This paper discribes the pathogenicity of the pathogen Sarocladium oryzae(Sawada) Gams & Hawksw.causing rice sheath rot at different growing stages of rice and on the different parts of pllant above the ground.The studies show that it infected the rice plants at all stages of growth while the most distructive was after booting.The pathogen infected rice leaf sheath midrib of leaf blade and rice grains.The symptoms consisted of typical sheath rot lesions and what is called "purple sheath" or "purple sheath with yellow leaves".The disease could be transmitted by infected rice seeds.

A virus disease of asparagus bean characterized by a dwarfing of plant and curling or rugosity of leaves,has been found in Nanjing area in 1983.The isolate C-7 of this virus was transmitted by three species of aphids,efficiently by Aphis craccivora and less efficiently by Aphis gossypii and Myzus persicae in the persistent manner,but not by Aphis glycine.The C-7 isolate was not transmitted by sap inoculation.Of 28species of plant in 4 families which were inoculated by the aphids(A.craccivora),15 leguminous species and 1 solanaceous species were found to be infected with the virus.The aphid was able to acquire the virus by feeding on the infected asparagus bean plant for at least 3 hours and the inoculation feeding period was at least 10 minutes.The latent period in the aphid vector was 24-36 hours.In serial transmission tests,individual aphids seemed to transmit the virus as long as they livedand retained their infectivity through molting,although not every plant in a series was infected.Based on symptoms,host range and vector transmission,the virus can be considered as a persistent aphid-tran-smitted virus belonging to the group of Luteoviruses.

The contents of chlorophyll and protein were reduced to 20.3% and 41.7%,respectively,and the activities of RUBP case and PEP case were decreased to 65% and 46%,respectively,in virus-infected leaves as compared with that of healthy leaves.The decrease of ratio of acticity of RUBP case to that of PEP case was also observed.It seemed thatRUBP case was apparently closer than PEP case in response to the infection of mosaic virus in papaya leaves.
The decrease of the activity of malic enzyme and malate dehydro-genase were also found.This results might show that the decrease of ab-sorption of light by decreasing the content of chorophyll and the decrease of the ability of leaf assimilation by reducing the activity of photo-synthetic carboxylase occurred during papaya leaves were infected with ringspot masaic.

The rice transitory yellowing and rice dwarf are two important virus diseases of rice in South China.An equation for the prediction of transitory yellowing and dwarf diseases was verified by results from cooperative research in 6 different disease-prone areases of Zhejiang and Anhui provinces during 1978-1980.The percentages of diseased plants calculated with this equation from the experimental resultsin 12 years all approximated to those observed in the late rice fields.It shows that this equation was able to predict fairly accurately both diseases when their incidences were with in the range of 0~33.74% in late rice fields.Simultaneously,it was also indicated that the detection of viruliferous rate of vector insects is a key technique for foreccasting the incidence of these diseases.

The infestation of potato tubers by the soft rot bacteria were detected by the direct isolation method,enrichment technique followed by isolation,the moist chamber technique and anaerobic wrapping technique.Results of comparison showed that anaerobic wrapping technique was the most effective method.Among 46 samples of potato tubers collected from 23 provinces of China percentage of tubers infested ran from 0~100 percent.Total 284 isolates of Erwinia were isolated from 33 samples of potato tubers.of cohich 75.5% of the isolates was Erwinia carotovora var.carotovora.The percentage of isolates of Erwinia carotovora var.atroseptica and Erwinia chrysanthemi were found to be 5.3% and 10.2% respectively.Another 34 isolates were found to be intermidiate types between E.carotovora var.carotovora and E.chrysanthemi.

Sixteen wheat varieties including high,resistant,semi-resistant and susceptible were obtained from our disease nursery to examine the haustoria of powdery mildew in relation to resistance by the rapid staining method(Wolf and Frič,1981) and lactophenol cotton blue solution as well.The results clearly pointed out that resistance in wheat to be infected by mildew could be conferred as follows:(1) delay the early haus-storia development,(2) increase of haustorial rate rather slow,(3) reduction the numbers and final size of haustoria,and(4) distortion and disintegration of haustria more quickly.It was also shown that more haustria happened in the seelings and juvenile plants than in the old plants.
The present experimental results probably could be used to detect some resistant materials early for breeding program.

