial growth and sporangia production of P. capsici. Inoculation with P. capsici considerably increased the content of MDA and the activities of SOD, CAT and POD in the capsicum. However, when co-inoculated with strain RS261 and P. capsici at the same time, the MDA content and SOD, POD and CAT activities were all lower than those inoculated with pathogen only. In addition, treatment by co-inoculation increased PAL activity, and the induced PAL activity might enhance anti-disease capability of the plants.

Root-knot nematode (Meloidogyne sp.) is a destructive pest of vegetable and difficult to be ma-naged, especially in greenhouse of continuous planting tomato. For determining the influence of continuous planting on soil nematodes, the dynamics of second-stage juveniles (RKN J2) of root-knot nematode and free-living nematode in rhizosphere soil were investigated during the tomato growing season. The individuals of RKN J2 increased with the longer planting years. The number of J2 at 0~30 cm in 0 and 5-year soil was significantly less than that of other tested soil (P<0.05), the average means were 1.1 and 2.1 per 100 g dry soil. While in 8, 10 and 12-year soil, J2 were 154.9, 68.3 and 861.8 per 100 g dry soil, respectively. The population of J2 increased with soil depth, and mainly distributed in 20~30 cm soil layer. The number of free-living nematode also increased with depth of soil. There was no relationship between the time of con-tinuous cropping and the number of soil free living nematode. The percentage of RKN J2 in total soil nematode was lower in 0 and 5-year, Meloidogyne sp. was the rare group and kept relative stable population structure with the other soil nematodes. However, RKN J2 in 8, 10 and 12-year soil was the dominant group. The adverse trend was found between the number of free living nematode and RKN J2, the proportion of RKN J2 in total soil nematode increased with the time of continuous planting, and the ratio of free-living nematodes to RKN J2 decreased significantly (P<0.05).

Soft rot disease often affects Phalaenopsis amabilis during the growing season. However, the pathogen of the disease is remaining poorly studied. In this study, bacterial strain R1 was isolated from soft rot tissues in Wuhan. The pathogenic, morphological, physiological, biochemical tests and 16S rDNA sequence analysis were carried out. The homology of 16S rDNA sequence between strain R1 and Pseudomonas grimontii was 99.72%, and its physiological and biochemical properties were also similar to those of Pseudomonas grimontiis. All these evidences indicated that strain R1 could be identified as a novel strain of Pseudomonas grimontii. The pathogenicity of the novel isolate was proved according to the Koch's postulates. This is the first report that Pseudomonas grimontii can cause soft rot disease of Phalaenopsis amabilis.

A multiplex reverse transcription polymerase chain reaction (multiplex RT-PCR) method was developed for the simultaneous detection and discrimination of three sweet potato potyviruses:Sweet potato feathery mottle virus (SPFMV), Sweet potato latent virus (SPLV) and Sweet potato virus G (SPVG). Three compatible sets of primers specific for each virus were designed in conserved regions of the coat protein (CP) gene for use in multiplex RT-PCR assay, and producing three distinct fragments 300, 420, and 600 bp, indicating the presence of SPFMV, SPLV and SPVG respectively. The individual RT-PCR assays and the multiplex assay were optimized for highest sensitivity and specificity. This study fulfilled the need for rapid and specific sweet potato potyvirus diagnostic tool and that also had the potential for investigating the epidemiology of sweet viral diseases.

The activity change of defensive enzymes and PR-1a gene expression of tobacco (Nicotiana tabacum) seedling induced by chito-oligosaccharides were studied. The results showed that high level systemic acquired resistance (SAR) was expressed in tobacco plants treated with chito-oligosaccharides solution at the concentration of 50 μg/mL. PAL activity increased greatly with 2 peaks, the activity of SOD decreased initially followed by an increase with higher increment, and the activity of POD peaked early followed by a gentle fall in chito-oligosaccharide treated plants. The PR-1a gene was strongly expressed in tobacco due to systemic acquired resistance induced by chito-oligosaccharides. At 168 h after inoculation the expression quantity (co-pies/2 μL) of PR-1a gene was increased to 2 469.6 in treated tobacco leaf, reached 392.6% than that at 0 h after inoculation, it was increased 3.05 times of that in untreated control.

