Rice blast disease is one of the most destructive diseases in rice plant. The short-live of the blast-resistance in rice plant is one of the main constraints in rice production. The easy breakdown of blast resistance for current rice cultivars may be attributed to inadequate techniques and methods in analyzing the pathogen population structure and their evolution, and what we still have not entirely known in the genetic basis of blast resistance in resistant cultivars. In this paper, we review the progress on the application of molecular markers to the analysis of blast pathogen population structure and genetics of blast resistance and on the development of molecular marker techniques in tagging the blast resistance genes. The strategies for sustainable management of blast disease through molecular genetic analysis are discussed. Several problems toward the practical applications in these studies are mentioned at the end of this paper.

Virulence on the single isolate and the two-mixed isolates of 18 Cryphonectria parasitica isolates were evaluated. The results suggested that virulence of the single isolates were significantly different from each other. Virulence association and dissociation were observed. Within the same population, 64.4% combinations of the mixed isolates were virulence associating, while between populations, 88% combinations of the mixed isolates were virulence dissociating. The degree of virulence associating of the mixed isolates from the same population was higher than that from different populations, but the degree of virulence dissociating of the mixed isolates was higher than that from the same population. In most cases, virulence association and dissociation of mixed isolates were observed repeatedly.

Twelve fungal diseases and their pathogens on Schefflera actinophylla (Endl.) Harms.were investigated in Guangzhou region. Of which, Leptosphaeria schefflerae P. G. Xi, P. K. Chi et Z. D. Jiang, Cercospora schefflericola P. G. Xi, P. K. Chi et Z. D. Jiang and Phomopsis schefflerae P. G. Xi, P. K. Chi et Z. D. Jiang are new species, Phoma scheffleri (Chen) P. G. Xi et P. K. Chi is new combination. Latin names, descriptions and illustrations of the new species were given. Stocks of the fungi were deposited at the Fungal Collection of South China Agricultural University.

Random amplified polymorphic DNA (RAPD) was used to analyze the relationship of Fusarium fungi collected from ear rot and stalk rot. High degree of homology was found between the isolates of Fusarium moniliforme from ear rot and the ones from stalk rot. No correlation was found between genetic variation of F. moniliforme and disease-occurring areas, environmental factors and plant organs, suggesting that F. moniliforme may be the common pathogen of ear rot and stalk rot. On the contrary, the isolates of Fusarium graminearum from ear and stalk were genetically varied with disease-occurring areas, environmental factors and plant organs. The ear rot and stalk rot can be caused by a single strain of F. graminearum as well as by mixed strains of the fungus.

Two typical Phytophthora strains which cause gingko wilt were chosen for taxonomic and identification experiment. According to morphological characteristics, physiological properties, host range and soluble protein electrophoresis, the pathogen was identified as P. nicotianae Breda de Hann. The pathogen has wide host range and its growth temperature is higher than 35℃. It is heterothallic and can not produce oospores in natural gingko growing region in the north of Guangxi. But it can produce a large number of chlamydospores in adverse environments such as low temperature. This cha-racteristics has an important significance to develop an effective method for controlling the disease.

To study phylogenetic relationships among 19 isolates of 17 species of Phomopsis on fruit trees in Guangdong Province, 15 suitable primers selected from 320 random primers screened were used for RAPD analysis. According to the phylogenetic tree constructed by UPGMA of Nei's similarity coefficients among the tested isolates based on the RAPD data, 2 isolates of Phomopsis mangiferae Ahmad and 2 isolates of P. macadami Z.D.Jiang et P.K.Chi collected from different areas could be clustered into one group with similarity of 63.6% and 58.9%, respectively. However, the similarity coefficients for different species were less than 54%, which indicated there were various differences among interspecies and intraspecies. No correlation was found between the groups and hosts of the isolates and different species could not be clustered into one group from the same host, even from the same part of a host. The RAPD data also supported the results from morphological identification, in which 8 isolates from wampee stem and citrus branch, Chinese bayberry leaf and branch, sand pear leaf and fruit and longan leaf could be identified to be independent of each other, but did not support the suggestion that P. mangiferae can be combined into P. cytosporella Penz. et Sacc. It is concluded from this research that RAPD technique can be used to analyze phylogenetic relationship of Phomopsis.

