The present paper deals with the further studies on one of the isolates of Turnip mosaic virus(TuMV_B).The Purified virus from infected leaves of Brassica juncea showed the following charateristics;A_260/280=1.21, a, ingle symmetrical absorbent peak appeared an analytical ltracentrifugation, s₂₀=145s, polyacr-ylamide gel electrophoresis in the presence of SDS showed that the subunit of coat protein is of a single component with a molecular weight of about 27, 000 Dalton.when the stored TuMV_B had been stored for two months, the coat pro-tein dissciated into two components, with molecular weight 25, 000 and 27, 000 respectivly.The molecular weight of TuMV_B-RNA was estimatedfrom its mobi-lity during electrophoresis to be about 3.2×10⁶ Dalton.Ultrasections of the infected leaves showed the appearance of a number of inclusion bodies inclu-ding pinwheels, rings and dense bands.Antiserum prepared from purified TuM-V_B resulted in a titre of 1/1024.During the Chinese cabbage growing season in 1986, samples of Chinese cabbage plants were collected from fields and detected with ELISA.It was shown that 75.4% of the samples tested containing TuMV_B.Now a faculty of Tianjin Academy of Agric.Science.

The preparations were separated and concentrated with differential centrifugation from vascular tissue sap which had been pumpted from twig or root segments of proliferation diseased and healthy persimmon.They were obseved by means of negative staining and ultrathin section with electron microscopy.Nu merous pleomorphic procaryotic cells were found exclusively in the preparations made from diseased plants.They are of varying sizes, usually 580-1600 nm in length and 510-1060 nm in width.The cell wall looks ripply externally, about 25 nm in thickness.No flagella but several prosthecae occur on the surface of the cells.The pleomorphic procaryote in question with all those cytological characteristics is distinct obviously from ordinary bacteria and it was identified as a sort of fastidious bacteria cteria.There is no microbe whatsoever to be found within the samples made from PPD-free pesimmon.This result is consistent with that of formal researches which elusidated the symptoms of PPD could be depressed by treatment with enicillin.Therefore, the fastidious bacterium seems to be the pathogen of PPD.

From 1986 to 1987, a same species of Aphelenchoides was isolated from the buds and leaflets of stunted strawberry plants (Fragaria ananassa) collected from individual fields in Nanjing and Jurong, Jiangsu province.On the ground of its conformity with the original descripsion of Aphelenchoides besseyi by Christie (1942) and its remarkble resemblence to Aphelenchoides besseyi isolatedfrom diseased rice seeds from Jurong, it was iden tified as Aphelenchoides besseyi Christie, 1942.
Artificial inoculation proved that A.besseyi from both strawberry and rice in Jiangsu can induce typical "dwarf" on strawberry (mainly severely stunted plants with crinkled leaflets) and "white tip" on rice.This further confirm-s that the concerned dwarf disease of strawberry in Jiangsu is the "summer dwarf" caused by Aphelenchoides besseyi.

Relation between papillae formation induced in epidermal cells of host and infection by Erysiphe graminis tritici was studied by using the leaves of the wheat lines which have single genes for resistance to the pathogen of powdery mildew in wheat.The percentage of conidia that induced papillae in the total test conidia were 58.8% on the resistant wheat lines, slightly less than 63.6% on the susceptible ones.This suggests that the frequency of papillae formation is not associated with degree of host resistance to powdery mildew.However, the papilla formed in the resistant and susceptible wheat lines had different capacity for stopping the development of the pathogen.In the leaves of the resistant lines, 88% of the conidia that induced papilla did not develop further after the stage of appressoria, only 12% of them could break through papilla and produce hau-storia.In contrast with this, for the susceptible lines 32% of such conidia did not develop after appressoria, but 68% of them could pass through papilla to form haustoria and infect host successfully.The present study shows that whet-her or not the papillae can obstruct the penetration of the pathogen might be related of time in which papillae appeared in host cells.

