This paper deals with the rust fungus on native susceptible safflower varieties.The spore stages and the life cycle pattern of puccinia carthami have been carefully observed and studied.The result indicates that when safflower seedlings was first infected after sowing the seeds dusted with teliospores of P.carthami,the sympotoms appeared.On the disease spot was present a series of spore forms,which were pycnia,primary uredinia and telia.According to the ontogeny of the rust fungus and by the comparison of different kinds of the spore morphogenesis,it has been identified that the spore form developed after pyenia ought to be regarded as the primary uredinial stage,not the aecium.Thus,P.carthami must be attributed to an autoecious,brachyform rust fungus.

This paper demonstrates that Phytophthora capsici is the chief cause of the capsicum plant wilt in Beijing.The isolates were obtained from green-house and field diseased plants in Dongsheng,Wenquan,Xiahongmen and Sijiqing,and their cultural and morphological properties were studied.The sporangia vary in size,length/breadth being 1.5-1.9:1,usually with single papilla,sporangia mostly with long sporangiophore (31-142.6 μm),No chlamydospores produced or produced rarely.This fungus is heterothallic.The oogonia are spherical,15.5-28.9μm in diameter.Oospores are spherical,yellowish to golden,15.0-28.0μm in diameter.The optimal temperature for growth is 25°-32℃,with low and high limitation of 10℃ and 37℃ respectively.Fungus has a rather wide host range including 8 families 19 species.By comparing with the properties of various Phytophthora species,this fungus was identified as Phyiophthora capsici.The fungus is very sensitive to Ridomil,Bavistin and Aliette in laboratory experiments,while the Daconil is the least effective.

The first strand of the cDNA was synthesized by using BYDV-RNA as temolate and calf thymus DNA hydrolysate as random primer.The second strand was obtained according to nick-translation procedure with slight modification.ds-cDNA With a BamHl linker was inserted into a plasmid pUC₈.The plasmid was then used to transform E.coli strain JM-83 and colonies containing cDNA inserts were identified by screening on α-gal substrate.Colony and blot hybridizations using ³²P-labelled BYDV-RNA fragments confirmed the inserts were of viral origin.Analysis of some clones suggested that the length of the inserted fragments ranges from 300bp to 1600bp.The sensitivity of dot blot assay of plasmid DNA was between 100pg-lng.Some viruses of luteovirus group and some strains of BYDV could be identified by using cDNA probe.

38 isolates of soft rot bacteria isolates from more than 13 places in Beijing were identified.10 isolates of soft rot bacteria from Chinese cabbage in late storage state were Pseudomonas spp.,24 isolates from tomato,peper,potato,cucumber,white gourd,pumpkin and towel gourd were Erwinia carotovora pv.carotovora(Ecc) and the other 4 isolates from tomato and towel gourd were Erwinia carotovora pv.atroseptica (Eca).Eca not only can cause black leg of potato but also can cause soft rot of summer vegetables in Beijing.

The angular leaf spot of cucumber is getting severel in recent years in northern part of China and has caused losses of 10-25% yield at some location.Ten isolates of bacteria obtained from diseased cucumber plants of different provinces or regions were examined for their pathogenicity,and morphological,cultural physiological as well as serological characteristics.The results demonstrated that all isolates belonged to Pseudomonas syringae pv.lachrymans (Smith and Bryan) Young,Dye and Wilkier,1978.The inoculation tests showed that the pathogen could infect cucurbit (Lagenaria siceraria) moderately,and muskmelon (Cucumis melo),pumpkin (Cucurbita pepo) and suakwa vegetable sponge(Luffa cylindrica) weakly,besides cucumber (Cucumis sativus).

The physiological and biochemical characteristics of 50 isolates of causal bacterium of rice brown sheath disease and 5 check strains of Xanthomonas campestriz pathovars,(pv.campestris.pv.translucens.pv.oryzae.pv.oryzicola and pv.citri) were tested showing no difference.The DMA GtC mol% of 4 isolates of the pathogen and that of the 5 check strains were determined to be similar.The DNA-DNA hybrid rate of the isolates of the pathogen with the 5 check strains was low,and so was the rate among the check strains.But in contrast,the hybrid rate among the 4 isolates of the pathogen was high.The results demonstrated that the pathogen of rice brown sheath disease was a new pathovar.of Xanthomonas campestris and designated as X.campestris pv.brunneivaginae nov.pv.Luo,Liao et Chen.

