Abstract: Statistics of codon usage in the genomes of bacterial phytopathogen Xanthomonas campestris pv. campestris and X. axonopodis pv. citri were calculated based on the published genomic data. Codon usages in these bacteria were dominated by codons containing high-GC content, with the average GC content at synonymously variable third position of codons (GC3s) being 0.806±0.077 （Xcc）and 0.791±0.075（Xac）, respectively. Calculation of effective number of codon usage (Nc) and codon adaptation index (CAI) revealed that highly expressed genes exhibited higher frequencies of GC content and tend to use biased number of codons, while for lowly expressed genes, the opposite tendencies was true. Correspondence analyses based on absolute numbers of codon usage (N) were according to the above results. Comparative analysis revealed little difference between genes from leading and lagging DNA strands, so that gene location was not acontributive factor. Our findings suggest that for Xanthomonas genomes, highly GC content, gene expression level, and gene family and origination are fundamental factors to shape the pattern of biased codon usage.

Preliminary identification of bacterial strain causing Anthurium bacterial blight
JI Guang-hai1, WEI Ya-dong2, JIANG Gui-zhi3, GUAN Xu-fang1, YU Sheng-fu1, LIU Chang-fen3(1Key Laboratory for Plant Pathology of Yunnan Province,Yunnan Agricultural University, Kunming 650201, China; 2Tianjin Animal and Plant Quarantine Bureau, Tianjin 300457, China; 3Yunnan Institute of Tropical Crops, Jinghong 666100, China)

Abstract: In April 2002, a serious Anthurium disease broke out in a commercial plantation in Xishuangbanna, Yunnan Province, P. R. China. The early symptom appeared as irregular water-soaked spots on the margin or in the middle of leaves. Eventually, brown to blighted areas were often observed together with striking yellow zones along leaf margins. Yellow, mucoid colonies were consistently isolated from infected tissues. The strains reproduced the typical symptom after spraying or rubbing on both Anthurium and Dieffenbachia leaves. The colonies re-isolated from inoculated leaves were as same as those from infected tissues. The pathogen was preliminarily identified as genus Xanthomonas, based on bacterial morphological, cultural, physiological and biochemical properties. The pathogen was further identified as Xanthomonas axonopodis pv. dieffenbachiae (McCulloch and Pirone) Dye by carbon source utilization and pathogenicity tests.Key words： Anthurium andraeanum; bacterial blight; pathogen identification; Xanthomonas

Identification and sequencing of ribosomal DNA-ITS of Phytophthora sojae in
Fujian CHEN Qing-he1,2， WENG Qi-yong1， WANG Yuan-chao2, ZHENG Xiao-bo2
(1Institute of Plant Protection, Fujian Academy of Agricultural Sciences, Fuzhou 350013, China; 2Key Lab of Monitoring and Management of Plant Diseases and Insets of Chinese Ministry of Agriculture, College of Plant Protection, Nanjing Agricultural University, Nanjing 210095， China)

Abstract: Six typical Phytophthora strains which cause soybean root rot in Longhai, Fujian were chosen for identification. The morphological characteristics, pathogen
icity, host range and the sequence of ribosomal DNA-ITS were studied. Based on
its abundant, rounded hyphal swellings in chains, right-angle and shrinking in
branch, non-papillate, ovoid sporangium, internal proliferation of sporangiopho
re, zoospores formed within sporangium, homothallism, rounded oogonia and paragy
nous antheridium as well as its narrow host range, the symptom of Soybean Phyto
phthora blight after inoculation, the pathogen was identified as Phytophthora
sojae. The sequence of ribosomal DNA-ITS of Fujian isolates was closest
relative to that of Phytophthora sojae published in GenBank with 99.8% identity. The results indicated that these strains were Phytophthora sojae. This is the
first report that Phytophthora sojae exits in Fujian, China.

Identification of Schisandra sphenanthera rust and the hyperparasite
HUANG Yun， YE Hua-zhi, LIU Zi-ying， DONG Bao-cheng， HUANG Chun-yan(Department of Plant Protection, Sichuan Agricultural University, Ya'an 625014, China)

Abstract: Schisandra is Chinese traditional medicinal materials. The rust caused by Aecidium schisandrae is an important disease of S. sphenanthera in LaBa
River nature protective area. The percentage of diseased plant and the diseased le
af reach 91% and 36% respectively when the disease occurs seriously. The disease
caused leaf spot, leaf cast and weakened the development of the tree. A hyperpa
rasite (Tuberculina sp.) of A. schisandrae was first time reported. The natural hyperparasitic percentage averaged 35.5% in LaBa River nature protective
area. The hyperparasites attack aecium of A. schisandrae and hinder the rel
ease of aeciospores. This paper reported the symptom of the rust and the
morphological characteristics of the rust pathogen. The hyperparacitism and the
morphological characteristics of the Tuberculina sp. were also reported.