Deoxynivalenol (DON) is one of the trichothecenes produced by Fusarium graminearum (teleomorph:Gibberella zeae), an important pathogen causing wheat head scab (WHS). The role of DON in WHS pathogenesis was investigated using GZ3639, a DON producing wild type strain, and GZT40, a trichothecene non-producing strain due to disruption of a trichothecene biosynthesis gene Tri5. In inoculation experiments, GZ3639 caused typical WHS symptoms, whereby the pathogen colonized the inoculated floret and spread to neighboring spikelets, and GZT40 only colonized the inoculated floret, producing atypical symptoms. When the inoculum was added with DON (400 μg·mL^-1), GZT40 could successfully earlier by colonize the inoculated floret earlier by 2 days (on a susceptible cultivar) to 4 days (on a resistant cultivar) in comparison with DON-free treatment. Moreover, with DON treatment, GZT40 was able to spread 1-3 spikelets upward or downward from the point of inoculation on both susceptible and resistant cultivars. The mean percentage of diseased spikelets was 2.8% when the plants were inoculated with GZT40, while it was 12.5% when DON was added. Similar results were obtained for GZ3639. When the plants were treated with DON, the time needed for successful colonization of a floret was shortened by 1 day (on a susceptible cultivar) to 2 days (on a resistant cultivar), and the percentage of diseased spikelets was 100% in comparison with 78% when inoculated with GZ3639 alone. Therefore, it is concluded that trichothecenes play a key role in symptom development as well as in pathogen spread within host tissues. If a pathogen strain has lost its ability to produce trichothecenes, it is still able to colonize, but is unable to spread. Spread within host tissues is restored to some extent with the addition of DON.

The study on biology of conidia of Ustilaginoidea virens (Cke.) Tak. indicated that nutrient in media had an important effect on germination of conidia. Pure water was not good for germination. PSA was the optimum media for germination. Glucose inhibited germination strongly. Potato juice could counteract the inhibition of glucose and stimulate germination. The germination rate was higher in solid agar media than that in liquid media. The suitable temperature for germination was 22-31℃, with the optimum of 28℃. The pH value had a sharp effect on germination, and pH 6-7 was optimum for germination. The germination rate of conidia began to decrease after growing 10 days by shaking culture. Water had a significant effect on viability of the conidia. In the case that conidia were kept in water for 8 days, germination rate of the conidia did not decrease, and in the case that they were kept in 100% RH for 8 days, the germination rate declined slightly, but in the case that they were kept in 25% RH for 5 hours, the germination rate dropped sharply. Based on these cha-racteristics, hypothesis about behavior of the conidia in the field was proposed.

Organic thiocyanic chemicals, methylene dithiocyanate (TH-88, chemical formula:SCN-(CH₂)₂-SCN) can control rice "Bakanane" disease caused by Fusarium moniliforme, both carbendazim -resistant and -sensitive strains. The EC 50 of TH-88 varies from 0.393 3 to 1.641 2 μg/ml. Biochemically, this chemical increases mycelium seepage with no effect on mycelium and conidium at the concentration of 1 μg/ml, but decreasing the respiration of mycelium and conidium of F. moniliforme, especially during the period of conidium germination with the decrease of 64.15% compared with CK 5 minutes after treatment at the concentration of 2 μg/ml. Methylene dithiocyanate doesn't inhibit the activity of NADH cytochrome C reductase, while it decreases 54.32% of NADH cytochrome terminal oxidase activity at the concentration of 2 μg/ml. Respiration control rate and the rate of P/O are 27.67% and 9.3% lower than CK, respectively, when the mitochondria of beer yeast (Saccharomyces cerevisiae) was treated at the concentration of 1 μg/ml. More

