| The clubroot disease is a serious disease of cruciferous crops.The pathogen has three stages in its life cycle: survival in soil,root hair infection,and cortical infection.These resting spores release primary zoospores.When a zoospore reaches the surface of a root hair,it penetrates through the cell wall.The secondary zoospores released from the root hair and penetrate the cortical tissues of the main roots.The root hair infection stage is also called Primary infection,It is generally believed that clubroot disease is a single-circulation disease,and there is no specific report on whether there is re-infection.In this study,field experiments were carried out to prove whether winter rape in Chengdu area had reinfection and its damage degree.Studies on the physiological race identification,biological characteristics and genetic diversity of P.brassicae have been carried out,mainly in the field of root tumors of clubroot disease.The identification of single spores in the physiological roots of field root tumors indicates that it contains multiple physiological races.Therefore,the results of the above studies should be the results of a mixed population study.In this study,single spores were isolated and were used as materials to study the single spores,biological characteristics and genetic diversity of physiological races to obtain the results of single spores and compare them with tumors..The following results were obtained through research1.Reinfection of P.brassicaeThrough field trials,high-incidence areas and non-incidence areas were selected,and the reinfection of P.brassicae was studied by the method of combining primary plants with healthy plants.This experiment first observed the reinfection phenomenon discussed in this experiment in Chengdu,Sichuan.The incidence and disease index of reinfection were:5.56~6.67%,3.33~4.81.By measuring the growth of the plants,it was found that there was no significant difference between the re-infected disease plants and the healthy plants.2.Establishment of P.brassicae single-spore sytem and Study on the biological characteristics of the single spores system of P.brassicaeUsing the two physiological races No.4 and No.9 identified by the Williams identification system,Through the improvement of the method of single spore inoculation and cultivated of inoculation.21 single-spore tumors of 2 physiological race are acquired;with three times propagation of one of these single spore tumors,62 root tumors were obtained and a single spore system was successfully established.Among them,there were30 single-spore lines from the 4th race and 32 single-spore lines from the 9th race.The single spores obtained in the laboratory and established in the laboratory were used to analyze the biological characteristics of P.brassicae,and the biological characteristics of the single spores were slightly different.The effect of the single-spore spores of the diseased soil extract was greater than that of the non-sterilized root exudates,but in the single spores of No.1 and No.3,the effect was reversed;the lethal temperature of the single spores of No.1 the temperature was 46 ° C,and the lethal temperature of the single spores of No.2 and No.3 was 48 ° C;24 ° C was the optimum temperature of three single spores,but the effect of single spores No.1 and No.2 at 23 ° C when the temperature is greater than 25 ° C,the germination rate of the single spore system No.3 at 25 ° C is higher than23 ° C.The germination rate of the three single spores was the highest at pH=6.5,and the light inhibited the spore germination of the three single spores.3.Analysis of specific primers for P.brassicae and genetic diversity of P.brassicaeAccording to the reported molecular identification methods in the literature,48 single spores of three physiological races were identified by physiological races,and physiological races 4,5,7,9,and 11 were identified.The RAPD and SRAP methods were used to analyze the genetic diversity of 48 48 single spores,and the results were compared with the molecular identification results.It was found that RAPD and SRAP can be used to some extent according to physiological races and geography.Locations are classified,but they are not completely accurately distinguished. |
