Total 45 isolates of Pseudomonas syringae pv. tabaci collected from Yunnan province were inoculated on the fifteen tobacco cultivars,a set of differential host system was selected,by means of 20% incidence as the limit action between resistance and susceptible,forty five isolates of P.s. pv. tabaci were divided into four races(i.e.physiological raceⅠ、Ⅱ、Ⅲ、Ⅳ).

Three fluorescent Pseudomonas strains and their pseudobactin siderophore-minus mutants were investigated in suppression of eucalypt grey mould caused by Botrytis cinerea. Results from in vitro antagonistic tests showed that Pseudomonas fluorescens WCS374r and P. putida WCS358r inhibit mycelial growth of B. cinerea by competition for iron. When WCS358r,WCS374r and WCS417r were applied to wounded leaves 10 h prior to the inoculation of pathogen,they suppressed eucalypt grey mould,and reduced the percentage of necrotic spots on leaves by 48.9%, 58.3% and 40.3%,respectively. Strains WCS358r and WCS374r were effective as well when the mixture of either strain and pathogen was applied to wounds on leaves. However,if three strains were applied to wounds 12 h or 24 h posterior to inoculation of pathogen,the control effects decreased sharply. The pseudobactin-minus mutants of WCS358r,WCS374r and WCS417r partially or fully lost their suppressive ability of the disease. These results demonstrate that siderophores are important bacterial determinants in suppression of eucalypt grey mould.

Red heart of radish was proved to be a viral disease,and the isolate of samples was identified to be Turnip mosaic virus (TuMV) with evidences at biological,serological and molecular levels. The virus isolate could produce systemic mosaic symptom on Datura metel,Brassica campestris,Cucumis sativus cv. Xianyang, Luffa acutangula,Brassica campestris ssp. pekinensis, and Nicotiana tabacum, local necrotic lesions on Chenopodium amaranticolor, local chlorotic lesions on Nicandra physaloides. It could not infect Pisum sativum. The virus particles were flexuous filamental,with an average length of 700 nm. It produced pin-wheel inclusion bodies and laminated aggregates in infected radish root tissue. The virus isolate could react with antibody to TuMV in SDS-agarose gel double-diffusion test. The coat protein gene contained 867 nucleotides and en-coded 288 amino acids,with molecular weight of 32.98 kD. The phylogenetic analysis result of this isolate and other 20 TuMV isolates indicated that the virus shared higher homology with two Japanese isolates (H1J and KYD81J) and one Italian isolate (ITA7).

Universal primers for 16S rRNA gene was used to detect phytoplasmas in sunshine tree(Cassia surattensis)showing witches'-broom symptom. A 1.2 kb DNA fragment was amplified by nested-PCR. The result indicated existence of phytoplasma associated with this diseased plant. The amplified fragment was ligated into pGEM-T easy vector and transformed into the competent cell of E.coli JM109 strain. Cloned DNA fragments were verified by PCR,sequencing and phylogenetic analysis. The results showed that the content of G+C in the sequenced 16S rDNA was 45.8%. This strain (STWB) shared highest homology (99.4%) with phytoplasma strains in Elm yellows (16SrV group) but is obviously under 97.0% with other groups. So the results made it clear that this phytoplasma strain is one of the members of Elm yellows phytoplasma group.

Seven Rhizoctonia isolates collected from different ecological origins in Jiangsu province were classified into CAG1,non-CAG1 of binuclear Rhizoctonia and AG-2 of R. solani by using anastomosis reactions and pathogenic potential. The internal transcribed spacer (ITS) region of the ribosomal DNA from these 7 isolates were amplified using universal prmers ITS1 (TCC GTA GGT GAA CCT GCG G) and ITS4 (TCC TCC GCT TAT TGA TAT GC). Sequence comparison revealed that 5.8S rDNA sequence was highly conserved,whereas the ITS rDNA sequence was variable among AG-2 isolate of R. solani,CAG1 and non-CAG1 isolates of binucleate Rhizoctonia. These results suggest that sequence analysis of ITS rDNA regions may be a valuable tool for identifying pathogens of Wheat sharp eyespot.