The growth and sporulation of Clonostachys rosea strain 67-1 in PD broth was observed and figured out. A large amount of submerged spores were obtained in shake flask with proprietary Czapek me-dium. Meanwhile, the colonies of strain 67-1were cultured in PDA plate and aerial spores were collected by elution. Resistances of submerged spores and aerial spores to high temperature, dry condition and UV treatment were determined. The results showed that the survival of the submerged spores kept in 60℃ for 30 min was 76.7%, while the aerial spores were hardly germinated in the same condition. After two weeks' drying treatment, the spore activities were 89.2% and 29.3%, respectively. Similarly, the activity of submerged spores was 72.6% and that of aerial spores was 19.7% when exposing to UV for 1 min. It is illuminated that deep submerged fermentation is more efficient than solid culture for strain 67-1 to produce chlamydospores, which act as main component in biopesticide mass production.

The sensitivity of 113 isolates of wheat powdery mildew (Blumeria graminis f. sp. tritici) sampled from 6 provinces or cities in 2008 to temperature was tested by detached leaf segment method with setting up 5 different temperatures indoor. The results showed the mean ET₅₀ (which represents the temperature that is required to obtain 50% of the maximum effect) of all isolates tested was 23.02℃. ET₅₀ values of 17.70% isolates were more than 24℃. The highest and the lowest ET₅₀ of isolates were 25.22℃ and 19.42℃, respectively. There were a certain differences for isolates sensitivity to temperature among different provinces or cites. It was also found that when temperature increased during 22-26℃, the latent period of isolates prolonged, and the latent period of different isolates was different at the same temperature, too. These results will provide a reference for the oversummering division of wheat powdery mildew, as well as the effect of climate to the disease.

Primers R16mF2/R16mR1 and rp (Ⅱ)F1/rp (Ⅱ)R1 were used to amplify phytoplasma DNA from infected pigeon pea samples, then the amplified fragments were cloned and sequenced. The 16S rDNA (1 430 bp) and rp gene (1 170 bp) were amplified from infected pigeon pea. Homology analysis and phylogenetic tree showed that Hainan pigeon pea witches'-broom phytoplasma belonged to the 16S rⅡ group, ⅲ subgroup. Pigeon pea witches'-broom phytoplasma was firstly identified by molecular biotechnology and confirmed its taxonomic status in Hainan, it provided a theoretical basis for research on the epidemiology and control of the disease.

Chinese cabbage cultivars Qinbai No.2 was used as resistant species and 06J31 as susceptible one. They were infectted by (Xanthomonas campetris pv. campestris) YL-17. The dynamic changes of defensive enzymes activity, O₂^-_· and malondial dehyde (MDA) content in the seedlings were studied. The results showed that, O₂^-_· content declined firstly, and then rose sharply, superoxide dismutase (SOD) activity declined gradually, peroxidase (POD) activity and malondial dehyde (MDA) content rose gradually all the time in the two species after infection. However, the changes of catalase (CAT) activity were different. In the resistant cultivar Qinbai No.2, it rose firstly, declined then, and finally rose again. Whereas, in the susceptible cultivar 06J31, it declined firstly and then rose. It demonstrated that more O₂^-_· were bursted after infection, and SOD and POD activities were higher in resistant cultivar, which were helpful to improve the resistance to black rot and membrane lipid oxidation.

The coat protein gene of a Chinese isolate of Grapevine leafroll associated virus-3 was amplified by RT-PCR. Sequence analysis showed that the cp was 942 bp, and it had different similarities with that of other reported GLRaV-3 isolates ranging 91%-99% at nucleotide sequence level and 95%-100% at amino acid sequence level. This gene was cloned into the prokaryotic expression vector pET-28a (+), then trans formed into E. coli BL-21 (DE3 plysS), and subsequently induced by IPTG at final concentration of 1 mmol/L. It was shown that the recombinant CP was expressed with the molecular weight of 35 kDa by SDS-PAGE and Western blotting analysis. Antiserum was prepared after the rabbits were immunized with purified recombinant CP. Results showed that the special antiserum against CP could be used efficiently to detect GLRaV-3 in infected grapevine samples by protein A sandwich-enzyme-linked immunosorbent assay (PAS-ELISA) and dot-blot immunobinding assay (DBIA).

