| In recent years,the trend of the cruciferous clubroot disease occurred and harmed in Sichuan Province was increasing year by year,the soil-borne diseases caused by Plasmodiophora brassicae,because of the lack of resources and difficulty to control,it has become the main disesse of cruciferous crops.Bast on the seeking of the cruciferous clubroot disease's agents and occurred,test want to find the nosogenesis and judged by fastness of some rape's breeds,according to Trichoderma's preparation and screening,hope to control the disease and reform of wood mould.The results showed that:1.Each villages of Sichuan Province Tianquan county could be find P.brassicae in 2006 and in 2007,the mainly damage crop includes rape,Chinese cabbsge,green vegetables,radish etc.Extent of injury rape＞Chinese cabbage＞green vegetables＞radish,the most morbidity was 100%,the morbidity degree is unable to completely identical among the different crop breed of the same crop.Rape can be invaded by P. brassicae during all its growth period,especially when it is young.The disease only damage the root,its root will outgrow a lot of tumours when rape is invaded by P. brassicae,different shape and different size.Commonly,the tumours are bigger and fewer in taproot than in fibre.To sum up,the symptom of clubroot disease in rape is similar to it in cruciferae.2.It is closely among the type of soil,the number of dormant in the soil,soil PH value and the occurrence of swollen root and extent of harm.The soil pH is the important factor which could arouse P.brassicae,and in acidic soil is ease to happen, pH5.5-pH6.2 is common,PH6.3 is the optimum;The unlike soil property occurrence damage is clay＞loam＞sand,then be effected by the soil humidity too;when the spore concentration reached 1.0×10~7～10~8 entry/g P.brassicae could be happen;when the spore concentration reached 3.0×10~7entry/g the incidence rate of P.brassicae increased significantly.3.The plants' relict and the fungus-soil is the main source of infection.P. brassicae could intrude Chinese cabbage and cause disease in the whole year,April to October is the condign time,June to September is the fastigium,October to December is the resting time,October to November is the main time of arouse the P. brassicae,November 6 disease have the highest value reached 83.4 percent,after mid-November the disease entered the slow development period,the next March it will begin to develop.4.Adult plant's high,length of main root,fresh weight and so on,it has a different disease rate because of different variety.Rong-oil 10,de-oil 5 and others,the plants physiological characteristics of the growth trends and morbidity in line,Rong-oil 8,Qian-oil 16 et cetera grown worse disease arises heavily,oil-yan 10 et cetera grown better disease arises lightly;all of 25 varieties are the feeling sickness varieties,thereinto Rong-oil 10,Sheng-oil 2,Rong-oil 8,Yi-oil 13,Nan-oil 11,Qian-oil 16 and Rong-oil 4 are highly susceptible.5.264 Trichoderma isolated from 25 soil samples.There were 132 isolates of T.harzianum,38 isolates of T.koningii,18 isolates of T.pseudokoningii,15 isolates of T.aureoviride,28 isolates of T.viride,3 isolates of T.hamatum.The test of hyphal growth rate and inhibit spore germination rate showed that T1,T3,T5,T20 were more excellent,T1 was the best.After each one and L24 were applied as parent strains to conduct fusion,then has been 96 strains of fusion,pass the ten eras continous foster has been 25 genetic steady strains of fusion.For more filtration we has been 5 biocontrol-strains,their hyphal growth rate was higher than another parente stains besides L24,the inhibit spore germination rate of fh5 was lower than T1,fh23 inherit the excellence from parente stains,the hyphal growth rate and inhibit spore germination rate were significantly higher than other strains.6.All of use for biological control's Trichoderma have a certain effect for P. brassicae.The effect of fh23 was the best,to 53.74%,which was significantly higher than other strains;the effects offh23 and fk3 were higher than parente stains;the effect of fh5 was improved 2.32%than L24,but lower than T1 which was significantly difference for others;fk3,fh5and T3 did not have significantly difference,the fh8 has the lowest effect,only 11.76%.
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