The urghum (S.vulgare) rrd-stripe virus disease is of economic importance in North China,because it usually causes great loss of sorghum yields.

The cabbage blackleg pathogen Phoma lingam induces brown necrotic on stems and leaves of cabbage plants.From these lesions two kinds of Phoma isolated were isolated one pathogenic and another non-pathogenic.They were tested for growth rate,production of brown water-soluble pigment and allozyme banding patterens.The pathogenic isolates was different from the non-pathogenic isolates in the above stated characters.The isozyme patterns were correlated with the pathogenicity of the isolates tested on crucifer hosts,namely on starch-gel-electrophoresis,10 of the 25 isolates were non-pathogenic which produced faster moving enzyme bands than the other 15 pathogenic isolates. The enzymes were AAT,EST,GPT,IDH,MDH and PGM.The enzyme 6PG of pathogenic isolates moved faster than that of the non-pathogenic ones.Some non-pathogenic isolates prodaced only two bands of the isozym es.

Direct dissection method,Baermann funnel technique,Direct isolation procedure,Differential centrifugation method,Baermann funnel technique+ Drechsler's method and Direct isolation procedure+Drechsler's method were tested to isolate the nematodedestroying fungi of M.incognita.From the cotton rhizosphere at Jinhua and Buxus sinica rhizosphere at Hangzhou in Zheiiang Province,nine fungi parasitic on M,incognita were isolated,i.e.Verticillium insectorum,V.cephalosporium,V.sp.,Monacrosporium endermata,M.cystoporium,M.fusiformis,Harposporium anguillulae,H.oxysporum and Nematoctonus Pachysporus,Direct dissection method and Diffrential centrifugation technique have been proved to be more effective than the other four procedures tested.

Interference betwcen cucumber mosaic virus(CMV) and tobacco mosaic virus (TMV-T) was studied since 1981 to 1985.Pre-inoculation of Nicotiana abacum with CMV decrease TMV infection to 85.6%,and pre-inoculation with TMV-T decrease CMV infection to 95% in the same plant.Vaccination of N.fabacum Var.Samsum Nc and N·glutinosa with satellite containing CMVS-52and S-52 protect TMV-P infection to 65%.

The morphological variation of Verticillium dahliae was studied.36 isolates of fungus,which were originally isolated from cotton,eggplant,pepper and other plants were used.Conidiospores were diluted and cultured for detecting the variation rate of monospore progenies.Among 92947 monospore progenies of the wild type(type A) strains,5.85% changed into fluffy mycelium type(type B) and 0.07% changed into appressed mycelium type(type C).Among 1773 monospore progenies of the fluffy mycelium type (type B) stra-ins,0.19% changed into appressed mycelium type (type C).The frequency of morphological variation in wild type strains (type A) of V.dahliae varied with the fungal isolate studied in monospore progeny,culture medium,store temperature and time.The cultural characteristic of The fluffy type (type B) strains was rather stable.The methods of strain-store were discussed.

Application of ISEM method in the diagnosis of three potyviruses-Soybean mosaic virus (SMV),peanut mottle virus (PMV) and Cowpea aphid borne mosaic virus (CAMV) was carried out.Virus particles Were traped on the films of EM.grids which were coated with antiserum.Over 20-50 times of virus particles was trapped on homologous antiserum-coated grid than heterlogous or coating with normal serum.The sensitivity and specificity of ISEM depended on the concentration of antiserum coated on grids and the incubation times with the crude extracts from the diseased leaf.Results shoucd that the optimal dilution of antiserum were Ⅰ:Ⅰ,000.A short incubation time with virus suspenion trapped virus particles while prolonged incubation time increased trapping activity,but no increase happened after 10-20 hours incubation.

The stripe rust of wheat caused by Puccinia striifromis West.has become a severe problem in wheat production in Hnbei province in recent years.it is not clear whether the pathogen comes from other provinces or is of local origin,In order to clarify this problem,studies on the capability of oyersummering of the stripe rust in Hubei province were carried out during 1984-1985.The result showed that although the rust might oversummer in this region yet it was hard to do so at the temperature from 18.7 to 19.7℃ in the high mountain region with altitude of 1700-2050 m.during the most hot ten days in July and August of Yunyang area and Shennongjia area,Hubei province.Through extensive survey,no wheat and rye plants or volunteer wheat were detected to be infected by the stripe rust.It was primarily considerd that this pathogen on the high altitude might not be the source of infection for the vast region of winter wheat during the seedling stage in the lower range or plain.No wild grasses were found to be the host of the rust,except the Gluceria was found to be poorly infected by stripe rust which was proved to be able to infect wheat by inoculation test in greenhoure.However its function to induce an epidemic seems to be negligible.

The changing of peroxidase isoenzymes in witches' broom and healthy plants of beef wood and the diseased gradations were studied by polyacrylamide gel elecyrophoresis.The peroxidase isoenzymes activity healthy plant is stronger and the number of enzyme bands is 2-6 more than diseased plant.The changing of peroxidase isoenzymes among the diseased gradations opposed to the one which shows symptom,i.e.the heavier the disease symptom appeared,the enzyme activity and the number of enzyme bands will be lower.The variation of such a "biological symptom" inside the plant of beef wood can be used as a simple and effective method in determination of the diseased plant.

Two viruses named Hami-melon necrosis virus and Hami-melon vein necrosis virus have been isolated from some early ripening varieties of Hamimel-on showing necrosis symptoms in the field of Xinjiang.They infected Hamimelon 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.