A new method is mentioned in this paper for studying the plant-disease epidemic dynamics by means of Fuzzy theory.
Formerly the author attempted to proceed from uniform point ofview about the disease progress intensity and spatial dynamics of the epidemic and took rice sheath blight [Pellicularia sasakii(Shirai) S.Ito] as an example.If the epidemic dynamics of rice sheath blight may be depicted by the mean disease plant(X) of the colony,the index of pa-tchiness(Ṁ/M) and the percentage of hole plants(P),they are only the point set in the three dimensional space.This set is determined by X,Ṁ/M and P.Establishing the similar matrices R=[r_ij].

According to the microbiologic assay,oxytetracyline-HCl solution is absorbed and translocated upwardly by China tree(Melia azedarcch) through the immersed roots and soil treatment.The absorption amount increases graduately from 1~5 days by immersed roots and 5~6 days by soil treatment,and reduces graduately thereafter.The oxytetracyline-HCl solution through immersed roots remains in the plant tissues more than 20 days,while through soil treatment 9 days only.

The gummosis of peach is a serious problem of peach production in Nanjing,China.The causal organism Botryosphaeria dothidea(B.ribis) was identified to be similar to that by Weaver described in 1974.The organism that produces two stages(imperfect and perfect) occasionally bearing in the same stroma in it life cycle have been observered.The conidia of Dothiorella gregaria(imperfect stage) measures 13~32.5×5.2~11.7 μ,and the ascospores of Botryosphaeria dothidea(perfect stage) measures 23.4~28.6×7.8~13μ.

The correlation coefficient between scoring systems developed in China and IRRI,based on infection of Xanthomonas campestris pv.oryzae by clipping method of inoculation,was highly significant.
The international differential varieties including Japanese-Kinmaze,Kogyoku,Te-tep,Wase Aikoku 3,and Java 14;IRRI-IR8,IR20,IR1545-339,DV85 and Cas 209;and Chinese differential varieties-TN1,Bao-Tai-Ai and IR26,with special genes for pv.oryzae resistance were evaluated in South China(Guangdong) and in the Philippines for resistance to local pathotypes.Kinmaze and Te-tep were susceptible,and Wase Aikoku 3 and Java 14 were resistant to the four Philippine and the five South China pathotypes.Kogyoku was resistant to South China pathotypes Ⅰ and Ⅱ,but susceptible to South China pathotypes Ⅲ and Ⅳ,and to the four Philippine races.IRRI differential varieties,IR8 and Cas209 were susceptible and only DV85 was resistant to all South China pathotypes,IR20 and IR1545-339 were resistant to South China pathotypes Ⅰ,Ⅱ,Ⅲ,and Ⅳ but susceptible to pathotype Ⅴ.Chinese differntial varieties,TN1 and Jin-gang30 were susceptible to all South China pathotypes and IRRI races.IR26 was resistant to South China pathotypes Ⅰ,Ⅱ,Ⅲ and Ⅳ,and Philippine race Ⅰ,but susceptible to South China pathotype Ⅴ and Philippine race Ⅱ,Ⅲ,Ⅳ.Results indicated that the isolates in terms of virulence of South China pathotype Ⅲ and Ⅳ may correspond to Philippine race Ⅰ,and the pathotype Ⅴ to Philippine race Ⅳ respectively.

It was identified in our earlier studies that there were three biotypes of Agrobacterium tumefaciens(Smith & Town.) Conn.the casual bacterium of crown gall of grapevine isolated from Beijing,Neimenggu Autonomous Region,Jilin,Liaoning and Shandong provinces in China.When these three biotypes were inoculated on grapevine seedlings of variety Muscat Hamburg they exhibited different degrees of virulence.Biotype Ⅲ isolates Were most virulent,producing medium to large sized galls;while biotype Ⅰ and Ⅱ were less virulent,producing small galls or galls not enlarging.Biotype Ⅲ isolated from different localities or different grapevines cultirars differed in their host range and virulence on a number of plants including grapevine,sunflower,tobacco,tomato,etc.They might be separated into two different host range groups:one group infecting grapevine only,the narrow host range group;the other infecting grapevine,sunflower,tobacco,tomato,and some other plants,the wide host range group.Among 20 grapevine varieties tested,varietyMuscat Hamburg was most susceptible;and Pearl of Cszba,Beta show-ed resistance to these three biotypes.Some isolates of biotype Ⅲ and Ⅰwere found to be pathogenic to Pyrus betulifolia,Prunus salicina,P.armeniaca L.var.ansu,P.davidiana,p.pseudocerasus,and P.triloba when needlings were inoculated with isolates of biotype Ⅰ and Ⅲ.The opines synthesised in the galls of grapevine seedlings inoculated with different biotypes were also identified.Teratomas were produced from galls on tobacco,datura and tomato seedlings inoculated with biotype Ⅲ isolate BS33-10 from grapevine variety collected in Shandong province.