This paper reported symptoms of discolored rice grains, species and their pathogenicity on rice caused by the Curvularia.The symptoms varied with the species of Curvularia, varieties of rice and methods of incoulation.Five symptoms, the entirely dark brown, semi-darkbrown, dark brown lesions, dark brown spots and discoloration were usually observed on rice grains, and the light to deep black symptoms on the husted rice.The nine of Curvularia were isolated on discolored rice grains from different regions of China, which were C.lunata, C.genicu-ata, C.affinis, C.inaequalis, C.intermedia, C.clavata, C.pallescense, C.eragrostidis and C.fallax, of which six species (C.inaequalis, C.intermedia, C.clavata, C.pall-escens, C.eragrostidis and C.fallax) were first reported in China.The results of the artificial inoculation of the species on rice from booting stage to flowering showed all the species were virulent and produced a great number of discolor-ed rice grains.

The stinking smut of millet (Tilletia setariae Ling), which infects and completes its lifecycle in the same year, causes a localized and nonsystemic flower symptoms.Following inoculation of the florets with stinking smut spores, the ovary is invaded and the disease develops.
The factors influencing infection are atmospheric humidity, daylightlength, wind direction and maturation period of the host varieties.Higher atmospheric humidity, longer daylightlength with seasonal wind and late maturing varieties favor diseases occurrence.The dormancy of teliospores was broken by any of the following treatments:dimethylsulfoxide (DMSO), ultraviolet radiation and overwintering in the soil.Teliospores treated with ultraviolet rediation germinate at 15 to 30℃, (optimum 25℃).The treated teliospores germinate at pH 4-7(optimum pH 6).Both carbon and nitrogen soureces do not appear to stimulate spore germination.On artificial culture medium the smut grows an optimum of 20℃ and pH 7.O.Potato-dextrose agar is the best culture medium so far tested.Raffinose, gluco-se, soluble starch and DL-serine are the best carbon and nitrogen sources for the smut.
The teliospores belong to the type "T"(Tuberculiform), as observed by scan-ning electron microscopy.The highest number of sporidia is about one hundred, and they resemble a "wool brush".Teliospores can also also be produced on artificial cultural medium.

A purification procedure of barley yellow mosaic virus (BaYMV) was improved:The infected barley leaves were homogenized with high molarity (0.5M) potassium phosphate buffer pH7.0 containing 0.1% ME and 0.01M EDTA.After clarification with 1/4 V carbon tetrachloride, the virus was concentrated by precipitation with 6% PEG and 3% NaCl added 1% Triton x-100, and resuspended with the same buffer containing 0.5M urea, 0.1% ME and 0.01M EDTA, followed by ultracentrifugation with a 20% suctose cushion added 0.3% Triton X-100, and futher purified by 10-40% sucrose density gradient centrifugation.The purified BaYMV thus obtained showed the following characteristics:A260/A280 ratio of 1.20, Max.260/Min.240 ratio of 1.04.The yield of purifed BaYMV was about 5.5-8.0mg/kg infected leaves.Not any contaminats from host materials were observed in the purified preparation under electron microscopy.

Fourteen elements were analysed in tubers of 3 varieties which have signi-ficant difference in resistance to bacterial soft rot.The content of Cu and Zn, and less obviousely, those of K and Ni in medullar tissues were correlated with resistance to wound infection, while Ca and Mg levels were similar among the 3 varieties.In dipping tests, only CuSO₄·5H₂O could sharply inhibit the disease, with a complete control at 500 mg/L, Zn, Fe, A1 showed weak effect, and Mg treatment was not effective.After dipping in Ca solution, soft rot surface of tubers was slightly reduced, but the number of diseased tubers was not, in comparing with control.

