| Head cabbage is a variant of Brassica oleracea L., whose terminal bud can form leafy head. Cabbage is widely grown in Northern China and plays a significant role in all-year supply of vegetables as well as in earning foreign exchanges through exports. In recent years, cabbage grown in Northern China are suffering from increasingly great production loss from Fusarium wilt caused by Fusarium oxysporum.Cabbage Fusarium wilt was firstly discovered in USA and then spreaded rapidly in many countries where cabbage was grown. After years of breeding work, varieties with Fusarium resistance have been cultivated. In China, cabbage wilt was a new disease which was discovered not long ago. Correlational research was relatively less in this field. The most effective method to control this disease was usage of varieties with Fusarium wilt resistance. At present, both the resistance of the breeding resources and the race type of the pathogen that caused cabbage wilt in Northern China are unclear. Therefore, it is extremely necessary to make clear of the resistance of the existing cabbage germplasm resource as well as the race type of the pathogen.Pathogen type and race type was studied through collecting and identifying pathogens from areas which were seriously attacked by Fuasrium wilt in Northern China. 117 cabbage inbred lines were evaluated for their resistance to Fusarium wilt through being inoculated with pathogen FGLâ‘¢-6, which was isolated from diseased cabbage in Yanqing County in Beijing. 8 cabbage hybrids-all with one parent resistant and the other susceptible, and F2, BC1-P1 and BC1-P2 of two combinations were used for resistance inheritance analysis. The results were as follows:1. Results of pathogen studies: pathogens collected from Shanxi, Hebei province and Beijing and pathogens used in literatures at home and abroad were studied using morphological as well as ITS region sequencing methods. The results of pathogenicity tests and morphological and molecular identification showed that isolations with pathogenicity were all identified as Fusarium oxysporum and they were all from Yanqing County in Beijing and Shouyang and Taiyuan in Shanxi Province. Results of comparison tests between pathogen from Yanqing County and different pathogen race type were as follows: Comparison experiment between FGLâ‘¢-6 from Yanqing and Race 1 FOAM from USA were performed on 21 materials and the results suggested that the same material exhibited similar resistance level to the two pathogen races, indicating that FGLâ‘¢-6 may belong to Race 1; Another comparison test between FGLâ‘¢-6 and Race 2 from USA showed that the latter possessed stronger pathogenicity.2. Screening of resistant cabbages: 117 cabbage inbred lines from Cabbage and Broccoli Breeding Group of Institute of Flowers and Vegetables, Chinese Academy of Agricultural Sciences were evaluated for their resistance to Fusarium wilt through being inoculated with pathogen isolated from diseased cabbage in Yanqing County in Beijing. 47 materials were resistant, with 37 of them showing high resistance. The correlations of their resistance with geographic origins, with types and leaf colors were analyzed respectively. The result showed that materials with high resistance were mostly from Japan, Korea, Russia, Netherlands, etc.; More inbred lines with high resistance possessed flat head and grey-green leaf, while no resistant material was found in pointed head type. With repeated experiments and field tests, 5 inbred lines with high resistance to cabbage wilt and excellent economic traits were screened out and could be used in preparing mating combinations. In addition, two hybrids were confirmed to be with high resistance to Fusarium wilt and this result was of great help in their commercial generalization.3. Results of inheritance analysis: 8 cabbage hybrids, all with one parent resistant and the other susceptible, were evaluated for resistance inheritance and the result showed that the resistance gene accorded to dominant inheritance; 2 of the 8 F1 hybrids were used for creating F2, BC1-P1 and BC1-P2 separately and all populations produced above were used for resistance inheritance analysis. It showed that the inheritance of resistance to Fusarium wilt in cabbage was dominant single gene pattern.In our study, the pathogen that caused cabbage wilt in Northern China was confirmed to be Fusarium oxysporum; the race type was preliminarily discussed; cabbage inbred lines with high resistance to Fusarium wilt as well as with excellent economical traits screened out in resistance identification tests set the foundation for cabbage resistance breeding; Inheritance analysis result showed that the resistance gene was single dominant pattern, which provided theoretical support for further studying DNA molecular markers as well as cloning of the resistance gene. |
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