Antifungal protein produced by Bacillus subtilis B9601-Y₂ led to deformation,bread string-like,perforation,irregular decomposition,protoplasm leakage and death of Fusarium moniliforme (causing fusarium rot of cotton) hyphae. The optimal condition for the protein yield was to grow in potato sugar juice at pH 7.0 and 37℃ for 48 h,in which crude protein could be obtained about 0.1 mg/mL with ammonium sulphate at 80% saturation. The protein yield was positively related to air volume and the bacterial population. The protein could tolerate 80℃ and pH 9.0 and keep its antifungal activity stable for 60 days at 4℃.

Infection of U. virens was observed with microscope on various rice cultivars inoculated with conidia suspension at the heading stage. The results showed that the conidia could germinate and form mycelia on the surface of glume and further extend inside the glume hull,which may provided evidence of infecting panicle by conidia directly. By histochemical observation on the grains,a higher level of lignin content was found in the resistant variety Shuijing 3 (R) than in the susceptible variety 9522 (S). Abundant polyphenolic compounds in epidermis and endosperm of grain were detected in R,but not in S. A sort of "butterfly" structure was repeatedly observed under the UV light in each sclerotium of U. virens. No peroxidase,tannins,suberines or lignins was found in the "butterfly" structures by histochemical observation.

Activation of membrane lipid peroxidation and defense enzymes was investigated on both incompatible and compatible rice leaves treated with M. grisea-derived elicitor GP66. Compared with the compatible rice,the GP66 treatment caused rapid and remarkable O₂^· generation and an increasing of lipoxygenase (LOX) activity in incompatible rice leaves. These changes further led to lipid peroxidation,concomitant with an increasing of the relative conductance rate and an accumulation of the maloondiadehyde (MDA). Peroxidase (POD) was also stimulated in the early stage of the incompatible reaction. By contrast,treatment of GP66 caused a decline of superoxide dismutase (SOD) activity and catalase (CAT) activity in both compatible and incompatible rice cultivars. The results suggest that lipid peroxidation in rice leaves induced by GP66 elicitor may play an important role in the resistance of rice seedlings.

Under the infection by Meloidogyne incognita,continuous changes of several physiological and chemical indexes in ginger were studied. Results showed that physiological and chemical changes mainly behaved at the earlier stage of first and second infection of M.incognita,and there were little or no changes in the rest stage. Furthermore,there were great differences of physiological and chemical changes in different parts of ginger,leaf was the highest,root was the second,and rhizome was the lowest. Combined with the life cycle of M.incognita,the conclusions that physiological and chemical changes of ginger mainly showed at the first infection; and then lost to some extent at next infection were proposed.

In this study two proteinous elicitors in extracellular supernatant during interaction between Xanthomonas oryzae pv. oryzae JXOV and suspension-cultured incompatible rice IRBB4 cells were isolated and identified. Proteins in extracellular supernatant collected 36 h after the interaction between JXOV and incompatible rice IRBB4 suspension cells or compatible rice IR24 suspension cells were fractioned by HPLC using an anion exchange column Q-Sepharose. Two fractions obtained in incompatible interaction showed elicitor effect for that length of leaf lesion on rice IR24 inoculated JXOV observably decreased after treatment with substance in that fractions. Further purification by HPLC using anion exchange column Mono-Q and preparative PAGE revealed 2 elicitors with molecular mass 17.2 kD and 49.2 kD,and pI 5.8 and 6.2. Treatment with these eli-citors at the concentration of 100 μg/mL before inoculation of JXOV not only decreased leaf lesion,but also increased the activity of defence enzymes PAL and POD in leaves of compatible rice IR24.

An alien disomic addition line,Shannong Line15,which derived from the progeny of Elytrigia intermedium and common wheat Yannong 15(BC₃F₆),was identified by morphology,powdery mildew resis-tance,cytology,genome in situ hybridization (GISH)and random amplified polymorphic DNA (RAPD)analysis.The results demonstrated that Shannong Line15,with the chromosome number of 2n=44 in root tip cells and chromosome configuration of 2n=22Ⅱat PMC MⅠ,was highly resistant or immune to powdery mildew and its main morphological traits were between that of their parents. The results of GISH with the probe of total genomic DNA of E. intermedium further proved that Shannong Line15 was an alien disomic addition line with a pair of E.intermedium chromosomes in wheat background.Genetic analysis showed that powdery mildew resistant genes of Shannong Line15 most probably came from the chromosomes of E.intermedium. Among 120 RAPD primers,the primer S170 (-5'-ACA ACG CGA G-3'-) could amplify specific bands of E.intermedium which could be used as RAPD markers for additional E.intermedium chromosomes of Shannong Line15.