On CPG and similar media supplemented with TTC(2, 3, 5-triphenyl tetra-zolium chloride), the naturally occured colonial mutant strains of Erwinia carotovora pv.carotovora Dye(EccM), isolated from soft rot potato tubers, showed white and small colonies, compared with large and red ones of the common wild strains(EccW).This difference can not be used as an indicator to represent their differences in dehydrogenase activity because they had similar activities when determined with cell suspensions washed from the same medium.The white and small form of EccM on CPG+TTC plate is a false negative reaction for their dehydrogenase activity.This is resulted from the following facts:1) EccM strains produced much more acid than EccW when grown on medium with glucose, suc-rose, fructose or related sugars as carbon source, their acid production ability co-uld be visualized by the clear zone around colony on CPG+CaCO₃ plates;2) the buffering capacity of CPG medium was very weak, only 1/8-1/10 of that of K'SB;the pH value in the medium soon reduced to less than 6 after growing of the bacteria;3) under such acidic conditions, the growth of the bacteria was severelyretarded, and their dehydrogenase activity was inhibited to almost undetectable level.
Thus, the white colony form of EccM on CPG tetrazolium agar is a state determined by the immediate pH around the colony, which is resulted from both the peculiar fermentation type of the strains and the weak buffering capacity of the medium.

The interactions between seven wheat cultivars, Yupi 2, Heiwangmai, A-fu, Xinyang 751, Jimai 3, Yian 52 Xuan and Pingyuan 50, and four physiologic races 60, 61, 360, 376 of Puccinia recondita f.sp.tritici have been studied.In field experiments, the areas under the disease progress curve of the slow rusting cultivars were 0.6840-1.4928, while that of the fast rusting cultivar was 3.8499.In green-house experiment, the slow rusting cultivars compared with the fast rusting cultivar showed "slowing" characteristics in every component of resistance.However, variability of slow rusting has been abserved in different developing stages of host and by using different amounts of inoculum.The two-way analysis of variance on components of slow rusting showed that differences were significant either between cultivars, races, or the interaction between cultivars and eces.These specificities warn that a slow rusting cultivar may turn into fast rusting under different conditions.

Based on the results of a four-year laboratory and granary study, it was shown that ethylene oxide is very effective against Stewart's bacteria wilt of corn.The effectiveness and mode of action of this fungicide was diseased.
The results indicated that a 72-hour fimigation at a dose of 50-75g/m³ and a temperature of 15-25℃ was sufficient to destroy this bacterial disease.A lo-wer dose of 50g/m³ was less effective.
Study also showed that fumigation also produced residual effects on the elimination of the Stewart's bacterial wilt.Besides ethylene oxide was also effective in controlling mould and stored-grain pests, Thus the present treatment was proved to be an appropriate protective method for stored grains.
In analysis of the gas in the granary, it was shown that the result was influenced by the persistence of the concentrations gas, and the selected location for gas release.The fumigation time is to be last for 3-5 days.The location of gas release should be selected on the basis of the current temperature of the bulk grain.
However, at dose of 50-75g/m³ ethylene oxide resulted in some detrimental effect on the germination vigor of corn.So, it was not recommended for treating imported materials for propagation.

This study deals with the peach disease caused by lesion nematodes——a new disease in China.The disease was common and serious in Jiangsu prov-ince,especially at a peach nurseary in Xuzhou where all the plants were infe-ctes,with a hight root incident of 81%.The infected yound roots showed varying degree of discoloration and necrosis.Aboveground symptoms were usu-ally in the form retarded growth,eventual stunting and clorosis.The causal nematodes did not infect corkified roots.
Pathogenicity experiments demonstrated that the peach disease in Nanjing was caused by the same species of lesion nematode as that in Xuzhou which was identified as Pratylenchus vulnus.The causal nematode is very similar to P.vulnus,but differs slightly from it in shape of perma the ca(oblong to sub-spherical viz.oblong),tail annules of female 27(20-34)viz.24(22-26) and tail shape variation of female.It was comfirmed that strawberry is also a nutural host of P.vulnus in Nanjing.