The development of wheat leaf rust (Puccinia recondita f.sp.tritici) in the susceptible cultivar 5389 and its ultrastructural features were studied by using fluorescent microscopy, differential interference contrast microscopy, and electron microscopy. Several development stages were investigated in this research including germination of urediospores, formation of a series of structures such as appressoria, substomatal vesicles, primary and secondary infection hyphae, haustorial mother cells, and haustoria, and finally the production of uredinial beds, uredinia, and urediospores. The intercellular hyphae of P. recondita f.sp.tritici grew and ramified along host cell walls in intercellular space. A haustorial mother cell was induced while the hypha came into contact with the host cell, then a penetration peg was formed. The peg penetrated the wall, extended and formed a haustorium inside the cell. Both hypha and haustorial mother cell were dikaryotic, while the typical mature haustorium was mono-karyotic. The results from conventional staining showed that the walls of intercellular hyphae and haustorial mother cells had multilayers, so did their septa.

A TAC library of rice blast fungus, Magnaporthe grisea, was constructed in a vector pYLTAC7. The library contains 16 128 individual clones and approximately 74% of the clones harbor foreign DNA inserts with an average size of 59 kb. The content of the library corresponds to 18 equivalents of the genome. To confirm the representative of the library, three single-copy DNA markers were used as probes to hybridize with the library clones on the high-density membranes. Sixteen, 17 and 16 positive clones were obtained respectively from the library screening, and the numbers of positive clones matching corresponding probes are consistent with the estimated coverage of the library. Further analysis of the restriction enzyme maps of 8 positive clones screened with a single copy marker, MH18S1, revealed that the contigs covered a 153 kb region without chimerism or deletion. It is suggested that the TAC library is suitable for genome analysis of M. grisea.

The resistant mutant of X. citri (XcR) to amicarthiazol was obtained by dual treatments with amicarthiazol ta-ming and ultraviolet irradiation with a frequency lower than 10^-6. XcR possessed the similar growth velocity as the sensitive isolate (XcS), and had positive cross resistance to carboxin and bismerthiazol fungicides, but not to diisothiocyanatomethane. Investigation on physiological characters showed that XcR could secrete extracellular enzymes, such as amylase, pectase, cellulosase, proteinase and lipase. The bioactivities of these enzymes were usually higher than that of XcS, especially for amylase. The activity of succinate dehydrogenase of XcR was obviously reduced and not sensitive to the inhibition of amicarthiazol. Moreover, XcR could induce the hypersensitive reaction of tobacco leaves but lost the pathogenicity to ci-trus leaves. The characters of XcR indicated that the resistance of X. citri to amicarthiazol occurred with low frequency and accompanied with reduced fitness of XcR in field. The activity changes of succinate dehydrogenase could be used to tag the occurrence of resistance of X. citri to amicarthiazol fungicide.

Crude toxins were extracted from culture filtrate of Exserohilum turcicum race 2 in modified Fries medium after freeze-dried at -40℃ and precipitated with methanol. Eight fractions (peak 3-10) were isolated from the crude toxins by means of HPLC analysis with C₁₈ column. Peak 7 and 10 had distinct toxicity to the corn leaves and peak 7 had special toxicity to the corn with Ht1 resistant gene. Both the toxic fractions were scanned by infrared spectrum. It was shown that the two toxic fractions (peak 7 and 10) had analogous spectrum,similar shape of peaks,but a little difference in the wavenumbers.