The fermentation filtrate (FF) in barnyardgrass decoction dextrose liquid (BDDL) of barnyardgrass pathogenic fungi Helminthosporium gramineum Rabenh f. sp. echinochloae (HGE) and Exserohilum monoceras (EM) showed significantly inhibiting effect to the barnyardgrass seeds germination. The FF of HGE in both of modified Fries liquid (MFL) and BDDL,and the FF of EM in MFL give higher efficacy to inhibit growth of the roots and shoots of barnyardgrass. Mixture of HGE conidia and its FF showed higher efficacy to control barnyardgrass than that of each alone in applying. The percentage of infected,mortality and di-sease index of barnyardgrass seedlings were 86.3%,69.5% and 78.7,respectively. Application of FF combination with HGE conidia (spraying one after another) also gave higher efficacy to barnyardgrass,the percen-tage of infected,mortality and disease index were 83.9%,67.9% and 72.8,respectively. Control efficacy to barnyardgrass of mixture spraying of HGE and Curvularia lunata spores is better than that of alone using.

single spore isolates causing capsium anthracnose collected from Jiangsu and Hainan provinces were identified into C. gloeosporioides and C.capsici based on the morphological characteristics. Of these isolates, 64.4% was C. gloeosporioides. Sensitivity of the C.gloeosporioides and C. capsici isolates to azo-xystrobin was determined on AEA and WA media suitable for conidium production and for spore germination test,respectively. The mean EC₅₀ value of the azoxystrobilurin inhibiting spore germination of the 45 isolates of both species was 0.047 μg/mL with a standard error of 0.040 and a range of 0.009 to 0.091 μg/mL. The mean EC₅₀ values of 29 isolates of C. gloeosporioides and 16 isolates of C. capsici isolates were (0.051±0.047) μg/mL and (0.041±0.024) μg/mL,respectively. There was coordinate synergism between azoxystrobin and salicylhydroxamic acid(SHAM) as an inhibitor of alternative oxidase against spore germination of C.gloeosporioides and C.capsici. However,azoxystrobin and SHAM inhibited mycelial growth solely and azoxystrobin was much less effective against mycelial growth.

The dynamics of Agrobacterium vitis strain E26,a potential grapevine crown gall biocontrol agent,in Vitis vinifera cv. Muscat Humburg rhizoplane and rhizosphere under field conditionswere studiedby using gfp -marked bacterial strain to evaluate its colonization on diseasesuppression. Attachment of strain E26 and pathogen A. vitis strain K308 to plant wound cells were also compared in vitro. Colonization and survival of strain E26 in the rhizospherewere observed in field. Average population of 10⁴ cfu/g of E26 was detected in fresh root and dry soil respectively 5 months after planting. Attachment of E26 and K308 was at a similar level to both stem explants and roots of Muscat Humburg in vitro. However,K308 was blocked attach to grape cells by E26 in both the stem explants and seedling root systems. Scanning electron microscope also revealed that strain E26 could attach to the wounded cells of grape root with the same manner as that of strain K308.

Twenty-five isolates of Rice sheath blight pathogen (Rhizoctonia solani AG-1-IA) from several different geographic locations were analysed for pathogenicity and electrophoretic profiles of soluble proteins and esterase isozymes.These isolates showed different pathogenicities. The patterns of esterase were similar among these isolates except somewhat difference in stain degree and band's number. However,the patterns of soluble proteins showed remarkable difference. The isolates with relatively strong pathogenicity showed some specific bands and had 3 to 5 more protein bands than the weaker isolates.