Ultrastructural localizations of ATPase activity in the infected and non-infected leaves by sugarcane mosaic virus str.A(SCMV-A) with 7 sugarcane varieties were compared by a routine enzyme cytochemical technique.Results showed that ATPase activity the cytoplasmic membrane of mesophyll cells,phloem sieve and companion cells in 3 types of bundle and cytoplasm of com-panion cells in SCMV-A-infected leaves with 7 different resistance varieties,i.e.Mintang 70/611,Minxian 703,F 134,Fuyin 79/8,Fuyiu 79/9,NCo 310 and Co 740,was obviously higher than that in the healthy leaves correspon-dingly,whereas ATPase activity in the cytoplasmic membranes of bundle shea-th in SCMV-A-infected leaves was lower than that in the healthy sugarcane leaves.Chlorophylls in the mesophylls with chlorotic lesions were almost dege-nerated or disappeared.Bundle sheath cells with abundant chlorophylls origi-nally were occupied by starch particles after their infection by SCMV-A.The change level of ATFase activity between infected and non-infected leaves seemed to correlate to the resistability and susceptibility of sugarcane variety.

Roots of ginseng(Panax ginseng) from diseased(with Cylindrocarpon des-tructans) and healthy plants were processed for the analysis of many organic materials.The experiments showed that the content of total saponins,starch,total sugars,6 amino acids in the diseased roots decreased and the content of fatty acids,lignin,reducing sugar,10 amino acids were higher than those in healthy ginseng roots.

Gel electrophoretic analysis revealed marked alterations in the pattern of base-extractable proteins from tomato leaves of susceptible line,GCR-26 after inoculation with tobacco mosaic virus(TMV)tomato strain O when compared to the pattern from healthy leaves.Four new proteins,Rf0.31,0.33,0.39,and 0. 45,were present 7 days after infection which is most dramatic in the case of the proteins with the Rf value of 0.33 and 0.39.Besides,adecrease was observed in some proteins.10 days after inoculation protein Rf0.31 and 0.45 were not de-tected,while Rf 0.33 and 0.39 accumulated largely.Protein Rf0.33 was charac-terized as TMV coat protein by coelectrophoresis and double immunodiffusion test.Protein Rf 0.39 is not related to virus coat protein and not a new isozyme of peroxidase,polyphenoloxidase,acid phosphatase,esterase,malate dehydrogenase, glucose-6-phosphate dehydrogenase,or glutamate dehydrogenase.It showed a ne-gative reaction with Schiff's stain for carbohydrates and only gave one poly-peptide with MW.14200 on SDS-gels.
From tomato leaves of resistant line,GCR-267,plants we did not observed the same changes in soluble proteins as from GCR-26 plants.
These facts showed that changes in soluble leaf protein constitution could be correlated with the symptom development and virus multiplication in tomato plants.

In order to identify the persistence of the resistance of grapes to Plosmo-para viticola,the relation between the host and the pathogen was studied The specific inoculation of using 15 natural pathogen groupes and 5 host var-ieties showed that the pathogenecity of the natural groupes of the pathogen and the resistance of the host varieties were both differnet,but there was no specific interaction between the host and the Pathogen.The results showedthat although resistant host varieties might strenthen the pathogenecity of the pathogen groupes,continuous inoculation on specific varieties had not induced specific interaction.Consequently,horizontal theory was suqqested.If this the-ory will be proved,we may increase the resistance level of grapes to P,viti-cola by intraspecific hybridization of Uitis vinjfera.

Soybean plants infected by SMV could become the acquisition hosts for the aphidsvectors,Only after appearance of systemic symptom.The rate of the syste-mic symptom appearance of soybean plants mechanically inoculated with the cru-de sap of 1:10 dilution was similar to that transmitted by aphid vectors.The soy-bean plants of V₁-R₅ growing stages of five susceptible cultivars were inocul-ated with the crude sap and by aphid vectors and the experiments were repeated more than 30 times,the results suggested the rate of the systemic symptom app-earance of infected plants was greatly correlated with the temperature.The mi-nimum temperature for the symptom appearance was 9℃,the optimal temperature was about 26℃.
The effective accumulative temperature for the rate of symptom appearance of plants since infection by SMV during V₁-R₂ growing stages were very sim-ilar,but those during R₃-R₅ were little higher than that during V₁-R₂.The figures of correlation points between the data of accumulative rate of systemic symptom appearance and those of accumulative effective temperature showed sig-mold curve.Among 8 formulas used to describe the data,the Gompertz was the best suitable for that during V₁-R₂,the forecasting model is:PPi₁=Exp (-103021.196 Exp(-0.1329TT_i).and the Weibull was the during R₃-R₅,the forecasting model is:PPi₂=1-Exp[-(0.02222(TTi-65)^2.581].