Induction of hypersensitive cell death, changes of phenylalanine ammonia-lyase (PAL) activity and activation of PR5 (osmotin) in tobacco by 90 kD extracellular elicitor protein, a hypersensitive response (HR) elicitor, isolated from Phytophthora boehmeriae were studied. At 24 hours after infiltration of the elicitor into tobacco (cv. W38) leaves at dosage of 10 nmol/L, a bright blue autofluorescence became visible under UV light in a ring of cells surrounding the necrosis tissue, which indicated compounds derived from the phenylpropanoid pathway were accumulated during HR. By Evans blue and trypan blue staining, it was observed that cell death occurred only in infiltrated tissue and was completed within 20 hours after treatment. Comparing with water-treated leaves, the activity of PAL, a key enzyme in plant defense response was increased in elicitor-treated leaves and in the immediate neighbor leaves. The elevated level of PAL was positively correlated with the enhancement in disease resistance in tobacco induced by elicitor that we reported previously. Moreover, the elicitor could rapidly induced transcription of PR5 in elicitor-treated tobacco leaves. Results showed that 90 kD elicitor could induce hypersensitive cell death, phenylpropanoid metabolite pathway and transcription of PR5 gene. Results also indicated that there are some systemic molecules that can transmit rapidly from infiltrated leaves to the non-elicitor-treated neighbor leaves.

The strain of B-9987 (Bacillus sp.) was obtained by screening 317 bacteria strains isolated from Bohai Sea mud and water during the period 1998-1999. The secreted substances of B-9987 were strongly antibiotic to some plant pathogenic fungi including Alternaria solani, Verticillium dahliae, Cladosporium fulrum, Fusarium oxysporum, Bremia lactucae, Rhizoctonia solani. The substances were studied by ethyl ether extraction, TLC detection, color reactions, and ultraviolet scan. The effect of B-9987 on these fungi was investigated. The results were as follows:Fungi cells of hypha and spore tubes dilated to deformed spherical structure, then the cell walls were broken and the protoplasm leaked out after the treatment with the antibiotic substances. The inhibited hypha cells of F. oxysporum and B. lactucae became obviously shortened. It was supposed that the antibiotic substances were phenolic compounds.

A strain B34 against Thanatephorus cucumeris was screened from rice plant. On the PDA plate a wide inhibition zone appeared. After using fermentation production treatment, the serious malformation effect was observed with electric microscope,the inhibition rate was 71.5%,and mycelial germination reduced rate of sclerotial was 69.0%. It showed that the control effect in vitro and in field reached 80% and 48.74% respectively,the result was higher than those of the water and Jinggangmycin treatments. From chemical components of cell wall, physiological and biochemical character of B34, the result showed it was Pseudomonas aureofaciens.

Some bacteria in the genus Bacillus, which are both resistant to adverse environment and usually against bacterialand fungal pathogens, are among the dominant microorganisms in the soil and plant microecologial systems, and a lot of na-tural isolates with great potency have been screened and applied widely in biocontrol of plant diseases. The biocontrol mecha-nisms of Bacillus include antagonism, competition and induced plant systenmic resistance. Antagonism of Bacillus mainlyowed to the production of antimicrobial proteins, e. g. bacteriocin, chitinase, glucanase, etc., and antibiotics as well asantifungal volatiles synthesized by secondary metabolism pathways. Improvement of the expression level of native antimicro-bial genes and coexpression of foreign insecticidal or antimicrobial genes in one cell were of the most efficient approaches togeneically modify biocontrol Bacillus with stronger activities against plant diseases or against both plant diseases and insectpests. With the rapid progress of genomics and proteomics programs, research and development on antimicrobial molecularmechanism and genetic engineering of Bacillus will be greatly acceleraed in the future.

Arabidopsis thaliana is a model plant to study the interplays between plants and pathogens. Plants exhibiting re-sistance or causing disease follow the hypothesis of "gene for gene", in which only when the products from the avirulencegene of pathogen and the resistance gene of host recognize each other, can plants arise a series of defense responses andshow resistance, otherwise plants develop diseases. Small molecules such as salicylic acid, jasmonic acid, ethylene playimportant roles in the defense responses, and the signal transduction pathways can be divided according to their effects in aparticular system of the pathogen and plant interactions. Their roles in systemic acquired resistance and induced systemic re-sistance will be discussed in detail.

