Research On Inheritance Of Resistance To Black Rot And Changes Of Defense Enzymes Activity And Ultrastructure In Broccoli

Black rot is one of the most important diseases endangering broccoli severely, and it is caused by campestris bacillus Xcc. and it results in not only reducing yields but also seriously affecting the quality of the broccoli. Besides cruciferae crops, this infection also spreads to many of other vegetables. This study conducted the resistance identification to293copies of broccoli materials by artificial inoculation in the seedling stage and created the six generations populations, analyzed the inheritance of resistance of broccoli black rot. After inoculated black rot, the resistance differences in different age of seedling of broccoli was studied; and analyzed the change of defense enzyme activity. We observed the leaf ultrastructure of disease-resistant and susceptible variety by transmission electron microscopy techniques, analyzed the different periods of resistance and susceptible variety leaves in response to the black rot fungus infection similarities and differences. Specific results are as follows:1. Resistance identification of293broccoli materials by artificial inoculation with black rot at seedling stage, we screened out1highly resistant wild material (12B756),6resistant materials (12B415、12B481、12B741、12B743、12B839、11B908).194moderately resistant materials.85susceptible materials.7highly susceptible materials (11B16、11B438、11B588、12B6、12B37、12B610、12B738), and no immune materials. The screening rate was68.6%, which including0.34%high resistant materials,2.05%resistant materials,66.21%moderately resistant materials; and7highly susceptible materials can be used as well as the susceptible disease control materials.2. According to the separation of F2group resistance type, with the knowledge of classical genetics, we proposed that the black rot resistance of broccoli may be the quality genetic traits, which primary controlled by2pairs of dominant genes, and accompanied by joint action and influence of recessive gene, but we couldn’t rule out the possibility of environmental impact and modifier genes.3. Through a comparative study of three ages of seedling of the resistance differences, we found that three ages of seedling after inoculating black rot of the onset time and speed were different, the onset time showed:cotyledon period>3～4true leaf stage>6～7true leaf stage:and the onset speed showed:cotyledon period>6～7true leaf stage>3～4true leaf stage. Through the comparison, it is determined that the optimum seedling age was3～4true leaf stage for broccoli black rot resistance identification, this conclusion shortened the resistance identification of time about7days’around.4. Through the study of changes of defense enzyme activity after inoculating black rot in different resistant types of broccoli materials, resistant materials have higher POD, PPO and PAL activity than susceptible materials, but there is higher SOD activity in susceptible materials. After inoculation, resistant materials SOD, POD, CAT, PPO and PAL activity were higher than that of the control, and higher than that of susceptible materials. Comparing the three ages of seedling, we found that POD、SOD and PPO activity were showed6～7leaf stage>3～4leaf stag>cotyledon period, PAL activity was6～7leaf stage>3～4leaf stag>cotyledon period in resistant materials, but showed3～4leaf stage>6～7leaf stage> cotyledon period in susceptible materials, there was no obvious regularity of CAf activity. Suggesting that the priority of the resistance indexes is PAL and PPO, SOD and POD, CAT.5. Observation of the ultrastructure of leaves of resistant and susceptible materials inoculated with black rot, we discovered that the resistant materials of cell membrane system and organelle were damaged to a lesser extent and later than susceptible materials, and appeared the cell wall thickened and the membrane vesicles increased of the phenomenons, there were many dense aggregates around the cell wall. Susceptible materials were severely damaged and earlier, organelle swelling deformation, and loss of function, at last, the whole cell disintegration and death.