cDNA amplified fragment length polymorphism (cDNA-AFLP) was conducted to analyze dif-ferential expression of Ht2-related genes between near-isogenic lines (NILs) Huangzaosi (HZS) and HuangzaosiHt2 (HZSHt2) after inoculation with race 1 of Exserohilum turcicum. Seventy-six transcript-derived fragments (TDFs), designated Ex01 to Ex76, were specifically expressed in HZSHt2. BLAST analysis showed that 52 of them were homologous to the genes in the GenBank database. The TDFs with significant protein homology were classified into eight functional categories:basal energy metabolism, transmembrane transport protein, defense/resistance protein, protein metabolism, protein of chromosome and proteins of DNA replication and transcription, signal transduction, growing development mediator and transcription factor. Most of these genes were associated with basal energy metabolism and defence/resistance gene. Analyzing the space-time trait of 52 TDFs showed that they were ranged from chromosome 1 to 9. Signal transduction genes expressed at 6 h after inoculation and defense/resistance genes started to express at 48-72 h. Ht2-related gene expressions profiling in response to inoculation of E. turcicum were analyzed by means of cDNA-AFLP. The identification of Ht2-related genes in the study are important for further study of Ht2 gene and the mechanism of resistance to E. turcicum in maize.

Pseudomonas fluorescens 2P24, a biocontrol agent isolated from suppressive soil of wheat take-all, protects plants against soil-borne diseases. Production of antibiotic 2, 4-diacetylphloroglucinol (2, 4-DAPG) is a major mechanism contributed to its biocontrol activities. Biosynthesis of 2, 4-DAPG is encoded by a genetic locus phlACBD and regulated by a number of regulators. A mutant with an enhanced phlA transcription was created by Tn5 mutagenesis, and the Tn5-targeted gene, phlF, was identified. Compared to the wild-type strain 2P24, the transcription of phlA and the production of 2, 4-DAPG in phlF defective mutant increased about 100 and 492 times, respectively. Moreover, the phlF mutant had enhanced inhibitory effect on the myce-lial growth of pathogenic fungi in culture medium compared to the wild type 2P24. After coated on seeds, the phlF mutant showed obvious inhibitory effect on root growth in several crops.

HPLC and Real-time PCR experiments were conducted for investigating the dynamics of GA₃, IAA and ABA in response to Rice dwarf virus (RDV) infection on rice variety Yixiang 2292 (Oryza sativa L. ssp. indica cv. Yixiang 2292). The results showed that GA₃ content was significantly lower in RDV infected rice than that in healthy plants, being 6.28 and 5.92 times lower at 1 and 10 days after symptom appearance, respectively. The content of IAA in RDV infected rice plants was fluctuated, but always lower than that in healthy one. The lowest point was at 10^th day after symptom appearance, which was 3.58 times lower than that in healthy plants. In contrast to GA₃ and IAA, the level of ABA in infected rice plants was always higher, the most significant increase was at 1 and 13 days after symptom appearance, 2.29 and 2.84 times more in the diseased plants than in control. Real-time PCR experiments were conducted to investigate expression change of hormone regulated genes. The results showed that oxidoreductase, a GA₃ related gene decreased after RDV infection. Cullin-1 and P-glycoprotein 1 genes involved in the metabolism of IAA and ABA, were up-regulated to various extents. All these indicated that the symptom induced by RDV infection might be the result of phytohormones disruption.