Soybean frogeye leaf spot produced by Cercospora sojina Hara is a worldwide disease, which had caused heavylosses in soybean production in China. In order to improve the disease control and resistance breeding, the biological characteristics, infection cycle, incubation period and forecast of this disease were summarized, at the same time, the differen-tiation of the physiological races, the inheritance of resistance to this disease and the application of toxins were also dis-cussed in this paper.

Eight inbred lines were selected from more than 20 dominant maize cultivars and 18 major inbred lines asdifferential hosts to identify the physiological differentiation of Curvularia lunata, they were Shen135, 78599-1, Mo17,477, C8605, E28, 7922 and Huangzao 4. The identification of physiological differentiation during seedling period in green-house was consistent with that in adult period, so identification in seedling period was selected as a most effective methodsince it was easily operative and easy to control environmental factors. Twenty isolates of Curvularia lunata were identifiedin 8 differential hosts as 6 pathogenic differential types in which type A with higher pathogenicity was distributed widely inheavily-occurring areas, however, type D with weak pathogenicity was distributed in less-occurring area, therefore type Acould be considered as the dominant pathogenic group. Other major factors such as humidity, temperature and nutrition, tosome extent, influencing identification of physiological differentiation were also investigated, and which produced some re-markable effect on identification of physiological differentiation of pathogen by the mentioned factors. The result mentionedabove provided a sound basis for breeding and identification of resistant cultivars, reasonable distribution of resistant culti-vars and monitoring of pathogen differentiation.

The mating type, chemical response and physiological race of Phytophthora infestans collected from YunnanProvince were determined. In total, 134 isolates of P. infestans were used in this study, among which 124 isolates collectedfrom potato planted in autumn of 2000 in Luliang, Jianshui, Nanjian areas and 10 isolates collected from potato planted inspring of 1999-2000 in Kunming and Qujing areas. Among 18 isolates collected from Luliang County, 3 isolates belongedto A₂ mating type, while 15 isolates belonged to A₁ mating type. Only A₁ mating type was detected in 106 isolates collectedfrom potato in autumn of 2000 in Jianshui, Nanjian and in 10 isolates collected from 1999 to 2000 in Kunming and Qujingareas. The response of 83 isolates to metalaxyl showed that 71.1% were sensitive, 16.9% were intermediate resistant, and 12.0% were resistant. The percentage of metalaxy sensitive isolates is higher in Luliang, Kunming and Qujing than in Nan-jian and Jianshui. All of 83 isolates detected were sensitive to dimethomorph. Results also showed that the physiologicalraces in Yunnan Province consisted of races 3.4, 0, 3 and 4, representing 48.0%, 32.5%, 15.6% and 3.9% of thepopulation, respectively. However, only 0 and 3.4 races were detected in Nanjian, while races 0, 3, 3.4 and 4 races weredetected in Kunming and races 0, 3 and 3.4 were detected in Luliang. This indicated tha population of P. infestans inKunming and Luliang areas is more diversified in race composition than tha in Nanjian area.

Vegetative compatibility was determined in 92 isolates of Botrytis cinerea Pers. collected from Jinzhong,Yuncheng, Linfen, Changzhi and Datong in Shanxi Province by confront culture and observed under microscope. The resultsshowed that 92 isolates could be classilied into 7 different anastomosis groups (AG1, AG2, AG3, AG4, AG5, AG6, AG7)according to the vegetative compatibility and incompatibility. Four of the anastomosis types were distributed in Jinzhong(AG1, AG2, AG3, AG4), 3 types in Yuncheng (AG1, AG2, AG5), 4 types in Linfen (AG1, AG2, AG3, AG6), 4types in Changzhi (AG1, AG2, AG5,AG7) and 3 types in Datong (AG2, AG, AG6). AG2 was a prevailing group and was widely distributed in Shanxi Province.