The 16S rRNA gene-based PCR has been developed as a routine method for phytoplasma detection. When P1/P7 (or U5/P7) nested U3/U5 primers were used in PCR,the normal 0.85 kb product band was often accompanied by an unexpected 0.36 kb fragment. The occurrence and intensity of this extra band was tightly related to the normal band. This phenomenon was only observed in the nested-PCR detection using P1/P7 (or U5/P7) nested U3/U5 primers,and never occurred in routine PCR using P1/P7,U5/P7 or U3/U5 primer pairs. So far,the extra PCR band was found at least in grapevine yellows (stolbur) and elm yellows phytoplasma detection. Further PCR amplification and nucleotide analysis revealed that this extra fragment located on phytoplasma 16S rRNA gene with a partial complement site of U5 primer. These results revealed the potential usage of this extra band in phytoplasma detection.

pGEM-PSTVd with monomeric PSTVd cDNA (359 bp) was used as a template and the dUTP was partically replaced by biotin-11-dUTP. The cDNA probe was prepared by PCR amplification technique. Colori-metric and chemiluminescent detection for biotinylated probe were used in this test. They were capable of detecting 50 pg purified total RNA by colorimetric assay and 5 pg by chemiluminescent assay. Nonradioactive probes produced with PCR amplification are particularly suitable for practical diagnosis, as they are sensitive and can be rapidly prepared in large quantities. This two assay methods were 26 times and 260 times as sensitivity as R-PAGE respectively. The diagnosis was sensitive, specific, quick and easy to follow.

Based on rapid extraction procedure of potato ssRNA viruses of seedling potato,specific primer pairs for PVX,PVY,PLRV and PVS from the coat protein region,the primers for PVA from the P1 gene region,multiplex reverse transcription polymerase chain reaction (M-RT-PCR) approach was well established. It was capable to detect at least two or three viruses from seedlings potato simultaneously and the sensitivity of M-RT-PCR was 100 folder than that of ELISA. The M-RT-PCR detection kit utilizing unique stabilizer of bio-activation technique was developed for detection various target viruses of seedlings potato both from field and breading greenhouse. Total 248 seed potato samples with or without symptom from 15 counties of potato plantation in Chongqing area and Sichuan province were tested. The results showed that two or three viruses often mix-infected (PVX,PVA,PVS or PLRV,PVY) in these area.

Highly pure total RNA for reverse transcription-polymerase chain reaction (RT-PCR) was extracted from strawberry with modified CTAB method. The specific segment of SMoV was amplified with the designed primers,and testified by cloning and sequencing. The results showed it shared 91%-97% nucleotide acid identity with the published sequences. In order to detect the effectiveness of the RNA extraction and RT-PCR,the gene encoding mitochondrial NADH dehydrogenase ND2 subunit (ndh B gene) was used as an internal control. By locating one of the primers across the splice junction with the last two 3' nucleotides being in the second exon,the primers were shown to amplify only the spliced RNA derived cDNA but not the intron containing DNA. This is the first report that SMoV was detected by RT-PCR in China. By using total RNA as template,in combination with specific internal control,the detection provides a quick and effective method for routine diagnosis of SMoV in strawberry cultivars and virus indicator plants.

Top pruning, a new inoculating method of bacterial canker of tomato, was developed based on the traditional methods including leaf shearing, root soaking and needle penetrating in this study. Tomato seedlings of three staple tomato cultivars (Jiafen 10, Hezuo 908 and Huanan Hongbaoshi) with 2-3 true leaf and two representative strains of C. m. subsp. michiganensis (Cmm) from China and United States, were used for the pathogenicity test. Under the green house condition with daily min. and max. temperature 15-18℃, 32-35℃ respectively, and 30%-60% RH, top pruning engendered the typical bacterial canker symptoms on 87.5%-100.0%. The disease index stably increased up to 23.96-82.29 in three experimental cultivars con-sistently with the concentration of inocula. On the other hand, disease rates yielded by leaf shearing, root soaking, and needle penetrating were lower than 40%, and their disease index lower than 20 without significantly difference between the above cultivars. With a selective medium mSCM, isolates obtained from the infected tomato plants were identical in culture characteristic as the inocula. With ImmunoStrip and polymerase chain reaction, the isolates were identified as Cmm. These results indicate that top pruning, as a convenient and efficient inoculation method, is applicable for further evaluating the resistance of tomato seedlings to bacterial canker and chemical control effect to this disease.