Tobacco curly shoot virus (TbCSV) Y35 isolate and Tomato yellow leaf curl China virus (TYLCCNV) Y10 isolate isolated from tobacco in Yunnan Province, were monopartite begomoviruses and associa-ted with satellite DNAβ molecules Y35β and Y10β respectively. Nicotiana benthamiana and N. glutinosa were inoculated with the combinations of Y35 or Y10 associated with cognate or noncognate satellite DNAβ (Y35β or Y10β) respectively. Symptoms induced by Y10 or Y35 with their cognate DNAβ were different from those induced by co-infection with noncognate DNAβ, and high pathogenicity was found in plants inoculated with Y10β and Y35. Southern blot results showed that both Y10β and Y35β could be stablly trans-replicated by noncognate geminivirus, but DNAβ molecules associated with noncognate helper virus accumulated in plants at a lower level compared with those associated with cognate helper virus. No direct correlation existed between symptom severity and accumulation level of virus and satellite in plants.

FMRFamide-like peptides (FLPs) play an important role in infection, feeding and propagation of parasitic nematodes. FLPs signaling systems are also well-established targets for nematode control. In this research, the full length cDNA sequence of Rs-flp-14 was obtained through RT-PCR and RACE from Radopholus similis designated Rs-flp-14 (Gene Bank:FJ534855). It consisted of 569 bp in length, with a 357 bp ORF encoding a 119 amino acids protein. The putative protein had the molecular weight of 12.85 KD and a pI of 9.41. Sequence analysis showed that Rs-flp-14 coded two copies of FLPs (2x KHEYLRFG), with a 27 amino acids signal sequence at the N terminus. Southern blot analysis indicated that there was single copy of Rs-flp-14 within R. similis genome. Genomic analysis suggested that Rs-flp-14 contained three introns and four extrons. According to the cluster analysis, the gene exhibited homology to As-flp-14 with the highest extent (64%). In situ hybridization, it was showed Rs-flp-14 was expressed in neurons associated with the nerve ring. This study will provide the foundation and theoretical basis for research on the gene function and developing novel plant parasite control targets.

Some microbial elicitors were screened to induce the resistance against Phytophthora infestans in potato and the mechanism of induced resistance was explored. The potato tuber slices were treated with the fermented filtrates (F-0), the extracts from intracellular component (F-1) and cell wall (F-2) of 31 species of microorganisms. The bioactive ingredients of the elicitors were analyzed. 9 kinds of elicitors with inducing efficiency (IE) of up to 50% were acquired, and among them fermented filtrates of A5295 had the best effect (IE 63.97%). Moreover, the mixture of MK in combination with A32910b fermented filtrates seemed much better (IE 66.67%). Bioactive ingredients of both MK and A32910b were the substances obtained by 100% saturation ammonium sulfate precipitation (A component) and alcohol fractional precipitation after sulfate ammonium treatment (B component). The activities of POD, PAL and PPO in potato tubers were significantly enhanced by induction compared with control. The soluble protein contents increased obviously by 41.53%, and some new soluble proteins activated. It suggested that the induced resistance was related to the enhanced activities of POD, PAL and PPO, as well as the increase of soluble protein contents and the appearance of new soluble proteins.

The F₁, B₁C₁ and F₂ populations derived from bacterial leaf streak (Xanthomonas oryzae pv. oryzicola) susceptible variety 9311 crossed with 4 wild rice resistant accessions DY3, DY16, DY17 and DY20 were used for genetic analysis by pricking inoculation with Guangxi prevailing strain JZ28 at the tillering stage. The results showed that the segregation ratio of resistance to susceptibility was 39:544 in F₂ generation from cross 9311/DY3, fitting the expected ratio of 1R:15S (x²=0.124 5 < x_{0.05, 1}²). The segregation ratios in F₂ generation from 9311/DY16, 9311/DY17 and 9311/DY20 were 94:343, 41:501 and 43:489, fitting the expected ratio of 1R:3S (x²=2.655 < x_{0.05, 1}²), 1R:15S (x²=1.382 < x_{0.05, 1}²) and 1R:15S (x²=2.745_{0.05, 1}²), respectively. In addition, all plants of the F₁ and B₁C₁ generations were susceptible or highly susceptible to bacterial leaf streak. The results of present study indicated that the resistance conferred by DY3、DY17、DY20 to bacterial leaf streak was controlled by two pairs of recessive genes, and the resistance possessed by DY20 was controlled by a single recessive gene.