The reniform nematode (Rotylenchulus reniformis) is one of the root pathogenic nematodes on vegetables in Sorth China.It occurs with wide host ranges.According to surveys made in 1985-1986 at Guangzhou suburb,we found that this nematode was parastic on 29 species of 11 families of vegetable crops.The species of Leguminosae,Solanaceae and Cucubitaceae are major host plants.Among other things,the bitter gourd,chidh,chieh-qua,butter lettuce,water spinach,edible amaranth,leek,ginger,garlic,water cress,chinese box thorn are first reported.This nematode infect the host plant by young females and often attach to the cuticula of the root for feeding.The part of infection is generaly at the elongation zone of root.Around the infection cells,the symptoms are necrosis and browning.The reniform nematodes were usually located in the soil layer about at 0-20 cm deep,but most of them were at 0-10 cm deep.

During 1975-1986,the resistance of the important varieties and resistant resources of wheat at adult stage to 39 strains of stripe rust were studies.4-10 isolated nurseries were set up for each year and 200-550entries for each nursery,which was tested by single strain,By analysing the 12-years data,certain results are as follows.

The authors have studies the mechanism of the enduring effect of triadimefon for controlling wheat stripe rust in seed treatment.Based on the study,the effective concentration of triadimefon was very low.

The interactions between 59 isolates of Pyricularia oryzae Cav.and 33 varieties of rice,inculding 7 differentials and 26 cultivars,were investigated during seedling stage according to the national unified method used to identify the races of P.oryzae.The variability of virulence of the fungus,the resistance of the cultivars and the value of the resistantones were studied and evaluated by the methods used in interorganismal genetics.The results showed that the pathogenicity of various isolates from the same rice is different on the cultivars except the differential ones.8 isolates among the 21 ones inoculated back to their original susceptible cultivars becomes no more virulent.The test of virulent frequency (VF) for cultivars to react with a greatnumber of the isolates shows more significant than test depending on number of the races.Among commercial cultivars,Shanyou 63,Shanyou 64 and Hongtu 31 are more resistant to rice blast and their VFs are not more than 0.3.

The variation of the virulence and some biological properties of four isolates of Xanthomonas campestris pv.oryzae were studied by successive culture.The results indicated that the virulence,rate of growth,production of extra-cellular polysaccharide and activities of proteolytic enzyme of the pathogen were rapidly decreased after the successive culture,but there was no distingushed change of extra-cellulase activity and the serotype.The causes of variation of the pathogenic bacterium and its pathogenic mechanism were discussed.

The resistance of wheat leaves tothe toxin preparation of Helminthosporium sativum was detected with the variation of electrical resistance.This method could obtain the same result as done by the inoculation from suspension of pathogenic spores.This method has close relationship to outer osmosis of electrolyte which,in general,expressed the level of the injured membrane.This method was in correspondence with the resistant stages of the wheat varieties and visible symptoms on wheat leaves.

Different components of the two BMV strains-RNA are isolated by means of two phases phenol method in the presence of bentonite and SDS.The results of polyacrylamide gel electrophoresis of BMV-RNAs further confirm that BMV-G has a new component RNA3a.The infectivity of mixtures of different RNA components has been investigated on Chenopodium quinoa.Theinoculation results reveal that the three largest nucleic acid components are required for infection,and the addition of RNA3a and RNA₄ can increase their infectivity.The cDNAs to the BMV-E-RNAs and RNA3a were prepared by reverse transcription.Northern blot hybridization with E-RNAs and G-RNAs reveal that the nucleotide sequence homology between RNA₃ and RNA3a is present,RNA3a belongs the subgenomic RNA of RNA₃.

