Inheritance Of Cabbage Resistance To Clubroot Disease

In order to offer basis of theory to breeding of Cabbage for clubroot resistance, speed course of breeding and promote method of breeding, in this experiment, inoculation techniques for Cabbage resistance in the seedling stage in the room were perfected and the most adequate density of inoculation was studied. A four-parent diallel cross was studied through analysis of general combing ability and special combing ability in according to Griffing method I > pattern I . Through a diallel table of FI cross, variance (Vr) of every array and covariance (Wr) of every array and their common parents were caculated in according to Hayman's method. Through analysis of regression and estimation of relevant genetic parameter, inheritance of Cabbage resistance tc clubroot disease was made clear in the end. The main results were as followed: 1. Inoculation techniques of ciubroot disease in the seedling stageThe study compared with two inoculation techniques, which were mixture of resting spores and soil, dipping the root of seedling with spore suspension. The result indicated that the disease of Cabbage in the seedling stage using the soil inoculation occurred more seriously than another method. The former's disease index was 51.2 and disease percentage was 74.87%, but the latter's disease index was 12.5 and disease percentage was 46.7%. In the study of inoculation density, the highest the density of inoculation was, the bigger the disease percentage was. When the concentration of inoculated spore was 2X 108 spores in one gram soil, inoculated result is stable between repeats, there was a obvious variety of resistance between different materials, and there was a evident variance. Other inoculated density also resulted in variety of resistance, but analysis of variance is not obvious.In the experiment, there was a inoculated comparison between P. brassicae on leafmustard in ChongQing municipal, FuLing district and P.brassicae on Cabbage in SiChuan province, ChengDu municipal. Results indicated disease index that P.brassicae on Cabbage inoculated was 53.5, but disease index that P.brassicae on leaf mustard was 67.6, and the latter was more susceptive than the former. 2.Appraisal of resistance to different materialsIn the experiment, taking P.brassicae on leaf mustard in ChongQing municipal,FuLing district as pathogeny, there was a appraisal of resistance to four parents material (99076> 99046^ 99033 > 99037) through inoculation in seedling stage in the room ?inoculation in seedling stage in the field and nature inducation in the field. Trend of appraisal of three methods was consistent, affimming two resistant materials(99033 > 99037) and two susceptive materials(99076, 99046). S.Inquiry on standard of grade for statement of clubroot diseaseIn the experiment, there was grade of clubroot disease through ration's grade. Individual plant's standard of grade and colony resistance's standard of grade, which were united in our country, were adapted. There was not united standard of grade in appraising resistance of inoculation in seedling stage in the field, so a new standard of grade on statement of Cabbage clubroot disease in the field was defined through referencing other standard of grade on individual plant's statement of disease of crucifer in the field and linking reality. 4. Genetic analysis of Cabbage resistance to clubroot diseaseGenetic analysis showed that Cabbage resistance to clubroot disease was imcomplete recession. Average degree of dominance was fewwer than one. Effect of backcross was very obvious, but effect of reciprocal cross is not obvious. Resistance was dominated by nuclear gene, and effect of cytoplasm was very small. Through analysis of FI and p2 generation, at least there were more tJ&n two pairs of nuclear genes to control the resistance. To some evident, the resistance to clubroot disease was a quantitative character. Narrow heritability is comparatively high, and this showed in the inheritance of Cabbage resistance to clubroot disease, there was a comparatively big additive variance...