In greenhouse the pathotype of 41 strains of V.dahliae were studied by inoculating the seedlings of 4 cotton dif-ferentiators, Ejing 1 (S), Zhongmiansuo 12(T),Wen-5(R) and Tangmian 2(R). Forty-one strains were clustered into 2groups:defoliating and nondefoliating strains. System cluster analysis based on 169 polymorphic bands from results ampli-fied with 8 effective primers was used to generate a dendrogram. Forty-one strains of V.dahliae tested were clustered into2 groups:10 nondefoliating strains and 1 intermediate strain; 30 defoliating strains. According to dendrogram, discoveredcertain relevant relationship in the strains of different geographical source. Amplified fragment length polymorphism (AFLP)was performed on 41 strains of V.dahliae of cotton in search of DNA probes specilic for nondefoliating strains. Two pairsof primers (screened from 25 pairs) were used for AFLP, E64 (GACTGCGTACCAATTCGAC), M53 (GATGAGTCCTGAG-TAACCG) and E49(GACTGCGTACCAATTCAG), M65 (GATGAGTCCTGAGTAAGAG), and yielded bands of 433 basepairs(bp) and 110 bp which were amplified only from nondefoliating strains and named EM443 and EM₁₁₀, respectively.

A cDNA clone containing cylindrical inclusion (CI) protein gene from Luotian isolate of Wheat yellow mosaic virus (WYMV) in Hubei Province was obtained by RT-PCR, and the nucleotide sequence of the CI gene was determined.The CI gene of this isolate comprised 1977 nucleotides and encoded 659 amino acids containing consensus nucleotidebinding motif. When the CI gene sequence of the isolate was compared with those of previously reported WYMV isolatesfrom Huangchuan in Henan, Ya' an in Sichuan, Yangzhou in Jiangsu and Japan, the nucleotide and amino acid sequencesimilarities ranged between 95.0% and 97.5%, and between 93.2% and 97.1%, respectively. The function of CI proteinwas also discussed in this paper.

A simple and rapid method for detecting Cucumber mosaic virus (CMV) was developed. CMV 2b gene fragments(300 bp) of 9 different isolates were successfully amoplified by one step RT-PCR from virus samples prepared by grinding inan extraction buffer. RT-PCR products of 9 isolates were cloned into pMD18-T vector and 7 of them were sequenced. Thecomparison of these sequences revealed that 2b gene fragments of different CMV isolates were highly conservative, and theidentity of nucleotide and amino acid sequences were over 93% and 90%, respectively. It showed that all the Chinese iso-lates used belong to the subgroup Ⅰ of CMV.

A randomly amplified polymorphic DNA (RAPD) marker, OPO12₁₀₀₀, which is closely linked to the avirulencegene AVR-Pik^m conferring avirulence in Magnaporthe grisea on rice cultivar Tsuyuake, was cloned and sequenced. Se-quence analysis showed that OPO12₁₀₀₀ was 946 bp in length and did not contain any sequence homologous with the previ-ously reported Mg-SINE, Fosburry, Magyy, Grasshopper, Pot2 and Pot3. According to the sequence, a pair of 24 merprimers was designed and used in PCR with templates for an avirulent parental strain S1522, a virulent parental strainS159 and 108 progenies from the cross S1522×S159. The PCR amplification produced a single DNA band of ahaut 1000 bpwhich was as the same as OPO12₁₀₀₀ in the avirulen strains while no amplification was detected in the virulent strains exceptfor 5 virulent recombinants. The results indicated that the RAPD marker, OPO12₁₀₀₀, was converted into a SCAR markersuccessfully and it could be used to initiate chromosome walking for cloning of the target gene.