Water stress-induced resistance to wheat stripe rust
SHANG Hong-sheng, LI Yue-ren（College of Plant Protection,Northwest Sci-Tech University of Agriculture and Forestry,Yangling, Shaanxi 712100， China）

Abstract:Reactions to water stress were studied on the stripe rust-tolerant wheat cultivars and the typical susceptible cultivars after infection of the pathogen
Puccinia striiformis West. The results showed that these stripe rust-tolerant cultivars exhibited tolerance to water stress as well. These cultivars expressed the compatible reaction to pathogen infection under normal water supply conditions, whereas turned to the incompatible reaction to pathogen infection under water stress conditions. Water transpiration in these diseased leaves slightly increased at early stage of infection. However, after then the water transpiration rate, water diffusive resistance, relative water content, and water potential of these di-seased leaves gradually turned to the same levels as those of healthy leaves. Additionally, lower osmotic potential and higher turgor potential than those of healthy leaves were also observed in these cultivars, indicating the characteristics of water balance in leaves. In contrast, on the stripe rust susceptible cultivars, the water transpiration rate increased sharply, leaf diffusive resistance, relative water content, water potential, osmotic potential and turgorpotential decreased remarkably in diseased leaves under water stress conditions after infection of the pathogen, indication the characteristics of losing of water balance.

Purification and characterization of an elicitor (GP66) from Magnaporthe grisea
LI Yun-feng， WANG Zhen-zhong*， JIA Xian-lu (College of Natural Resources and Environment, South China Agricultural University， Guangzhou 510642, China）

Abstract: A water soluble elicitor (GP66) was isolated and purified from hyphal cell wall of the strain 97-151a of Magnaporthe grisea race ZC13 through centrif ugation, ultra-filtration and chromatography. SDS-PAGE showed that the elicitor GP66 had only one band of 66 kDa. Sephadex G-100 gel filtration showed that molecular weight of the elicitor was 64 kDa. Anthrone-colorimetric assay and Coomassie blue G-250 staining showed that the carbohydrate and protein contents were in a ratio of 3.84. Bioassay detection indicated that GP66 could increase the levels of the activity of POD and PAL in rice leaves. Digestion with trypsin and boiling at 100℃ for 10 min did not abolish the elicitor activity, but complete loss of activity was observed after periodate treatment. The results suggest that the carbohydrate moiety contains the active site of the elicitor, and the protein moiety may not be necessary for elicitor activity.

Comparison of resistance to Potato virus Y mediated by direct and inverted
repeats of the coat protein gene segments in transgenic tobacco plants
ZHU Jun-hua1, ZHU Chang-xiang2, WEN Fu-jiang1*, SONG Yun-zhi2(1College of Plant Protection, Shandong Agricultural University, Taian 271018, China; 2College of Life Sciences, Shandong Agricultural University, Taian 271018, China)

Abstract: It has been demonstrated that RNA-mediated resistance to virus infection in plants is associa-ted with RNA silencing, in which dsRNA in the transgenic pla
nts may play an important role in trig-gering the silencing process. In this rese
arch, we designed cDNA constructs using direct repeat (DR) and inverted repeat (IR) of the coat protein gene segments of Potato virus Y (PVY)，or introduced these
constructs into tobacco plants via Agrobacterium tumefaciens-mediated transfor
mation system. Resistant assays of the transgenic plants showed that highly resi
stant plants to PVY infection were obtained in both DR- and IR-transgenic plants. However, higher proportion of resistant plants was obtained from the IR-tra
nsgenic plants than that from DR-transgenic plants. Further analysis demonstrated that the resistance was RNA-mediated. These results indicate that using IR constructs of viral gene segments as transgenes may be a feasible strategy to pro
duce virus-resistant plants by genetic engineering.

Comparison of the RNA1 segments between Chinese isolates and Japanese isolates of Rice stripe virus WEI Tai-yun, LIN Han-xin, WU Zu-jian, LIN Qi-ying,
XIE Lian-hui(Institute of Plant Virology, Fujian Agriculture and Forestry University, Fuzhou 350002, China)