Genetic diversity of one hundred rice sheath blight isolates of Rhizoctonia solani from ten counties, Fujian Province, was investigated by the inter-simple sequence repeat (ISSR) technique, with three specific and stable primers selected from 16 primers. A total of 41 sites were generated, among which 90.2% were polymorphic. The data were analyzed by PopGene. The average percentage of polymorphic loci of populations is 55.14% and demonstrated high genetic diversity (the average value of Shannon index I is 0.295 3). The genetic variation was significant among populations (average Nei's index h is 0.199 1, and average G_st is 0.642 3). The tested isolates could be classified into 5 ISSR groups. At the same time, the growth rate and pathogenicity of the isolates were surveyed. The ISSR clustering groups had obvious correlation with geographical origin of the isolates, but had no significant correlation with growth rate and pathogenicity variation. The results will contribute to further study on the population of R. solani and control of the disease.

Bioactive components from extracts of Tagetes patula root against Fusarium oxysporum f. sp. niveum (FON) were isolated and their influence on watermelon was investigated. The results showed that the essential oil content was the highest (up to 59.8%), and its inhibitory effect on FON was the best, which was 62.83%, 58.31% and 56.30% at the time point of 24, 36 and 48 h, respectively. The essential oil was applied at three main infection periods of watermelon Fusarium wilt:seedling, bloom and fruit setting stage. The essential oil remarkablely inhibited the mycelial growth of FON, and promoted the growth of watermelon plant. At the same time, it enhanced the enzymatic activities of superoxide dismutase (SOD) and peroxidase (POD), maintained catalase (CAT) activity, and reduced the harm of crude toxin of FON to watermelon plant.

The lipopeptide-like antifungal substances produced by Bacillus amyloliquefaciens strain YN-1 were identified and relative quantified. Four primers designed based on the known lipopeptide genes were used to amplify the corresponding genes from YN-1. The PCR products were cloned and sequenced. The extract from YN-1 fermentation liquid was prepared by the acid precipitation, detected by the plate experiment of antagonism, and analyzed with HPLC-ESI-MS and MALDI-TOF-MS methods. The PCR products with three primer pairs were cloned and sequenced. The BLAST analysis showed that the sfp, fenB, ituA or bamA genes exist in the genome of B. amyloliquefaciens YN-1. The extract from YN-1 fermentation liquid could inhibit the mycelial growth of the pathogen Fusarium oxysporum f. sp. vasinfectum. Nine kinds of lipopeptides C14-Iturin A, C15-Iturin A, C16-Iturin A, C14-Fengycin A, C15-Fengycin A, C16-Fengycin A, C17-Fengycin A, C16-Fengycin B and C17-Fengycin B were identified in the antimicrobial extract by the mass spectrum analysis, from which five substances C16-Iturin A, C14-Fengycin A, C16-Fengycin A, C17-Fengycin A and C17-Fengycin B were the major components. Study on B. amyloliquefaciens YN-1 provided a foundation for the development of the micro-fungicide.

Thielaviopsis basicola is a soil-borne plant pathogen which causes root rot disease in tobacco plants. Detection and monitoring of T. basicolain soil is of great significance to control this disease. Based on the differences in internal transcribed spacer (ITS) sequences of T. basicola and other fungal pathogens, a specific primer pair Tb1/Tb2 for T. basicola was developed. The results showed that the primer pair gave a single amplicon of 330 bp from T. basicola and revealed no undesirable cross-reaction with other seven soil-borne pathogen isolates and three tobacco rhizosphere dominant fungi isolates. With a series of 10-fold genomic DNA dilutions of T. basicola, the detection limit of 1 pg/μL in conventional PCRand100 fg/μL in real-time quantitative PCR was achieved. With DNA from the soil inoculated with different numbers of T. basicola conidia, the detection limit was 10 conidia per reaction in conventional PCR and 0.4 conidia per reaction in real-time quantitative PCR.

The rDNA-IGS of 11 Ustilaginoidea virens isolates from different geographical regions in China were amplified by PCR and sequenced. The results showed that the rDNA-IGS fragments consisted of one cen-tral variable region and two lateral conservative regions. The two conservative sequences among the11 isolates shared the sequence similarity of 99.44%. The variable region consisted of 2, 4, or 6 of 77 bp-length-repeats in the isolates and the sequences of the repeat units were high conservative. Primers UIGS Ⅲ and UIGS IV were designed for amplification of the variable region in the rDNA-IGS.