Pseudorecombination of a Cucumber mosaic virus CNa strain (CNa) and a satellite RNA, CNa-SatC382,was obtained by in vitro transcription. The results showed that CNa and CNa-SatC382 can coexist steadily in Nicotiana glutinosa by dsRNA extraction, RT-PCR and sequencing. CNa-SatC382 was inoculated on 14 different hosts and the disease index of Chenopodium quinoa, Nicandra physanodes, N. glutinosa and Cucurbita pepo in 7,14,21,28 days post-inoculation was analyzed. The results showed that CNa either with or without satellite imposed no obvious influence on disease symptom of all tested host plants or disease index. In short, SatC382 had no influence on host symptom caused by helper virus CMV-CNa.

Meloidogyne incognita, M. javanica and M. arenaria have their representative isozyme phenotypes. Primers #C2F3 and #1108 were utilized to amplify the intergenic region between COⅡ and LrRNA genes of mtDNA of 42 Meloidogyne populations. Specific amplified fragments were about 1.7 kb for 35 Meloidogyne populations, including 29 M. incognita populations and 6 M. javanica populations; about 1.1 kb for 3 M. arenaria populations; about 0.7 kb for 1 population of a new record root-knot nematode species; and about 0.5 kb for 3 M. hapla populations. The PCR results gained from DNA of the single juvenile and the mass juveniles were the same. The amplified products were digested with the restriction enzyme HinfⅠ, and the results showed that all populations of M. incognita can be digested into two restriction fragments of about 1.3 and 0.4 kb, but the PCR product of specific region on mtDNA of M. javanica can not be digested. It concluded that mtDNA was a rapid and reliable approach for molecular identification of common Meloidogyne species.

Alternaria alternata is one of the host fungi of Olpitrichum tenellum, which is a biotrophic contact mycoparasite. The recognition mechanism between them has not been reported. This research focused on the purification, and characterization of a lectin isolated from A. alternata mycelial cell walls, in order to reveal the recognition mechanism between mycoparasite and mycohost. The A. alternata lectin, abbreviated to AAL, was purified using ammonium sulfate fraction, DEAE-Sepharose Fast Flow chromatography and Sephacryl S-100 chromatography. AAL is a glycoprotein with an apparent molecular weight 37.2 kDa as determined by gel filtration, and may be a recognition molecule which mediates the adhesion of O.tenellum cells to A.alternata cells. From adhesion experiments between AAL and conidia of O.tenellum, >90% of conidia adhered within 30 min at concentrations as low as 3.325 μg/mL. The control has no significant effect on spore adhesion.

RNA-mediated virus resistance is an effective way to obtain virus resistant plants. The strategy is provided with the advantages of high bio-safety and long resistant duration. The method is regarded as a potential strategy with broad application value and practical significance in plant genetic engineering against viruses. In this study,we used untranslatable CP genes of Potato virus X(PVX-CP) and Potato virus Y(PVY-CP) to construct a chimeric cDNA fragment,which was then introduced into the plant expressing vector pROKⅡ. The recombinant binary vector pROKXY was introduced into tobacco (NC89) plants via Agrobacterium tumefaciens-mediated transformation,six transgenic plants immune to the co-infection with PVX and PVY^N were obtained. Molecular analysis demonstrated that the resistance was RNA-mediated virus resistance.

HrmA gene,isolated from Pseudomonas syringae pv. syringae,is functionally like an avirulence gene on the host tobacco plants. In this study,we expressed the recombinant hrmA protein on a pET-29(b) vector in Escherichia coli BL21 (DE3). The hrmA histidine-tagged fusion protein was expressed at very high amount as inclusion bodies. The partial purified proteins were used for the study of biological function on rice. The hrmA protein induced rapidly the burst of active oxygen species in suspension-cultured rice cells,with a peak about 20 min post the treatment. The expression of PBZ1,a pathogenesis-related gene,in hrmA-treated rice cells was observed by northern blot analysis. Treatment of rice seedlings with the recombinant hrmA protein induced strongly the accumulation of mRNA of phenylalanine ammonia-lyase gene. These results suggest that the hrmA protein has an elicitor activity on rice cells.

