Screening Of Clubroot Resistant Resources And Creation Of Germplasm Resistant To Clubroot In Brassica Napus

Clubroot is a worldwide soil-borne disease caused by Plasmodiophora brassica Woronin,and has been spreading widely in 60 countries all over the word.In recent years,the damage of clubroot is aggravating in China year by year,which restricts the development of rapeseed production of our country.Brassica napus has the largest area in China among the three main cultivated rapeseed types.However,it is urgent to creat the the clubroot resistant B.napus since the resource of B.napus resistant to clubroot is very deficient.Researches have shown that Chinese cabbage,black mustard and radish,which are relative species of rapeseed,have some resources resistant to clubroot,therefore distant hybridization,synthetic and other methords can be used to transfer the resistant genes from these materials to B.napus,cultivatethe new germplasms of clubrootresistant B.napus,which can lay a foundation for breeding new germplasms resistant to clubroot and guarantee the oilseed rape industry healthily.This research was conducted in screenning of resources resistant to clubroot,creating and identifying the clubrootresistantB.napus,and the main results are as follows:1.The injection method was used to identify the resistance of 50 Cruciferae accessions collected and breeded?3 cabbage rapeseed,4 cabbage rape,3 mustard rape,5 cabbage,3cabbage,1 radish,1 part of kale,5 kale,8 white cauliflower,7 blue and white dish?.The correlation analysis of resistance and clustering analysis on testedaccessions showed that the resistances between different accessions have significant difference,and finally all accessions were divided into four groups including resistant,moderate susceptible,susceptible,highly susceptible.And eight resistant varieties?3 cabbage,2 head cabbage,1 radish,1 mustard rape,1 part of kale?,two moderate susceptible,fourteen susceptible,andtwenty-six highly susceptible accessions were screened.The resistant accessions obtained are used for the creation of clubrootresistant B.napus.2.Eight hybridized combinations containing 40 hybrided seedlings were obtained by distant hybridization combined with embryo rescue technology using fourclubroot susceptible B.napus?female?and three clubroot resistant Chinese cabbages?male?in our laboratory.Four hybrided combinations derived from 2 clubroot resistant cabbages and three clubroot resistant Chinese cabbageswere synthesized by embryo rescue technology.3.Three methods including morphological identification,cytology identification and molecular markers-assisted selection were used to identify the true or false hybrids for the 40hybrided seedlings from distant hybrided F₁ obtained by embryo rescue and 40 hybrided F₁from fructified naturally in field.The results showed that thirty-six seedlings were identified as the true hybrids from 40 seedlings obtained by embryo rescue,the rate of true hybrids was90%;thirty-seven seedlings were true hybrids from 40 field materials,the rate of true hybrids was 92.5%,and the both rates of true hybrids are in agreement.The combination of the three methods increased the reliability of the test identification,so that the results are more authentic and reliable.4.Resistances of F₁ hybrids were evaluated by the two methods of marker-assisted selection identification and inoculation identification.Resistance of F₁ hybrided seedlings by embryo rescue were identified by marker-assisted selection and the proportion of susceptible offsprings were universally between 25.00%and 66.67%,the total susceptible proportion was about 46.85%.The Plasmodiophorafrom Chengdu,Sichuan to innoculate the hybrided seedlings fructified naturally in field and the results showed that the disease incidence of F₁was generally between 30.00%and 60.00%,the average morbidity was 44.55%,and all showed resistance segregation,which also indicated that the resistant gene locus of Chinese cabbage used in this research was heterozygous.5.According to identification of true and false hybrids and resistance identification,eight hybridized combinations fromembryo rescue containing 21 hybrided seedlings were obtained,and these intermediate materials can be used a'bridge materials'of clubroot resistance for subsequent researches.