The damage and symptoms of jujube fruit soft rot in Xinzheng, Henan Province, were investigated from 2006 to 2008, and the pathogen was identified based on the morphological characteristics and the ITS se-quence of ribosome DNA. The results showed that the aerial mycelium of colony was white in color in the first four days, then turned gray after incubation on PDA for 5-6 d at 25℃ and became black two weeks later. The mycelia grew luxuriantly with velvet character. The pycnidium was flask-shaped with a height of 196.9μm and a width of 213.3μm on the avereage. The conidium was colorless with single cell and had the shape of spindle, its size was (15.0-20.0)μm× (4.5-6.5)μm. The conidiophore was fastigiate. The homology of ITS sequence of ribosome DNA between the tested strain NXK and Botryosphaeria dothidea (GenBank ac-cession number:AJ938005) reached 99.87%, with a difference of only two base pairs. Based on the results of both morphological characters and molecular identification, the pathogen of jujube fruit soft rot in Xinzheng was identified as B. dothidea (Moug. ex Fr.) Ces. et de Not..

The effect of silica nano-particles, tetraethyl orthosilicate (TEOS) and sodium silicate in solution culture on wheat powdery mildew and its action mechanism to pathogen attack were studied. The results showed that wheat seedlings cultured in nutrient solution with silicon compounds alleviated wheat powdery mil-dew, the control efficacies of TEOS and sodium silicate treatments were 54.08% and 51.36%, respectively, but that of silica nano-particles treatment was only 1.02%. Scanning electron micrograph and X-ray energy dispersive analysis (SEM-EDX) showed that wheat leaves cultured in nutrient solution with TEOS and sodium silicate had more silicon deposition than that of silica nano-particles. It indicated that wheat possessed the equal good imbibe ability to TEOS and sodium silicate, but poor to silicate nano-particles. When wheat leaves were infected with Blumeria graminis f. sp tritici, silicon might has a physical prohibition effect to pathogen spore penetration.

Root-knot nematode (RKN) is one of the most destructive plant pathogens in the world-wide agriculture production, and there is no effective and environmentally safe method available to control this disease. Exploring the molecular mechanism of the interaction between parasitic nematodes and host plants will con-tribute to resistance breeding by biotechnology, which was considered to be the most promising novel strategy. In the research on genomics, An AFLP genetic linkage map of Meloidogyne hapla was constructed and the genome sequence had been completed for M. incognita and M. hapla. The genomic composition of RKNs was revealed by genome annotation and comparative genomics research. Large-scale identification of important genes from RKNs was processed based on the analysis of difference expression patterns and comparative genomics approach. Significant progress in functional genomics research of RKNs has been made by application of RNA interference, transgenic plant and the approaches of protein-protein interactions. This article reviewed the recent progress on RKNs genomics, discussed the orientation of genomics in future and the prospect of novel strategies for sustainable control of nematode.

Acidovorax avenae subsp. cattleyae (AACa), the pathogen causing bacterial brown spot of orchid, is a quarantine organism in China. However, with conventional methods it is difficult to distinguish this pathogen quickly and reliably from other closely related pathogen in the genus of Acidovorax. In this study, a TaqMan-MGB probe was designed based upon the ITS sequence of Acidovorax and a real time PCR method was developed. AACa can be distinguished from other 28 bacteria strains including other species of genus Acidovorax and subspecies in avenae with this method. The absolute sensitivity threshold was approximately 9×10^-9 μg bacterial genomic DNA. By this method AACa could be detected easily from infected orchid plant directly without bacteria culture. This real time PCR method could assist in the implementation of quarantine measures for prevention and control of the disease caused by AACa.