Fragments of γ-tubulin genes from wild-type of carbendazim(MBC)-sensitive, field and induced MBC-resistant mutants of F. graminearum were amplified, sequenced and spliced into the whole sequence of γ-tubulin gene with 5 pairs of primers synthesized in accordance with the γ-tubulin gene of the reference isolate, NRRL31084(PH-1) by polymerase chain reaction (PCR). γ-tubulin gene had 1 868 bp length, including 5 introns, encoding 493 amino acids. The homology of deduced amino acid sequence of the F. graminearum γ-tubulin gene with that of the other 7 species fungi γ-tubulin genes was from 31% to 72%. The whole nucleotide sequence comparison indicated that there was 10-nucleotide difference between Chinese isolates and PH-1, but with 100% predicted amino acid sequence homology. Sequence comparison among MBC-sensitive, field and induced MBC-resistant isolates revealed there was no mutation, even one.

The role of the protein elicitor PB90 in compatible interaction between P. boehmeriae and cotton was studied. The elicitor was previously shown to be an efficient elicitor of the hypersensitive reaction and an AVR factor conditioning nonhost resistance in Nicotiana tobacum. The treatment of P. boehmeriae zoospore with antiserum raised against the elicitor PB90 resulted in the loss of virulence activity on host cotton, indicating that the elicitor could contribute to virulence of P. boehmeriae on cotton (Fig.4). However, the hypersensitive reaction was also observed in nonhost tobacco leaf infiltrated with zoospore treated by different doses of antiserum (Fig.2). The antiserum did not inhibit zoospore germination and creation of effective single zoospore isolates in vitro (Table 1 &Fig.3). The antiserum allowed localization of PB90 by immunogold-labeling on the cell wall of the mycelium and encysting zoospores when the fungus was grown in vitro (Fig.2). The results provide strong evidence that PB90 has dual functions with promoting virulence on host cotton and functioning as avirulence factor by eliciting hypersensitive reaction and resistance in nonhost tobacco.

The identification of resistance of maize germplasms to sheath blight was conducted in 1997-2000. Inbred line CML270 was highly resistant to pathogen AG-1-IA collected from different locations. The inheritance analysis indicated that maize resistance to sheath blight would be controlled by about 4-7 pairs of major genes.

Biocontrol of Cucumber Fusarium wilt with T. viride T23 was detected through bioassay, and its induction of several defense enzymes in cucumber was examined. Treatments with conidiospores and chlamy-dospores of T. viride T23 on cucumber seedlings reduced the disease index of Fusarium wilt from 33.69 to 13.12 and 10.28, respectively. The activities of defense enzymes, such as phenylalanine ammonia lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO) and catalase(CAT), was measured in roots. Significantly higher levels of these enzymes were detected in T23-treated plants than in control.The maximum peaks of PAL, POD, PPO and CAT activities were enhanced by 2.75,2.49, 2.42 and 15.84 times over control, respectively, indicating that the production of phytoalexin or lignin might be involved in the disease suppression. The enzyme activities in conidiospore-treated cucumber reached their peaks earlier than those in chlamydospores treatment, however, the latter showed higher enzyme activity peaks in cucumber.

Cotton leaf curl disease (CLCuD) is a severe disease of cotton. It caused destructive damage on cotton production in Pakistan and India. Seven distinct begomoviruses had been identified to be associated with CLCuD occurred in Asia and Africa. In field, it is common that cotton plants are mix-infected by these begomoviruses and genomic recombination occurred frequently among them. Diverse small DNA molecules were found to be associated with CLCuD, and a novel satellite DNA, referred to as DNAβ plays an important role in CLCuD pathogenicity and is essential for typical symptom induction. Genomic recombination resulted in genetic diversity of CLCuD-causing begomoviruses and DNAβ could interact with diverse begomoviruses, these are the possible important reasons leading to CLCuD epidemic. In this paper, distribution and damage of CLCuD, discovery of disease-causing agents, interaction among the components of CLCuD complexes, variability and evolutionary relationships among begomoviruses and their associated small DNA molecules, disease epidemic and control are discussed.