Detection tests for Citrus tatter virus (CTLA) were performed by using Troyer,Carrizo,Rusk citrange and Kalpi lime (Ctirus excelsa) as indicator,using Poncirus trifoliata or the Goutoucheng (a sour orange variety) as the grafting stock.Some of the plants of the citrus varieties growing in Huangyan were found to be infected with CTLV.The varieties infected were:Bendi-zao(Citrus succesa),Man-ju (C.tardiferox),Zhao-ju (C.subcomprassa),Zhu-hong (C.erythrosa),Ru-ju (Kinokuni),Bejjing lemon (C.limon×C.sinensis?),Pon-kan (C.poonensis),Luchen sweet orange (C.sinensis) and Okitsu-wase Satsuma (C.unshin).The Troeyr citrange leaves,being infected with CTLV,showed characteristic symptoms of blotching and distortion.Light-colored streaks appeared on the young stems.Also the leaves of C.excelsa.showed blotchy spotting.

Panax quinquefolium has been found to be infected with an unreported disease since 1983 in Jilin,China.The disease in question causes phyllody and severe phloem necrosis especially at the root part.It was,therefore called as Panax quinquefolium phloem necrosis disease (PPAN).

Tea crinkle caused by Bacteria-like organism (BLO) is one of the most destructive disease cf tea trees (Camelliae sinensis) in south China.The pathogen was detected for the first time in Guangdong,China 1986.Symptoms appeared most frequently in youngest leaves and stems.Symptoms of infected leaves were curled or crinkled and deep green or yellowish green mottle.Leaves became deformed and shrunk;semitransparent leaf veins were appreciable on some older leaves:shoots were weak and internodes shortened.

Since 1983,the writers had collected a great number of typical RSV-like rice samples from Beijing and Hangzhou paddy rice fields.Many ultrathin sections were prepared from the diseased rice leaves and observed under electron microscope.No virus particles either spherical or filamentous were ever observed.The extract of the disease rice plants was not reactive with the RSV antiserum sent from Japan.However,the agent of the RSV-like disease could be specifically transmitted by the same vector plant-hopper(Laodelphax striatellus) of RSV from rice plant to rice plants and to wheat plants but not to maize plants or any other graminous plants so far tested.

Ten strains of Fusarium oxysporum f.sp.vasinfectum collected from Xinjiang and twenty strains collected from other provinces have been studied.There were no clear relationship between the production of fusaric acid and the physiological types.For the purpose to know the relation between virulence and the production of fusaric acid in modified Richard's medium,the culture was incubated at 25-26℃ on a rotating shaker.The resistance of ten varieties of G.hirsutum L.to fusaric acid was correlated with their resistance to cotton wilt disease.

Writers find out that Hishimonus sellatus Uhler is one of the major vectors of jujube witches' broom disease (JWBD).The experiment was carried out in field and greenhouse condition 1981 to 1985.The vectors usually migrates from jujube to nearby pine(Pinus tabulaeformis Carr.)and arborvitae(Platycladus orientalis Franco) from the end of August through October every year to overwinfer there in North China,The imagoes surviving after winter begin to leave the pine and arborvitae at about 15 th April the next year.However,H.sellaius does not breed any progeny on evergreen trees mentioned above.The inoculation on jujube seedlings with the wintered Ieaf hoppers demonstrated that the insects remained effecient for transmission of JWBD.When 2-5 insects were settled on each seedling,the incidence of JWBD varied from 7.1 to 76.2 per cent.The progeny of the insects fed on diseased jujube do not induce JWBD,if it was fed on healthy plant as soon as it was born.These facts additionally proved that Hishimonus sellatus Uhler were not only a vector of jujube witches' broom disease but also transmitted pathogen during the period between getting pathogen and death.

Pathogenicity of population of Erysiphe graminis f.sp,tritici in Henan Province was analysed by calculating virulence frequencies to single lines and by analysing association of pathogenicity and association of virulence to ten combinations of two lines within a set of nine wheat lines,each with a different resistant gene to Erysiphe graminis f.sp.tritici.Combinations of wheat varieties which have high PAC and low VAC can be effectively used for controlling powdery mildew of wheat.The combination of Huapei 28 and Zhou 80-48 or Zhou 80-48 and Zhengzhou 831 are good enough for controlling this disease.How to improve the method of study so as to better the use of the data obtained from pathogenicity survey was disscussed.