The infection of poplar leaf rust fungi(Melampsora magnusiana) resulted in an increase in peroxidase and phynelalanine ammonia lyase(PAL) activities in dise-ased poplar leaves.The increase of the enzymes level was greater in highly sus-ceptible clones than in highly resistant ones.The appearance of the peak of pero-xidase activity coincided with the symptom emergence,distinctly different bet-ween highly resistant and highly susceptible clones.PAL activity reached a maxi-mum in all tested clones after 10 days of inoculation.Infection also caused changes of isoperoxidase patterns.Additional isoperoxidase bands appeared in most of infected clones.However,these changes could not reflect the different resistance of the hosts.

In order to identify the persistence of the resistance of grapes to Plosmo-para viticola,the relation between the host and the pathogen was studied The specific inoculation of using 15 natural pathogen groupes and 5 host var-ieties showed that the pathogenecity of the natural groupes of the pathogen and the resistance of the host varieties were both differnet,but there was no specific interaction between the host and the Pathogen.The results showedthat although resistant host varieties might strenthen the pathogenecity of the pathogen groupes,continuous inoculation on specific varieties had not induced specific interaction.Consequently,horizontal theory was suqqested.If this the-ory will be proved,we may increase the resistance level of grapes to P.viti-cola by intraspecific hybridization of Uitis vinjfera.

A sensitive plaint biassay,etiolated wheat coleoptile biassay,was used to detect biological activity of mycotoxins produced by Furarium graminearum and response of various wheat varieties to these mycotoxins.The significant difference was presented between mycotoxins and between wheat cultivars.The biological activity of deoxynivalenol was strongest and the sensitivity of wheat cultivar,Wang Suibai,to seven te sted mycotoxins was the lowest.The interac-tion of mycotoxins and wheat cultivars preliminarily studied.

During 1983-1987,the data of poplar leaf rust disease caused by Melamp-sora magnusiana and meteorological items of corresponding were taken from many nurserys in Huabei region.Through stepwise regression calculation,18 related factors were designed for selection.As a result,the factor-interaction between the number(X₁)of diseased poplar buds in early spring and the total quantity(X₃) of rainfall was selected.The regression equation for prediction of the disease(Y)is as follows:
Y=2.4229+0.0133X₁X₃
The regression equation was obtained in X²-test.The model was also exa-mined using both actual disease indexes and relative meteorological factorswhich were outside the model for many times.A better fittingness was observed between the actual and theoretical values.
The model could be use in predection of poplar leaf rust disease in nur-sery and would bo benefitial to make decision in the disease management such as fungicide application.

King's medium B (KB) is the most widely used medium for the detection of fluorescent pseudomonads, but some of the recommended ingredients which couse this medium to enhance fluorescent pigment production are not readily available in China.KB made with locally available peptone, tryptone, and agar was compared with KB made with Proteose Peptone No.3 and Bacto Agar (Difco). The plating efficiency of six isolates of fluorescent pseudoraonads on KB made with local materials was not significantly different from KB made with Difco products. However, as many as 90% and 100% of the colonies failed to fluoresce on KB made with peptone or agar powder (Shanghai Biochemical Reagents), respectively.Consistent and intense fluorescent pigment production was obtained on KB made with Tryptone(Oxoid)(20 g/l) and agar strips (Shenzhen Agar Industry)(15 g/l). This latter medium promoted slightly greater recovery of non-fluorescent organisms when plated in combination with fluorescent pseudomonads as compared to KB made with Difco products.