Luocheng Moulao Autonomous County is the main production area of Vitis heyneana Roem. et Schult in Guangxi, China. Brown rachis rot is the major disease at florescence stage, and becoming a constraint for fruit production of V. heyneana in recent years. The pathogen was identified as Lasiodiplodia theobromae according to the morphology, pathogenicity and sequence analysis of the internal transcribed spacer region of the ribosomal DNA (ITS). The optimum temperature for mycelial growth was 28-30℃. The pathogen could grow under pH 3-11.5 and pH 3-4 was the suitable range for sporulation. Sucrose and sodium nitrate could be used as better carbon and nitrogen sources for growth of L. theobromae, respectively.

A normalized full-length cDNA library was constructed with the mycelium of Curvularia lunata, a causal organism of maize leaf spot, by DSN duplex-specific nuclease normalization method combined with SMART (switching mechanism at 5' end of RNA transcript) technique. This library was characterized by a plaque titer of 1.4×10⁶ pfu/mL and a 96.9% recombination ratio, of which the fragment length of inserted average cDNA sequences was above 1.0 kb. The 173 high quality expressed sequence tags (EST) including 5 coting and 168 singlet was obtained from 192 cDNA clones randomly picked. Based on bioinformatics analysis, the full-length cDNA accounted for 57% of total sequences. BLASTx analysis revealed that 81.5% of the EST displayed significant homology to known or unknown genes from GenBank database.

To explore the relationship between oligosaccharides molecular structure and induced disease resis-tance of plants, induced resistance of tobacco to black shank disease with seven synthesized oligosaccharides as elicitors was studied. The tobacco plants induced by β-1, 3-N-acetyl-glucosamine tetrasaccharide, β-1, 4-N-acetyl-glucosamine trisaccharide and β-1, 4-N-acetyl-glucosamine tetrasaccharide showed resistance to the disease with relative efficiency of 62.5%, 50.0% and 75.0%, respectively. The tobacco detached leaves induced by β-1, 3-N-acetyl-glucosamine tetrasaccharide, β-1, 4-N-acetyl-glucosamine trisaccharide and β-1, 4-N-acetyl-glucosamine tetrasaccharide showed resistance to the disease with relative efficiency of 56.25%, 50.0% and 62.5%, respectively. It was suggested that the degree of polymerization and chain backbone linkage structures of oligosaccharides might be the important factors affecting the induced disease resistance. Moreover, the induced disease resistance by oligosaccharides varied with treated oligosaccharide concentrations.

To understand the role of reactive oxygen species (ROS) and cytosolic free calcium in plant defense responses to pathogen infection, changes of ROS, activities of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX), the enzymes known to detoxify ROS in plant, permeability of cell plasma membrane and concertration changes of cytosolic free calcium were investigated in the incompatible and compatible interaction systems, Lovrin13/CY25 and Lovrin13/CY29, respectively. The time course of ROS detected by ESR showed that two peaks of ROS production were observed in leaves inoculated with avirulent or incompatible rust strain CY25. The first peak occurred on the second day whereas the second peak was on the fifth day after inoculation. However, only one single peak of ROS production was observed in leaves on the sixth day after inoculation with virulent or compatible strain CY29. HR occurred in the incompatible inte-raction system was associated only with the early oxidative burst of ROS. This implicated that early oxidative burst could mediate the occurrence of HR. Accompanied with a big amount of ROS production in the infected wheat leaves at late oxidative burst period, plasma membrane was damaged, cell substances leaked out and the cell died soon. The results indicated that strong ROS could cause cell death. According to the activity changes of SOD, CAT and APX at the two periods of oxidative burst, the main component of ROS was H₂O₂ at the early period in incompatible interaction and O₂^-_· and H₂O₂ at the late period in both incompatible and compatible interactions. This suggested that H₂O₂ was the signaling substance in HR of wheat to avirulent or incompati-ble rust strains, whereas O₂^-_· was responsible for cell death. Detecting of cytosolic free calcium in wheat leaves inoculated with stripe rust through laser scanning confocal microscope (LSCM) showed that the occurrence of HR was associated with an increase of[Ca²⁺]_cyt in cellular matrix. Decline of[Ca²⁺]_cyt in cellular matrix could delay the occurrence of HR. It implied that increase in cytosolic calcium was necessary for hypersensitive cell death, and Ca²⁺ was involved in pathogen defense processes as a vital intracellular second messenger.