Treatments of spore suspension of M. grisea with microtubule inhibitor oryzalin and two microfilament inhibitorscytochalasin A(CA) and cytochalasin D(CD) indicated that 5-50 μmol/L oryzalin, 0.5-1.0μg/L CA and 1-20μg/mL CD treatment had no effects on spore germination and appresorium formation. When rice leaf sheath was treated withthese inhibitors, an enhanced fungal development was observed in host cells compared with that in untreated rice leaf sheathafter M. grisea inoculation. The enhancement of fungal development was associated with the delay and suppression of hostdefense responses such as cytoplasm aggregation, phenolic compounds accumulation and hypersensitive cell death. The re-sults indicated that rice resistance to M. grisea invasion was closely related to microtubules and microfilaments in rice cells.

Twenty two transgenic rice lines with basic chitinase gene and β-1, 3-glucanase gen were screened for blast re-sistance by. conducting seedling screening, resistant spectrum test, and field resistance test in the blast are nursery. Aseries of transgenic rice plants with improved resistance were obtained. Among them, seven transgenic lines with high resis-tance were selected from transgenic rice line F4-9, and these highly resistant lines also expressed stable resistance in the R7generations based on the tests of resistant spectrum to blast fungus in greenhouse and the neck resistance in blast nursery.The transgenic rice lines with high resistance and quality were obtained successfully in this experiment. The data showedthat genetic engineering was a powerful approach to improve the resistance of rice variety to blast and alleviate the negativecorrelation between blast resistance and quality in southern rice area.

High humidity was a primary determinant of the spore germination of Botrytis cinerea, the causal agent of tomatogray mould. At least 80% of relative humidity(RH) was needed for the spore germination, and the highest germination ratiocould be obtained when the spores were placed in water drops. At optimal temperature, spores and hyphae could infect thetomato plant to develop softening and rot lesion when RH reached over 85% and 80% respectively. In one day, sustainingtime of high humidity directly influenced the development of tomato gray mould, the pathogen could infect tomato successful-ly when sustained time of high humidity(RH>85%) was longer than 8 hrs.

Two strains of the endophytic Bacillus subtilis BS-2 and BS-1 isolated from foliage and stem of capsicum respec-tively were used as biological control agents to control the anthracnose of capsicum. The results showed that the anthracnoseof the capsicum seedlings and fruits caused by Colletotrichum gloeosporioides was controlled effectively by these two strains,with the control efficacy of 81.5%-93.3% and 66.1%-79.2% for the seedling anthracnose, and 80.0%-100% and60.0%-100% for the fruits anthracnose by BS-2 and BS-1 respectively. It also indicated that the growth of the capsicumseedlings was promoted significantly by the two strains. The effects of the disease control and growth promotion of BS-2 werebetter than those of the BS-1. The biological control mechanism of the two strains was discussed in this paper.

Nine hundred and seventy-sir bacterial isolates were obtained in this study, among which a bacterial antagonisticisolate, Bacillus subtilis S9 from sugarcane rhizosphere showed cell-lytic det on the plant pathogens, Rhizoctonia solani,Pythium ultimum and Fusarium oxysporum f. sp. niveum after 4-day-confronting incubation on PDA plates. However, S9could not cause obvious inhibitory zones on PDA plates during this incubation. Lytic spots of hyphae of R.solani caused byS9 were clearly presented under scanning electronic microscope. The cell-lytic process of S9 is as follow:Bacterial cells ofS9 absorb on hypae of R.solani firstly, and grow and reproduce as the fungal hrphae grow, and then secrete some cell-lyticsubstances to decompose the hyphae. However, this study revealed that S9 hardly interfered with the growth of the fungalantagonists, such as Trichoderma viride, Chaetomium cupreum and Chaetomium globosum. Pot experiments proved that S9could effectively control root disease of tomato caused by R.solani. It suggested tha S9 mixed with above fungal antagonistscould potentially synergistically control plant diseases caused by pathogenic fungi.