The studies revealed that the temperatures for the growth and development of the pathogen were 15~35℃ with the optimum of 30℃.The pH values of the substrates were relatively broader from pH 3 to pH 9 with the optimum at pH 5.5 for the mycelial growth and sporulation.Continuous light treatments inhibited while complete dark favoured the growth and sporulation.The fungus grew and sporulated better in sucrose and glucose followed by soluble starch as the carbon sources.Ti utilized effectively all the nitrogen sources tested.The best medium forthe fungus was PDA.
The extracts of flag leaf sheath and young panicle of rice plant stimulated spore germination.

The esterase isozymes of the Fusarium sp.causing headblight of wheat and barley were studied by polyacrylamide gelelectrophoresis.Twenty four fungal isolates representing 17 species and varieties of the genus Fusarium were used in this study.They were F.graminiarum,F.cul-morum,F.moniliforme,F.avenaceum,F.avenaceum var.herarum,F.nivale,F.acuminatum,F.sulphureum,F.equiseti,F.eqiseti var.longipes,F.poae,F.camptoceras,F.semitectum,F.concolor,F.fusarieides,F.oxysporum,F.oxysporum var.vasinfectum.

In air-borne diseases,such as wheat stripe rust,distance of disease spread brought about by one cycle of infection can be predicted through the infection gradient model X_i=a·d_i^-b,provided Z,the total amount of disease resulted from the infection,and b,the gradient coefficient,can be predicted and thereafter "a" can he estimated,Three approaches to the prediction were designed and tested with observed values of disease spread.Among the three,the "center square" approach seems to be the most hopeful.Further works of verification and validation are needed.

The root and basal stalk rot of corn is one of the most serious diseases of corn in China in recent years.
From 1979-1983,252 diseases samples were collected from several areas in Shandong province.Results of isolation and inculation test in laboratory and field proved that the main pathogenic fungi are Pythium aphanidermaturn(Edson) Fitzp.and Fusarium graminearum Schw.,but the pathogenicity of Pythium aphanidermatum is stronger.

The condition for the formation of ascospore of wheat powdery mildew(Erysiphe graminis f.sp.tritici EL.Marchae) was the moisture for clothecium.The temperature range of ascospore formation was 1-27℃,(optium 11-15℃).Ultra violet light,diffused light and darknesc had no influrence on the formation.Ascospore might be produced in pH3.0-9.0.(optium pH 5.0-7.0) and germinated at 1-36℃(optium 11-20℃),in pH 2.2-12.4(optium pH 5.0-8.0) with various relative humidity,yet the highest germinated percentage was obtained in saturated moisture(100%).Darkness and diffused light had no influrence on the ascospore germination.
The longivity of clothecium was intimately related to the temperature and humidity.The higher temperature and higher humidity,shortened the longivity of clothecium on diseased leaf.

F₁.F₂.F₃ and B₁ F₁ plants of crosses of resistant parents Zhen-long No.13 and Zhai-Ye-qing No.8 with susceptible parents Zhao-lu-zao and Zhai-yiang No.1 were inoculated with two strains,75-49(ZB₁) and 0206-1(ZC13) of Pyricularia oryzae.The results suggest that the resistance of Zhen-long No.13 to fungus strain 0206-1 is controlled by a single dominant gene,Py-1;the resistance of Zhai-ye-qing No.8 to two fungus strains,75-49 and 0206-1,is controlled by two genes,Py-2 and Py-3.

It was proved that the inhibition concentration to wheat rusts by sulfanilic acid were very low,and those to leaf rust and stem rust were close,around 400 ug/g fresh leaf when applied 3 days after inoculattion and assayed 8~10 days after application.The later it was applied,the higher concentrations were needed for inhibition.The transfer of sulfanilic acid is rather rapid,reaching the second leaf 30 hrs after application on the first.It was also proved that sulfanilic acid can be retained fairly long in leaves at inhibition concentrations.
The therapeutic mechanism of sulfanilic acid is due to its structural analog with PABA,hence competitive inhibition,since PABA has been regarded as a vitamin for rust growth.PABA is a moiety of folic acid which is an indispensable cofactor in nucleic acid metabolism.Strong antagonism of PABA,nucleic acid,thyminic acid,adenine,and hypoxanthine against sulfanilic acid was therefore found in our experiments;the degree of antagonism is dependent on the time of PABA application.