The temperature range of spore germination of B.sorokiniana is 3-39℃ in wheat leaf juice,and 6-30℃ in water,the opt.temp,of both are 22℃.On PDA medium,the temp.range of the mycelial growth is 4-37℃,that of sporulation 11-35℃,The opt.temp,for mycelial growth and sporulation started from mycelial transfer is 22-24℃,while that from spore transfer is 20-22℃.Conidia germinated in bufferred phosphate solutions from PH2.2-12.4,but mycelial growth occured only on PH2.7-10.3 in liquid media.

An investigation on the infection Period of Valsa mali Was made in experimental plot of the institute,situated in Xingcheng County,Liaoning province,during 1982-1984.The modified methods employea in these trials,consi-dering the behaviour of latent infection,were detailcd.

By assessing the reaction to stem rust of seedling plants of P,F.and F₂-rom half diallel cross between four resistant varieties and one susceptible variety Little Club and F₂ Progenies of back-cross between resistant and Little Club,the inheritance to three physiologic races of Puccinia graminis var tritici has been studied in four spring varieties as importunt resistant sources to stem rust in China.Difference or likeness betwcen the resistant genes carried by resistant source varieties and the Sr genes denominased by internation organization has been compared.The results of the analysis of genes are as follws.

In recent years,the rice bacterial foot rot become serious in some parts of China.The pathogenic bacteria was identified as Erwinia chrysenthemi pv.zeae (Sabet 1954) Victoria,et al.Research on inoculation by various methods and observation of the infected plant tissues by scanning electron macroscopeindicated that the pathogenic bacteria might invade plants through wounds and water pores on leaves,causing leaf blight and through wounde leaf sheath and roots,causing various types of symptoms including leaf blightSheath blight and heart blight.

In 1984,a lot of maize seeds (inbred line ZPL 773) imported from Yugoslavia were planted in provinces Gansu and Xinjiang in China Serious wilts and light brown to black colored vascular bundle were observed through longitudinal section of stem during tasseling.The infection in field was 66-98.9% in Gansu.The pathogen was isolated from colored vascular bundles and identified as Acremonium stricium W.Gams (=Cephalosporium acremonium Corda.).

104 isolates of the pathogen of black shank from 14 counties of Shandong province during 1982-1984 Were indexed on six indicator tobacco varieties or species:L8(with resistance from N.longiflora).NC1071(with resistance from N.plumba-ginifolia),and N.nudicaulis was served differentiators of the fungus races.Alse,disease-resistant (Florida 301 and Jin-Xing 6007) and highly susceptibie N.tabacum cultivars (Xiao Huang Jin 1025) was used.

An isolate from a mosaic disesed bean plant in the vicinity of Beijing showing flexuous particles(700 to 750 nm) was studied during 1983 to 1986.Inoculation tests in greenhouse resulted in the infection of Phaseolus vulgaris,vicia faba,Pisum sativum,Glycinc mcx,Cassia tora,Chenopodiun amaranticolor and C.quinoa and in the non-infection of the Solanaceous plants so fartested.In host reactions,it differed from bean common mosaic virus by noninfection of Nicotiana rustica and Petuiia hybrida as well as no production of local lesions on any cultivar of Phaseolus vulgaris.Furthermore,the present iso-la e infected broad bean,soybean,pea and Cassia iora,while BCMV did not BCMV infected cowpea.(Vigna sinensis) while the present isolate did not.It was readily transmitted by Myzus Persicae The physical properties so far tried are as follows,TIP=56-58℃,(10 minutes),DEP=10-3 to 10-4,Longevity(18℃) 3 days,A260/280=1.12.It induced to produce optical inclusion bodies in the infected tissues of bean plants.pinwheell-like bodies and laminate agg-regates were observed in E.M.The subunit of coat protein was estimated as of a M.W.32,000.No serological reaction occurred between this isolate and the antiserum of any of the following viruses,namely bean common mosaic virus,bean yellow mosaic virus,black eye cowpea mosaic virus,pea seedborne mosaic virus,clover yellow vein virus,lettuce mosaic virus and beet mosaic virus.It is therefore considered that the present lsotate is a new and inde-pendent virus and designated as bean mild yellow mosaic virus.

A Strain of Wheat Yellow dwarf virus(WYDV),GPV,differed from GAV and RMV previously studied in Beijing because it was transmitted by Schizaphis graminum and Rhoplosiphum padi not by Macrosiphum avenae and Rhopalosiphum maidis.The relative vector specificity of GPV strain was the same whether virus was acquired by aphids feeding on the infected leaves,through membranes on Purified virus Preparationsior by different temperatures for acquisition and inoculation feeding,The results from ELIA assays showed that GPV strain was distinct from five strains of BYDV in the United State and GAV strain of WYDV in China.GPV strain might be a new strain of WYDV not only in China but also in the world.

The Qinhai spruce (picea crassifolia Kom.) leaf rust became widespread and caused heavy losses in the forest of Qilian Mountain.Experimenting and investigating on this disease in the sample land for 4 years showed its symptom,causal factor,infective circulation and main law of pathogenesis.

The studies revealed that the temperatures for the growth and development of the pathogen were 5-30℃,with the optimum of 25℃,The pH values from pH4-12,with the optimum at pH 6 for the mycelial growth.Continuous ultraviolet light and fluorescent light treatments favoured the sporulation while complatc dark in hibited the sporulation.The best medium for the fungus growth was PDA and the best medium for the fungus sporulation was ginseng roots medium.The fungus grew better in soluble starch and malt sugar as the carbon sources.The fungus grew better in glutamic acid acid and sodium nitrate.The extracts of stem and root of ginseng plant stimulated spore germination.