After the seedlings and in vitro seedling twigs of pine (Pinus massoniana) were inoculated with pine wood nematode(PWN)(Bursaphelenchus xylophilus),the content changes of water, free proline and chlorophyll in host plant and the mutual relations between these changes were studied. The results showed that the relative water content was decreased gradually in the stems of the hosts after infected by PWN and it was faster at the late stage than at the early stage. The water changes in the needles were behind those in the stems. Before the infected symptoms on the needles appeared, the relative water content in the needle did not fall down, but it had decreased obviously in the stems. The obvious decrease of the relative water content in the needle appeared at late stage of disease development. The reduction of contents of free proline and chlorophyll was consistent with the decrease of the relative water content in the needles. The water regime in the needles was the key factor influencing the contents of free proline and chlorophyll. A comparison between the wilt pine seedlings caused by drought and those caused by PWN showed that there were distinct differences in the ways of wilt and the water content changes in the stems and needles.

The ToLCGDV-[G3] was isolated from tomato plants showing leaf curl symptoms in Guangdong. The complete nucleotide sequence of ToLCGDV-[G3] DNA-A was determined. It contains 2744 nucleotides and encodes six potential ORFs, with two (AV1 and AV2) in virion-sense strand and four (AC1, AC2, AC3 and AC4) in complementary strands. BLAST results showed that all sequences homologous to ToLCGDV-[G3] DNA-A belonged to the genus Begomovirus of family Geminiviridae. Pairwise comparisons of ToLCGDV-[G3] DNA-A with those of other begomoviruses indicated that the overall identities were less than 88.0%. The identities of intergenic region (IR), AV1, AV2, AC1, AC2, AC3 and AC4 were 59.0%-85.3%, 73.6%-95.2%, 64.0%-95.4%, 71.7%-87.7%, 69.6%-93.9%, 67.7%-95.1% and 64.1%-94.2% respectively, and that of their encoded amino acid sequences were 76.3%-99.2%, 52.6%-95.7%, 69.7%-88.1%, 51.9%-88.9%, 63.4%-92.5% and 33.0%-90.7% respectively. Phylogenetic analysis of DNA-A of ToLCGDV-[G3] and the selected begomoviruses showed that ToLCGDV-[G3] is most closely related to ToLCGDV-[G2] than the other begomoviruses, and that the two viruses were clustered in a separate branch. These results suggest that ToLCGDV-[G3] should be a previously unreported begomovirus.

Total RNA of Soybean mosaic virus (SMV) was extracted successfully from soybean dry seed with improved SDS-phenol-chloroform procedure. The improvement of procedure lay in 1/4 volume of 100% ethanol and 1/10 volume of 5 mol/L potassium acetate were added to pellet polysaccharides selectively before pelleting RNA. A pair of specific primers was designed based on the nucleotide sequence of coat protein (CP) gene of SMV G2 strain, and then it was used to detect SMV in soybean dry seed by reverse transcription-polymerase chain reaction (RT-PCR). Meanwhile, DAS-ELISA was performed for testing same samples. The result showed that a rapid, sensitive and specific RT-PCR assay was established for detection of SMV in soybean dry seed.

cDNA arrays comprising of 1 106 uni-genes were used to monitor the expression profile of rice genes of near-isogenic line H7R/H7S 8 h after the infection by Magnaporthe grisea. The results showed that expression profile of rice genes changed remarkably. Of the 980 genes which were available in the cDNA arrays, 106 genes were up-regulated and 64 genes were down-regulated by at least two-fold. BLAST analysis against GenBank rice database revealed that 33 genes are homologous to known genes, including β-1,3-glucanase and glycine-rich protein genes. By bioinformatics analysis to 10 unknown genes, a clone, T007F02, contained a full-length new gene with BTB/POZ domain (http://www.estarray.org) was defined and sequenced, which was now named as OsBTB. The analysis results of RNA blot indicated that OsBTB was highly expressed in early stage of resistant rice samples inoculated by pathogen, and not changed in susceptible varieties. These results implied that OsBTB might play an important role in disease resistance to rice blast.