Abstract: The complete nucleotide (nts) sequences of RNA1 of two isolates of Rice stripe virus (RSV), isolated from Chuxiong (CX), Yunnan Province, and Hongze (HZ), Jiangsu Province, were determined. RNA1 of both CX and HZ isolates were 8970 nts. Comparison of the nucleotide and amino acid sequences of seven ORFs among these three isolates demonstrated that the closer phylogenetic relationship between HZ and T isolates than that between CX and T isolates. Comparison of the L proteins of Tenuiviruses RSV and Rice grassy stunt virus (RGSV) with those of Bunyaviruses indicated that Tenuiviruses were most closely related to the genus Phlebovirus. The alignment data showed that Tenuiviruses L protein shared with Bunyaviruses the three conserved regions corresponding to the so-called polymerase module. These comparisons also showed the existence of an additional fourth conserved region in the L protein of Tenuiviruses that contains at least two active sites, indicating that this region has an important role in the function of this protein. Further analysis showed that the two active sites were necessary for primer mRNA synthesis with cell-derived capped primers in influenza virus. The result indicated that Tenuiviruses could also have the cell-derived capped primer mechanisms.

Studies on the metabolism of active oxygen species during the interactions of co
wpea and rust pathogen ZENG Yong-san1, WANG Zheng-zhong2 (1Department of Plant Protection, Zhongkai Agrotechnical College, Guangzhou 510225, China; 2College of Natural Resources and Environment, South China Agricul-tural University, Guangzhou 510642, China)

Abstract: Relationships between regulations in the generation rates of active oxygen species (AOS), activities of defensive enzymes, levels of membrane lipid peroxidationand resistance of the cultivars during the interactions of cowpea（Vigna sesquipdalis Wight） and rust pathogen（Uromyces vignae Barcl） were analyzed. The results showed that superoxide dismutase (SOD) activity increased in immune and susceptible cultivars, and the peaks appeared at 12 hours after inoculation(a.i.), but decreased at first and increased at 12 hours a.i. in resistant ones, the peaks appeared at 24 hours （in highly resistant one） and 48 hours a.i.（in moderately resistant one）. At 24 hours a.i., SOD activity in immune and resistant cultivars were higher than that in susceptible ones. Within 12 hours a.i.,the catalase (CAT) activities decreased in all immune and resistant cultivars, but increased in susceptible ones and the first increase peak appeared at 12 hours a.i. The results also showed that superoxide anion (O.-2) generated in all cultivars infected with rust pathogen, and net change of O.-2 generation rates in immune and resistant cultivars were lower than that in susceptible ones at most determination stages. A negative relationship between net change in malondialdehyde (MDA) content and resistance was found, being basically in conformity with the tendency of change of O.-2 generation rate. These results indicated that metabolism of AOS played an important role in the interactions of cowpea and rust pathogen.

Effects of environment factors on conidia germination, appressoria formation and
pathogenicity of the persimmon anthracnose pathogens Colletotrichum gloeosporioides ZHANG Jing-ze， HU Dong-wei(Biotechnology Institute, Zhejiang University, Hangzhou 310029, China)

Abstract: The conidia germination and appressoria formation of Colletotrichum gloeosporioides, the pathogen of persimmon anthracnose, was tested on concave glass slides in different environment. As the concentration of glucose went up, rates of conidia germinating increased but the percentage of appressoria formation decreased, and the length of germ tubesaugmented and the diameter of appressoria was steady; with time prolonging, thepercentage of conidia germinating and appressoria formation all climbed. The conidia could germinate and form appressoria over wide pH range from 2.0 to 9.0; the optimal pH for conidia germination and appressoria formation was between pH 5.0 and pH 6.0. The pathogenicity test under different pH condition illuminated that the disease occurred on twigs at 23℃ within pH 4.0-8.0, also appeared at 17℃ and pH 6.0 without spore masses on lesions of twigs surface, however, was absent at 17℃ and pH 5.0 as well as at 15℃ and pH 5.0 to pH 6.0. The optimal temperature for the mycelium growth was about 25℃, and higher temperature inhibited its growth. The scanning electron microscopy examination showed that the length of germ tube, growing longitudinally along the ridge and transversely cross the ridges and grooves, varied greatly, and the appressoria formation occurred at the bottom of groove or near.

Biological control of Capsicum bacterial wilt by compound bacterial mixture AR99
GE Hong-lian2， GUO Jian-hua1， QI Hong-ying3， GUO Ya-hui4， HUANG Yan-xia1
(1 Department of Plant Pathology， Nanjing Agricultural University, Nanjing 210095, China; 2 Department of Biology, Zhoukou Normal University, Zhoukou 466001, China; 3 Huaian Modern Horticulture Technology Centre, Jiangsu Province, Huaian 223003, China; 4 Food Department, Handan Agricultural College, Hebei Province, Handan 057150, China)

Abstract: Five bacterial strains with complementary biocontrol activities were selected and mixed as one biocontrol agent AR99 for the control of Capsicum bacterial wilt.In the greenhouse test,the biocontrol efficiencies of the mixture and individual bacterium suspension R1, A9, J3, R9 and A6 strains were 91.1%, 88.9%, 80.5%, 80.5%, 66.7% and 57.0%, respectively, with that of the mixture AR99 being the highest. Field plot tests for the biocontrol of Capsicum bacterial wilt were done by composting method and root-drenching method in Huaian,Jiangsu in 2000 and 2001. The average disease control effieciencies of AR99 were 94.0% and 77.0%, with the average yield increasing efficiencies of 367.0% and 57.8%, respectively, by the composting method and root-drenching method 70 days after treatment.