Under greenhouese condition,4-5 leaf-stage wheat seedlings of seven cultivars,including 5 representative slow-rusters,one susceptible check and one vertical resistant check,were inoculated separately with four isolates of wheat yellow rust each belonging to different race.By histological observations,it was found that early from the third day after inoculation,there occurred the phenomena of cell necrosis in the infected sites of all the slow-ruster-isolate combinations,while no cell necrosis occurred in the susceptible check,Yianda 1817.The area of the mycelial colony and the amount of sporulation in the slow-rusters were found to be smaller and lower than that in the susceptible check.
The possibility of evaluating the slow-rusting resistance of cultivars by histological method was discussed.

About 250 isolates of Rhizoctonia solani,representing a wide range of geographic origins,hosts and types of diseases in China,were collected and identified.According to anastomosis,these isolates belong to five anastomosis groups(AG1-AG5),which were consistent with Parmeter & whitney's(1969) and Ogoshi's(1972) groups.With the way of soil over-culture,each one of AG2-1 and AG-4 isolates was induced to produce perfect stage in vitro,their identificaion turned out to be Thanatephorus cucumeris.(Frank) Donk.The pathogenic,ecological and taxonomical implications were discussed.

The effect of satellite RNA on host range,symptom and aphide transmission of CMV and CMV-S51(containing satellite RNA) were studied.The host range of CMV-S51 was much more narrow than CMV.CMV can infect 20 plant species of 6 families,while CMV-S51 can only infect 10 species of 3 families.CMV-S51 was symptomless on the infected plants except pumpkin。CMV caused severe mosaic,fern leaf and necrosis in most of the infected plants.The transmission efficiency of CMV-S51 by Myzus persicae was lower and the incubation period was longer than CMV.

We have used the refined Anti TRSV-IgG,which has been passed through the Protein A-Sepharose CL-4B Column Chromatography,it was very sensitive for the ELISA.
In this experiment we used polystyrene beads as the solid phase for the double sandwich ELISA,to test the optimum coating ratio of Anti TRSV-IgG.At the condition of the concentration of the antigen(TRSV) was 1μg/ml,and the concentration of the enzyme conjugated antiserum was 2.5μg/ml,the proper concentration of coating antiserum of Anti TRSV-IgG for bead ELISA was 5 μg/ml,but 1.25μtg/ml of Anti TRSV-IgG seems also effective.
The bead ELISA technique requires only microquantity of antiserum,just as the microplate ELISA needs,and it seems more sensitive than that of the mieroplate ELISA.

Infection,colonization and sporulation can be made by "Gui Bai" No.64 race of Erysiphe graminis DC.f.sp.tritici on the four wheat cultivars Pan Jiang 4,Bai Mian 3,Ken Guial and Bai Quan 565.Incubation rate is basically the same for them.Both infection and sporulation rates are relatively higher on Bai Quan 565 then on the others.So it's parasitic fitness ranks the first.On Ken Guia 1,though it's infection rate is higher,sporulation rate is lower.It's parasitc fitness ranks the second.Both infection and sporulation rates are lower on cultivars Bai Mian 3 and Pan Jiang 4.Therefore their parasitic fitness should rank the third.Ken Guia 1,Pan Jiang 4 and Bai Mian 3 are lower in epidemic rates to race No.64 during the Seedling stage in comparing to Bai Quan 565.Sporulation rate is reduced on Ken Guia 1.But on PanJiang 4 and Bai Mian 3 the percentage of infection and rate of sporulation of the Gui Bai No.64 race are also reduced.

Two viruses named Hami-melon necrosis virus and Hami-melon vein necrosis virus have been isolated from some early ripening varieties of Hami-melon showing necrosis symptom in the field of Xinjiang.They infected Hami-melon systematically,and serious stunting of growth occured after the plants were infected by the viruses.But the necrotic symptoms caused by HmNV and HmVNV were different.