Antifungal substances of Bacillus subtilis strain G3 and their properties
GU Zhen-rong， WU Wei， GAO Xin-hua， MA Cheng-zhu (Plant Protection Research Institute, Shanghai Academy of Agricultural Sciences,Shanghai 201106, China)

Abstract: Bacillus subtilis strain G3, a chitinase-produing biocontrol agent, showed a strong activity to inhibit the growth of pathogenic fungi Botrytis cinerea
and Cladosporium fulvum. The antifungal substances were prepared from the solid culture filtrate. They were iturin and surfactin extracted from acid precipi
tate and the chitinase obtained in crude proteins by ammonium sulfate precipitat
ion. Iturin showed a relatively weak activity to inhibit spore germination of
C. fulvum, but a strong activity to break the germ-tube and new hyphae. Surfa
ctin and chitinase were inhibitory to spore germination and suppressive to germ
-tube elongation. In the antibiosis detection with B. cinerea on plate,itur
in inhibited mycelial growth and caused the vesicle structures in the tips of hyp
hae,then the cell wall broken and the protoplasm leaked out. Chitinase also inhi
bited mycelial growth and caused the hyphae abnormal. Surfactin showed no antifu
ngal activity to B. cinerea.

Biological control of Pepper Phytophthora blight by endophytic TB2 (Bacillus sp.) QIU Si-xin1， HE Hong2， RUAN Hong-chun1， GUAN Xiong1， HU Fang-ping1(1 College of Plant Protection, Fujian Agriculture and Forestry University, Key Laboratory of Pesticide, FAFU, MOE, Fuzhou 350002, China; 2Agricultural College of Zhanjiang Ocean University, Zhanjiang 524088, China)

Abstract: Endophytic Bacillus sp. strain TB2 isolated from stem of tobacco was an efficient biological control agent to control Pepper Phytophthora blight. Seed c
oating and root drenching with TB2 cultures gave 70.0% and 88.1% control efficacies respectively, on capsicum seedlings 20 d after inoculation of the pathogen P. capsici, while spraying on fruits gave 65.2% control efficacy to the fruit Phytophthora blight 14 d after inoculating the pathogen. The research on biological control mechanisms showed that the strain TB2 could inhibit the mycelial growth and reduce the sporangia and zoospores production of P. capsici. The treatment with strain TB2 considerably increased the SOD and POD activities in the capsicum fruits. Inoculation with P. capsici on fruit also significantly increased the MDA content and SOD, POD and CAT activities. However, the MDA content and SOD, POD and CAT activity of the capsicum fruits co-inoculated with the strain TB2 and P. capsici at the same time did not remarkably change comparing with fruits inoculating with sterile water.

The effect of soil habitat factors on survival of microsclerotia of Verticillium dahliae of cotton YANG Jia-rong, SHANG Hong-sheng， GAO Li-qiang (The Key Laboratory of Plant Protection Resources and Pests Management of Chinese Ministry of Education, College of Plant Protection, Northwest Sci-Tech University of Agriculture and Forestry, Yangling 712100, China)

Effects of Turnip mosaic virus infection on the functions of PSII in host plant leaves
FU Dong-ya1，2, HONG Jian2, CHEN Ji-shuang1, JIANG De-an1 (1 College of Life Science, Zhejiang University, Hangzhou 310029, China；

Effects of SA on resistance of cucumber seedlings to downy mildew
SUN Yan1, YANG Shu-ying2 (1College of Horticulture, Northwest Sci-Tech University of Agriculture and Forestry, Yangling, Shaanxi 712100, China； 2College of Life Sciences， Northwest Sci-Tech University of Agriculture and Forestry, Yangling, Shaanxi 712100, China)

CMV subgroup identification of sweet pepper in parts of China
TIAN Zhao-feng1, QIU Ji-yan1, LIU Wei-cheng1, LI Yong-dan2（1Institute of Plant & Environment Protection, Beijing Academy of Agriculture & Forestry Sciences， Beijing 100089, China; 2Department of Plant Pathology, China Agricultural University, Beijing 100094, China）