Soft rot of Chinese cabbage was considerably severe in cold storage in Nanjing and caused loss to 40% as the total weight of the plants frenqently.Since 1982,500 mature plants without any visible symptom from fields,market and cold storage were examined with anaerobic technique and 99.6% of plants were found to be infected by soft rot bacteria.The examination of all detached leaves of 10 plants showed that the pathogenic bacteria were present in most of both outer and inner leaves of all the plants tested and the ratio of diseased plants was from 4.5% to 82.8% with a average value of 47.7%.The decay of the surface-steri-lized leaves due to the latent bacteria by the anaerobic technique was almost as severe as the decay of the non-sterilized leaves.The macerated lesions appeared in the petiole tissues in line parallel to the vascular bundles.17 cultivars of Chinese cabbage planted in two plots in Nanjing were investigated to compare the resistance to the latent bacteria.Latent infection of different cultivars from the two plots had a identical tendency basically and three groups in resistance could be divided based on severity of the soft rot.

Between 1983 and 1984,Periwinkle(Vinca rosea) was used as an indicator plant for the sweet potato witches'broom which was trans feredby dodder(Cuscuta australis).The results of the experiment showed that 6 of 10 inoculated plants of periwinkle were diseased and the incubation periods were 65-98 days.The diseased plants showed the phyllody of the flower,The axillary buds of the diseased plant were increased,then they were grown into small leaves and witches'broom appearance.

Forty three isolates of Pseudomonas solanacearum obtained from diseased potatoes in different provinces or areas were examed for pathogenicity on some solanaceous plants and oxidation of three disaccharides(maltose,lactose and cellobiose) and three hexose alcohols(mannitol,dulcitol and sorbitol).Results indicated that all isolates caused weak to severe infection on potato(Sotanum tuberosum L.cv."zhongzhaihuangpi" and "Jing-feng No 1"),tomato(Lycopersicon esculentum Mill,cv."Mangsi") and eggplant(Solannm melongena L.cv."Six Leaves").According to oxidation of above described carbohydrides most isolates(38/43) were identified to blong to Biotype Ⅱ,four-Biotype Ⅲ,and one-Biotype Ⅳ.

Leaves of burdock(Arctium tomentosum) from diseased(with BSV RNA-1 and BSV RNA-2) and healthy plants were fixed and processed for transmission electron microscopy.No virus-like particle was found in diseased thin sections.The variation of the cells of diseased leaves from the healthy ones is the alteration of the cell plasmalemmasomes.Some of the malformed plasmalemmasomes looks like pin-wheels.No significant difference was observed in chloroplasts and nuclei between healthy and diseased cells.

Virus multiplication,peroxidase activity and isoperoxidases were investigated with leaves of resistant,tolerant and susceptible tomato cultivars at two days interval up to 30days after inoculation of TMV.Virus infection resulted in an increase in peroxidase activity and changes in isoperoxidase patterns.In tolerant and susceptible cultivars,coinciding with TMV multiplication and symptom development,the peroxidase activity increased greatly after 15 days of inoculation and reached a maximum after 3 weeks of inoculation.Two additional isoperoxidase bands A and B appeared in the case of infected plants,whereas in healthy plants,only 6 isozyme bands occured at the peak of peroxidase activity.In resistant cultivar,TMV multiplication was inhibited so that the infected plants were almost symptomless,however,the peroxidase activity increase was associated with appearance of isoperoxidases A and B at the 12th day and 21th day after TMV inoculation.

Basic model describing the circular spread from the infection focus of wheat yellow rust was developed based on the disease gradient modelXi=a·exp(-bdⁿ).The whole field under study was divided into square compartments with side length being one unit of distance "d",facilating the determination of the distance between each compartment and the focus center.Parameter "b" can be predicted from a regression equation of "b" upon the wind velocity "w",and parameter "a" was deducted based on there lationship between a and b,and the total amount of disease infection.Assuming the velocities of multi-directional wind are more or less the same(ie,in case of circular spread),the number of emerging diseased leaves of each compartment could be calculated according to the equationXi=a·exp(-bdⁿ),and the predicted values were further transformed by random-process and multiple-transformation.By uniting this model with the preexisting temporal model(such as TXLX),a comprehensive model,named XRZD-1,was constructed and run to describe both the temporal and the spatial dynamics of the epidemic in early phase.

A sesd-borne virus isolate,Bd,was isolated from broad bean(Vicia faba) in Anhui,China.Its host range was very narrow,only broad bean and pea(Pisum sativum) could be infected.The dilution end-point was determined to be 10-4 the thermal inactivation point was between 80 and 85℃(10 minutes),and the longevity in vitro at a room temperature(20-25℃) was 6 days.It was transmitted by sap inoculation and also transmitted by seed,but failed to be vectored by alfalfa aphids(Aphis medicaginis).